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Inwardly rectifying potassium (Kir) channels play a pivotal role in physiology by establishing, maintaining, and regulating the resting membrane potential of the cells, particularly contributing to the cellular repolarization of many excitable cells. Dysfunction in Kir2.1 channels is implicated in several chronic and debilitating human diseases for which there are currently no effective treatments. Specifically, Kir2.1-R312H and Kir2.1-C154Y mutations are associated with Andersen-Tawil syndrome (ATS) in humans. We have investigated the impact of these two mutants in the trafficking of the channel to the cell membrane and function in Xenopus laevis oocytes. Despite both mutations being trafficked to the cell membrane at different extents and capable of binding PIP 2 (phosphatidylinositol-4,5-bisphosphate), the main modulator for channel activity, they resulted in defective channels that do not display K + current, albeit through different molecular mechanisms. Coexpression studies showed that R312H and C154Y are expressed and associated with the WT subunits. While WT subunits could rescue R312H dysfunction, the presence of a unique C154Y subunit disrupts the function of the entire complex, which is a typical feature of mutations with a dominant-negative effect. Molecular dynamics simulations showed that Kir2.1-C154Y mutation induces a loss in the structural plasticity of the selectivity filter, impairing the K + flow. In addition, the cryo-EM structure of the Kir2.1-R312H mutant has been reconstructed. This study identified the molecular mechanisms by which two ATS-causing mutations impact Kir2.1 channel function and provide valuable insights that can guide potential strategies for the development of future therapeutic interventions for ATS., (© 2024 The Author(s). The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.)

Bone Morphogenetic Protein (BMP) signaling is essential for craniofacial development, though little is known about the mechanisms that govern BMP secretion. We show that depolarization induces calcium-dependent BMP4 release from mouse embryonic palate mesenchyme. We show endogenous transient changes in intracellular calcium occur in cranial neural crest cells, the cells from which embryonic palate mesenchyme derives. Waves of transient changes in intracellular calcium suggest that these cells are electrically coupled and may temporally coordinate BMP release. These transient changes in intracellular calcium persist in palate mesenchyme cells from embryonic day 9.5 to 13.5 mice. Disruption of a potassium channel called Kcnj2 significantly decreases the amplitude of calcium transients and the ability of cells to secrete BMP. Kcnj2 knockout mice have cleft palate and reduced BMP signaling. Our data suggest that temporal control of developmental cues is regulated by ion channels, depolarization, and intracellular calcium for mammalian craniofacial morphogenesis., Competing Interests: Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Background: The KCNJ11 gene belongs to the potassium channel gene family. It has a major role in the secretion of insulin. Genetic variations in KCNJ11 are possibly responsible for the progression of type 2 diabetes mellitus (T2DM). In this study, we investigated the possible correlation between KCNJ11 (rs5210) gene polymorphism and T2DM., Subjects and Method: This study included 92 individuals divided into two groups. Group 1 included 46 type 2 diabetic patients. Group 2 (control group) included 46 healthy participants. A complete history was taken and a full physical examination was performed. Anthropometric data were measured. Laboratory investigations included fasting blood glucose (FBG), two hours post-prandial blood glucose (2HPPBG), glycated hemoglobin (HbA1c), and fasting lipid profile. KCNJ11 (rs5210) single nucleotide polymorphism was detected by polymerase chain reaction restriction-fragment length polymorphism (PCR-RFLP)., Results: Both AG and GG genotypes were associated with increased risk for T2DM (OR 5.2, 95% CI 1.32-20.5, P = 0.01 for AG; and OR 18.2, 95% CI 2.99-31.7, P = 0.002 for GG). Also, the frequency of the G allele was significantly higher in type 2 diabetic patients compared to healthy controls (50% versus 23.9%, respectively). The G allele of rs5210 in KCNJ11 contributed to an increased risk of T2DM (OR 3.18, 95% CI 1.31-7.75, P = 0.01). There was a statistically significant association between increased 2HPPBG and HbA1c levels and the carrier of AG and GG genotypes (P = 0.01 and 0.007, respectively). There was a statistically significant association between total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-c), and high-density lipoprotein-cholesterol (HDL-c) levels and the carrier of AG and GG genotypes (P < 0.001, 0.02, and 0.007, respectively). Regression analysis detected that body mass index (BMI), 2HPPBG, TC, triglycerides (TG), and the G allele of rs5210 in KCNJ11 gene showed a significant association with T2DM (P = 0.004, 0.042, 0.003, 0.006, and 0.01, respectively) while no association was observed with FBG, HbA1c, LDL-c or HDL-c (P = 0.099, 0.123, 0.522, and 0.765, respectively)., Conclusion: KCNJ11 rs5210 genetic polymorphism may raise the risk for the occurrence of T2DM among Egyptians., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Background: Individuals with maturity-onset diabetes of the young (MODY) are often misdiagnosed as type 1 or type 2 diabetes and receive inappropriate care. We aimed to investigate the characteristics and treatment of all MODY types in a multicenter, real-world setting., Methods: Individuals with MODY from the diabetes prospective follow-up (DPV) registry were studied. We compared clinical parameters during the first year of diabetes and the most recent treatment year after MODY diagnosis., Results: A total of 1640 individuals were identified with GCK-MODY (n = 941) and HNF1A-MODY (n = 417) as the most frequent types. Among these, 912 individuals were available with information during the first and the most recent treatment year (median duration of follow-up: 4.2 years [2.6-6.6]). Positive beta cell autoantibodies were present in 20.6% (15.2% IAA). Median age at diagnosis ranged from 9.9 years in GCK-MODY (Q1-Q3: 6.2-13.1 years) and INS-MODY (2.7-13.7 years) to 14.3 years (5.0-17.1) in KCNJ11-MODY. Frequency of oral antidiabetic agents (OAD) use increased and insulin decreased in HNF4A-MODY (OAD: 18% to 39%, insulin: 34% to 23%) and in HNF1A-MODY (OAD: 18% to 31%, insulin: 35% to 25%). ABCC8-MODY was characterized by a decrement in nonpharmacological treatment (26% to 16%) and "insulin only" treatment (53% to 42%), while the proportion of individuals treated with OAD but no insulin increased from 0% to 21%., Conclusions: Our results indicate that some teams caring for individuals with MODY are hesitant with regard to current recommendations. Registries are an essential source of information and provide a basis for discussing treatment guidelines for MODY., (© 2024 The Author(s). Journal of Diabetes published by Ruijin Hospital, Shanghai Jiaotong University School of Medicine and John Wiley & Sons Australia, Ltd.)

Major depressive disorder (MDD) is a prevalent mental health condition characterized by persistent feelings of sadness and hopelessness, affecting millions globally. The precise molecular mechanisms underlying MDD remain elusive, necessitating comprehensive investigations. Our study integrates transcriptomic analysis, functional assays, and computational modeling to explore the molecular landscape of MDD, focusing on the DLPFC. We identify key genomic alterations and co-expression modules associated with MDD, highlighting potential therapeutic targets. Functional enrichment and protein-protein interaction analyses emphasize the role of astrocytes in MDD progression. Machine learning is employed to develop a predictive model for MDD risk assessment. Single-cell and spatial transcriptomic analyses provide insights into cell type-specific expression patterns, particularly regarding astrocytes. We have identified significant genomic alterations and co-expression modules associated with MDD in the DLPFC. Key genes involved in neuroactive ligand-receptor interaction pathways, notably in astrocytes, have been highlighted. Additionally, we developed a predictive model for MDD risk assessment based on selected key genes. Single-cell and spatial transcriptomic analyses underscored the role of astrocytes in MDD. Virtual screening of compounds targeting GPR37L1, KCNJ10, and PPP1R3C proteins has identified potential therapeutic candidates. In summary, our comprehensive approach enhances the understanding of MDD's molecular underpinnings and offers promising opportunities for advancing therapeutic interventions, ultimately aiming to alleviate the burden of this debilitating mental health condition. KEY MESSAGES: Our investigation furnishes insightful revelations concerning the dysregulation of astrocyte-associated processes in MDD. We have pinpointed specific genes, namely KCNJ10, PPP1R3C, and GPR37L1, as potential candidates warranting further exploration and therapeutic intervention. We incorporate a virtual screening of small molecule compounds targeting KCNJ10, PPP1R3C, and GPR37L1, presenting a promising trajectory for drug discovery in MDD., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objective: Gain-of-function (GOF) variants of KCNJ11 cause neonate diabetes and maturity-onset diabetes of the young (KCNJ11-MODY), while loss-of-function (LOF) variants lead to hyperinsulinemia hypoglycemia and subsequent diabetes. Given the limited research of KCNJ11-MODY, we aimed to analyse its phenotypic features and prevalence in Chinese patients with early-onset type 2 diabetes (EOD)., Design, Patients and Measurements: We performed next-generation sequencing on 679 Chinese EOD patients to screen for KCNJ11 exons variants. Bioinformatics prediction and the American College of Medical Genetics and Genomics guidelines was used to determine the pathogenicity and diagnosed KCNJ11-MODY. A literature review was conducted to investigate the phenotypic features of KCNJ11-MODY., Results: We identified six predicted deleterious rare variants in six EOD patients (0.88%). They were classified as uncertain significance (variant of uncertain significance [VUS]), but more common in this EOD cohort than a general Chinese population database, however, without significant difference (53/10,588, 0.50%) (p = .268). Among 80 previously reported patients with KCNJ11-MODY, 23.8% (19/80) carried 9 (32.1%) LOF variants, who had significantly older age at diagnosis, higher birthweight and higher fasting C-peptide compared to patients with GOF variants. Many patients carrying VUS were not correctly diagnosed., Conclusions: Some rare variants of KCNJ11 might contribute to the development of Chinese EOD, although available evidence has not enough power to support them as cause of KCNJ11-MODY. The clinical features of LOF variants were different from GOF variants in KCNJ11-MODY patients. It is necessary to evaluate the pathogenicity of VUS through function experiments., (© 2024 John Wiley & Sons Ltd.)

