Novel compound heterozygous mutations in SLC26A4 gene in a Chinese family with enlarged vestibular aqueduct.

In order to investigate the genetic causes of hearing loss in a Chinese proband with nonsyndromic hearing loss and enlarged vestibular aqueduct (EVA), we conducted clinical and genetic evaluations in a deaf proband and her parents with normal hearing. 20 exons and flanking splice sites of the SLC26A4 gene were screened for pathogenic mutations by PCR amplification and bidirectional sequencing. As a control, a group of 400 healthy newborns from the same ethnic background were subjected to SLC26A4 gene screening using the same method. The proband harbored two mutations in the SLC26A4 gene in the form of compound heterozygosity. She was found to be heterozygous for a novel mutation c.574delC (p.Leu192Ter) in exon 5 and for the known mutation c.919-2A>G(c.IVS7-2A>G). Her mother was a heterozygous carrier of the c.919-2A>G mutation, and her father was a heterozygous carrier of the c.574delC and therefore co-segregated with the genetic disease. The c.574delC mutation was absent in 400 healthy newborns. The frameshift mutation causes the leucine (Leu) at amino acid position 192 to become a termination codon, leading to termination of protein sequence coding. This study demonstrates that the novel frameshift mutation c.574delC (p.Leu192Ter) in compound heterozygosity with c.919-2A>G in the SLC26A4 gene is the main cause of deafness in a family. Our study will expand the spectrum of known SLC26A4 mutations in the Chinese population, providing more information on genetic counseling, and diagnosis in hearing loss with EVA.