Identification of a Novel Homozygous Nonsense Mutation in a Fetus with Bardet-Biedl Syndrome

Abstract

Background: Bardet-Biedl syndrome (BBS) is a rare autosomal recessive genetic disorder with clinical and genetic heterogeneity. BBS is more commonly reported in adults and children than in fetuses. Here, we reported the intrauterine phenotype and molecular characterizations of a fetus with BBS. Methods: Chromosome karyotype analysis, whole exome sequencing (WES), and a single nucleotide polymorphism array (SNP-array) were used to analyze the genetic etiology of a fetus with enlarged kidneys, enhanced echo, and oligohydramnios. Results: The results of chromosome karyotype analysis and SNP-array on the fetus were normal. WES, however, revealed homozygous mutation of c.1177C>T (p.Arg393*) on exon 12 of the BBS1 gene, and heterozygous variation of c.2704G>A (p.Asp902Asn) on exon 22 of the CC2D2A gene. According to ACMG guidelines, c.1177C> T was identified as a pathogenic mutation and c.2704G>A was identified as an uncertain significance. Sanger sequencing showed that there was heterozygous mutation of c.1177C>T and heterozygous variation of c.2704G>A in the parents of the fetus. Conclusions: WES identified a novel homozygous nonsense mutation c.1177C>T in the BBS1 gene of a Chinese fetus. The finding provides more insight into BBS1 mutations in Asian populations in general, and provides a basis for genetic counseling.