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Arif O Khan Eye Institute, Cleveland Clinic Abu Dhabi, Abu Dhabi, United Arab Emirates I congratulate the authors on their retrospective study of rhegmatogenous retinal detachment in patients (mostly children) diagnosed with Stickler syndrome in Saudi Arabia1. However, I would like to point out that this work would more appropriately be considered a retrospective study of vitreoretinopathies in general rather than of Stickler syndrome specifically because a percentage of cases were likely recessive vitreoretinopathies. In my experience, children in Saudi Arabia with pediatric retinal detachment and high myopia are often labeled as having Stickler syndrome while in fact recessive vitreoretinopathies such as Knobloch syndrome2 or LRPAP1-related high myopia3 comprise a significant percentage of cases. View original article by Alshahrani et al.

Introduction: Round atrophic macular scars with a hyperpigmented rim in an otherwise healthy child are characteristic for prior ocular toxoplasmosis infection, the most common etiology of self-resolved retinitis in immunocompetent patients. However, a specific homozygous gene mutation (NM_148960: CLDN19 :c.263T>A; p.Val88Glu) can result in a similar phenotype., Methods: Retrospective case series (2018-2023) of children homozygous for the gene mutation CLDN19 :c.263T>A; p.Val88Glu. Five children (3 families) were identified., Results: All 5 identified affected children had been referred for reduced vision and had bilateral central macular scars. Three children (2 families) were originally diagnosed with presumed prior ocular toxoplasmosis infection. All 5 children have stable ophthalmic finding over 5-6 years of follow-up. Although other CLDN19 mutations are associated with early-onset pediatric renal disease, none from this cohort with this specific CLDN19 variant has evidence for renal disease to date., Conclusions: CLDN19 -related maculopathy can resemble and be mistaken as prior ocular toxoplasmosis infection. Unlike other CLDN19 mutations, the homozygous variant in this cohort has not been associated with renal disease to date. Genetic maculopathy should be considered in children with macular scars presumed to be related to prior ocular toxoplasmosis infection, particularly when the scarring is bilateral or familial.

Aims: Reduced left atrial PITX2 is associated with atrial cardiomyopathy and atrial fibrillation (AF). PITX2 is restricted to left atrial cardiomyocytes (aCMs) in the adult heart. The links between PITX2 deficiency, atrial cardiomyopathy, and AF are not fully understood., Methods and Results: To identify mechanisms linking PITX2 deficiency to AF, we generated and characterized PITX2-deficient human aCMs derived from human induced pluripotent stem cells (hiPSC) and their controls. PITX2-deficient hiPSC-derived atrial cardiomyocytes showed shorter and disorganized sarcomeres and increased mononucleation. Electron microscopy found an increased number of smaller mitochondria compared with isogenic controls. Mitochondrial protein expression was altered in PITX2-deficient hiPSC-derived atrial cardiomyocytes. Single-nuclear RNA-sequencing found differences in cellular respiration pathways and differentially expressed mitochondrial and ion channel genes in PITX2-deficient hiPSC-derived atrial cardiomyocytes. PITX2 repression in hiPSC-derived atrial cardiomyocytes replicated dysregulation of cellular respiration. Mitochondrial respiration was shifted to increased glycolysis in PITX2-deficient hiPSC-derived atrial cardiomyocytes. PITX2-deficient human hiPSC-derived atrial cardiomyocytes showed higher spontaneous beating rates. Action potential duration was more variable with an overall prolongation of early repolarization, consistent with metabolic defects. Gene expression analyses confirmed changes in mitochondrial genes in left atria from 42 patients with AF compared with 43 patients with sinus rhythm. Dysregulation of left atrial mitochondrial (COX7C) and metabolic (FOXO1) genes was associated with PITX2 expression in human left atria., Conclusion: PITX2 deficiency causes atrial mitochondrial dysfunction and a metabolic shift to glycolysis in human aCMs. PITX2-dependent metabolic changes can contribute to the structural and functional defects found in PITX2-deficient atria., Competing Interests: Conflict of interest: L.F. has received institutional research grants and non-financial support from European Union, British Heart Foundation, Medical Research Council (U.K.), DFG, German Centre for Heart Research DZHK and several biomedical companies. P.K. has received additional support for research from the European Union, British Heart Foundation, Foundation Leducq, Medical Research Council (U.K.), and German Centre for Cardiovascular Research, from several drug and device companies active in AF, Honoria from several such companies, but not in the last three years. P.K. and L.F. are listed as inventors on two patents held by University of Birmingham (AFTherapy WO 2015140571, Markers for AF WO 2016021783). U.S. has received consultancy fees or honoraria from Università della Svizzera Italiana (USI, Switzerland), Roche Diagnostics (Switzerland), EP Solutions Inc. (Switzerland), Johnson & Johnson Medical Limited, (U.K.), Bayer Healthcare (Germany). U.S. is co-founder and shareholder of YourRhythmics BV, a spin-off company of the University Maastricht. K.G. has received additional support for research from the British Heart Foundation, Medical Research Council (U.K.), and Rocket Pharmaceuticals Inc. All other authors declare they have no competing interests., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)

We report the case of a 7-year-old girl with Knobloch syndrome who presented with retinal detachment due to a macular hole, which was treated with vitrectomy and silicone oil tamponade. The macular hole persisted, and recurrent silicone oil emulsification required exchanges, with two subsequent vitrectomies. Finally, an amniotic membrane graft was used to seal the macular hole in an effort to avoid silicone oil dependence for retinal attachment. The macular hole was successfully closed, and the retina remained attached 6 months after surgery., (Copyright © 2024 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.)

Purpose: Usher syndrome, a common form of syndromic inherited retinal dystrophy in the Arabian Gulf, has not been molecularly defined in the United Arab Emirates. The current study addresses this gap in knowledge., Methods: A retrospective case series of Emirati patients referred to the Ocular Genetics Clinic of Cleveland Clinic Abu Dhabi who (1) were clinically diagnosed with Usher syndrome and underwent genetic testing (whole exome sequencing, 2019 to 2023, inclusive) and (2) were identified to have biallelic pathogenic variants in Usher syndrome genes during the same time period., Results: Ten probands (thirteen patients) were identified-seven probands (nine patients) with clinically diagnosed Usher syndrome and three additional probands (four patients) with biallelic homozygous USH2A variants. Among the seven probands initially diagnosed with Usher syndrome, six had different homozygous variants (three in MYO7A , one in ADGRV1 , and one in CLRN1 ), one had dual diagnoses rather than Usher syndrome (i.e. separate cause for retinal dystrophy and deafness), and one had no identifiable genetic cause. Regarding the three additional probands identified with homozygous USH2A variants, all three had retinitis pigmentosa only rather than Usher syndrome and all three had different variants., Discussion: Clinically diagnosed Usher syndrome was genetically heterogenous without evidence for founder effect in this Emirati cohort. MYO7A was the most common associated gene. Dual diagnosis rather than single cause can mimic Usher syndrome. Homozygous USH2A variants were not identified as a cause for Usher syndrome in this cohort but were a recurrent cause for retinitis pigmentosa without hearing impairment and without founder effect.