Purpose: This study aimed to describe the clinical features, diagnostic and therapeutic course of a patient with MODY13 caused by KCNJ11 (c.101G > A, p.R34H) and how it contributes to the pathogenesis of MODY13, and to explore new therapeutic targets., Methods: Whole-exome sequencing was used to screen prediagnosed individuals and family members with clinically suspected KCNJ11 mutations. Real-time fluorescence quantitative PCR, western blotting, thallium flux of potassium channels, glucose-stimulated insulin secretion (GSIS), and immunofluorescence assays were used to analyze the regulation of insulin secretion by the KCNJ11 mutant in MIN6 cells. Daily blood glucose levels were continuously monitored for 14 days in the proband using the ambulatory blood glucose meter (SIBIONICS)., Results: Mutation screening of the entire exon of the gene identified a heterozygous KCNJ11 (c.101G > A, p.R34H) mutation in the proband and his mother. Cell-based GSIS assays after transfection of MIN6 using wild-type and mutant plasmids revealed that this mutation impaired insulin secretory function. Furthermore, we found that this impaired secretory function is associated with reduced functional activity of the mutant KCNJ11 protein and reduced expression of the insulin secretion-associated exocytosis proteins STXBP1 and SNAP25., Conclusion: For the first time, we revealed the pathogenic mechanism of KCNJ11 (c.101G > A, p.R34H) associated with MODY13. This mutant can cause alterations in KATP channel activity, reduce sensitivity to glucose stimulation, and impair pancreatic β-cell secretory function by downregulating insulin secretion-associated exocytosis proteins. Therefore, oral sulfonylurea drugs can lower blood glucose levels through pro-insulinotropic effects and are more favorable for patients with this mutation., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The aim of this work was to identify the underlying genetic cause in a four-generation family segregating an unusual phenotype comprising a severe form of skeletal Class II malocclusion with gingival hyperplasia. SNP array identified a copy number gain on chromosome 1 (chr1); however, this chromosomal region did not segregate correctly in the extended family. Exome sequencing also failed to identify a candidate causative variant but highlighted co-segregating genetic markers on chr17 and chr19. Short- and long-read genome sequencing allowed us to pinpoint and characterize at nucleotide-level resolution a chromothripsis-like complex rearrangement (CR) inserted into the chr17 co-segregating region at the KCNJ2-SOX9 locus. The CR involved the gain of five different regions from chr1 that are shuffled, chained, and inserted as a single block (∼828 kb) at chr17q24.3. The inserted sequences contain craniofacial enhancers that are predicted to interact with KCNJ2/KCNJ16 through neo-topologically associating domain (TAD) formation to induce ectopic activation. Our findings suggest that the CR inserted at chr17q24.3 is the cause of the severe skeletal Class II malocclusion with gingival hyperplasia in this family and expands the panoply of phenotypes linked to variation at the KCNJ2-SOX9 locus. In addition, we highlight a previously overlooked potential role for misregulation of the KCNJ2/KCNJ16 genes in the pathomechanism of gingival hyperplasia associated with deletions and other rearrangements of the 17q24.2-q24.3 region (MIM 135400)., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The essential role of the inwardly rectifying potassium channel K ir 5.1 (KCNJ16) in controlling electrolyte homeostasis and blood pressure has been demonstrated in human and animal studies. Previous studies have identified several bi-allelic mutations of KCNJ16 in humans, causing severe hypokalemia, renal salt wasting, and disturbed acid-base homeostasis. Here, we identified a novel homozygous variant of KCNJ16, I26T, in an Amish patient affected with polydipsia, developmental delay, and chronic metabolic acidosis with low serum bicarbonate concentration. Subsequently, we generated the rat model with I26T mutation using Dahl salt-sensitive rat (I26T rat) to characterize this variant. The male mutant rats displayed similar blood pressure and electrolyte homeostasis under baseline and with a high salt (4% NaCl) challenge. Blood pH, HCO 3 - and renal damage also remained similar between WT and I26T rats after high salt challenge. Additionally, single-channel patch clamp analysis revealed similar channel activity in CHO cells overexpressed with WT and I26T mutant K ir 4.1/5.1 channels. In summary, this study reported a novel variant in KCNJ16, namely I26T, which is likely a benign variant and not associated with pathologic phenotype in either human or Dahl salt-sensitive rats, indicating that the type/location of variant should be considered when diagnosing and treating patients with KCNJ16 mutations., (© 2024 The Author(s). Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.)

Background: Renal hypokalemia is associated with mutation. This study aimed to investigate the clinical features and pathogenic mutations in patients with renal hypokalemia., Methods: The patients with hypokalemia were enrolled, and the renal function, thyroid function, renin-aldosterone system, urinary potassium excretion, and exome sequencing were performed. The correlation between the clinical phenotypes and causative genes was assessed., Results: Five patients with hypokalemia were enrolled and diagnosed as tubular hypokalemia. The patients with common clinical manifestations were difficult to differentiate based on atypical laboratory findings. The results of the genetic analysis were as follows: both patient 1 and patient 2 were heterozygous for the c.C625T mutation of the KCNJ1 gene, which is responsible for Bartter syndrome. Patient 3 was heterozygous for the c.G298A mutation of the ATP6V1B1 gene, which is responsible for renal tubular acidosis. Patient 4 had a compound heterozygous mutation of c.G893A of the BSND gene, responsible for Bartter syndrome, and c.1029+5G>A, the ATP6V0A4 gene responsible for distal renal tubular acidosis. Patient 5 had Gitelman syndrome and carried the compound heterozygous mutations c.C1963T and c.G2029A of the SLC12A3 gene. All the above loci were known heterozygous mutations., Conclusions: The unusual heterozygous mutations were identified in five renal hypokalemia patients. Molecular diagnosis of tubular hypokalemia was conducive to accurate diagnosis and treatment.

Hypertension is associated with decreased endothelial function through reduced contributions of nitric oxide (NO). We previously discovered that flow-induced NO production in resistance arteries of mice and humans critically depends on endothelial inwardly rectifying K + (Kir2.1) channels. The goal of this study was to establish whether these channels contribute to the impairment of endothelial function, measured by flow-induced vasodilation (FIV) in peripheral resistance arteries of humans with hypertension. We measured FIV in vessels isolated from subcutaneous fat biopsies from 32 subjects: normotensive [ n = 19; 30.6 ± 9.8 yr old; systolic blood pressure (SBP): 115.2 ± 7 mmHg; diastolic blood pressure (DBP): 75.3 ± 5.7 mmHg] and hypertensive ( n = 13; 45.3 ± 15.3 yr old; SBP: 146.1 ± 15.2 mmHg; DBP: 94.4 ± 6.9 mmHg). Consistent with previous studies, we find that FIV is impaired in hypertensive adults as demonstrated by a significant reduction in FIV when compared with the normotensive adults. Furthermore, our data suggest that the impairment of FIV in hypertensive adults is partially attributed to a reduction in Kir2.1-dependent vasodilation. Specifically, we show that blocking Kir2.1 with ML133 or functionally downregulating Kir2.1 with endothelial-specific adenoviral vector containing dominant-negative Kir2.1 (dnKir2.1) result in a significant reduction in FIV in normotensive subjects but with a smaller effect in hypertensive adults. The Kir2.1-dependent vasodilation was negatively correlated to both SBP and DBP, indicating that the Kir2.1 contribution to FIV decreases as blood pressure increases. In addition, we show that exposing vessels from normotensive adults to acute high-pressure results in loss of Kir2.1 contribution, as high pressure impairs vasodilation. No effect is seen when these vessels were incubated with dnKir2.1. Overexpressing wtKir2.1 in the endothelium resulted in some improvement in vasodilation in arteries from all participants, with a greater recovery in hypertensive adults. Our data suggest that hypertension-induced suppression of Kir2.1 is an important mechanism underlying endothelial dysfunction in hypertension. NEW & NOTEWORTHY Impairment of endothelial function under high blood pressure is linked to the loss of inwardly rectifying K + (Kir2.1) channels activity in human resistance arteries, leading to a reduction in flow-induced vasodilation and possibly leading to a vicious cycle between elevation of blood pressure, and further impairment of Kir2.1 function and flow-induced vasodilation.

