Contribution of NOTCH1 genetic variants to bicuspid aortic valve and other congenital lesions

INTRODUCTION: Bicuspid aortic valve (BAV) affects 1% of the general population. NOTCH1 was the first gene associated with BAV. The proportion of familial and sporadic BAV disease attributed to NOTCH1 mutations has not been estimated. AIM: The aim of our study was to provide an estimate of familial and sporadic BAV disease attributable to NOTCH1 mutations. METHODS: The population of our study consisted of participants of the University of Leicester Bicuspid aoRtic vAlVe gEnetic research-8 pedigrees with multiple affected family members and 381 sporadic patients. All subjects underwent NOTCH1 sequencing. A systematic literature search was performed in the NCBI PubMed database to identify publications reporting NOTCH1 sequencing in context of congenital heart disease. RESULTS: NOTCH1 sequencing in 36 subjects from 8 pedigrees identified one variant c.873C>G/p.Tyr291* meeting the American College of Medical Genetics and Genomics criteria for pathogenicity. No pathogenic or likely pathogenic NOTCH1 variants were identified in 381 sporadic patients. Literature review identified 64 relevant publication reporting NOTCH1 sequencing in 528 pedigrees and 9449 sporadic subjects. After excluding families with syndromic disease pathogenic and likely pathogenic NOTCH1 variants were detected in 9/435 (2.1%; 95% CI: 0.7% to 3.4%) of pedigrees and between 0.05% (95% CI: 0.005% to 0.10%) and 0.08% (95% CI: 0.02% to 0.13%) of sporadic patients. Incomplete penetrance of definitely pathogenic NOTCH1 mutations was observed in almost half of reported pedigrees. CONCLUSIONS: Pathogenic and likely pathogenic NOTCH1 genetic variants explain 2% of familial and <0.1% of sporadic BAV disease and are more likely to associate with tetralogy of Fallot and hypoplastic left heart

Analysis of genetic variation within urotensin-II system in regulation of blood pressure and renal function

Elevated blood pressure (BP) and reduced glomerular filtration rate (GFR) are risk factors for cardiovascular disease. BP and GFR are influenced by heritable factors. Only small proportion of this heritability has been explained so far. This project aimed to identify genetic loci contributing to population variation in BP or GFR through application of candidate gene and large scale genotyping approaches. The candidate gene approach utilised tagging single nucleotide polymorphisms (SNP) in genes of the urotensin-II (U-II) pathway in a sample of white European subjects (3 family collections and 5 unrelated subject studies – altogether 10,748 subjects). This was followed by gene expression studies in 2 collections of human kidneys and phylogenetic analysis of the system to examine its evolutionary conservation from fish to human. The large scale genotyping project utilised data from 50K IBC genotyping array in a cohort of families (520 pedigrees) from general population of UK. None of the 28 SNPs in U-II pathway genes was associated with BP or GFR. Gene expression levels of UTS2 and UTS2R were strongly correlated (r=0.83, p<0.0001) but renal expression was not associated with human hypertension. The phylogenetic analysis showed that strong purifying selection acting on this system in lower vertebrates was lost in primates. The large scale genotyping approach showed strong signal of association in the 5,10-methylenetetrahydrofolate reductase (NAD(P)H) gene (MTHFR) locus with clinic diastolic BP. Each minor copy (G) of rs17037388 was associated with 2.03mmHg reduction in clinic diastolic BP (p=3.01x10[superscript -06]). Gene candidate and large scale genotyping approaches performed in parallel provide useful information about genetic architecture of complex traits. The data from genetic association in candidate U-II system genes did not provide evidence on its association with BP or GFR. Large scale genotyping experiment led to identification of genuine association signal with clinic diastolic BP