Background: Founder variants are ancestral variants shared by individuals who are not closely related. The large effect size of some of these variants in the context of Mendelian disorders offers numerous precision medicine opportunities., Methods: Using one of the largest datasets on Mendelian disorders in the Middle East, we identified 2,908 medically relevant founder variants derived from 18,360 exomes and genomes and investigated their contribution to the clinical annotation of the human genome., Findings: Strikingly, ∼34% of Arab founder variants are absent in gnomAD. We found a strong contribution of Arab founder variants to the identification of novel gene-disease links (n = 224) and the support/dispute (n = 81 support, n = 101 dispute) of previously reported candidate gene-disease links. The powerful segregation evidence generated by Arab founder variants allowed many ClinVar and Human Gene Mutation Database variants to be reclassified. Overall, 39.5% of diagnostic reports from our clinical lab are based on founder variants, and 19.41% of tested individuals carry at least one pathogenic founder variant. The presumptive loss-of-function mechanism that typically underlies autosomal recessive diseases means that Arab founder variants also offer unique opportunities in "druggable genome" research. Arab founder variants were also informative of migration patterns in the Middle East consistent with documented historical accounts., Conclusions: We highlight the contribution of founder variants from an under-represented population group to precision medicine and inform future prevention programs. Our study also sheds light on the added value of these variants in supplementing other lines of research in tracing population history., Funding: There is no funding for this work., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Purpose: Achromatopsia (ACHM) is a genetically heterogenous relatively stationary congenital autosomal recessive cone disorder characterized typically by photophobia, low vision, nystagmus, hyperopia, grossly normal retinal appearance, and absent photopic responses by full-field electroretinography. Incomplete forms occur as well. This study investigates the genetic basis of clinically suspected ACHM in the United Arab Emirates., Methods: Retrospective case series (January 2016-December 2023) of patients with (1) clinically suspected ACHM or (2) mutations in ACHM-associated genes ( CNGA3 , CNGB3 , GNAT2 , PDE6C , PDE6H , AT6 )., Results: Twenty-two clinically suspected patients (19 probands) were identified. Biallelic disease genes and the number of probands were CNGA3 (9), CNGB3 (6), PDE6C (1), GNAT2 (1), RGS9BP (1), and CNNM4 (1). Some mutant alleles were recurrent across different families. Two probands had their diagnoses revised after genetic testing and phenotypic reassessment to RGS9BP -related bradyopsia and CNNM4 -related Jalili syndrome. Three additional cases (making 22 total probands) were identified from ACHM gene mutation review-one each related to PDE6C , to AT6 , and to CNGB3 in concert with CNGA3 (triallelic disease). All three presented with macular discoloration, an atypical finding for classic ACHM., Conclusion: CNGA3 was the single most frequent implicated gene. Bradyopsia and Jalili syndrome can resemble incomplete ACHM. Recurrent mutant alleles may represent founder effects. Macular discoloration on presentation can occur in PDE6C -related disease, AT6 -related disease, and triallelic CNGB3 / CNGA3 -related disease. The possibility for triallelic disease exists and requires genetic counseling beyond that of simple autosomal recessive inheritance.

Myeloproliferative neoplasms are stem cell-driven cancers associated with a large burden of morbidity and mortality. Most patients present with early-stage disease, but a substantial proportion progress to myelofibrosis or secondary leukemia, advanced cancers with a poor prognosis and high symptom burden. Currently, it remains difficult to predict progression, and therapies that reliably prevent or reverse fibrosis are lacking. A major bottleneck to the discovery of disease-modifying therapies has been an incomplete understanding of the interplay between perturbed cellular and molecular states. Several cell types have individually been implicated, but a comprehensive analysis of myelofibrotic bone marrow is lacking. We therefore mapped the cross-talk between bone marrow cell types in myelofibrotic bone marrow. We found that inflammation and fibrosis are orchestrated by a "quartet" of immune and stromal cell lineages, with basophils and mast cells creating a TNF signaling hub, communicating with megakaryocytes, mesenchymal stromal cells, and proinflammatory fibroblasts. We identified the β-galactoside-binding protein galectin-1 as a biomarker of progression to myelofibrosis and poor survival in multiple patient cohorts and as a promising therapeutic target, with reduced myeloproliferation and fibrosis in vitro and in vivo and improved survival after galectin-1 inhibition. In human bone marrow organoids, TNF increased galectin-1 expression, suggesting a feedback loop wherein the proinflammatory myeloproliferative neoplasm clone creates a self-reinforcing niche, fueling progression to advanced disease. This study provides a resource for studying hematopoietic cell-niche interactions, with relevance for cancer-associated inflammation and disorders of tissue fibrosis.

Anti-tumor necrosis factor monoclonal antibodies are an important tool in the management of rheumatologic disease. However, paradoxical inflammation can be precipitated by their use. This case report describes the development of keratitis and dermatitis following adalimumab treatment for chronic recurrent multifocal osteomyelitis in a 6-year-old girl. The keratitis and dermatitis subsided once topical steroids were started and the adalimumab was held., (Copyright © 2024 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.)

Purpose: Occult macular dystrophy (OMD) is a cause of visual loss in young adults with a grossly normal fundus appearance. It is considered an autosomal dominant disorder, related to heterozygous pathogenic variants in the gene RP1L1 . The purpose of this study is to report a biallelic form of the disease., Results: A 29-year-old female had undergone neurological workup and ophthalmic examinations for transient visual loss in her left eye over the past two years but there was no definitive diagnosis. The best-corrected visual acuity was 20/30, 20/20. Indirect ophthalmoscopy with a 78D lens revealed subtle central retinal pigment epithelium mottling and optical coherence tomography confirmed subtle central thickening of the ellipsoid zone. Full-field electroretinography was normal, but pattern electroretinography showed decreased p50 responses. OMD was suspected. Retinal gene panel testing was significant only for a homozygous variant in RP1L1 (NM_178857.6: c.3571 G>T; p.Glu1191*). The parents and older brother were unavailable for segregation analysis. By history they did not have visual complaints other than a need for glasses., Conclusions: This report presents the clinical and genetic findings of a biallelic form of OMD associated with a novel pathogenic variant in RP1L1 . It would be of interest to carefully assess macular function in heterozygotes with this variant.

Background/aims: To investigate genotype-phenotype associations in patients with KCNV2 retinopathy., Methods: Review of clinical notes, best-corrected visual acuity (BCVA), molecular variants, electroretinography (ERG) and retinal imaging. Subjects were grouped according to the combination of KCNV2 variants-two loss-of-function (TLOF), two missense (TM) or one of each (MLOF)-and parameters were compared., Results: Ninety-two patients were included. The mean age of onset (mean±SD) in TLOF (n=55), TM (n=23) and MLOF (n=14) groups was 3.51±0.58, 4.07±2.76 and 5.54±3.38 years, respectively. The mean LogMAR BCVA (±SD) at baseline in TLOF, TM and MLOF groups was 0.89±0.25, 0.67±0.38 and 0.81±0.35 for right, and 0.88±0.26, 0.69±0.33 and 0.78±0.33 for left eyes, respectively. The difference in BCVA between groups at baseline was significant in right (p=0.03) and left eyes (p=0.035). Mean outer nuclear layer thickness (±SD) at baseline in TLOF, MLOF and TM groups was 37.07±15.20 µm, 40.67±12.53 and 40.38±18.67, respectively, which was not significantly different (p=0.85). The mean ellipsoid zone width (EZW) loss (±SD) was 2051 µm (±1318) for patients in the TLOF, and 1314 µm (±965) for MLOF. Only one patient in the TM group had EZW loss at presentation. There was considerable overlap in ERG findings, although the largest DA 10 ERG b-waves were associated with TLOF and the smallest with TM variants., Conclusions: Patients with missense alterations had better BCVA and greater structural integrity. This is important for patient prognostication and counselling, as well as stratification for future gene therapy trials., Competing Interests: Competing interests: MG and MM consult for MeiraGTx. KF consults for Astellas Pharma, Kubota Pharmaceutical Holdings, Acucela, Novartis AG and Janssen Pharmaceuticals. Ester Carreño consults for Active Biotech and Alimera. EZ consults for Acucela, IVERIC bi, Janssen Pharmaceuticals, ProQR Therapeutics N.V., Gyroscope Therapeutics and Biogen MA. AV consults for Adverum Biotechnologies. MEP consults for Spark Therapeutics. Susanne Kohl consults for Novartis AG. CA consults for Novartis AG, Janssen Pharmaceuticals and Santen. The rest of the authors have no conflicts of interest to disclose., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.)