Introduction: Neonatal diabetes mellitus (NDM) is a rare non-immunological monogenic disorder characterized by hyperglycemic conditions primarily occurring within the first 6 months of life. The majority of cases are attributed to pathogenic variants in genes affecting beta-cell survival, insulin regulation, and secretion. This study aims to investigate the genetic landscape of NDM in Iran., Methods: We recruited a total of 135 patients who were initially diagnosed with diabetes at <12 months of age in Iran and referred to pediatric endocrinology clinics across the country. These patients underwent genetic diagnostic tests conducted by the Exeter Molecular Genetics Laboratory in the UK. The pathogenic variants identified were sorted and described based on type, pathogenicity (according to ACMG/AMP criteria), novelty, and the affected protein domain., Results: Genetic defects were identified in 93 probands, presenting various pathogenic abnormalities associated with NDM and its associated syndromes. 76% of the patients were born as a result of consanguineous marriage, and a familial history of diabetes was found in 43% of the cases. A total of 58 distinct variants in 14 different genes were discovered, including 20 variants reported for the first time. Causative variants were most frequently identified in EIF2AK3, KCNJ11, and ABCC8, respectively. Notably, EIF2AK3 and ABCC8 exhibited the highest number of novel variants., Discussion: These findings provide valuable insights into the genetic landscape of NDM in the Iranian population and contribute to the knowledge of novel pathogenic variants within known causative genes., (© 2024 The Author(s). Journal of Diabetes Investigation published by Asian Association for the Study of Diabetes (AASD) and John Wiley & Sons Australia, Ltd.)

Objective: Most paroxysmal kinesigenic dyskinesia (PKD) cases are hereditary, yet approximately 60% of patients remain genetically undiagnosed. We undertook the present study to uncover the genetic basis for undiagnosed PKD patients., Methods: Whole-exome sequencing was performed for 106 PRRT2-negative PKD probands. The functional impact of the genetic variants was investigated in HEK293T cells and Drosophila., Results: Heterozygous variants in KCNJ10 were identified in 11 individuals from 8 unrelated families, which accounted for 7.5% (8/106) of the PRRT2-negative probands. Both co-segregation of the identified variants and the significantly higher frequency of rare KCNJ10 variants in PKD cases supported impacts from the detected KCNJ10 heterozygous variants on PKD pathogenesis. Moreover, a KCNJ10 mutation-carrying father from a typical EAST/SeSAME family was identified as a PKD patient. All patients manifested dystonia attacks triggered by sudden movement with a short episodic duration. Patch-clamp recordings in HEK293T cells revealed apparent reductions in K + currents of the patient-derived variants, indicating a loss-of-function. In Drosophila, milder hyperexcitability phenotypes were observed in heterozygous Irk2 knock-in flies compared to homozygotes, supporting haploinsufficiency as the mechanism for the detected heterozygous variants. Electrophysiological recordings showed that excitatory neurons in Irk2 haploinsufficiency flies exhibited increased excitability, and glia-specific complementation with human Kir4.1 rescued the Irk2 mutant phenotypes., Interpretation: Our study established haploinsufficiency resulting from heterozygous variants in KCNJ10 can be understood as a previously unrecognized genetic cause for PKD and provided evidence of glial involvement in the pathophysiology of PKD. ANN NEUROL 2024;96:758-773., (© 2024 American Neurological Association.)

Tuberculosis caused by the pathogen Mycobacterium tuberculosis leads to increased mortality and morbidity worldwide. The prevalence of highly drug-resistant strains has reinforced the need for greater understanding of host-pathogen interactions at the cellular and molecular levels. Our previous work demonstrated critical roles of calcium ion channels in regulating protective responses to mycobacteria. In this report, we deciphered the roles of inwardly rectifying K+ ion channel Kir2.1 in epithelial cells. Data showed that infection of epithelial cells (and macrophages) increases the surface expression of Kir2.1. This increased expression of Kir2.1 results in higher intracellular mycobacterial survival, as either inhibiting or knocking down Kir2.1 results in mounting of a higher oxidative burst leading to a significant attenuation of mycobacterial survival. Further, inhibiting Kir2.1 also led to increased expression of T cell costimulatory molecules accompanied with increased activation of MAP kinases and transcription factors nuclear factor κB and phosphorylated CREB. Furthermore, inhibiting Kir2.1 induced increased autophagy and apoptosis that could also contribute to decreased bacterial survival. Interestingly, an increased association of heat shock protein 70 kDa with Kir2.1 was observed. These results showed that mycobacteria modulate the expression and function of Kir2.1 in epithelial cells to its advantage., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for Leukocyte Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

The functioning of the human heart relies on complex electrical and communication systems that coordinate cardiac contractions and sustain rhythmicity. One of the key players contributing to this intricate system is the K IR 2.1 potassium ion channel, which is encoded by the KCNJ2 gene. K IR 2.1 channels exhibit abundant expression in both ventricular myocytes and Purkinje fibers, exerting an important role in maintaining the balance of intracellular potassium ion levels within the heart. And by stabilizing the resting membrane potential and contributing to action potential repolarization, these channels have an important role in cardiac excitability also. Either gain- or loss-of-function mutations, but also acquired impairments of their function, are implicated in the pathogenesis of diverse types of cardiac arrhythmias. In this review, we aim to elucidate the system functions of K IR 2.1 channels related to cellular electrical signaling, communication, and their contributions to cardiovascular disease. Based on this knowledge, we will discuss existing and new pharmacological avenues to modulate their function., (© 2024. The Author(s).)

Hypertension affects one billion people worldwide and is the most common risk factor for cardiovascular disease, yet a comprehensive picture of its underlying genetic factors is incomplete. Amongst regulators of blood pressure is the renal outer medullary potassium (ROMK) channel. While select ROMK mutants are prone to premature degradation and lead to disease, heterozygous carriers of some of these same alleles are protected from hypertension. Therefore, we hypothesized that gain-of-function (GoF) ROMK variants which increase potassium flux may predispose people to hypertension. To begin to test this hypothesis, we employed genetic screens and a candidate-based approach to identify six GoF variants in yeast. Subsequent functional assays in higher cells revealed two variant classes. The first group exhibited greater stability in the endoplasmic reticulum, enhanced channel assembly, and/or increased protein at the cell surface. The second group of variants resided in the PIP 2 -binding pocket, and computational modeling coupled with patch-clamp studies demonstrated lower free energy for channel opening and slowed current rundown, consistent with an acquired PIP 2 -activated state. Together, these findings advance our understanding of ROMK structure-function, suggest the existence of hyperactive ROMK alleles in humans, and establish a system to facilitate the development of ROMK-targeted antihypertensives., Competing Interests: Conflict of interest: The authors declare no conflicts of interest.

Genetic testing is recommended in the diagnosis of short QT syndrome. This rare inherited lethal entity is characterized by structural normal hearts with short QT intervals in the electrocardiogram. Few families diagnosed with this arrhythmogenic disease have been reported worldwide so far, impeding a comprehensive understanding of this syndrome. Unraveling the origin of the disease helps to the early identification of genetic carriers at risk. However, only rare variants with a definite deleterious role should be actionable in clinical practice. Our aim was to perform a comprehensive update and reinterpretation, according to the American College of Medical Genetics and Genomics recommendations of all rare variants currently associated with short QT syndrome. We identified 34 rare variants. Reanalysis showed that only nine variants played a deleterious role associated with a definite short QT syndrome phenotype. These variants were located in the four main genes: KCNQ1, KCNH2, KCNJ2 or SLC4A3. Additional rare variants located in other genes were associated with other conditions with phenotypic shortened QT intervals, but not definite diagnosis of short QT syndrome. Periodically updating of rare variants, especially those previously classified as unknown, helps to clarify the role of rare variants and translate genetic data into clinical practice., Competing Interests: Declarations Ethical approval Not necessary. Consent to participate Not necessary. Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Vascular smooth muscle ATP-sensitive potassium (K ATP ) channels play critical roles in modulating vascular tone and thus represent important drug targets for diverse cardiovascular pathologies. Despite extensive research efforts spanning several decades, the search for selective inhibitors that can discriminate between vascular K ATP (i.e. Kir6.1/SUR2B) and pancreatic and brain K ATP (i.e. Kir6.2/SUR1) channels has, until recently, been unsuccessful. Our group therefore carried out a high-throughput screen of chemically diverse compounds with the goal of discovering specific Kir6.1/SUR2B inhibitors. This screen identified several novel classes of Kir6.1/SUR2B inhibitors, including the first potent (IC 50 ~100 nM) and selective inhibitor published to date, termed VU0542270. Here, we expand on this work by disclosing the identity and pharmacological properties of four additional Kir6.1/SUR2B inhibitors that are structurally unrelated to Kir to VU0542270. These inhibitors, named VU0212387, VU0543336, VU0605768, and VU0544086, inhibit Kir6.1/SUR2B with IC 50 values ranging from approximately 100 nM to 1 µM and exhibit no apparent inhibitory activity toward Kir6.2/SUR1. Functional analysis of heterologously expressed subunit combinations of Kir6.1, Kir6.2, SUR1, SUR2A, and SUR2B and demonstrated that all four inhibitors act on SUR2 to induce channel inhibition. Interestingly, VU0543336 and VU0212387 exhibit paradoxical stimulatory effects on Kir6.2/SUR1 at higher doses. This study broadens our understanding of K ATP channel pharmacology, generally, and reveals novel chemical matter for the development of Kir6.1/SUR2-selective drugs, specifically.

Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Background: The KCNJ16 gene has been associated with a novel kidney tubulopathy phenotype, viz. disturbed acid-base homeostasis, hypokalemia and altered renal salt transport. KCNJ16 encodes for Kir5.1, which together with Kir4.1 constitutes a potassium channel located at kidney tubular cell basolateral membranes. Preclinical studies provided mechanistic links between Kir5.1 and tubulopathy, however, the disease pathology remains poorly understood. Here, we aimed at generating and characterizing a novel advanced in vitro human kidney model that recapitulates the disease phenotype to investigate further the pathophysiological mechanisms underlying the tubulopathy and potential therapeutic interventions., Methods: We used CRISPR/Cas9 to generate KCNJ16 mutant (KCNJ16 +/- and KCNJ16 -/- ) cell lines from healthy human induced pluripotent stem cells (iPSC) KCNJ16 control (KCNJ16 WT ). The iPSCs were differentiated following an optimized protocol into kidney organoids in an air-liquid interface., Results: KCNJ16-depleted kidney organoids showed transcriptomic and potential functional impairment of key voltage-dependent electrolyte and water-balance transporters. We observed cysts formation, lipid droplet accumulation and fibrosis upon Kir5.1 function loss. Furthermore, a large scale, glutamine tracer flux metabolomics analysis demonstrated that KCNJ16 -/- organoids display TCA cycle and lipid metabolism impairments. Drug screening revealed that treatment with statins, particularly the combination of simvastatin and C75, prevented lipid droplet accumulation and collagen-I deposition in KCNJ16 -/- kidney organoids., Conclusions: Mature kidney organoids represent a relevant in vitro model for investigating the function of Kir5.1. We discovered novel molecular targets for this genetic tubulopathy and identified statins as a potential therapeutic strategy for KCNJ16 defects in the kidney., (© 2024. The Author(s).)

Type 2 diabetes mellitus (T2DM) is a complex chronic disease characterized by decreased insulin secretion and the development of insulin resistance. Previous genome-wide association studies demonstrated that single-nucleotide polymorphisms (SNPs) present in genes coding for ion channels involved in insulin secretion increase the risk of developing this disease. We determined the association of 16 SNPs found in CACNA1D , KCNQ1 , KCNJ11 , and CACNA1E genes and the increased probability of developing T2DM. In this work, we performed a case-control study in 301 Mexican adults, including 201 cases with diabetes and 100 controls without diabetes. Our findings indicate a moderate association between T2DM and the C allele, and the C/C genotype of rs312480 within CACNA1D . The CAG haplotype surprisingly showed a protective effect, whereas the CAC and CGG haplotypes have a strong association with T2DM. The C allele and C/C genotype of rs5219 were significantly associated with diabetes. Also, an association was observed between diabetes and the A allele and the A/A genotype of rs3753737 and rs175338 in CACNA1E . The TGG and CGA haplotypes were also found to be significantly associated. The findings of this study indicate that the SNPs examined could serve as a potential diagnostic tool and contribute to the susceptibility of the Mexican population to this disease.

Sodium and potassium channels, especially Nav1.5 and Kir2.1, play key roles in the formation of action potentials in cardiomyocytes. These channels interact with, and are regulated by, synapse-associated protein 97 (SAP97). However, the regulatory role of SAP97 in myocyte remains incompletely understood. Here, we investigate the function of SAP97 phosphorylation in the regulation of Nav1.5 and Kir2.1 channel complexes and the upstream regulation of SAP97. We found that SAP97 is phosphorylated by casein kinase II (CK2) in vitro. In addition, transfection of casein kinase 2 interacting protein-1 (CKIP-1) into cardiomyocytes to drive CK2 from the nucleus to the cytoplasm, increased SAP97 phosphorylation and Nav1.5 and Kir2.1 current activity. These findings demonstrated that CKIP-1 modulates the subcellular translocation of CK2, which regulates Nav1.5 and Kir2.1 channel complex formation and activity in cardiomyocytes., (© 2024 Wiley Periodicals LLC.)

Cantú syndrome is a multisystem disorder caused by gain-of-function (GOF) mutations in KCNJ8 and ABCC9, the genes encoding the pore-forming inward rectifier Kir6.1 and regulatory sulfonylurea receptor SUR2B subunits, respectively, of vascular ATP-sensitive K+ (KATP) channels. In this study, we investigated changes in the vascular endothelium in mice in which Cantú syndrome-associated Kcnj8 or Abcc9 mutations were knocked in to the endogenous loci. We found that endothelium-dependent dilation was impaired in small mesenteric arteries from Cantú mice. Loss of endothelium-dependent vasodilation led to increased vasoconstriction in response to intraluminal pressure or treatment with the adrenergic receptor agonist phenylephrine. We also found that either KATP GOF or acute activation of KATP channels with pinacidil increased the amplitude and frequency of wave-like Ca2+ events generated in the endothelium in response to the vasodilator agonist carbachol. Increased cytosolic Ca2+ signaling activity in arterial endothelial cells from Cantú mice was associated with elevated mitochondrial [Ca2+] and enhanced reactive oxygen species (ROS) and peroxynitrite levels. Scavenging intracellular or mitochondrial ROS restored endothelium-dependent vasodilation in the arteries of mice with KATP GOF mutations. We conclude that mitochondrial Ca2+ overload and ROS generation, which subsequently leads to nitric oxide consumption and peroxynitrite formation, cause endothelial dysfunction in mice with Cantú syndrome.

During diabetes progression, β-cell dysfunction due to loss of potassium channels sensitive to ATP, known as KATP channels, occurs, contributing to hyperglycemia. The aim of this study was to investigate if KATP channel expression or activity in the nervous system was altered in a high-fat diet (HFD)-fed mouse model of diet-induced obesity. Expression of two KATP channel subunits, Kcnj11 (Kir6.2) and Abcc8 (SUR1), were decreased in the peripheral and central nervous system of mice fed HFD, which was significantly correlated with mechanical paw-withdrawal thresholds. HFD mice had decreased antinociception to systemic morphine compared with control diet (CON) mice, which was expected because KATP channels are downstream targets of opioid receptors. Mechanical hypersensitivity in HFD mice was exacerbated after systemic treatment with glyburide or nateglinide, KATP channel antagonists clinically used to control blood glucose levels. Upregulation of SUR1 and Kir6.2, through an adenovirus delivered intrathecally, increased morphine antinociception in HFD mice. These data present a potential link between KATP channel function and neuropathy during early stages of diabetes. There is a need for increased knowledge of how diabetes affects structural and molecular changes in the nervous system, including ion channels, to lead to the progression of chronic pain and sensory issues., (© 2024 by the American Diabetes Association.)

Objective: To explore the clinical characteristics and molecular basis for children and adolescents with monogenic diabetes., Methods: A retrospective analysis was carried out for the clinical manifestations and laboratory data of 116 children and adolescents diagnosed with diabetes at Ningbo Women and Children's Hospital from January 2020 to March 2023. Whole exome sequencing and mitochondrial gene sequencing were carried out on 21 children with suspected monogenic diabetes., Results: A total of 10 cases of monogenic diabetes were diagnosed, all of which were Maturity-onset Diabetes Of the Young (MODY). Six cases of MODY2 were due to GCK gene mutations, 1 case of MODY3 was due to HNF1A gene mutation, 2 cases of MODY12 were due to ABCC8 gene mutations, and 1 case of MODY13 was due to KCNJ11 gene mutation. Nine of the 10 patients with MODY had no typical symptoms of diabetes. A family history of diabetes was significantly more common in the MODY group compared with the T1DM and T2DM groups (P < 0.05). The BMI of the MODY group was higher than that of the T1DM group (P < 0.05). The initial blood glucose level was lower than that of the T1DM group (P < 0.05), and there was no significant difference compared with the T2DM group. The fasting C-peptide level of the MODY group was higher than that of the T1DM group (P < 0.05), and there was no significant difference compared with the T2DM group. Glycosylated hemoglobin of the MODY group was lower than both the T1DM and T2DM groups (P < 0.05)., Conclusion: In this study, MODY has accounted for the majority of monogenic diabetes among children and adolescents, and the common mutations were those of the GCK gene in association with MODY2. Blood glucose and glycosylated hemoglobin of children with MODY were slightly increased, whilst the islet cell function had remained, and the clinical manifestations and laboratory tests had overlapped with those of type 2 diabetes. WES and mitochondrial gene sequencing can clarify the etiology of monogenic diabetes and facilitate precise treatment.

