Genetics of non-syndromic hearing loss in the Middle East

Hearing impairment is the most common sensory disorder, present 1 in every 500 newborns. About 80% of genetic HL is classified as non-syndromic deafness. To date, over 115 non-syndromic loci have been identified of which fifty associated with autosomal recessive non-syndromic hearing loss (ARNSHL). In this review article, we represent the 40 genes function and contribution to genetic deafness in different Middle Eastern populations as well as gene frequencies and mutation spectrum. The wide variety of mutations have so far detected in 19 countries reflects the heterogeneity of the genes involved in HL in this region. The deafness genes can cause dysfunction of cochlear homeostasis, cellular organization, neuronal transmission, cell growth, differentiation, and survival, some coding for tectorial membrane-associated proteins, and the remaining with unknown functions. Non-syndromic deafness is highly heterogeneous and mutations in the GJB2 are responsible for almost 30-50% in northwest to as low as 0-5% in south and southeast of the Middle East, it remain as major gene in ARNSHL in Middle East. The other genes contributing to AR/ADNSHL in some countries have been determined while for many other countries in the Middle East have not been studied or little study has been done. With the advancement of next generation sequencing one could expect in next coming year many of the remaining genes to be determine and to understand their function in the inner ear.