Pulmonary hypoplasia, Diaphragmatic anomalies, Anophthalmia/microphthalmia, and Cardiac defects (PDAC) syndrome is a genetically heterogeneous multiple congenital malformation syndrome. Although pathogenic variants in RARB and STRA6 are established causes of PDAC, many PDAC cases remain unsolved at the molecular level. Recently, we proposed biallelic WNT7B variants as a novel etiology based on several families with typical features of PDAC syndrome albeit with variable expressivity. Here, we report three patients from two families that share a novel founder variant in WNT7B (c.739C > T; Arg247Trp). The phenotypic expression of this variant ranges from typical PDAC features to isolated genitourinary anomalies. Similar to previously reported PDAC-associated WNT7B variants, this variant was found to significantly impair WNT7B signaling activity further corroborating its proposed pathogenicity. This report adds further evidence to WNT7B-related PDAC and expands its variable expressivity., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The bone marrow supports and regulates hematopoiesis, responding to physiological requirements for blood cell production over ontogeny and during pathological challenges. Interactions between hematopoietic cells and niche components are challenging to study mechanistically in the human context, but are important to delineate in order to explore the pathobiology of blood and bone marrow disorders. Organoids are proving transformative in many research settings, but an accurate human bone marrow model incorporating multiple hematopoietic and stromal elements has been lacking. This protocol describes a method to generate three-dimensional, multilineage bone marrow organoids from human induced pluripotent stem cells (hiPSCs), detailing the steps for the directed differentiation of hiPSCs using a series of cytokine cocktails and hydrogel embedding. Over 18 days of differentiation, hiPSCs yield the key lineages that are present in central myelopoietic bone marrow, organized in a well-vascularized architecture that resembles native hematopoietic tissues. This presents a robust, in vitro system that can model healthy and perturbed hematopoiesis in a scalable three-dimensional microenvironment. Bone marrow organoids also support the growth of immortalized cell lines and primary cells from healthy donors and patients with myeloid and lymphoid cancers, including cell types that are poorly viable in standard culture systems. Moreover, we discuss assays for the characterization of organoids, including interrogation of pathogenic remodeling using recombinant TGF-ß treatment, and methods for organoid engraftment with exogenous cells. This protocol can be readily adapted to specific experimental requirements, can be easily implemented by users with tissue culture experience and does not require access to specialist equipment., (© 2024. Springer Nature Limited.)

Abstract: Megakaryocytes (MKs) generate thousands of platelets over their lifespan. The roles of platelets in infection and inflammation has guided an interest to the study of extramedullary thrombopoiesis and therefore MKs have been increasingly reported within the spleen and lung. However, the relative abundance of MKs in these organs compared to the bone marrow and the scale of their contribution to the platelet pool in a steady state remain controversial. We investigated the relative abundance of MKs in the adult murine bone marrow, spleen, and lung using whole-mount light-sheet and quantitative histological imaging, flow cytometry, intravital imaging, and an assessment of single-cell RNA sequencing (scRNA-seq) repositories. Flow cytometry revealed significantly higher numbers of hematopoietic stem and progenitor cells and MKs in the murine bone marrow than in spleens or perfused lungs. Two-photon intravital and light-sheet microscopy, as well as quantitative histological imaging, confirmed these findings. Moreover, ex vivo cultured MKs from the bone marrow subjected to static or microfluidic platelet production assays had a higher capacity for proplatelet formation than MKs from other organs. Analysis of previously published murine and human scRNA-seq data sets revealed that only a marginal fraction of MK-like cells can be found within the lung and most likely only marginally contribute to platelet production in the steady state., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

Background: Long-read whole genome sequencing (lrWGS) has the potential to address the technical limitations of exome sequencing in ways not possible by short-read WGS. However, its utility in autosomal recessive Mendelian diseases is largely unknown., Methods: In a cohort of 34 families in which the suspected autosomal recessive diseases remained undiagnosed by exome sequencing, lrWGS was performed on the Pacific Bioscience Sequel IIe platform., Results: Likely causal variants were identified in 13 (38%) of the cohort. These include (1) a homozygous splicing SV in TYMS as a novel candidate gene for lethal neonatal lactic acidosis, (2) a homozygous non-coding SV that we propose impacts STK25 expression and causes a novel neurodevelopmental disorder, (3) a compound heterozygous SV in RP1L1 with complex inheritance pattern in a family with inherited retinal disease, (4) homozygous deep intronic variants in LEMD2 and SNAP91 as novel candidate genes for neurodevelopmental disorders in two families, and (5) a promoter SNV in SLC4A4 causing non-syndromic band keratopathy. Surprisingly, we also encountered causal variants that could have been identified by short-read exome sequencing in 7 families. The latter highlight scenarios that are especially challenging at the interpretation level., Conclusions: Our data highlight the continued need to address the interpretation challenges in parallel with efforts to improve the sequencing technology itself. We propose a path forward for the implementation of lrWGS sequencing in the setting of autosomal recessive diseases in a way that maximizes its utility., (© 2023. The Author(s).)

Purpose: Bialleic RPGRIP1 pathogenic variants are typically associated with severe Leber congenital amaurosis (non-recordable electroretinography [ERG]) and less commonly with cone-rod dystrophy. This report highlights isolated cone dysfunction as an alternative RPGRIP1 -related presenting phenotype., Methods: Retrospective case series., Results: Four individuals (two sibships from two unrelated families) had low vision, nystagmus, photophobia, and a grossly normal retinal appearance since soon after birth. ERG confirmed non-recordable photopic function with normal scotopic function. Genetic testing revealed affected members from the two families to harbor two different homozygous RPGRIP1 variants (Family 1: c.3565C>T; p.Arg1189*; Family 2: c.2711_2741delinsATATTAG; p.Gly904_Lys914delinsAspIIeArg). Follow-up for Family 1 revealed deterioration of pan-retinal function (non-recordable ERGs by 11 and 7 years old) and thus a final diagnosis of cone-rod dystrophy. Follow-up for Family 2 showed stable retinal function (normal ERG scotopic tracings maintained at 12 and 21 years old) and thus a diagnosis of isolated cone dysfunction., Conclusions: Isolated cone dysfunction that progresses to pan-retinal dysfunction or remains relatively stationary is an alternative phenotype related to biallelic RPGRIP1 pathogenic variants.