Diabetes is closely associated with K + disturbances during disease progression and treatment. However, it remains unclear whether K + imbalance occurs in diabetes with normal kidney function. In this study, we examined the effects of dietary K + intake on systemic K + balance and renal K + handling in streptozotocin (STZ)-induced diabetic mice. The control and STZ mice were fed low or high K + diet for 7 days to investigate the role of dietary K + intake in renal K + excretion and K + homeostasis and to explore the underlying mechanism by evaluating K + secretion-related transport proteins in distal nephrons. K + -deficient diet caused excessive urinary K + loss, decreased daily K + balance, and led to severe hypokalemia in STZ mice compared with control mice. In contrast, STZ mice showed an increased daily K + balance and elevated plasma K + level under K + -loading conditions. Dysregulation of the NaCl cotransporter (NCC), epithelial Na + channel (ENaC), and renal outer medullary K + channel (ROMK) was observed in diabetic mice fed either low or high K + diet. Moreover, amiloride treatment reduced urinary K + excretion and corrected hypokalemia in K + -restricted STZ mice. On the other hand, inhibition of SGLT2 by dapagliflozin promoted urinary K + excretion and normalized plasma K + levels in K + -supplemented STZ mice, at least partly by increasing ENaC activity. We conclude that STZ mice exhibited abnormal K + balance and impaired renal K + handling under either low or high K + diet, which could be primarily attributed to the dysfunction of ENaC-dependent renal K + excretion pathway, despite the possible role of NCC. NEW & NOTEWORTHY Neither low dietary K + intake nor high dietary K + intake effectively modulates renal K + excretion and K + homeostasis in STZ mice, which is closely related to the abnormality of ENaC expression and activity. SGLT2 inhibitor increases urinary K + excretion and reduces plasma K + level in STZ mice under high dietary K + intake, an effect that may be partly due to the upregulation of ENaC activity.

The renal epithelium is sensitive to changes in blood potassium (K + ). We identify the basolateral K + channel, Kir4.2, as a mediator of the proximal tubule response to K + deficiency. Mice lacking Kir4.2 have a compensated baseline phenotype whereby they increase their distal transport burden to maintain homeostasis. Upon dietary K + depletion, knockout animals decompensate as evidenced by increased urinary K + excretion and development of a proximal renal tubular acidosis. Potassium wasting is not proximal in origin but is caused by higher ENaC activity and depends upon increased distal sodium delivery. Three-dimensional imaging reveals Kir4.2 knockouts fail to undergo proximal tubule expansion, while the distal convoluted tubule response is exaggerated. AKT signaling mediates the dietary K + response, which is blunted in Kir4.2 knockouts. Lastly, we demonstrate in isolated tubules that AKT phosphorylation in response to low K + depends upon mTORC2 activation by secondary changes in Cl - transport. Data support a proximal role for cell Cl - which, as it does along the distal nephron, responds to K + changes to activate kinase signaling., (© 2024. The Author(s).)

Maturity-onset diabetes of the young (MODY) is part of the heterogeneous group of monogenic diabetes (MD) characterized by the non-immune dysfunction of pancreatic β-cells. The diagnosis of MODY still remains a challenge for clinicians, with many cases being misdiagnosed as type 1 or type 2 diabetes mellitus (T1DM/T2DM), and over 80% of cases remaining undiagnosed. With the introduction of modern technologies, important progress has been made in deciphering the molecular mechanisms and heterogeneous etiology of MD, including MODY. The aim of our study was to identify genetic variants associated with MODY in a group of patients with early-onset diabetes/prediabetes in whom a form of MD was clinically suspected. Genetic testing, based on next-generation sequencing (NGS) technology, was carried out either in a targeted manner, using gene panels for monogenic diabetes, or by analyzing the entire exome (whole-exome sequencing). GKC -MODY 2 was the most frequently detected variant, but rare forms of KCNJ11 -MODY 13, specifically, HNF4A -MODY 1, were also identified. We have emphasized the importance of genetic testing for early diagnosis, MODY subtype differentiation, and genetic counseling. We presented the genotype-phenotype correlations, especially related to the clinical evolution and personalized therapy, also emphasizing the particularities of each patient in the family context.

Cholesterol is a negative regulator of a variety of ion channels. We have previously shown that cholesterol suppresses Kir2.2 channels via residue-residue uncoupling on the inter-subunit interfaces within the close state of the channels (3JYC). In this study, we extend this analysis to the other known structure of Kir2.2 that is closer to the open state of Kir2.2 channels (3SPI) and provide additional analysis of the residue distances between the uncoupled residues and cholesterol binding domains in the two conformation states of the channels. We found that the general phenomenon of cholesterol binding leading to uncoupling between specific residues is conserved in both channel states but the specific pattern of the uncoupling residues is distinct between the two states and implies different mechanisms. Specifically, we found that cholesterol binding in the 3SPI state results in an uncoupling of residues in three distinct regions; the transmembrane domain, membrane-cytosolic interface, and the cytosolic domain, with the first two regions forming an envelope around PI(4,5)P2 and cholesterol binding sites and the distal region overlapping with the subunit-subunit interface characterized in our previous study of the disengaged state. We also found that this uncoupling is dependent upon the number of cholesterol molecules bound to the channel. We further generated a mutant channel Kir2.2 P187V with a single point mutation in a residue proximal to the PI(4,5)P2 binding site, which is predicted to be uncoupled from other residues in its vicinity upon cholesterol binding and found that this mutation abrogates the sensitivity of Kir2.2 to cholesterol changes in the membrane. These findings suggest that cholesterol binding to this conformation state of Kir2.2 channels may destabilize the PI(4,5)P2 interactions with the channels while in the disengaged state the destabilization occurs where the subunits interact. These findings give insight into the structural mechanistic basis for the functional effects of cholesterol binding to the Kir2.2 channel., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [Katie Beverley reports financial support was provided by National Institutes of Health. Irena Levitan reports financial support was provided by National Institutes of Health.]., (Copyright © 2024. Published by Elsevier Inc.)

Stomata govern the gaseous exchange between the leaf and the external atmosphere, and their function is essential for photosynthesis and the global carbon and oxygen cycles. Rhythmic stomata movements in daily dark/light cycles prevent water loss at night and allow CO 2 uptake during the day. How the actors involved are transcriptionally regulated and how this might contribute to rhythmicity is largely unknown. Here, we show that morning stomata opening depends on the previous night period. The transcription factors PHYTOCHROME-INTERACTING FACTORS (PIFs) accumulate at the end of the night and directly induce the guard cell-specific K + channel KAT1. Remarkably, PIFs and KAT1 are required for blue light-induced stomata opening. Together, our data establish a molecular framework for daily rhythmic stomatal movements under well-watered conditions, whereby PIFs are required for accumulation of KAT1 at night, which upon activation by blue light in the morning leads to the K + intake driving stomata opening., (© 2024. The Author(s).)

Congenital hyperinsulinism (CHI) is a rare disorder of glucose metabolism and is the most common cause of severe and persistent hypoglycemia (hyperinsulinemic hypoglycemia, HH) in the neonatal period and childhood. Most cases are caused by mutations in the ABCC8 and KCNJ11 genes that encode the ATP-sensitive potassium channel (K ATP ). We present the correlation between genetic heterogeneity and the variable phenotype in patients with early-onset HH caused by ABCC8 gene mutations. In the first patient, who presented persistent severe hypoglycemia since the first day of life, molecular genetic testing revealed the presence of a homozygous mutation in the ABCC8 gene [deletion in the ABCC8 gene c.(2390+1&#95;2391-1)&#95;(3329+1&#95;3330-1)del] that correlated with a diffuse form of hyperinsulinism (the parents being healthy heterozygous carriers). In the second patient, the onset was on the third day of life with severe hypoglycemia, and genetic testing identified a heterozygous mutation in the ABCC8 gene c.1792C>T (p.Arg598*) inherited on the paternal line, which led to the diagnosis of the focal form of hyperinsulinism. To locate the focal lesions, (18)F-DOPA (3,4-dihydroxy-6-[ 18 F]fluoro-L-phenylalanine) positron emission tomography/computed tomography (PET/CT) was recommended (an investigation that cannot be carried out in the country), but the parents refused to carry out the investigation abroad. In this case, early surgical treatment could have been curative. In addition, the second child also presented secondary adrenal insufficiency requiring replacement therapy. At the same time, she developed early recurrent seizures that required antiepileptic treatment. We emphasize the importance of molecular genetic testing for diagnosis, management and genetic counseling in patients with HH.

