Researchers in Ghana identify gene responsible for major cause of inherited deafness

A Ghanaian Doctor of Philosophy (PhD) candidate, Mr. Mawuli Adade, has led a team of Ghanaian researchers to identify a gene responsible for a major cause of inherited deafness in the West African country.

With a population of 30 million, Ghana has 16 schools for the deaf and many individuals with hearing impairment on the street begging for alms.

The field research conducted by a research team from the University of Ghana was approved by the Noguchi Memorial Institute for Medical Research Ethical Review Board and the Special Education Unit of the Ghana Education Service.

The Ghana National Association for the Deaf (GNAD) says approximately 0.4 per cent out of Ghana’s population of almost 29 million is deaf, or 110,625 people; by contrast, the Ghana Statistical Service, reports 211,712 as deaf. Whichever the case is, the numbers deserves to be looked into.

The test subjects were pupils from 11 of Ghana’s 16 schools for the hearing impaired by scientists at the West African Centre for Cell Biology of Infectious Pathogens (WACCBIP) at the university.

About 166 individuals with no family hearing impairment history and 97 families with at least two members living with hearing impairment were identified.

With information derived from the participants, a medical geneticist and an ear, nose and throat (ENT) specialist undertook test while blood samples were taken from all available family members for their DNA.

According to graphic.com.gh: “The researchers looked for mutation (alterations in the structure) of the connexin 26 gene, which was earlier identified in 2001 and linked to 50 per cent or more cases of inherited deafness in the 11 schools for the deaf in Ghana and the Adamorobe village near Aburi, where inherited deafness was estimated above the global average. The scientists looked for the GJB2 and GJB6 variants in the blood samples of the 97 families with the hearing impairment and the 166 single cases identified.”

It added: “Although the GJB6 gene, which was found globally, was absent in the Ghanaian cases, the GJB2-R143W gene was found to have accounted for over a quarter of familial hearing impairment cases among the groups that were screened. That suggested that one out of every four families with deafness would have the ‘gene-mistake’.”

It is hoped the discovery will make it possible to offer genetic testing in the country while enabling families know the causative factor for their impairment.

“The findings also indicated a 1.4 per cent carrier frequency rate among 145 healthy Ghanaians who were screened randomly, suggesting that among every 145 Ghanaians, two are likely to carry the defective gene that can be passed on to their children. Known as the Gap junction beta 2 (GJB2) or Connexin 26, the gene directs the production of proteins that make up part of the inner ear. Being recessive, carriers of the gene, who inherit just one defective copy from a parent, have normal hearing. But those with two flawed copies, one from each parent, have hearing loss that can range from moderate to profound,” graphic.com.gh reported.

According to Mr. Adade, the field research revealed genetics was a major contributory factor to hearing impairment in the country adding the carrier rate of GJB2 variants among healthy populations indicated what accounted for an increase in the percentage of GJB2-patients in the country.

To better understand Ghana’s hearing impairment numbers, Mr. Adade is employing next generation sequencing techniques to identify other gene variants, adding, “ultimately, we hope to develop appropriate and cost-effective diagnostic approaches for newborn genetic screening to contribute to the reduction of the burden of the condition in Ghana.”