A patient who had been diagnosed with infantile retinal dystrophy developed renal failure in his twenties, at which time the diagnosis was revised to Senior-Loken syndrome. He was poorly compliant. At 36 years old, he experienced a sudden drop in visual acuity in the setting of cramping and fatigue and was found to be in uremic crisis. Six months after the event and its treatment, his vision failed to improved. Optic nerve pallor was out of proportion to the retinal dystrophy, and the presumed reason for his new visual loss was uremic optic neuropathy. The patient's younger sister also had been diagnosed with infantile retinal dystrophy, and metabolic screening confirmed subclinical renal dysfunction that was to be carefully followed going forward. Infantile retinal dystrophy can be associated with later systemic disease. Early detection of such disease can potentially decrease morbidity. Patients with retinal dystrophy can develop new visual loss from causes other than the retinopathy itself., Competing Interests: There are no conflicts of interest., (Copyright: © 2023 Saudi Journal of Ophthalmology.)

Multimodal imaging and genetic testing allow sophisticated assessment of suspected inherited retinal disease. Given the availability of such technology, some question whether the full-field electrogram (ffERG) is needed anymore. In fact, a ffERG remains essential for certain clinical scenarios. The goal of this case-based review is to provide a clear understanding of what clinical situations warrant a ffERG. All practicing ophthalmologists should be familiar with this information., Competing Interests: There are no conflicts of interest., (Copyright: © 2023 Saudi Journal of Ophthalmology.)

Introduction: Recent advances in human cardiac 3D approaches have yielded progressively more complex and physiologically relevant culture systems. However, their application in the study of complex pathological processes, such as inflammation and fibrosis, and their utility as models for drug development have been thus far limited., Methods: In this work, we report the development of chamber-specific, vascularised human induced pluripotent stem cell-derived cardiac microtissues, which allow for the multi-parametric assessment of cardiac fibrosis., Results: We demonstrate the generation of a robust vascular system in the microtissues composed of endothelial cells, fibroblasts and atrial or ventricular cardiomyocytes that exhibit gene expression signatures, architectural, and electrophysiological resemblance to in vivo -derived anatomical cardiac tissues. Following pro-fibrotic stimulation using TGFβ, cardiac microtissues recapitulated hallmarks of cardiac fibrosis, including myofibroblast activation and collagen deposition. A study of Ca 2+ dynamics in fibrotic microtissues using optical mapping revealed prolonged Ca 2+ decay, reflecting cardiomyocyte dysfunction, which is linked to the severity of fibrosis. This phenotype could be reversed by TGFβ receptor inhibition or by using the BET bromodomain inhibitor, JQ1., Discussion: In conclusion, we present a novel methodology for the generation of chamber-specific cardiac microtissues that is highly scalable and allows for the multi-parametric assessment of cardiac remodelling and pharmacological screening., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Reyat, di Maio, Grygielska, Pike, Kemble, Rodriguez-Romero, Simoglou Karali, Croft, Psaila, Simões, Rayes and Khan.)

Axenfeld-Rieger spectrum is a range of anterior segment dysgenesis (ASD) phenotypes often related to heterozygous pathogenic variants in the ocular transcription factor genes FOXC1 or PITX2 . Microcornea with myopic chorioretinal atrophy, a less common ASD, is distinct, recognizable, and secondary to biallelic pathogenic variants in the metalloproteinase gene ADAMTS18 . This report describes the case of a boy with ADAMTS18 -related ASD that was mistaken for Axenfeld-Rieger syndrome and highlights distinguishing features., Competing Interests: The author declares that there are no conflicts of interests in this paper., (Copyright: © 2023 Taiwan J Ophthalmol.)

Lipids contribute to hematopoiesis and membrane properties and dynamics; however, little is known about the role of lipids in megakaryopoiesis. Here we show that megakaryocyte progenitors, megakaryocytes and platelets present a unique lipidome progressively enriched in polyunsaturated fatty acid (PUFA)-containing phospholipids. In vitro, inhibition of both exogenous fatty acid functionalization and uptake as well as de novo lipogenesis impaired megakaryocyte differentiation and proplatelet production. In vivo, mice on a high saturated fatty acid diet had significantly lower platelet counts, which was prevented by eating a PUFA-enriched diet. Fatty acid uptake was largely dependent on CD36, and its deletion in mice resulted in low platelets. Moreover, patients with a CD36 loss-of-function mutation exhibited thrombocytopenia and increased bleeding. Our results suggest that fatty acid uptake and regulation is essential for megakaryocyte maturation and platelet production and that changes in dietary fatty acids may be a viable target to modulate platelet counts., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Background: Pulmonary hypoplasia, Diaphragmatic anomalies, Anophthalmia/microphthalmia and Cardiac defects delineate the PDAC syndrome. We aim to identify the cause of PDAC syndrome in patients who do not carry pathogenic variants in RARB and STRA6 , which have been previously associated with this disorder., Methods: We sequenced the exome of patients with unexplained PDAC syndrome and performed functional validation of candidate variants., Results: We identified bi-allelic variants in WNT7B in fetuses with PDAC syndrome from two unrelated families. In one family, the fetus was homozygous for the c.292C>T (p.(Arg98*)) variant whereas the fetuses from the other family were compound heterozygous for the variants c.225C>G (p.(Tyr75*)) and c.562G>A (p.(Gly188Ser)). Finally, a molecular autopsy by proxy in a consanguineous couple that lost two babies due to lung hypoplasia revealed that both parents carry the p.(Arg98*) variant. Using a WNT signalling canonical luciferase assay, we demonstrated that the identified variants are deleterious. In addition, we found that wnt7bb mutant zebrafish display a defect of the swimbladder, an air-filled organ that is a structural homolog of the mammalian lung, suggesting that the function of WNT7B has been conserved during evolution for the development of these structures., Conclusion: Our findings indicate that defective WNT7B function underlies a form of lung hypoplasia that is associated with the PDAC syndrome, and provide evidence for involvement of the WNT-β-catenin pathway in human lung, tracheal, ocular, cardiac, and renal development., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: To describe the features of retinal detachments and high myopia in patients with novel pathogenic variants in LEPREL1 and report a possible association with nephropathy., Methods: Retrospective study of 10 children with biallelic LEPREL1 pathogenic variants. Data included ophthalmic features, surgical interventions, and genetic and laboratory findings., Results: 10 patients (8 females) from three families with homozygous (2) or compound heterozygous (1) variants in LEPREL1 were included. At presentation, mean age was 9.9 ± 2.6 years. Mean axial length was 28.9 ± 1.9 mm and mean refraction was -13.9 ± 2.8 diopters. Bilateral posterior subcapsular cataracts were present in eight patients (80%), with lens subluxation in five eyes of three patients (30%). Rhegmatogenous retinal detachments (RRD), associated with giant retinal tears (GRT), developed in seven eyes of five patients (50%) at a mean age of 14.14 ± 5.9 years. Six were successfully reattached with mean Snellen best-corrected visual acuity improving from 20/120 preoperatively to 20/60 at last follow-up. Urinalysis in nine patients revealed microhematuria and/or mild proteinuria in six patients (67%)., Conclusion: LEPREL1 -related high myopia confers a high risk of early-onset GRT-related RRD. The ocular phenotype may be confused with that of ocular Stickler syndrome if genetic testing is not performed. Further investigations into a potential association with renal dysfunction are warranted.

