GJB2 and MTRNR1 contributions in children with hearing impairment from Northern Cameroon

Abstract

Abstract

Objective: the aim of this work was to evaluate the possible different impacts of genetic and environmental factors in childhood deafness in northern Cameroon. GJB2 mutations are responsible for more than half of all cases of prelingual nonsyndromic recessive deafness in Caucasians, representing the most important deafness-causing factor in the industrialized world. Other genes such as MTRNR1 are also involved. In sub-Saharan Africa, environmental factors seem to dominate genetic contributions, but few studies on the etiology of deafness in Africa are available for comparison. Design: prospective cross sectional study. Study Sample: we performed a molecular screen of the GJB2 and MTRNR1 genes in 70 deaf children and 67 unaffected controls in Maroua (Cameroon) and a literature analysis focused on deafness epidemiology in developing countries. Results: no GJB2 mutations emerged, and only a single MTRNR1 variant that may be pathogenic was found. Conclusion: environmental factors turn out to be more relevant than genetic factor in the Maroua population.

Sumario

Objetivo: la finalidad de esta investigación es la de evaluar los diferentes y posibles impactos que los factores genéticos y ambientales tienen en la sordera infantil en el norte de Camerún. La mayoría de los casos de hipoacusia prelingual no sindrómica en los caucásicos se debe a las mutaciones GJB2 que representan también la causa más importante de sordera en el mundo industrializado. Hay otros genes implicados como el gen MTRNR1. En el África subsahariana son los factores ambientales los que parecen aportar mayor contribución y no los genéticos, pero hay pocos estudios sobre la etiología de la sordera en África para hacer una comparación. Modalidad de estudio: Estudio prospectivo trasversal. Muestra representativa del estudio: 70 niños sordos sometidos a screening molecular de los genes GJB2 y MTRNR1 y 67 revisiones sobre individuos no enfermos en Maroua (Camerún) y un análisis específico sobre la epidemiología de la sordera en los países del tercer mundo/en desarrollo. Resultados: No han aparecido mutaciones de GJB2 y se ha encontrado una única variación del gen MTRNR1 que podría ser patógena. Conclusiones: En la población de Maroua resulta que es el factor ambiental el que tiene mayor relevancia, respectivamente más relevante que el factor genético.

Key Words::

• Childhood hearing loss
• Connexin 26
• GJB2
• MTRNR1
• Cameroon
• sub-Saharan Africa

Acknowledgements

We thank all of the staff of the Bethlem Foundation in Maroua for their help, and all children who hopefully and enthusiastically participated in the study. We also thank Dr. A. Piccinini (Università degli Studi di Milano, Istituto di Medicina Legale - Laboratorio di Genetica forense), who shared part of his technical expertise. Finally, we sincerely thank Associazione Ascolta e Vivi, Milan, who partially granted this research, and its former President, dott. Elena Amigoni, whose kind help goes further than just this work.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.