A novel mutation in TRIOBP gene leading to congenital deafness in a Chinese family.

BACKGROUND The autosomal recessive non-syndromic deafness DFNB28 is characterized by prelingual sensorineural hearing loss. The disease is related with mutations in TRIOBP (Trio- and F-actin-Binding Protein) gene, which has three transcripts referred to as TRIOBP-5, TRIOBP - 4 and TRIOBP-1. Among them, TRIOBP-5/- 4 are expressed in the inner ears and crucial for maintaining the structure and function of the stereocilia. METHODS The proband is a 26-year-old Chinese female. She and her younger brother have being suffered from severe deafness since birth, whereas her parents, who are cousins, have normal communication ability. Hearing impairment of the two siblings was determined by pure tone audiometry. Whole Exome Sequencing (WES) was performed on the genomic DNA of the proband and Sanger sequencing was conducted on the DNA samples of the four family members. RESULTS Tests of pure tone hearing thresholds showed a severe to profound symmetric hearing loss for the proband and her younger brother. Moreover, a novel TRIOBP c.1342C > T (p.Arg448*) variant was identified by WES in the DNA sample of the proband and confirmed by Sanger sequencing in DNA of the family members. CONCLUSIONS The TRIOBP c.1342C > T (p.Arg448*) variant is predicted to disrupt TRIOBP-5 and TRIOBP-4, which may lead to the congenital deafness. The results will broaden the spectrum of pathogenic variants in TRIOBP gene. The characteristics of deafness in the family imply that marriage between close relatives should be avoided.