A lack of models that recapitulate the complexity of human bone marrow has hampered mechanistic studies of normal and malignant hematopoiesis and the validation of novel therapies. Here, we describe a step-wise, directed-differentiation protocol in which organoids are generated from induced pluripotent stem cells committed to mesenchymal, endothelial, and hematopoietic lineages. These 3D structures capture key features of human bone marrow-stroma, lumen-forming sinusoids, and myeloid cells including proplatelet-forming megakaryocytes. The organoids supported the engraftment and survival of cells from patients with blood malignancies, including cancer types notoriously difficult to maintain ex vivo. Fibrosis of the organoid occurred following TGFβ stimulation and engraftment with myelofibrosis but not healthy donor-derived cells, validating this platform as a powerful tool for studies of malignant cells and their interactions within a human bone marrow-like milieu. This enabling technology is likely to accelerate the discovery and prioritization of novel targets for bone marrow disorders and blood cancers., Significance: We present a human bone marrow organoid that supports the growth of primary cells from patients with myeloid and lymphoid blood cancers. This model allows for mechanistic studies of blood cancers in the context of their microenvironment and provides a much-needed ex vivo tool for the prioritization of new therapeutics. See related commentary by Derecka and Crispino, p. 263. This article is highlighted in the In This Issue feature, p. 247., (©2022 The Authors; Published by the American Association for Cancer Research.)

Background: Rare diseases collectively impose a significant burden on healthcare systems, especially in underserved regions, like the Middle East, which lack access to genomic diagnostic services and the associated personalized management plans., Methods: We established a clinical genomics and genetic counseling facility, within a multidisciplinary tertiary pediatric center, in the United Arab Emirates to locally diagnose and manage patients with rare diseases. Clinical genomic investigations included exome-based sequencing, chromosomal microarrays, and/or targeted testing. We assessed the diagnostic yield and implications for clinical management among this population. Variables were compared using the Fisher exact test. Tests were 2-tailed, and P < .05 was considered statistically significant., Results: We present data on 1000 patients with rare diseases (46.2% females; average age, 4.6 years) representing 47 countries primarily from the Arabian Peninsula, the Levant, Africa, and Asia. The cumulative diagnostic yield was 32.5% (95% CI, 29.7-35.5%) and was higher for genomic sequencing-based testing than chromosomal microarrays (37.9% versus 17.2%, P = 0.0001) across all indications, consistent with the higher burden of single gene disorders. Of the 221 Mendelian disorders identified in this cohort, the majority (N = 184) were encountered only once, and those with recessive inheritance accounted for ~ 62% of sequencing diagnoses. Of patients with positive genetic findings (N = 325), 67.7% were less than 5 years of age, and 60% were offered modified management and/or intervention plans. Interestingly, 24% of patients with positive genetic findings received delayed diagnoses (average age, 12.4 years; range 7-37 years), most likely due to a lack of access to genomic investigations in this region. One such genetic finding ended a 15-year-long diagnostic odyssey, leading to a life-threatening diagnosis in one patient, who was then successfully treated using an experimental allogenic bone marrow transplant. Finally, we present cases with candidate genes within regions of homozygosity, likely underlying novel recessive disorders., Conclusions: Early access to genomic diagnostics for patients with suspected rare disorders in the Middle East is likely to improve clinical outcomes while driving gene discovery in this genetically underrepresented population., (© 2023. The Author(s).)

Oculocutaneous albinism (OCA) is a group of Mendelian disorders characterized by hypopigmentation of skin, hair and pigmented ocular structures. While much of the genetic heterogeneity of OCA has been resolved, many patients still lack a molecular diagnosis following exome sequencing. Here, we report a consanguineous family in which the index patient presented with OCA and Hirschsprung disease but tested negative for known genetic causes of OCA. Instead, he was found to have a homozygous presumptive loss of function variant in PMEL. PMEL encodes a scaffolding protein that is essential for the normal maturation of melanosomes and normal deposition of the melanin pigment therein. Numerous PMEL vertebrate ortholog mutants have been reported and all were characterized by conspicuous pigmentary abnormalities. We suggest that the patient we report is the first human equivalent of PMEL loss of function., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

S100A8/A9, also known as "calprotectin" or "MRP8/14," is an alarmin primarily secreted by activated myeloid cells with antimicrobial, proinflammatory, and prothrombotic properties. Increased plasma levels of S100A8/A9 in thrombo-inflammatory diseases are associated with thrombotic complications. We assessed the presence of S100A8/A9 in the plasma and lung autopsies from patients with COVID-19 and investigated the molecular mechanism by which S100A8/A9 affects platelet function and thrombosis. S100A8/A9 plasma levels were increased in patients with COVID-19 and sustained high levels during hospitalization correlated with poor outcomes. Heterodimeric S100A8/A9 was mainly detected in neutrophils and deposited on the vessel wall in COVID-19 lung autopsies. Immobilization of S100A8/A9 with collagen accelerated the formation of a fibrin-rich network after perfusion of recalcified blood at venous shear. In vitro, platelets adhered and partially spread on S100A8/A9, leading to the formation of distinct populations of either P-selectin or phosphatidylserine (PS)-positive platelets. By using washed platelets, soluble S100A8/A9 induced PS exposure but failed to induce platelet aggregation, despite GPIIb/IIIa activation and alpha-granule secretion. We identified GPIbα as the receptor for S100A8/A9 on platelets inducing the formation of procoagulant platelets with a supporting role for CD36. The effect of S100A8/A9 on platelets was abolished by recombinant GPIbα ectodomain, platelets from a patient with Bernard-Soulier syndrome with GPIb-IX-V deficiency, and platelets from mice deficient in the extracellular domain of GPIbα. We identified the S100A8/A9-GPIbα axis as a novel targetable prothrombotic pathway inducing procoagulant platelets and fibrin formation, in particular in diseases associated with high levels of S100A8/A9, such as COVID-19., (© 2022 by The American Society of Hematology.)

Aims: Thrombotic complications and vasculopathy have been extensively associated with severe COVID-19 infection; however, the mechanisms inducing endotheliitis and the disruption of endothelial integrity in the microcirculation are poorly understood. We hypothesized that within the vessel wall, pericytes preferentially take up viral particles and mediate the subsequent loss of vascular integrity., Methods and Results: Immunofluorescence of post-mortem patient sections was used to assess pathophysiological aspects of COVID-19 infection. The effects of COVID-19 on the microvasculature were assessed using a vascular organoid model exposed to live viral particles or recombinant viral antigens. We find increased expression of the viral entry receptor angiotensin-converting enzyme 2 on pericytes when compared to vascular endothelium and a reduction in the expression of the junctional protein CD144, as well as increased cell death, upon treatment with both live virus and/or viral antigens. We observe a dysregulation of genes implicated in vascular permeability, including Notch receptor 3, angiopoietin-2, and TEK. Activation of vascular organoids with interleukin-1β did not have an additive effect on vascular permeability. Spike antigen was detected in some patients' lung pericytes, which was associated with a decrease in CD144 expression and increased platelet recruitment and von Willebrand factor (VWF) deposition in the capillaries of these patients, with thrombi in large vessels rich in VWF and fibrin., Conclusion: Together, our data indicate that direct viral exposure to the microvasculature modelled by organoid infection and viral antigen treatment results in pericyte infection, detachment, damage, and cell death, disrupting pericyte-endothelial cell crosstalk and increasing microvascular endothelial permeability, which can promote thrombotic and bleeding complications in the microcirculation., Competing Interests: Conflict of interest: none declared., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved.)

A 20-year-old woman with right-sided congenital cranial dysinnervation disorder (exotropia, ophthalmoplegia, and ptosis) presented for strabismus surgery. Exploration of the right eye confirmed abnormal extraocular muscles. Lateral rectus recession with medial rectus plication and inferior oblique recession improved primary position ocular alignment. However, an unusual pattern of inferior chemosis developed postoperatively and persisted during the next month. Excision and histologic examination of this tissue revealed areas of lacrimal gland and cartilage with surrounding inflammation, suggestive of a disrupted orbital choriostoma. [ J Pediatr Ophthalmol Strabismus . 2022;59(6):e66-e68.] .

