Screening for Mitochondrial A1555G Mutation among Assortative Mating Hearing Impaired Families in South India: Some Vital Insights

Genetic research into the mechanism of non-syndromic hearing loss (NSHL) have been hampered by a number of issues, including genetic variability, various phenotypes, consanguinity, and marriages between hearing impaired people. In numerous populations, the A1555G mutation in the MT-RNR1 gene has been found as one of the most prevalent mitochondrial mutations, and it has been linked to both NSHL and aminoglycoside-induced ototoxicity.

The goal of this study was to look for the prevalence of the mitochondrial A1555G mutation in hearing impaired families from South India who were assortatively mating.

Due to the variable phenotypic expressivity of this mutation, all family members (hearing and hearing impaired) in 106 assortatively mating hearing impaired families (60 DXD and 46 DXN mating type), totaling 616 members (277 HI individuals and 339 normal hearing family members) were screened for the presence of the A1555G mutation using the PCR-RFLP method. Mitochondrial A1555G mutation in the 12SrRNA gene was identified using the PCR-RFLP approach and validated using direct sequencing of the complete 12SrRNA gene with appropriate primers.

In addition, all A1555G mutation carriers and their family members were examined for GJB2 gene mutations using a direct sequencing approach.

Results: We detected seven members in a family with symptoms ranging from normal hearing to fairly severe hearing loss who had this mutation with unambiguous matrilineal transmission after screening 616 members from 106 assortatively mated families for the A1555G mitochondrial DNA mutation.

Conclusions: The A1555G mutation in the 12SrRNA gene has been linked to both non-syndromic hearing loss and aminoglycoside-induced ototoxicity, and it is one of the most prevalent mitochondrial mutations. This is the first data from India on the prevalence of the A1555G mutation in normal hearing people, suggesting the urgent need to screen for this widespread mitochondrial mutation on a massive scale, not just among hearing impaired families, but also among the general Indian community.

Author (s) Details

Pavithra Amritkumar
Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai 600113, India and Post Graduate and Research Department of Biotechnology, Women’s Christian College, Chennai-600006, India.

C. R. Srikumari Srisailapathy
Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai 600113, India.

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