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Kids First: Congenital Heart Defects and Laterality Birth Defects

Laterality defects occur in approximately 1:10,000 newborns and are associated with a range of structural birth defects and abnormalities of organ positioning. Gut malrotation, biliary atresia, asplenia or polysplenia, complex cardiovascular malformations, and midline defects such as neural tube defects, vertebral anomalies and rib fusions are found in various combinations in patients with laterality defects. In addition, a subset of laterality defects caused by abnormalities of cilia position or function are associated with additional medical problems such as chronic sinusitis and bronchiectasis that require specific preventive care; however these patients frequently are undiagnosed until late in disease course. The goal of this project is to elucidate the genetic architecture of laterality disorders in order to inform medical management and risk stratification and to prevent complications. Laterality disorders are genetically heterogeneous and we and others have previously identified single nucleotide variants inherited in an X-linked or autosomal recessive manner as explanations for a minority of cases. In addition, we have demonstrated copy number variants (CNVs) as a mechanism of disease that requires additional investigation. We hypothesize that the majority of cases result from complex genetic inheritance. We propose to investigate this hypothesis using a multifaceted analysis approach in our extremely well phenotyped cohort of 538 probands with laterality disorders. Nested within this cohort are 105 trios who have not had previous sequencing, probands who have had exome sequencing and are excellent candidates for gene discovery via whole genome sequencing (WGS), and families with multiple affected family members for family-based analysis. All trios will be analyzed by transmission disequilibrium test (TDT) including rare variant TDT. De novo mutations will also be identified from trios for potential gene discovery. Using all probands, we will identify the prevalence of pathogenic CNVs. In addition, we will perform burden analyses to identify genes, gene interactions, and pathways important for susceptibility to laterality disorders. Finally, our rare families with multiple affected members will be studied using family based segregation analysis. This comprehensive genetic analysis in patients with laterality disorders is necessary to identify the appropriate clinical diagnostic testing for risk stratification, to elucidate underlying genetic architecture and facilitate novel gene discovery, and to provide essential knowledge about genes and pathways impacting the development of laterality disorders.