Purpose: Ciliopathies are broadly classified as non-motile or motile (primary ciliary dyskinesia). Early-onset retinal dystrophy is common in non-motile ciliopathy, but retinal dystrophy is not considered a feature of primary ciliary dyskinesia. The subject of this report is woman referred as a case of Stargardt disease who in fact had retinal dystrophy apparently related to GAS8 -related primary ciliary dyskinesia., Methods: Retrospective case report., Results: A 43-year-old Emirati woman was referred for further evaluation of Stargardt disease. Her only ophthalmic complaints were related to dry eye disease. Past ocular history was significant for refractive surgery in her early 30's. Past medical history was significant for primary ciliary dyskinesia, which included recurrent bronchiectasis and sino-pulmonary infections since childhood. Clinical examination confirmed retinopathy resembling Stargardt disease. Electroretinography revealed cone-rod dysfunction. Whole exome sequencing with attention to ABCA4 was unrevealing for retinal dystrophy genes but did uncover a homozygous GAS8 deletion, molecularly confirming the diagnosis of primary ciliary dyskinesia. Literature review revealed a report of a 34-year-old North African male with GAS8 -related primary ciliary dyskinesia who also had been diagnosed with Stargardt disease in the absence of pathogenic ABCA4 variants., Discussion: Longer follow-up of individuals with primary ciliary dyskinesia may reveal findings more typically associated with non-motile ciliopathy such as retinal dystrophy. GAS8 -related retinal dystrophy can resemble Stargardt disease.

Background: The systemic inflammatory response post-SARS-CoV-2 infection increases pro-inflammatory cytokine production, multi-organ damage, and mortality rates. Mast cells (MC) modulate thrombo-inflammatory disease progression ( e.g. , deep vein thrombosis) and the inflammatory response post-infection., Objective: To enhance our understanding of the contribution of MC and their proteases in SARS-CoV-2 infection and the pathogenesis of the disease, which might help to identify novel therapeutic targets., Methods: MC proteases chymase (CMA1), carboxypeptidase A3 (CPA3), and tryptase beta 2 (TPSB2), as well as cytokine levels, were measured in the serum of 60 patients with SARS-CoV-2 infection (30 moderate and 30 severe; severity of the disease assessed by chest CT) and 17 healthy controls by ELISA. MC number and degranulation were quantified by immunofluorescent staining for tryptase in lung autopsies of patients deceased from either SARS-CoV-2 infection or unrelated reasons (control). Immortalized human FcεR1 + c-Kit + LUVA MC were infected with SARS-CoV-2, or treated with its viral proteins, to assess direct MC activation by flow cytometry., Results: The levels of all three proteases were increased in the serum of patients with COVID-19, and strongly correlated with clinical severity. The density of degranulated MC in COVID-19 lung autopsies was increased compared to control lungs. The total number of released granules and the number of granules per each MC were elevated and positively correlated with von Willebrand factor levels in the lung. SARS-CoV-2 or its viral proteins spike and nucleocapsid did not induce activation or degranulation of LUVA MC in vitro ., Conclusion: In this study, we demonstrate that SARS-CoV-2 is strongly associated with activation of MC, which likely occurs indirectly, driven by the inflammatory response. The results suggest that plasma MC protease levels could predict the disease course, and that severe COVID-19 patients might benefit from including MC-stabilizing drugs in the treatment scheme., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Krysko, Bourne, Kondakova, Galova, Whitworth, Newby, Bachert, Hill, Crispin, Stamataki, Cunningham, Pugh, Khan, Rayes, Vedunova, Krysko and Brill.)

Purpose: To highlight cases of adult-onset bestrophinopathy mistaken as central serous chorioretinopathy (CSCR)., Methods: Retrospective case series., Results: Two unrelated adult males (54 years old and 43 years old) with serous macular detachments were managed as CSCR. One had been treated with intraocular injections and oral mineralcorticoid inhibitors. Independently, each had an 8-year-old son who presented with classic Best disease, which raised suspicion for bestrophinopathy in their fathers. Bestrophin sequencing confirmed each son to be heterozygous for a pathogenic variant, and targeted testing confirmed each respective father to harbor the same heterozygous pathogenic variant as his son. Electro-oculography of the first father-son pair confirmed decreased Arden ratios. Review of multimodal imaging of the adult patients revealed a hyper-autofluorescent edge surrounding a serous macular detachment by short-wave autofluorescence and shaggy photoreceptors on the overlying edge of serous detachments by optical coherence tomography., Discussion: Adult-onset bestrophinopathy can be mistaken as CSCR. Multimodal imaging findings, examination of potentially affected family members, electrophysiology, and genetic testing facilitate the correct diagnosis.

Paradoxical pupillary reaction (initial pupillary constriction to darkness) has been most associated with the inherited retinal disorders congenital stationary night blindness and achromatopsia. However, underlying genotypes and associations with other pediatric retinal phenotypes are not well documented. A retrospective review for paradoxical pupillary reaction was performed at the Ocular Genetics Clinic of Cleveland Clinic Abu Dhabi (2016-2020). Four children from 4 different families were identified, all of whom had had genetic confirmation of the clinical diagnosis. Associated pathogenic variants were in TRPM1 (biallelic; two boys; congenital stationary night blindness), CABP4 (biallelic; one boy, congenital cone-rod synaptic disorder) and PAX2 (monoallelic; one girl, papillorenal syndrome). Genetically confirmed affected relatives of the 2 probands with TRPM1-related congenital stationary night blindness did not show the phenomenon. This study documents novel genotypes and phenotypes that can be associated with paradoxical pupillary reaction in children and confirms potential intrafamilial variable expressivity for the phenomenon., (Copyright © 2022 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.)

Germline defects affecting the DNA-binding domain of the transcription factor FLI1 are associated with a bleeding disorder that is characterized by the presence of large, fused α-granules in platelets. We investigated whether the genes showing abnormal expression in FLI1-deficient platelets could be involved in platelet α-granule biogenesis by undertaking transcriptome analysis of control platelets and platelets harboring a DNA-binding variant of FLI1. Our analysis identified 2,276 transcripts that were differentially expressed in FLI1-deficient platelets. Functional annotation clustering of the coding transcripts revealed significant enrichment for gene annotations relating to protein transport, and identified Sorting nexin 24 (SNX24) as a candidate for further investigation. Using an induced pluripotent stem cell-derived megakaryocyte model, SNX24 expression was found to be increased during the early stages of megakaryocyte differentiation and downregulated during proplatelet formation, indicating tight regulatory control during megakaryopoiesis. CRISPR-Cas9 mediated knockout (KO) of SNX24 led to decreased expression of immature megakaryocyte markers, CD41 and CD61, and increased expression of the mature megakaryocyte marker CD42b (P=0.0001), without affecting megakaryocyte polyploidisation, or proplatelet formation. Electron microscopic analysis revealed an increase in empty membrane-bound organelles in SNX24 KO megakaryocytes, a reduction in α-granules and an absence of immature and mature multivesicular bodies, consistent with a defect in the intermediate stage of α-granule maturation. Co-localization studies showed that SNX24 associates with each compartment of α-granule maturation. Reduced expression of CD62P and VWF was observed in SNX24 KO megakaryocytes. We conclude that SNX24 is required for α-granule biogenesis and intracellular trafficking of α-granule cargo within megakaryocytes.

