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Pathogenic variants in the Tenascin-XB (TNXB) gene are associated with autosomal recessive Ehlers Danlos Syndrome (classical-like). Here, we report the association of two or more TNXB variants with aneurysms and/or dissections in different arterial beds. We compared case and control data from exome sequencing (ES) or multigene panel testing (MGPT). Statistical analysis was performed by Fisher’s exact test. From 350 cases of vascular aneurysm and/or dissection referred for genetic testing by ES, we identified 5 individuals with two or more rare missense variants in the TNXB gene (1.4%) versus 16 individuals with two or more TNXB variants from 10, 968 matched controls (0.14%, pTNXB variants (1.5%, pTNXB variants compared to controls (1.8% vs 0.14%, pTNXB variants and vascular aneurysms and dissections.

Mutations in Dyrk1b are associated with metabolic syndrome and nonalcoholic fatty liver disease in humans. Our investigations showed that DYRK1B levels are increased in the liver of patients with nonalcoholic steatohepatitis (NASH) and in mice fed with a high-fat, high-sucrose diet. Increasing Dyrk1b levels in the mouse liver enhanced de novo lipogenesis (DNL), fatty acid uptake, and triacylglycerol secretion and caused NASH and hyperlipidemia. Conversely, knockdown of Dyrk1b was protective against high-calorie-induced hepatic steatosis and fibrosis and hyperlipidemia. Mechanistically, Dyrk1b increased DNL by activating mTORC2 in a kinase-independent fashion. Accordingly, the Dyrk1b-induced NASH was fully rescued when mTORC2 was genetically disrupted. The elevated DNL was associated with increased plasma membrane sn-1,2-diacylglyerol levels and increased PKCε-mediated IRKT1150 phosphorylation, which resulted in impaired activation of hepatic insulin signaling and reduced hepatic glycogen storage. These findings provide insights into the mechanisms that underlie Dyrk1b-induced hepatic lipogenesis and hepatic insulin resistance and identify Dyrk1b as a therapeutic target for NASH and insulin resistance in the liver.

Factors that underlie the clustering of metabolic syndrome traits are not fully known. We performed whole exome sequence analysis in kindreds with extreme phenotypes of early-onset atherosclerosis and metabolic syndrome and identified novel loss-of-function mutations in the gene encoding the pancreatic elastase CELA2A. We further show that CELA2A is a circulating enzyme that reduces platelet hyperactivation, triggers both insulin secretion and degradation, and increases insulin sensitivity. CELA2A plasma levels rise postprandially and parallel insulin levels in humans. Loss of these functions by the mutant proteins provides insight into disease mechanisms and suggests that CELA2A could be an attractive therapeutic target., Editorial summary: Exome sequencing identifies loss-of-function CELA2A mutations in families with early-onset atherosclerosis and metabolic syndrome. Functional studies show that CELA2A is a circulating enzyme that reduces platelet activation, triggers insulin secretion and degradation, and increases insulin sensitivity.

Rare gain of function mutations in the gene encoding Dyrk1b, a key regulator of skeletal muscle differentiation, have been associated with sarcopenic obesity (SO) and metabolic syndrome (MetS) in humans. So far, the global gene networks regulated by Dyrk1b during myofiber differentiation have remained elusive. Here, we have performed untargeted proteomics to determine Dyrk1b-dependent gene-network in differentiated C2C12 myofibers. This analysis led to identification of translational inhibitor, 4e-bp1 as a post-transcriptional target of Dyrk1b in C2C12 cells. Accordingly, CRISPR/Cas9 mediated knockout of Dyrk1b in zebrafish identified 4e-bp1 as a downstream target of Dyrk1b in-vivo. The Dyrk1b knockout zebrafish embryos exhibited markedly reduced myosin heavy chain 1 expression in poorly developed myotomes and were embryonic lethal. Using knockdown and overexpression approaches in C2C12 cells, we found that 4e-bp1 enhances autophagy and mediates the effects of Dyrk1b on skeletal muscle differentiation. Dyrk1bR102C, the human sarcopenic obesity-associated mutation impaired muscle differentiation via excessive activation of 4e-bp1/autophagy axis in C2C12 cells. Strikingly, the defective muscle differentiation in Dyrk1bR102C cells was rescued by reduction of autophagic flux. The identification of Dyrk1b-4e-bp1-autophagy axis provides significant insight into pathways that are relevant to human skeletal muscle development and disorders.

