Introduction
The common heritable condition of Bicuspid Aortic Valve (BAV) is phenotypically heterogeneous, with valve dysfunction and aortopathy the major complications. We report overrepresentation of rare, likely pathogenic variants in target genes in a large cohort of 176 patients with BAV. We also describe a more severe aortic phenotype in patients with more than one known or likely pathogenic variant, supporting a multi-hit hypothesis for development of complications of BAV.
Methods
We recruited 176 patients with BAV without known syndromic basis from two large tertiary referral centres. Phenotyping was performed with routine clinical MRI and/or echocardiography.
We identified 63 genes of interest with known or suspected links to BAV or to aortic /aortic valve (AV) pathology. We used genomic DNA from our patients for NGS of these target genes.
Control populations were provided by the Exome Variant Server (EVS; 6503 samples) and 1000 genomes project. We analysed called variants in silico , usingSIFT, Polyphen2, Grantham scoring and phastCONS, and categorised variants into the following groups based on likely pathogenicity using a combination of in silico tools: known links with disease, likely, possible, and unlikely pathogenicity.
Results
10 patients (5.7% of our cohort) had variants previously associated with aortic or AV pathology or with abnormalities of smooth muscle function; 3 in GATA5, 2 in FBN1, 2 in MYH11, 1 in NOTCH1 and 1 in COL3A1.
In silico analysis identified 45 further instances of 31 likely pathogenic, rare variants in 33 patients (a further 19% of our cohort), in 11 different genes: GATA5 (see Table 1), NOTCH1 (see Figure 1), MYH11, PLOD3, FBN1, MMP9, NKX2–5, JAG1, ACE, ENG, PDIA2 and KCNJ2.
Abstract 95 Figure 1
3D structure of NOTCH1 showing position of likely pathogenic variant Val2119Glu in intracellular signalling domain
The combined prevalence of these known or likely pathogenic variants in our cohort was significantly greater than in the EVS control populations (p < 0.0001).
10 patients had known or likely pathogenic variants in more than one gene of interest. These 10 patients had a significantly higher prevalence of significant aortopathy and/or coarctation of the aorta than the rest of our cohort (6/10 vs 20/176; p = 0.0006).
Abstract 95 Table 1
Classification of previously identified (red) / likely (orange) pathogenic variants found in our cohort in GATA5: example of analysis
Base change
c.8A >G
c.56C >G
c.1173G >T
c.698T >C
Amino acid change
p.Gln3Arg
p.Ser19Trp
p.Trp391Cys
p.Leu233Pro
dbSNP ID
rs113068438
rs200383755
Novel
rs116164480
No. of alleles in our cohort
3
1
1
1
Minor Allele Frequency (from EVS)
0.00328
0
0
0.00108
Polyphen 2 score
0.891 (possibly damaging)
1 (probably damaging)
1 (probably damaging)
0.723 (possibly damaging)
SIFT score
0.003 (damaging)
0.001 (damaging)
0.000 (damaging)
0.039 (damaging)
Grantham difference
43
177
214
98
phastCONS score
0.997
-
-
1
Previous evidence of pathogenicity
Previously associated with BAV; varian...