Background: Previous research has emphasized the potential benefits of anti-diabetic medications in inhibiting the exacerbation of Chronic Obstructive Pulmonary Disease (COPD), yet the role of anti-diabetic drugs on COPD risk remains uncertain., Methods: This study employed a Mendelian randomization (MR) approach to evaluate the causal association of genetic variations related to six classes of anti-diabetic drug targets with COPD. The primary outcome for COPD was obtained from the Global Biobank Meta-analysis Initiative (GBMI) consortium, encompassing a meta-analysis of 12 cohorts with 81,568 cases and 1,310,798 controls. Summary-level data for HbA1c was derived from the UK Biobank, involving 344,182 individuals. Positive control analysis was conducted for Type 2 Diabetes Mellitus (T2DM) to validate the choice of instrumental variables. The study applied Summary-data-based MR (SMR) and two-sample MR for effect estimation and further adopted colocalization analysis to verify evidence of genetic variations., Results: SMR analysis revealed that elevated KCNJ11 gene expression levels in blood correlated with reduced COPD risk (OR = 0.87, 95% CI = 0.79-0.95; p = 0.002), whereas an increase in DPP4 expression corresponded with an increased COPD incidence (OR = 1.18, 95% CI = 1.03-1.35; p = 0.022). Additionally, the primary method within MR analysis demonstrated a positive correlation between PPARG-mediated HbA1c and both FEV1 (OR = 1.07, 95% CI = 1.02-1.13; P = 0.013) and FEV1/FVC (OR = 1.08, 95% CI = 1.01-1.14; P = 0.007), and a negative association between SLC5A2-mediated HbA1c and FEV1/FVC (OR = 0.86, 95% CI = 0.74-1.00; P = 0.045). No colocalization evidence with outcome phenotypes was detected (all PP.H4 < 0.7)., Conclusion: This study provides suggestive evidence for anti-diabetic medications' role in improving COPD and lung function. Further updated MR analyses are warranted in the future, following the acquisition of more extensive and comprehensive data, to validate our results., (© 2024. The Author(s).)

Progressive neuronal loss is a hallmark feature distinguishing neurodegenerative diseases from normal ageing. However, the underlying mechanisms remain unknown. Extracellular K+ homeostasis is a potential mediator of neuronal injury as K+ elevations increase excitatory activity. The dysregulation of extracellular K+ and potassium channel expressions during neurodegeneration could contribute to this distinction. Here we measured the cortical extracellular K+ concentration ([K+]e) in awake wild-type mice as well as murine models of neurodegeneration using K+-sensitive microelectrodes. Unexpectedly, aged wild-type mice exhibited significantly lower cortical [K+]e than young mice. In contrast, cortical [K+]e was consistently elevated in Alzheimer's disease (APP/PS1), amyotrophic lateral sclerosis (ALS) (SOD1G93A) and Huntington's disease (R6/2) models. Cortical resting [K+]e correlated inversely with neuronal density and the [K+]e buffering rate but correlated positively with the predicted neuronal firing rate. Screening of astrocyte-selective genomic datasets revealed a number of potassium channel genes that were downregulated in these disease models but not in normal ageing. In particular, the inwardly rectifying potassium channel Kcnj10 was downregulated in ALS and Huntington's disease models but not in normal ageing, while Fxyd1 and Slc1a3, each of which acts as a negative regulator of potassium uptake, were each upregulated by astrocytes in both Alzheimer's disease and ALS models. Chronic elevation of [K+]e in response to changes in gene expression and the attendant neuronal hyperexcitability may drive the neuronal loss characteristic of these neurodegenerative diseases. These observations suggest that the dysregulation of extracellular K+ homeostasis in a number of neurodegenerative diseases could be due to aberrant astrocytic K+ buffering and as such, highlight a fundamental role for glial dysfunction in neurodegeneration., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Sudden cardiac death in children and young adults is a relatively rare but tragic event whose pathophysiology is unknown at the molecular level. Evidence indicates that the main cardiac sodium channel (Na V 1.5) and the strong inward rectifier potassium channel (Kir2.1) physically interact and form macromolecular complexes (channelosomes) with common partners, including adapter, scaffolding, and regulatory proteins that help them traffic together to their eventual membrane microdomains. Most important, dysfunction of either or both ion channels has direct links to hereditary human diseases. For example, certain mutations in the KCNJ2 gene encoding the Kir2.1 protein result in Andersen-Tawil syndrome type 1 and alter both inward rectifier potassium and sodium inward currents. Similarly, trafficking-deficient mutations in the gene encoding the Na V 1.5 protein (SCN5A) result in Brugada syndrome and may also disturb both inward rectifier potassium and sodium inward currents. Moreover, gain-of-function mutations in KCNJ2 result in short QT syndrome type 3, which is extremely rare but highly arrhythmogenic, and can modify Kir2.1-Na V 1.5 interactions in a mutation-specific way, further highlighting the relevance of channelosomes in ion channel diseases. By expressing mutant proteins that interrupt or modify Kir2.1 or Na V 1.5 function in animal models and patient-specific pluripotent stem cell-derived cardiomyocytes, investigators are defining for the first time the mechanistic framework of how mutation-induced dysregulation of the Kir2.1-Na V 1.5 channelosome affects cardiac excitability, resulting in arrhythmias and sudden death in different cardiac diseases., Competing Interests: Disclosures The authors declare no potential conflicts., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Aims/hypothesis: The ATP-sensitive potassium (K ATP ) channel couples beta cell electrical activity to glucose-stimulated insulin secretion. Loss-of-function mutations in either the pore-forming (inwardly rectifying potassium channel 6.2 [Kir6.2], encoded by KCNJ11) or regulatory (sulfonylurea receptor 1, encoded by ABCC8) subunits result in congenital hyperinsulinism, whereas gain-of-function mutations cause neonatal diabetes. Here, we report a novel loss-of-function mutation (Ser118Leu) in the pore helix of Kir6.2 paradoxically associated with sulfonylurea-sensitive diabetes that presents in early adult life., Methods: A 31-year-old woman was diagnosed with mild hyperglycaemia during an employee screen. After three pregnancies, during which she was diagnosed with gestational diabetes, the patient continued to show elevated blood glucose and was treated with glibenclamide (known as glyburide in the USA and Canada) and metformin. Genetic testing identified a heterozygous mutation (S118L) in the KCNJ11 gene. Neither parent was known to have diabetes. We investigated the functional properties and membrane trafficking of mutant and wild-type K ATP channels in Xenopus oocytes and in HEK-293T cells, using patch-clamp, two-electrode voltage-clamp and surface expression assays., Results: Functional analysis showed no changes in the ATP sensitivity or metabolic regulation of the mutant channel. However, the Kir6.2-S118L mutation impaired surface expression of the K ATP channel by 40%, categorising this as a loss-of-function mutation., Conclusions/interpretation: Our data support the increasing evidence that individuals with mild loss-of-function K ATP channel mutations may develop insulin deficiency in early adulthood and even frank diabetes in middle age. In this case, the patient may have had hyperinsulinism that escaped detection in early life. Our results support the importance of functional analysis of K ATP channel mutations in cases of atypical diabetes., (© 2024. The Author(s).)

Obesity imposes deficits on adipose tissue and vascular endothelium, yet the role that distinct adipose depots play in mediating endothelial dysfunction in local arteries remains unresolved. We recently showed that obesity impairs endothelial Kir2.1 channels, mediators of nitric oxide production, in arteries of visceral adipose tissue (VAT), while Kir2.1 function in subcutaneous adipose tissue (SAT) endothelium remains intact. Therefore, we determined if VAT versus SAT from lean or diet-induced obese mice affected Kir2.1 channel function in vitro. We found that VAT from obese mice reduces Kir2.1 function without altering channel expression whereas AT from lean mice and SAT from obese mice had no effect on Kir2.1 function as compared to untreated control cells. As Kir2.1 is well known to be inhibited by fatty acid derivatives and obesity is strongly associated with elevated circulating fatty acids, we next tested the role of the fatty acid translocase CD36 in mediating VAT-induced Kir2.1 dysfunction. We found that the downregulation of CD36 restored Kir2.1 currents in endothelial cells exposed to VAT from obese mice. In addition, endothelial cells exposed to VAT from obese mice exhibited a significant increase in CD36-mediated fatty acid uptake. The importance of CD36 in obesity-induced endothelial dysfunction of VAT arteries was further supported in ex vivo pressure myography studies where CD36 ablation rescued the endothelium-dependent response to flow via restoring Kir2.1 and endothelial nitric oxide synthase function. These findings provide new insight into the role of VAT in mediating obesity-induced endothelial dysfunction and suggest a novel role for CD36 as a mediator of endothelial Kir2.1 impairment. NEW & NOTEWORTHY Our findings suggest a role for visceral adipose tissue (VAT) in the dysfunction of endothelial Kir2.1 in obesity. We further reveal a role for CD36 as a major contributor to VAT-mediated Kir2.1 and endothelial dysfunction, suggesting that CD36 offers a potential target for preventing the early development of obesity-associated cardiovascular disease.

