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Dilated cardiomyopathy (DCM) represents the most frequent form of cardiomyopathy, leading to heart failure, cardiac arrhythmias and death. Accumulating evidence convincingly demonstrates the crucial role of genetic defects in the pathogenesis of DCM, and over 100 culprit genes have been implicated with DCM. However, DCM is of substantial genetic heterogeneity, and the genetic determinants underpinning DCM remain largely elusive. Whole-exome sequencing and bioinformatical analyses were implemented in a consanguineous Chinese family with DCM. A total of 380 clinically annotated control individuals and 166 more DCM index cases then underwent Sanger sequencing analysis for the identified genetic variation. The functional characteristics of the variant were delineated by utilizing a dual-luciferase assay system. A heterozygous variation in the MEF2A gene (encoding myocyte enhancer factor 2A, a transcription factor pivotal for embryonic cardiogenesis and postnatal cardiac adaptation), NM_001365204.1: c.718G>T; p. (Gly240*), was identified, and verified by Sanger sequencing to segregate with autosome-dominant DCM in the family with complete penetrance. The nonsense variation was neither detected in 760 control chromosomes nor found in 166 more DCM probands. Functional analyses revealed that the variant lost transactivation on the validated target genes MYH6 and FHL2, both causally linked to DCM. Furthermore, the variation nullified the synergistic activation between MEF2A and GATA4, another key transcription factor involved in DCM. The findings firstly indicate that MEF2A loss-of-function variation predisposes to DCM in humans, providing novel insight into the molecular mechanisms of DCM and suggesting potential implications for genetic testing and prognostic evaluation of DCM patients. [ABSTRACT FROM AUTHOR]

Introduction: As the most frequent type of birth defect in humans, congenital heart disease (CHD) leads to a large amount of morbidity and mortality as well as a tremendous socioeconomic burden. Accumulating studies have convincingly substantiated the pivotal roles of genetic defects in the occurrence of familial CHD, and deleterious variations in a great number of genes have been reported to cause various types of CHD. However, owing to pronounced genetic heterogeneity, the hereditary components underpinning CHD remain obscure in most cases. This investigation aimed to identify novel genetic determinants underlying CHD., Methods and Results: A four-generation pedigree with high incidence of autosomal-dominant CHD was enrolled from the Chinese Han race population. Using whole-exome sequencing and Sanger sequencing assays of the family members available, a novel SOX7 variation in heterozygous status, NM_031439.4: c.310C>T; p.(Gln104*), was discovered to be in co-segregation with the CHD phenotype in the whole family. The truncating variant was absent in 500 unrelated healthy subjects utilized as control individuals. Functional measurements by dual-luciferase reporter analysis revealed that Gln104*-mutant SOX7 failed to transactivate its two important target genes, GATA4 and BMP2 , which are both responsible for CHD. In addition, the nonsense variation invalidated the cooperative transactivation between SOX7 and NKX2.5, which is another recognized CHD-causative gene., Conclusion: The present study demonstrates for the first time that genetically defective SOX7 predisposes to CHD, which sheds light on the novel molecular mechanism underpinning CHD, and implies significance for precise prevention and personalized treatment in a subset of CHD patients., Competing Interests: None., (AJTR Copyright © 2022.)

Congenital heart defect (CHD) represents the most common birth deformity, afflicting 1% of all births worldwide, and accounts for substantial morbidity and mortality. Increasing evidence highlights the pivotal roles of genetic etiologies in the pathogenesis of CHD, and pathogenic mutations in multiple genes, including TBX5 encoding a cardiac core transcription factor key to cardiovascular morphogenesis, have been involved in CHD. However, due to pronounced genetic heterogeneity of CHD, the genetic determinants underlying CHD in most cases remain obscure. In this investigation, by sequencing analysis of the coding exons and flanking introns of the TBX5 gene in 198 unrelated patients affected with CHD, a novel heterozygous mutation, NM_000192.3: c.692C>T; p. (Pro231Leu), was identified in an index patient with familial double outlet right ventricle (DORV), ventricular septal defect (VSD), and atrioventricular block (AVB). Genetic analysis of the proband's pedigree showed that the mutation co-segregated with the diseases. The missense mutation, which altered the amino acid conserved evolutionarily, was absent from 266 unrelated healthy subjects. Functional analyses with a dual-luciferase reporter assay system unveiled that the Pro231Leu-mutant TBX5 was associated with significantly reduced transcriptional activity on its target genes MYH6 and NPPA. Furthermore, the mutation disrupted the synergistic transactivation between TBX5 and NKX2-5 as well as GATA4, two other transcription factors causally linked to CHD. This study firstly links TBX5 loss-of-function mutation to familial DORV, VSD, and AVB, which provides novel insight into the mechanism underpinning CHD and AVB, suggesting potential implications for genetic evaluation and individualized treatment of patients affected by CHD and AVB.