Childhood glaucoma is a treatable cause of blindness, provided it is recognized, diagnosed, and treated in time. WHO has estimated that it is responsible for Blind Years second only to cataracts. The fundamental pathophysiology of all childhood glaucoma is impaired outflow through the trabecular meshwork. Anterior segment Dysgeneses (ASD) are a group of non-acquired ocular anomalies associated with glaucoma, characterized by developmental abnormalities of the tissues of the anterior segment. The cause is multifactorial, and many genes are involved in the development of the anterior segment. Over the last decade, molecular and developmental genetic research has transformed our understanding of the molecular basis of ASD and the developmental mechanisms underlying these conditions. Identifying the genetic changes underlying ASD has gradually led to the recognition that some of these conditions may be parts of a disease spectrum. The characterization of genes responsible for glaucoma is the critical first step toward developing diagnostic and screening tests, which could identify individuals at risk for disease before irreversible optic nerve damage occurs. It is also crucial for genetic counseling and risk stratification of later pregnancies. It also aids pre-natal testing by various methods allowing for effective genetic counseling. This review will summarize the known genetic variants associated with phenotypes of ASD and the possible significance and utility of genetic testing in the clinic., Competing Interests: None

The glomerular filtration barrier (GFB) produces primary urine and is composed of a fenestrated endothelium, a glomerular basement membrane (GBM), podocytes, and a slit diaphragm. Impairment of the GFB leads to albuminuria and microhematuria. The GBM is generated via secreted proteins from both endothelial cells and podocytes and is supposed to majorly contribute to filtration selectivity. While genetic mutations or variations of GBM components have been recently proposed to be a common cause of glomerular diseases, pathways modifying and stabilizing the GBM remain incompletely understood. Here, we identified prolyl 3-hydroxylase 2 (P3H2) as a regulator of the GBM in an a cohort of patients with albuminuria. P3H2 hydroxylates the 3' of prolines in collagen IV subchains in the endoplasmic reticulum. Characterization of a P3h2ΔPod mouse line revealed that the absence of P3H2 protein in podocytes induced a thin basement membrane nephropathy (TBMN) phenotype with a thinner GBM than that in WT mice and the development of microhematuria and microalbuminuria over time. Mechanistically, differential quantitative proteomics of the GBM identified a significant decrease in the abundance of collagen IV subchains and their interaction partners in P3h2ΔPod mice. To our knowledge, P3H2 protein is the first identified GBM modifier, and loss or mutation of P3H2 causes TBMN and focal segmental glomerulosclerosis in mice and humans.

Purpose: Retinal arteriolar macroaneurysms with supravalvular pulmonic stenosis (RAMSVPS) is a rare syndrome that to date has only been reported in Saudi Arabian families. All tested patients have been homozygous for a single IGFBP7 splice variant (NM&#95;001553.2:c.830-1G>A). We report our experience with RAMSVPS in the United Arab Emirates., Methods: Retrospective case series., Results: Five affected individuals (two males and three females) from two unrelated Emirati families were known to our institution (age of first signs 6 months to 10 years of age, with one asymptomatic 6-year-old boy identified by sibling screening examination). Initial ophthalmic diagnoses had been Coats disease or traumatic retinal bleeding. Characteristic retinal arteriolar trunk beading and macroaneurysms led to the actual diagnosis of RAMSVPS. One child with esotropia at 6 months of age seemed to have unilateral Coats disease until retinal signs became apparent in the contralateral eye at 4 years old. One family consented to genetic testing, and both affected siblings were homozygous for the Saudi IGFBP7 splice variant (c.830-1G>A). The three children who underwent echocardiography were all confirmed to have cardiac valvular abnormalities (two supravalvular pulmonic stenosis and one tricuspid stenosis)., Discussion: The distinct ophthalmic phenotype of RAMSVPS is important to recognize because of systemic implications. Retinal findings can be misinterpreted as sequelae of trauma or Coats disease and can seem unilateral in very young children until changes in the contralateral eye become apparent years later. The homozygous IGFBP7 splice variant associated with the disease likely represents an ancestral founder effect for the Arabian Peninsula.

Background: A significant challenge is faced for the genetic diagnosis of inherited platelet disorders in which candidate genetic variants can be found in more than 100 bleeding, thrombotic, and platelet disorder genes, especially within families in which there are both normal and low platelet counts. Genetic variants of unknown clinical significance (VUS) are found in a significant proportion of such patients in which functional studies are required to prove pathogenicity., Objective: To identify the genetic cause in patients with a suspected platelet disorder and subsequently perform a detailed functional analysis of the candidate genetic variants found., Methods: Genetic and functional studies were undertaken in three patients in two unrelated families with a suspected platelet disorder and excessive bleeding. A targeted gene panel of previously known bleeding and platelet genes was used to identify plausible genetic variants. Deep platelet phenotyping was performed using platelet spreading analysis, transmission electron microscopy, immunofluorescence, and platelet function testing using lumiaggregometry and flow cytometry., Results: We report rare conserved missense variants (p.R182C and p.A183V) in TPM4 encoding tromomyosin-4 in 3 patients. Deep platelet phenotyping studies revealed similar platelet function defects across the 3 patients including reduced platelet secretion, and aggregation and spreading defects suggesting that TPM4 missense variants impact platelet function and show a disordered pattern of tropomyosin staining., Conclusions: Genetic and functional TPM4 defects are reported making TPM4 a diagnostic grade tier 1 gene and highlights the importance of including TPM4 in diagnostic genetic screening for patients with significant bleeding and undiagnosed platelet disorders, particularly for those with a normal platelet count., (© 2021 The Authors. Journal of Thrombosis and Haemostasis published by Wiley Periodicals LLC on behalf of International Society on Thrombosis and Haemostasis.)

Coronavirus disease 2019 (COVID-19) induces a hypercoagulatory state that frequently leads to thromboembolic complications. Whereas anticoagulation is associated with reduced mortality, the role of antiplatelet therapy in COVID-19 is less clear. We retrospectively analyzed the effect of anticoagulation and antiplatelet therapy in 578 hospitalized patients with COVID-19 and prospectively monitored 110 patients for circulating microthrombi and plasma markers of coagulation in the first week of admission. Moreover, we determined platelet shape change and also thrombi in postmortem lung biopsies in a subset of patients with COVID-19. We observed no association of antiplatelet therapy with COVID-19 survival. Adverse outcome in COVID-19 was associated with increased activation of the coagulation cascade, whereas circulating microthrombi did not increase in aggravated disease. This was in line with analysis of postmortem lung biopsies of patients with COVID-19, which revealed generally fibrin(ogen)-rich and platelet-low thrombi. Platelet spreading was normal in severe COVID-19 cases; however, plasma from patients with COVID-19 mediated an outcome-dependent inhibitory effect on naïve platelets. Antiplatelet medication disproportionally exacerbated this platelet impairment in plasma of patients with fatal outcome. Taken together, this study shows that unfavorable outcome in COVID-19 is associated with a profound dysregulation of the coagulation system, whereas the contribution of platelets to thrombotic complications is less clear. Adverse outcome may be associated with impaired platelet function or platelet exhaustion. In line, antiplatelet therapy was not associated with beneficial outcome., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Schrottmaier, Pirabe, Pereyra, Heber, Hackl, Schmuckenschlager, Brunnthaler, Santol, Kammerer, Oosterlee, Pawelka, Treiber, Khan, Pugh, Traugott, Schörgenhofer, Seitz, Karolyi, Jilma, Rayes, Zoufaly and Assinger.)

