A. O. Lasisi1, B. O. Yusuf2, B. O. Adedokun2, K. Omokanye3, A. O. Afolabi3, T. J. Lasisi4, F. Olatoke6, O. A. Sulaiman7, S. A. Ogunkeyede8, A. A. Salman8, A. O. Oluokun8, A. M. Oriyomi7, W. A. Adedeji5, H. O. Lawal9, M. O. Kelani9, T. Yusuf10, G. Bademci11, J. Foster II11, S. Blanton11, M. Tekin11 1Dept. of Otorhinolaryngology, University of Ibadan and Ladoke Akintola University Teaching Hospital, Osogbo, Nigeria 2Dept. of Epidemiology and Statistics, University of Ibadan, Nigeria 3Dept. of Otolaryngology, University of Ilorin, Ilorin Nigeria 4Dept of Physiology, University of Ibadan 5Dept. of Clinical Pharmacology, University College Hospital, Ibadan, Nigeria 6Dept. of Otolaryngology, Federal Medical Center, Lokoja 7Dept. of Otolaryngology, Federal Medical Center, Katsina 8Dept of Otorhinolaryngology, Ladoke Akintola University, Ogbomoso 9Dept of Otorhinolaryngology, General Hospital, Maitama, Abuja, Nigeria 10Department of Otorhinolaryngology, University College Hospital, Ibadan 11Dr. John T. Macdonald Foundation Department of Human Genetics and John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
Introduction:
The prevalence of deafness is high in sub Saharan Africa. The WHO reported the prevalence of hearing loss affecting communication in children in sub Saharan Africa (SSA) to be 1.8%, second only to the south Asia region (2.3%) [2] However, there is need for a recent survey to document an up to date figure in Nigeria among other SSA. Importantly too, the role of genetics have only been sparsely documented despite the fact that in Europe, America and Asia, genetics contributed about 50% of deafness and the main mutations include GJB2, GJB6, SLC26A4 and mitochondrial DNA 1555A>G among others. This Cross National Survey of Deafness started as collaboration between the University of Miami Florida, USA and my institution and it was sponsored by the grants from the National Institute of Health and Tertiary Education Trust Fund of Nigeria. This survey is aimed at determining critical epidemiological determinants of hereditary deafness and documenting the genetic mutations responsible for deafness among Nigerians
Method:
This survey was carried out in 6 states spread in 5geopolitical zones of Nigeria including all the major tribes – Hausa, Yoruba and Ibo. The participants were selected from various vocational and professional groups, schools and religious groups and using questionnaire, deafness was identified as hereditary and acquired. Blood samples were collected from those identified with hereditary deafness and DNA was extracted using a salting-out method with Qiagen, followed by genotyping using Sanger and Next Generation sequencing for the identification of the gene mutation. This study had ethical approval from the Ethics Committee of the Joint UI/University College Hospital Ibadan and the University of Miami.
Result:
There were 2600 deaf subjects, made up of 63% males and 37% females. The age at detection of deafness ranged between 0 and 8years, (mean=2.37±2.035). Molecular analysis identified a novel POU3f4 mutation involving c.987T>C; p.(Ile308Thr) in 5year old Nigeria from Yoruba ethnic group. However, the analyses did not identify a pathogenic or polymorphic variant in GJB2, GJB6, SLC26A4 and mitochondrial DNA 1555A>G genes. The important epidemiologic variables which significantly mitigated interest in genetic testing include male respondents and low level of education.
Conclusion:
Mutations in POU3f4 is the first documented gene mutation responsible for deafness among Nigerians, in addition, GJB2, GJB6, SLC26A4 and mitochondrial DNA 1555A>G gene mutations are not common causes of deafness in Nigeria. This suggests that this region may harbour uniquely infrequent genetic causes (compared to the rest of the world) of hearing loss and provides the impetus for conducting further genetic studies in the SSA. The use of the epidemiologic data in underpinning deafness control policy in SSA is discussed.