Identification of clinically significant variants in genes of cardiovascular embryonic development in sporadic ascending aortic aneurysm and “bovine aortic arch”

Introduction. Aortic arch anomalies, especially the “bovine arch”, can cause the development of an ascending aortic aneurysm. There is a high coefficient of heritability of this pathology, however, genetic studies are rare. Since the “bovine arch” is one of the variants of the development of the aortic arch and large vessels during embryogenesis, this pathology may be associated with genes encoding proteins involved in the embryonic development of the cardiovascular system.

Aim: To identify rare, clinically significant variants of genes of cardiovascular embryonic development in patients with sporadic ascending aortic aneurysm and a “bovine arch”.

Material and Methods. The study included 42 patients with a sporadic form of ascending aortic aneurysm, including 11 patients with a “bovine arch”. Analysis of the clinical exome was performed based on DNA sequencing data using Clinical Exome Solution (Sophia Genetics, Switzerland) and NextSeq 500 genetic sequencer (Illumina, USA). The search for rare, clinically significant variants (minor allele frequency <1%) was carried out in exons and adjacent introns of 120 genes of embryonic development of the cardiovascular system. Validation of identified variants was performed using Sanger sequencing.

Results. In patients with aortic aneurysm and “bovine arch”, the following clinically significant variants were identified: the pathogenic variant c.610-2A>G of the CCDC39 gene, which is a single-nucleotide substitution leading to the loss of the acceptor splice site (ΔScore = 0.97 Spliceailookup) and a variant of uncertain clinical significance (VUS) c.2564T>C in the ANKS6 gene, which has high pathogenicity rates on the CADD (Phred = 28.3) and AlphaMissense (0.972) scales. A likely pathogenic variant c.1151T>C of the ACVR2B gene was identified in the group of patients with aortic aneurysm without supraaortic vessels anomaly (AlphaMissense = 0.966). Among the 38 genes whose sequences revealed VUS in both groups of patients, the protein products of 17 (44.7%) are involved in the functioning of cilia and microtubules, and the proteins encoded by the genes MKS1, CCDC40, DNAAF1, ANKS6, CCDC39, DNAH5, DNAAF3 are also responsible for the development of the cardiovascular system.

Conclusion. Rare, clinically significant variants in the CCDC39 and ANKS6 genes, which are crucial for primary cilia function, contribute to the development of sporadic ascending aortic aneurysm in combination with a “bull’s arch.” When a normal aortic arch is present, variants in the ACVR2B gene, belonging to the TGF-beta signaling protein superfamily, play an important role.

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