The rocky road toward clinical genetic testing: insights into the physio-genetic basis of hearing loss

Application of SNPscan in Genetic Screening for Common Hearing Loss Genes

The current study reports the successful application of a fast and efficient genetic screening system for common hearing loss (HL) genes based on SNPscan genotyping technology. Genetic analysis of 115 variants in common genes related to HL, GJB2, SLC26A4 and MT-RNR, was performed on 695 subjects with non-syndromic hearing loss (NSHL) from the Northern China. The results found that 38.7% (269/695) of cases carried bi-allelic pathogenic variants in GJB2 and SLC26A4 and 0.7% (5/695) of cases carried homoplasmic MT-RNR1 variants. The variant allele frequency of GJB2, SLC26A4 and MT-RNR1 was 19.8% (275/1390), 21.9% (304/1390), and 0.86% (6/695), respectively. This approach can explain ~40% of NSHL cases and thus is a useful tool for establishing primary molecular diagnosis of NSHL in clinical genetics.

The role and spectrum of SLC26A4 mutations in Iranian patients with autosomal recessive hereditary deafness

OBJECTIVE

To determine the prevalence and types of SLC26A4 mutations and the relevant phenotypes in a series of Iranian deaf patients.

DESIGN

A descriptive laboratory study.

STUDY SAMPLE

One hundred and twenty-one families including 60 unrelated patients and 61 unrelated multiplex families with autosomal recessive deafness were included. In the 61 multiplex families, linkage was conducted for short tandem repeats (STRs) of the DFNB4. Selected individuals from the linked families and all of the 60 deaf individuals were subjected to sequencing of SLC26A4.

RESULTS

Seven out of the 61 (11.5%) families were linked to the locus which upon further inquiry led to identification of eight different mutations. Also, five out of the 60 (8.3%) patients were positive for the mutations. The SLC26A4 mutations clarified in 9.1% (12 families) of total investigated alleles included: c.2106delG, c.65-66insT, c.881-882delAC, c.863-864insT, c.1226G> A, c.1238A> G, c.1334T> G, c.1790T> C, c.1489G> A, c.919-2A> G (IVS7-2A> G), c.1412delT, and c.1197delT. Six out of 12 (50%) families with mutations were confirmed to be Pendred syndrome (PS).

CONCLUSIONS

The results probably suggest a high prevalence and specificity of SLC26A4 mutations among Iranian deaf patients. Molecular study of SLC26A4 may lead to elucidation of the population-specific mutation profile which is of importance in diagnostics of deafness.