Insulin resistance (IR) is fundamental to the pathophysiology of type 2 diabetes (T2D) and a major risk factor for cardiovascular disease (CVD). Therapeutic options for IR are limited, reinforcing the need to understand IR pathways with an aim to develop IR-specific medications. We previously identified human N-acetyl transferase 2 (NAT2) as a novel insulin sensitivity gene. In vitro and in vivo studies demonstrated an association of mouse Nat1 (ortholog of human NAT2) deficiency with both IR and mitochondrial dysfunction. However, the underlying mechanism of how Nat1 deficiency causes IR and mitochondrial dysfunction is unknown. Using engineered ascorbate peroxidase-proximity labeling in cells followed by mass spectrometry-based proteomic analysis, we are mapping Nat1 endogenous targets and Nat1 interacting proteins. Verification of the interacting proteins and functional validation will be achieved by co-immunoprecipitation, siRNA knockdown, glucose uptake and lipolysis assays, and mitochondrial functional assays in mouse liver cells and adipocytes. We have also created a liver specific Nat1-deficient mouse model and will determine whether this is sufficient to cause whole body changes in insulin sensitivity. Collectively, these studies will shed light on mechanism of how the novel IR gene Nat1 participates in the pathophysiology of IR, which is a necessary step for the development of new treatments for T2D and CVD. Disclosure P. Sangwung: None. M. Fathzadeh: None. J. Knowles: None. Funding American Diabetes Association (1-19-JDF-108 to J.K.); U.S. Public Health Service; National Institute of Diabetes and Digestive and Kidney Diseases (R01DK107437, R01DK106236, P30DK116074, 1R01DK116750 to J.K.)

The advent of human genetics has provided unprecedented opportunities for discovery of novel disease pathways. Mutations inDYRK1Bhave been associated with metabolic syndrome and sarcopenic obesity in humans, underscoring the critical role of the encoded protein in skeletal muscle development and homeostasis. By the novel creation of Dyrk1b knockout zebrafish models we demonstrate that Dyrk1b kinase activity is critical for specification of the paraxialmyoD. Mechanistically, Dyrk1b mediates and amplifies Fgf signaling in the paraxial domain by the transcriptional suppression of its negative feedback inhibitorsprouty1. In the adaxialmyoDdomain, Dyrk1b amplifies Shh signaling and partially rescues defects caused by its disruption. The investigations of C2C12 terminal differentiation revealed that Dyrk1b also plays a critical role in myofiber fusion. Combined biochemical and proteomic analysis of C2C12 myoblasts undergoing differentiation showed that Dyrk1b kinase activation is induced by shh inhibition, and triggers differentiation by inhibiting mTOR, subsequent upregulation of 4e-bp1 and induction of autophagy. In conclusion, we demonstrate that Dyrk1b plays a critical role in sustaining myocyte specification and differentiation by integrating Fgf, Shh and mTORC1 signaling pathways.

The mechanisms that unify the association of insulin-induced de novo lipogenesis (DNL) with hepatic insulin resistance in metabolic syndrome (MetS) are not understood. We had previously shown that rare mutations in the DYRK1B gene are associated with MetS. We now demonstrate that Dyrk1b is a missing link between DNL and hepatic insulin resistance. The increased levels of liver Dyrk1b promoted, while its disruption conferred protection against enhanced glucose production, liver insulin-resistance and steatosis in mice. Mechanistically, Dyrk1b facilitated insulin-induced DNL in a kinase-independent manner by displacing Fkbp12 from mTORC2, causing its activation. Accordingly, the disruption of the hepatic mTORC2 rescued Dyrk1b induced hepatic steatosis and hyperlipidemia. The significance of this disease pathway is further illustrated by increased hepatic Dyrk1b levels in mice and humans with hepatic steatosis. These findings identify Dyrk1b and Fkbp12 as regulators of DNL in the setting of hepatic insulin resistance and attractive therapeutic targets against metabolic syndrome.

Genetic variation in the FAM13A (Family with Sequence Similarity 13 Member A) locus has been associated with several glycemic and metabolic traits in genome-wide association studies (GWAS). Here, we demonstrate that in humans, FAM13A alleles are associated with increased FAM13A expression in subcutaneous adipose tissue (SAT) and an insulin resistance-related phenotype (e.g. higher waist-to-hip ratio and fasting insulin levels, but lower body fat). In human adipocyte models, knockdown of FAM13A in preadipocytes accelerates adipocyte differentiation. In mice, Fam13a knockout (KO) have a lower visceral to subcutaneous fat (VAT/SAT) ratio after high-fat diet challenge, in comparison to their wild-type counterparts. Subcutaneous adipocytes in KO mice show a size distribution shift toward an increased number of smaller adipocytes, along with an improved adipogenic potential. Our results indicate that GWAS-associated variants within the FAM13A locus alter adipose FAM13A expression, which in turn, regulates adipocyte differentiation and contribute to changes in body fat distribution., Genetic variants in the FAM13A locus have been associated with anthropometric and glycemic traits. Here, using fine-mapping, in vitro knockdown studies in pre-adipocytes and in vivo knockout in mice, the authors show that FAM13A is involved in regulating fat distribution and metabolic traits.