In specialised cells, the expression of specific tubulin isoforms and their subsequent post-translational modifications drive and coordinate unique morphologies and behaviours. The mechanisms by which β1-tubulin, the platelet and megakaryocyte (MK) lineage restricted tubulin isoform, drives platelet production and function remains poorly understood. We investigated the roles of two key post-translational tubulin polymodifications (polyglutamylation and polyglycylation) on these processes using a cohort of thrombocytopenic patients, human induced pluripotent stem cell (iPSC) derived MKs, and healthy human donor platelets. We find distinct patterns of polymodification in MKs and platelets, mediated by the antagonistic activities of the cell specific expression of Tubulin Tyrosine Ligase Like (TTLLs) and Cytosolic Carboxypeptidase (CCP) enzymes. The resulting microtubule patterning spatially regulates motor proteins to drive proplatelet formation in megakaryocytes, and the cytoskeletal reorganisation required for thrombus formation. This work is the first to show a reversible system of polymodification by which different cell specific functions are achieved.

Thromboembolic complications are frequently observed in Coronavirus disease 2019 (COVID-19). While COVID-19 is linked to platelet dysregulation, the association between disease outcome and platelet function is less clear. We prospectively monitored platelet activation and reactivity in 97 patients during the first week of hospitalization and determined plasma markers of platelet degranulation and inflammation. Adverse outcome in COVID-19 was associated with increased basal platelet activation and diminished platelet responses, which aggravated over time. Especially GPIIb/IIIa responses were abrogated, pointing toward impeded platelet aggregation. Moreover, platelet-leukocyte aggregate formation was diminished, pointing toward abrogated platelet-mediated immune responses in COVID-19. No general increase in plasma levels of platelet-derived granule components could be detected, arguing against platelet exhaustion. However, studies on platelets from healthy donors showed that plasma components in COVID-19 patients with unfavorable outcome were at least partly responsible for diminished platelet responses. Taken together this study shows that unfavorable outcome in COVID-19 is associated with a hypo-responsive platelet phenotype that aggravates with disease progression and may impact platelet-mediated immunoregulation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Schrottmaier, Pirabe, Pereyra, Heber, Hackl, Schmuckenschlager, Brunnthaler, Santol, Kammerer, Oosterlee, Pawelka, Treiber, Khan, Pugh, Traugott, Schörgenhofer, Seitz, Karolyi, Jilma, Rayes, Zoufaly and Assinger.)

Purpose: To describe the detailed retinal phenotype of KCNV2-associated retinopathy., Study Design: Multicenter international retrospective case series., Methods: Review of retinal imaging including fundus autofluorescence (FAF) and optical coherence tomography (OCT), including qualitative and quantitative analyses., Results: Three distinct macular FAF features were identified: (1) centrally increased signal (n = 35, 41.7%), (2) decreased autofluorescence (n = 27, 31.1%), and (3) ring of increased signal (n = 37, 44.0%). Five distinct FAF groups were identified based on combinations of those features, with 23.5% of patients changing the FAF group over a mean (range) follow-up of 5.9 years (1.9-13.1 years). Qualitative assessment was performed by grading OCT into 5 grades: (1) continuous ellipsoid zone (EZ) (20.5%); (2) EZ disruption (26.1%); (3) EZ absence, without optical gap and with preserved retinal pigment epithelium complex (21.6%); (4) loss of EZ and a hyporeflective zone at the foveola (6.8%); and (5) outer retina and retinal pigment epithelium complex loss (25.0%). Eighty-six patients had scans available from both eyes, with 83 (96.5%) having the same grade in both eyes, and 36.1% changed OCT grade over a mean follow-up of 5.5 years. The annual rate of outer nuclear layer thickness change was similar for right and left eyes., Conclusions: KCNV2-associated retinopathy is a slowly progressive disease with early retinal changes, which are predominantly symmetric between eyes. The identification of a single OCT or FAF measurement as an endpoint to determine progression that applies to all patients may be challenging, although outer nuclear layer thickness is a potential biomarker. Findings suggest a potential window for intervention until 40 years of age., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Purpose: To highlight recognizable patterns of subretinal fibrosis in enhanced S-cone syndrome (ESCS)., Design: Retrospective case series., Participants: Forty-seven patients with subretinal fibrosis identified from 101 patients with clinically diagnosed ESCS, confirmed by full-field electroretinography (35/47), genetic testing (34/47), or both., Methods: Multimodal retinal imaging, electroretinography, and genetic analysis., Main Outcome Measures: Patterns of subretinal fibrosis with angiographic, OCT, and genetic correlations., Results: Eighty-five eyes of 47 patients (24 male patients; 36 unrelated consanguineous families) had subretinal fibrosis. Mean age at presentation was 14 years. Best-corrected visual acuity ranged from 20/20 to hand movements. All 34 genetically tested patients were homozygous for pathogenic NR2E3 variants. Subretinal fibrosis was always in the macular area, although it extended beyond in some patients. Six recurrent patterns of submacular fibrosis were noted: central unifocal nodular, circumferential unifocal nodular, multifocal nodular, arcuate, helicoid, and thick geographic. Some patients showed a combination of patterns. Previous misdiagnosis as inflammatory disease was common. Fibrosis was fairly symmetrical in a given patient but not always present or identical in other affected individuals with a given homozygous mutation from the same or other families., Conclusions: These recognizable patterns of submacular fibrosis are part of the ESCS phenotypic spectrum and strongly suggest the disease. In addition to facilitating diagnosis, recognition of these patterns can spare patients unnecessary workup for an inflammatory cause., (Copyright © 2021 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

A 10-year-old girl initially diagnosed with functional visual loss was later diagnosed with progressive optic atrophy. Directed questioning at 13 years of age revealed difficulty hearing that had not been noted by the parents. Whole exome sequencing and subsequent metabolic testing confirmed biotinidase deficiency. Although biotinidase deficiency classically manifests in early childhood with multiple manifestations, such as seizures and failure to thrive, a delayed-onset form can present primarily as juvenile progressive optic atrophy. Early diagnosis is critical because biotin supplementation prevents disease and deterioration., (Copyright © 2021 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.)

Purpose: Alpha-methylacyl-CoA racemase (AMACR) deficiency is a peroxisomal disorder due to biallelic mutations in AMACR. At least 13 genetically confirmed patients have been reported to date. Seven had obvious pigmentary retinopathy; however, for the other six, no retinal phenotype was mentioned. The purpose of this report is to document subtle retinal findings in an additional affected family., Methods: Retrospective case series (three affected siblings and their unaffected parents)., Results: Three Arab siblings (16, 19, and 22 years old) with prior juvenile cholelithiasis had been diagnosed with AMACR deficiency based on biochemical analysis, whole exome sequencing, and confirmatory segregation analysis (AMACR NM&#95;001167595.1: c.877T>C; p.C293R). For all three, there were no visual complaints, but retinal multimodal imaging and electroretinography suggested subtle retinal dysfunction., Conclusions: Retinal dysfunction is a parameter that should be measured in patients with known or suspected AMACR deficiency even in the absence of visual symptoms. This may be helpful with clinical diagnosis and monitoring response to dietary interventions., (Copyright © 2021 Molecular Vision.)