Congenital hyperinsulinism (CHI; OMIM: 256450) is characterized by persistent insulin secretion despite severe hypoglycemia. The most common causes are variants in the ATP-binding cassette subfamily C member 8(ABCC8) and potassium inwardly-rectifying channel subfamily J member 11(KCNJ11) genes. These encode ATP-sensitive potassium (K ATP ) channel subunit sulfonylurea receptor 1 (SUR1) and inwardly rectifying potassium channel (Kir6.2) proteins. A 7-day-old male infant presented with frequent hypoglycemic episodes and was clinically diagnosed with CHI, underwent trio-whole-exome sequencing, revealing compound heterozygous ABCC8 variants (c.307C>T, p.His103Tyr; and c.3313&#95;3315del, p.Ile1105del) were identified. In human embryonic kidney 293 (HEK293) and rat insulinoma cells (INS-1) transfected with wild-type and variant plasmids, K ATP channels formed by p.His103Tyr were delivered to the plasma membrane, whereas p.Ile1105del or double variants (p.His103Tyr coupled with p.Ile1105del) failed to be transported to the plasma membrane. Compared to wild-type channels, the channels formed by the variants (p.His103Tyr; p.Ile1105del) had elevated basal [Ca 2+ ] i , but did not respond to stimulation by glucose. Our results provide evidence that the two ABCC8 variants may be related to CHI owing to defective trafficking and dysfunction of K ATP channels., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Melatonin is a pleiotropic biofactor and an effective antioxidant and free radical scavenger and, as such, can be protective in oxidative stress-related brain conditions including epilepsy and aging. To test the potential protective effect of melatonin on brain homeostasis and identify the corresponding molecular targets, we established a new model of oxidative stress-related aging neuroglia represented by U-87 MG cells exposed to D-galactose (D-Gal). This model was characterized by a substantial elevation of markers of oxidative stress, lipid peroxidation, and protein oxidation. The function of the inward rectifying K + channel Kir2.1, which was identified as the main Kir channel endogenously expressed in these cells, was dramatically impaired. Kir2.1 was unlikely a direct target of oxidative stress, but the loss of function resulted from a reduction of protein abundance, with no alterations in transcript levels and trafficking to the cell surface. Importantly, melatonin reverted these changes. All findings, including the melatonin antioxidant effect, were reproduced in heterologous expression systems. We conclude that the glial Kir2.1 can be a target of oxidative stress and further suggest that inhibition of its function might alter the extracellular K + buffering in the brain, therefore contributing to neuronal hyperexcitability and epileptogenesis during aging. Melatonin can play a protective role in this context., (© 2023 The Authors. BioFactors published by Wiley Periodicals LLC on behalf of International Union of Biochemistry and Molecular Biology.)

Background: Although the group of paroxysmal kinesigenic dyskinesia (PKD) genes is expanding, the molecular cause remains elusive in more than 50% of cases., Objective: The aim is to identify the missing genetic causes of PKD., Methods: Phenotypic characterization, whole exome sequencing and association test were performed among 53 PKD cases., Results: We identified four causative variants in KCNJ10, already associated with EAST syndrome (epilepsy, cerebellar ataxia, sensorineural hearing impairment and renal tubulopathy). Homozygous p.(Ile209Thr) variant was found in two brothers from a single autosomal recessive PKD family, whereas heterozygous p.(Cys294Tyr) and p.(Thr178Ile) variants were found in six patients from two autosomal dominant PKD families. Heterozygous p.(Arg180His) variant was identified in one additional sporadic PKD case. Compared to the Genome Aggregation Database v2.1.1, our PKD cohort was significantly enriched in both rare heterozygous (odds ratio, 21.6; P = 9.7 × 10 -8 ) and rare homozygous (odds ratio, 2047; P = 1.65 × 10 -6 ) missense variants in KCNJ10., Conclusions: We demonstrated that both rare monoallelic and biallelic missense variants in KCNJ10 are associated with PKD. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society., (© 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.)

Aims: Short QT syndrome type 3 (SQTS3) is a rare arrhythmogenic disease caused by gain-of-function mutations in KCNJ2, the gene coding the inward rectifier potassium channel Kir2.1. We used a multidisciplinary approach and investigated arrhythmogenic mechanisms in an in-vivo model of de-novo mutation Kir2.1E299V identified in a patient presenting an extremely abbreviated QT interval and paroxysmal atrial fibrillation., Methods and Results: We used intravenous adeno-associated virus-mediated gene transfer to generate mouse models, and confirmed cardiac-specific expression of Kir2.1WT or Kir2.1E299V. On ECG, the Kir2.1E299V mouse recapitulated the QT interval shortening and the atrial-specific arrhythmia of the patient. The PR interval was also significantly shorter in Kir2.1E299V mice. Patch-clamping showed extremely abbreviated action potentials in both atrial and ventricular Kir2.1E299V cardiomyocytes due to a lack of inward-going rectification and increased IK1 at voltages positive to -80 mV. Relative to Kir2.1WT, atrial Kir2.1E299V cardiomyocytes had a significantly reduced slope conductance at voltages negative to -80 mV. After confirming a higher proportion of heterotetrameric Kir2.x channels containing Kir2.2 subunits in the atria, in-silico 3D simulations predicted an atrial-specific impairment of polyamine block and reduced pore diameter in the Kir2.1E299V-Kir2.2WT channel. In ventricular cardiomyocytes, the mutation increased excitability by shifting INa activation and inactivation in the hyperpolarizing direction, which protected the ventricle against arrhythmia. Moreover, Purkinje myocytes from Kir2.1E299V mice manifested substantially higher INa density than Kir2.1WT, explaining the abbreviation in the PR interval., Conclusion: The first in-vivo mouse model of cardiac-specific SQTS3 recapitulates the electrophysiological phenotype of a patient with the Kir2.1E299V mutation. Kir2.1E299V eliminates rectification in both cardiac chambers but protects against ventricular arrhythmias by increasing excitability in both Purkinje-fiber network and ventricles. Consequently, the predominant arrhythmias are supraventricular likely due to the lack of inward rectification and atrial-specific reduced pore diameter of the Kir2.1E299V-Kir2.2WT heterotetramer., Competing Interests: Conflict of interest: none declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Fragile X syndrome (FXS) is an inherited form of intellectual disability caused by the loss of the mRNA-binding fragile X mental retardation protein (FMRP). FXS is characterized by neuronal hyperexcitability and behavioral defects, however the mechanisms underlying these critical dysfunctions remain unclear. Here, using male Fmr1 knockout mouse model of FXS, we identify abnormal extracellular potassium homeostasis, along with impaired potassium channel Kir4.1 expression and function in astrocytes. Further, we reveal that Kir4.1 mRNA is a binding target of FMRP. Finally, we show that the deficit in astroglial Kir4.1 underlies neuronal hyperexcitability and several behavioral defects in Fmr1 knockout mice. Viral delivery of Kir4.1 channels specifically to hippocampal astrocytes from Fmr1 knockout mice indeed rescues normal astrocyte potassium uptake, neuronal excitability, and cognitive and social performance. Our findings uncover an important role for astrocyte dysfunction in the pathophysiology of FXS, and identify Kir4.1 channel as a potential therapeutic target for FXS., (© 2024. The Author(s).)

Diabetes mellitus (DM) represents a problem for the healthcare system worldwide. DM has very serious complications such as blindness, kidney failure, and cardiovascular disease. In addition to the very bad socioeconomic impacts, it influences patients and their families and communities. The global costs of DM and its complications are huge and expected to rise by the year 2030. DM is caused by genetic and environmental risk factors. Genetic testing will aid in early diagnosis and identification of susceptible individuals or populations using ATP-sensitive potassium (K ATP ) channels present in different tissues such as the pancreas, myocardium, myocytes, and nervous tissues. The channels respond to different concentrations of blood sugar, stimulation by hormones, or ischemic conditions. In pancreatic cells, they regulate the secretion of insulin and glucagon. Mutations in the KCNJ11 gene that encodes the Kir6.2 protein (a major constituent of K ATP channels) were reported to be associated with Type 2 DM, neonatal diabetes mellitus (NDM), and maturity-onset diabetes of the young (MODY). Kir6.2 harbors binding sites for ATP and phosphatidylinositol 4,5-diphosphate (PIP2). The ATP inhibits the K ATP channel, while the (PIP2) activates it. A Kir6.2 mutation at tyrosine330 (Y330) was demonstrated to reduce ATP inhibition and predisposes to NDM. In this study, we examined the effect of mutations on the Kir6.2 structure using bioinformatics tools and molecular dynamic simulations (SIFT, PolyPhen, SNAP2, PANTHER, PhD&SNP, SNP&Go, I-Mutant, MuPro, MutPred, ConSurf, HOPE, and GROMACS). Our results indicated that M199R, R201H, R206H, and Y330H mutations influence Kir6.2 structure and function and therefore may cause DM. We conclude that MD simulations are useful techniques to predict the effects of mutations on protein structure. In addition, the M199R, R201H, R206H, and Y330H variant in the Kir6.2 protein may be associated with DM. These results require further verification in protein-protein interactions, Kir6.2 function, and case-control studies.