We recently identified human N-acetyltransferase 2 (NAT2) as an insulin resistance (IR) gene. Here we examine the cellular mechanism linking NAT2 to IR and find that Nat1 (mouse ortholog of NAT2) is co-regulated with key regulators of mitochondria. RNA-interference mediated silencing of Nat1 led to mitochondrial dysfunction characterized by increased intracellular reactive oxygen species and mitochondrial fragmentation as well as decreased mitochondrial membrane potential, biogenesis, mass, cellular respiration and ATP generation. These effects were consistent in 3T3-L1 adipocytes, C2C12 myoblasts and in tissues from Nat1 deficient mice including white adipose tissue, heart and skeletal muscle. Nat1 deficient mice had changes in plasma metabolites and lipids consistent with a decreased ability to utilize fats for energy and a decrease in basal metabolic rate and exercise capacity without altered thermogenesis. Collectively, our results suggest that Nat1 deficiency results in mitochondrial dysfunction, which may constitute a mechanistic link between this gene and IR.

Nonsyndromic patent ductus arteriosus (PDA) is a common congenital heart defect (CHD) with both inherited and acquired causes, but the disease mechanisms have remained elusive. Using combined genome-wide linkage analysis and whole-exome sequencing (WES), we identified independent mutations in PRDM6, which encodes a nuclear protein that is specific to vascular smooth muscle cells (VSMC), has histone methyl transferase activities, and acts as a transcriptional suppressor of contractile proteins. In vitro assays showed that the mutations cause loss of function either by intracellular redistribution of the protein and/or by alteration of its methyltransferase activities. Wild-type embryonic ductus arteriosus (DA) exhibited high levels of PRDM6, which rapidly declined postnatally as the number of VSMCs necessary for ductus contraction increased. This dynamic change suggests that PRDM6 plays a key role in maintaining VSMCs in an undifferentiated stage in order to promote their proliferation and that its loss of activity results in premature differentiation and impaired remodeling of the DA. Our findings identify PRDM6 mutations as underlying genetic causes of nonsyndromic isolated PDA in humans and implicates the wild-type protein in epigenetic regulation of ductus remodeling.

BackgroundGenetic analysis has been successful in identifying causative mutations for individual cardiovascular risk factors. Success has been more limited in mapping susceptibility genes for clusters of cardiovascular risk traits, such as those in the metabolic syndrome. MethodsWe identified three large families with coinheritance of early-onset coronary artery disease, central obesity, hypertension, and diabetes. We used linkage analysis and whole-exome sequencing to identify the disease-causing gene. ResultsA founder mutation was identified in DYRK1B, substituting cysteine for arginine at position 102 in the highly conserved kinase-like domain. The mutation precisely cosegregated with the clinical syndrome in all the affected family members and was absent in unaffected family members and unrelated controls. Functional characterization of the disease gene revealed that nonmutant protein encoded by DYRK1B inhibits the SHH (sonic hedgehog) and Wnt signaling pathways and consequently enhances adipogenesis....

