DNA Sequence Analysis of SLC26A5, Encoding Prestin, in a Patient-Control Cohort: Identification of Fourteen Novel DNA Sequence Variations

Prestin, encoded by the gene SLC26A5, is a transmembrane protein of the cochlear outer hair cell (OHC). Prestin is required for the somatic electromotile activity of OHCs, which is absent in OHCs and causes severe hearing impairment in mice lacking prestin. In humans, the role of sequence variations in SLC26A5 in hearing loss is less clear. Although prestin is expected to be required for functional human OHCs, the clinical significance of reported putative mutant alleles in humans is uncertain.To explore the hypothesis that SLC26A5 may act as a modifier gene, affecting the severity of hearing loss caused by an independent etiology, a patient-control cohort was screened for DNA sequence variations in SLC26A5 using sequencing and allele specific methods. Patients in this study carried known pathogenic or controversial sequence variations in GJB2, encoding Connexin 26, or confirmed or suspected sequence variations in SLC26A5; controls included four ethnic populations. Twenty-three different DNA sequence variations in SLC26A5, 14 of which are novel, were observed: 4 novel sequence variations were found exclusively among patients; 7 novel sequence variations were found exclusively among controls; and, 12 sequence variations, 3 of which are novel, were found in both patients and controls. Twenty-one of the 23 DNA sequence variations were located in non-coding regions of SLC26A5. Two coding sequence variations, both novel, were observed only in patients and predict a silent change, p.S434S, and an amino acid substitution, p.I663V. In silico analysis of the p.I663V amino acid variation suggested this variant might be benign. Using Fisher's exact test, no statistically significant difference was observed between patients and controls in the frequency of the identified DNA sequence variations. Haplotype analysis using HaploView 4.0 software revealed the same predominant haplotype in patients and controls and derived haplotype blocks in the patient-control cohort similar to those generated from the International HapMap Project.Although these data fail to support a hypothesis that SLC26A5 acts as a modifier gene of GJB2-related hearing loss, the sample size is small and investigation of a larger population might be more informative. The 14 novel DNA sequence variations in SLC26A5 reported here will serve as useful research tools for future studies of prestin

A Protective Mechanism against Antibiotic-Induced Ototoxicity: Role of Prestin

Hearing loss or ototoxicity is one of the major side effects associated with the use of the antibiotics, particularly aminoglycosides (AGs), which are the most commonly used antibiotics worldwide. However, the molecular and cellular events involved in the antibiotic-induced ototoxicity remains unclear. In the present study, we test the possibility that prestin, the motor protein specifically expressed in the basolateral membrane of outer hair cells (OHCs) in the cochlea with electromotility responsible for sound amplification, may be involved in the process of AG-induced apoptosis in OHCs. Our results from both mice model and cultured cell line indicate a previously unexpected role of prestin, in mediating antibiotic-induced apoptosis, the effect of which is associated with its anion-transporting capacity. The observed downregulation of prestin mRNA prior to detectable apoptosis in OHCs and hearing loss in the antibiotic-treated mice is interesting, which may serve as a protective mechanism against hearing loss induced by AGs in the early stage

Stem Cell Therapy: Pieces of the Puzzle

Acute ischemic injury and chronic cardiomyopathies can cause irreversible loss of cardiac tissue leading to heart failure. Cellular therapy offers a new paradigm for treatment of heart disease. Stem cell therapies in animal models show that transplantation of various cell preparations improves ventricular function after injury. The first clinical trials in patients produced some encouraging results, despite limited evidence for the long-term survival of transplanted cells. Ongoing research at the bench and the bedside aims to compare sources of donor cells, test methods of cell delivery, improve myocardial homing, bolster cell survival, and promote cardiomyocyte differentiation. This article reviews progress toward these goals