Cardiomyopathy (CMP) is a heritable disorder. Over 50% of cases are gene-elusive on clinical gene panel testing. The contribution of variants in non-coding DNA elements that result in cryptic splicing and regulate gene expression has not been explored. We analyzed whole-genome sequencing (WGS) data in a discovery cohort of 209 pediatric CMP patients and 1953 independent replication genomes and exomes. We searched for protein-coding variants, and non-coding variants predicted to affect the function or expression of genes. Thirty-nine percent of cases harbored pathogenic coding variants in known CMP genes, and 5% harbored high-risk loss-of-function (LoF) variants in additional candidate CMP genes. Fifteen percent harbored high-risk regulatory variants in promoters and enhancers of CMP genes (odds ratio 2.25, p = 6.70 × 10−7 versus controls). Genes involved in α-dystroglycan glycosylation (FKTN, DTNA) and desmosomal signaling (DSC2, DSG2) were most highly enriched for regulatory variants (odds ratio 6.7–58.1). Functional effects were confirmed in patient myocardium and reporter assays in human cardiomyocytes, and in zebrafish CRISPR knockouts. We provide strong evidence for the genomic contribution of functionally active variants in new genes and in regulatory elements of known CMP genes to early onset CMP.
The tweety genes encode gated chloride channels that are found in animals, plants, and even simple eukaryotes, signifying their deep evolutionary origin. In vertebrates, the tweety gene family is highly conserved and consists of three members—ttyh1, ttyh2, and ttyh3—that are important for the regulation of cell volume. While research has elucidated potential physiological functions of ttyh1 in neural stem cell maintenance, proliferation, and filopodia formation during neural development, the roles of ttyh2 and ttyh3 are less characterized, though their expression patterns during embryonic and fetal development suggest potential roles in the development of a wide range of tissues including a role in the immune system in response to pathogen-associated molecules. Additionally, members of the tweety gene family have been implicated in various pathologies including cancers, particularly pediatric brain tumors, and neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. Here, we review the current state of research using information from published articles and open-source databases on the tweety gene family with regard to its structure, evolution, expression during development and adulthood, biochemical and cellular functions, and role in human disease. We also identify promising areas for further research to advance our understanding of this important, yet still understudied, family of genes.
Cardiomyopathy (CMP) is a heritable genetic disorder. Protein-coding variants account for 20 to 30 percent of cases. The contribution of variants in noncoding DNA elements that regulate gene expression has not been explored. We performed whole genome sequencing (WGS) of 228 unrelated CMP families. Besides pathogenic protein coding variants in known CMP genes, 5% cases harbored rare loss of function variants in novel cardiac genes, with NRAP and FHOD3 being strong candidates. WGS also revealed a high burden of high risk variants in promoters and enhancers of CMP genes in an additional 20 percent cases (Odds ratio 2.14, 95 percent CI 1.60-2.86, p equals 5.26E-07 vs 1326 controls) with genes involved in alpha-dystroglycan glycosylation (FKTN, DTNA) and desmosomal signaling (DSC2, DSG2) specifically enriched for regulatory variants (False discovery rate less than 0.03). These findings were independently replicated in the Genomics England CMP cohort (n=1266). The functional effect of non-coding variants on transcription was functionally validated in patient myocardium and reporter assays in human cardiomyocytes, and that of novel gene variants in zebrafish knockouts. Our results show that functionally active variants in novel genes and in regulatory elements of CMP genes contribute strongly to the genomic etiology of childhood-onset CMP.
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