We have identified a novel nonconservative mutation in Minibrain related serine/threonine kinase (Mirk/ Dyrk1B) in outlier kindreds with metabolic syndrome. The mutation substitutes cysteine for arginine (R102C) and segregates with most traits of metabolic syndrome, including central obesity, diabetes and hypertension. Oral glucose tolerance test (OGTT) in young nondiabetic mutation carriers revealed insulin resistance compared to noncarrier family members. Since skeletal muscle (SM) is the largest organ for glucose uptake and metabolism, we obtained Vastus Lateralis biopsies of mutation carriers and their unaffected relatives and examined them for gene/protein expression by deep RNA sequencing (RNA-Seq) and Western blot analysis and for fiber composition by immunostaining. The fiber composition data demonstrated fewer slow-twitch fibers (35% vs. 75%) and more fast -twitch fibers (65% vs. 25%) in SM of mutation carriers vs. controls. Interestingly, there were increased protein expression levels of fast-twitch fiber type proteins (MYH11, MYLPF), pyruvate dehydrogenase kinase, pyruvate kinase, and neuronal nitric oxide synthase in SM of mutation carriers vs. noncarriers. Consistent with these findings, the protein expression levels of the master regulator of cellular energy metabolism mitochondrial biogenesis, PPAR-gamma coactivator (PGC-1a), were reduced and the nuclear expression levels of FOXO1 and NFAT were increased. Similar findings were observed when wildtype and mutant (R102C) Dyrk1B were overexpressed in C2C12 cells. The overexpression of the kinase deficient Dyrk1B (Y271/273F) similarly resulted in reduced expression of PGC-1a and increased expression of nuclear FOXO1, suggesting kinase independent effects. Taken together, these findings suggest that enhanced kinase-independent activities of Dyrk1B, either through increased expression or by its gain of function mutation R102C induce insulin resistance by promoting glycolytic metabolism and reducing oxidative phosphorylation. In conclusion, Dyrk1B is a potential target for development of novel drugs that aim to enhance skeletal muscle insulin sensitivity.

A rare mutation in LRP6 has been shown to underlie autosomal dominant coronary artery disease (CAD) and metabolic syndrome in an Iranian kindred. The prevalence and spectrum of LRP6 mutations in the disease population of the United States is not known. Two hundred white Americans with early onset familial CAD and metabolic syndrome and 2,000 healthy Northern European controls were screened for nonconservative mutations in LRP6. Three novel mutations were identified, which cosegregated with the metabolic traits in the kindreds of the affected subjects and none in the controls. All three mutations reside in the second propeller domain, which plays a critical role in ligand binding. Two of the mutations substituted highly conserved arginines in the second YWTD domain and the third substituted a conserved glycosylation site. The functional characterization of one of the variants showed that it impairs Wnt signaling and acts as a loss of function mutation.

Population based genetic counseling that promotes public health goals is an appropriate health care service. The genetic counseling center in Shiraz, southern Iran serves most of the clients in the region. During a 4-year period, 2,686 couples presented for genetic counseling. Data files revealed that 85% had consanguineous relationships (1.5% double first cousin, 74% first cousin, 8% second cousin, 1.5% beyond second cousin). Most prevalent reasons for referral were premarital counseling (80%), with 89% consanguinity, followed by preconception (12%), postnatal (7%), and prenatal counseling (1%). The most common abnormalities in probands or relatives were intellectual and developmental disabilities, hearing loss/impairment, and neuromuscular dystrophies. Family history of medical problem(s) and/or consanguinity was the main indication for referral in nearly every family. Premarital consanguinity poses unique challenges and opportunities. There is considerable opportunity for genetic counseling and education for couples in this population. The tradition of consanguinity, which is likely to persist in Iran, requires multidisciplinary agreement regarding the appropriate process of genetic counseling. Effective genetic counseling in Iran hinges on inclusion of data from genetic counseling services in national genomic and epidemiologic research programs.

Background: Apolipoprotein E (apoE) with three major alleles E2, E3 and E4 is one of the critical genes in lipid metabolism. Common apoE alleles are in association with an increase in risk for central nervous and cardiovascular diseases such as Alzheimer’s disease, dementia, multiple sclerosis, atherosclerosis, coronary heart disease, hyperlipoproteinemia and stroke. ApoE3 is known as the most frequent allele in all populations, while association of apoE gene polymorphism with reported diseases have mostly been related to other two major alleles especially apoE4. Objective: To determine of apoE alleles frequencies in Southern Iran and comparison of those frequencies with other populations. Methods: DNA was extracted from the whole blood of 198 healthy unrelated candidates from population of Fars Province, Southern Iran, for apoE genotyping who were checked up by a physician. The frequencies of apoE alleles were compared with other populations by χ2 test. Results: The frequencies of E2, E3 and E4 were 0.063, 0.886 and 0.051 respectively. These values were similar to those reported from populations of Kuwait, Oman, Lebanon, India, Turkey, Greece, Spain, Sardinia Islands of Italy and two Iranian populations but were different from South of Italy and Caucasians in other Europe regions, American, American-Indian, African, East Asian and Saudi populations (P

Left ventricular (LV) failure is the main cause of death in thalassemia. Iron overload in patients with thalassemia leads to the formation of oxygen free radicals. Of the various apolipoprotein E (apoE) alleles, apoE4 is the least efficient in conditions of oxidative stress in comparison with apoE2 and apoE3. Our results showed that apoE4 is a genetic risk factor for LV dysfunction in thalassemia.