Andersen-Tawil syndrome (ATS) is a multisystem channelopathy characterized by periodic paralysis, ventricular arrhythmias, prolonged QT interval, and facial dysmorphisms occurring in the first/second decade of life. High phenotypic variability and incomplete penetrance of the genes causing the disease make its diagnosis still a challenge. We describe a three-generation family with six living individuals affected by ATS. The proband is a 37-year-old woman presenting since age 16, with episodes of muscle weakness and cramps in the pre-menstrual period. The father, two brothers, one paternal uncle and one cousin also complained of cramps, muscle stiffness, and weakness. Despite normal serum potassium concentration, treatment with potassium, magnesium, and acetazolamide alleviated paralysis attacks suggesting a dyskalemic syndrome. Dysmorphic features were noted in the proband, only later. On the ECG, all but one had normal QT intervals. The affected males developed metabolic syndrome or obesity. The father had two myocardial infarctions and was implanted with an intracardiac cardioverter defibrillator (ICD). A genetic investigation by WES analysis detected the heterozygous pathogenic variant (NM&#95;000891.2: c.652C>T, p. Arg218Trp) in the KCNJ2 gene related to ATS, confirmed by segregation studies in all affected members. Furthermore, we performed a review of cases with the same mutation in the literature, looking for similarities and divergences with our family case.

Introduction: Congenital hyperinsulinism (HI) is the leading cause of persistent hypoglycemia in infants. Current models to study the most common and severe form of HI resulting from inactivating mutations in the ATP-sensitive potassium channel (K ATP ) are limited to primary islets from patients and the Sur1 -/- mouse model. Zebrafish exhibit potential as a novel K ATP HI model since they express canonical insulin secretion pathway genes and those with identified causative HI mutations. Moreover, zebrafish larvae transparency provides a unique opportunity for in vivo visualization of pancreatic islets., Research Design and Methods: We evaluated zebrafish as a model for K ATP HI using a genetically encoded Ca 2+ sensor (ins:gCaMP6s) expressed under control of the insulin promoter in beta cells of an abcc8 -/- zebrafish line., Results: We observed significantly higher islet cytosolic Ca 2+ in vivo in abcc8 -/- compared with abcc8 +/+ zebrafish larvae. Additionally, abcc8 -/- larval zebrafish had significantly lower whole body glucose and higher whole body insulin levels compared with abcc8 +/+ controls. However, adult abcc8 -/- zebrafish do not show differences in plasma glucose, plasma insulin, or glucose tolerance when compared with abcc8 +/+ zebrafish., Conclusions: Our results identify that zebrafish larvae, but not adult fish, are a demonstrable novel model for advancement of HI research., Competing Interests: Competing interests: DDDL has received consulting fees from Zealand Pharma A/S, Crinetics Pharmaceuticals, Hanmi Pharmaceuticals, Eiger Pharma and Rhythm Pharmaceuticals. DDDL has received research funding from Zealand Pharma A/S, Rezolute, Crinetics Pharmaceuticals, Hanmi Pharmaceuticals, Twist Biosciences, Eiger Pharma, and Ultragenyx for studies not discussed in this manuscript., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Potassium channels belong to the super family of ion channels and play a fundamental role in cell excitability. Kir channels are potassium channels with an inwardly rectifying property. They play a role in setting the resting membrane potential of many excitable cells including neurons. Although putative Kir channel family genes can be found in the Apis mellifera genome, their functional expression, biophysical properties, and sensitivity to small molecules with insecticidal activity remain to be investigated. We cloned six Kir channel isoforms from Apis mellifera that derive from two Kir genes, AmKir1 and AmKir2, which are present in the Apis mellifera genome. We studied the tissue distribution, the electrophysiological and pharmacological characteristics of three isoforms that expressed functional currents (AmKir1.1, AmKir2.2, and AmKir2.3). AmKir1.1, AmKir2.2, and AmKir2.3 isoforms exhibited distinct characteristics when expressed in Xenopus oocytes. AmKir1.1 exhibited the largest potassium currents and was impermeable to cesium whereas AmKir2.2 and AmKir2.3 exhibited smaller currents but allowed cesium to permeate. AmKir1 exhibited faster opening kinetics than AmKir2. Pharmacological experiments revealed that both AmKir1.1 and AmKir2.2 are blocked by the divalent ion barium, with IC 50 values of 10 -5 and 10 -6  M, respectively. The concentrations of VU041, a small molecule with insecticidal properties required to achieve a 50% current blockade for all three channels were higher than those needed to block Kir channels in other arthropods, such as the aphid Aphis gossypii and the mosquito Aedes aegypti. From this, we conclude that Apis mellifera AmKir channels exhibit lower sensitivity to VU041., (© 2024. The Author(s).)

Background: Diabetic retinopathy (DR) occurs due to high blood glucose damage to the retina and leads to blindness if left untreated. KATP and related genes (KCNJ11 and ABCC8) play an important role in insulin secretion by glucose-stimulated pancreatic beta cells and the regulation of insulin secretion. KCNJ11 E23K (rs5219), ABCC8-3 C/T (rs1799854), Thr759Thr (rs1801261) and Arg1273Arg (rs1799859) are among the possible related single nucleotide polymorphisms (SNPs). The aim of this study is to find out how DR and these SNPs are associated with one another in the Turkish population., Materials and Methods: This study included 176 patients with type 2 diabetes mellitus without retinopathy (T2DM-rp), 177 DR patients, and 204 controls. Genomic DNA was extracted from whole blood, and genotypes were determined by the PCR-RFLP method., Results: In the present study, a significant difference was not found between all the groups in terms of Arg1273Arg polymorphism located in the ABCC8 gene. The T allele and the TT genotype in the -3 C/T polymorphism in this gene may have a protective effect in the development of DR ( p  = 0.036 for the TT genotype; p  = 0.034 for T allele) and PDR ( p  = 0.042 and 0.025 for the TT genotype). The AA genotype showed a significant increase in the DR group compared to T2DM-rp in the KCNJ11 E23K polymorphism ( p  = 0.046)., Conclusions: Consequently, the T allele and TT genotype in the -3 C/T polymorphism of the ABCC8 gene may have a protective marker on the development of DR and PDR, while the AA genotype in the E23K polymorphism of the KCNJ11 gene may be effective in the development of DR in the Turkish population.

G protein-coupled receptor 37-like 1 (GPR37L1) is an orphan GPCR with largely unknown functions. Here, we report that Gpr37l1/GRP37L1 ranks among the most highly expressed GPCR transcripts in mouse and human dorsal root ganglia (DRGs) and is selectively expressed in satellite glial cells (SGCs). Peripheral neuropathy induced by streptozotoxin (STZ) and paclitaxel (PTX) led to reduced GPR37L1 expression on the plasma membrane in mouse and human DRGs. Transgenic mice with Gpr37l1 deficiency exhibited impaired resolution of neuropathic pain symptoms following PTX- and STZ-induced pain, whereas overexpression of Gpr37l1 in mouse DRGs reversed pain. GPR37L1 is coexpressed with potassium channels, including KCNJ10 (Kir4.1) in mouse SGCs and both KCNJ3 (Kir3.1) and KCNJ10 in human SGCs. GPR37L1 regulates the surface expression and function of the potassium channels. Notably, the proresolving lipid mediator maresin 1 (MaR1) serves as a ligand of GPR37L1 and enhances KCNJ10- or KCNJ3-mediated potassium influx in SGCs through GPR37L1. Chemotherapy suppressed KCNJ10 expression and function in SGCs, which MaR1 rescued through GPR37L1. Finally, genetic analysis revealed that the GPR37L1-E296K variant increased chronic pain risk by destabilizing the protein and impairing the protein's function. Thus, GPR37L1 in SGCs offers a therapeutic target for the protection of neuropathy and chronic pain.

(1) Background: Copy number variation (CNV) is a critical component of genome structural variation and has garnered significant attention. High-throughput screening of the KCNJ15 gene has revealed a correlation between the CNV region and the growth traits of goats. We aimed to identify the CNV of the KCNJ15 gene in five goat breeds and analyze its association with growth characteristics. (2) Methods: We utilized 706 goats from five breeds: Guizhou black goat (GZB), Guizhou white goat (GZW), Bohuai goat (BH), Huai goat (HH), and Taihang goat (TH). To evaluate the number of copies of the KCNJ15 gene using qPCR, we analyzed the correlation between the CNV and growth characteristics and then used a universal linear model. The findings revealed variations in the distribution of different copy number types among the different goat breeds. (3) Results: Association analysis revealed a positive influence of the CNV in the KCNJ15 gene on goat growth. In GZB, individuals with duplication types exhibited superior performance in terms of cannon bone circumference ( p < 0.05). In HH, individuals with duplication types exhibited superior performance in terms of body slanting length ( p < 0.05). Conversely, normal TH demonstrated better body height and body weight ( p < 0.05), while in GZW, when CN = 3, it performed better than other types in terms of body weight and chest circumference ( p < 0.05). However, in BH, it had no significant effect on growth traits. (4) Conclusions: We confirmed that the CNV in the KCNJ15 gene significantly influences the growth characteristics of four distinct goat breeds. The correlation between KCNJ15 gene CNVs and goat growth traits offers valuable insights to breeders, enabling them to employ precise and efficient breeding methods that enhance livestock welfare, productivity, and overall economic benefits in the industry.