The genetic basis of deafness in populations of African descent

Abstract

Hearing loss is the most common sensorineural disorder worldwide and is associated with more than 1000 mutations in more than 90 genes. While mutations in genes such as GJB2 (gap-junction protein β 2) and GJB6 (gap-junction protein β 6) are highly prevalent in Caucasian, Asian, and Middle Eastern populations, they are rare in both native African populations and those of African descent. The objective of this paper is to review the current knowledge regarding the epidemiology and genetics of hearing loss in African populations with a focus on native sub-Saharan African populations. Environmental etiologies related to poor access to healthcare and perinatal care account for the majority of cases. Syndromic etiologies including Waardenburg, Pendred and Usher syndromes are uncommon causes of hearing loss in these populations. Of the non-syndromic causes, common mutations in GJB2 and GJB6 are rarely implicated in populations of African descent. Recent use of next-generation sequencing (NGS) has identified several candidate deafness genes in African populations from Nigeria and South Africa that are unique when compared to common causative mutations worldwide. Researchers also recently described a dominant mutation in MYO3a in an African American family with non-syndromic hearing loss. The use of NGS and specialized panels will aid in identifying rare and novel mutations in a more cost- and time-effective manner. The identification of common hearing loss mutations in indigenous African populations will pave the way for translation into genetic deafness research in populations of African descent worldwide.

Mutation analysis of common deafness genes among 1,201 patients with non‐syndromic hearing loss in Shanxi Province

“…Together with our results, the c.235delC mutation in GJB2 shows the highest frequency in the Chinese population, followed by c.299‐300delAT with a frequency of 2.67% (32/1,201). It was reported that GJB2 mutations are also associated with a large proportion of non‐syndromic deafness patients in Austria and Africa (Parzefall et al, ; Rudman et al, ). Twenty‐five patients were found to carry heterozygous mutation of GJB2 c.109G>A, accounting for 2.08% (25/1,201).…”

The Hearing Impairment Ontology: A Tool for Unifying Hearing Impairment Knowledge to Enhance Collaborative Research

“…The 'Disease Attribute' class (see Figure 5) incorporates content similar to the SCDO's 'Association' class but notably also includes a 'Disease Cause' sub-class, which was found necessary due to the varied and often complex causes of hearing impairments [19][20][21][22]. The 'Disease Cause' class contains the term 'Unknown Etiology' and the two subclasses 'Environmental Disease Cause' and 'Intrinsic Disease Cause' [23][24][25], which are populated comprehensively with factors that cause or contribute in some way to HI. The 'Modifier' class includes the SCDO's 'Disease Modifier' upper class as a sub-class, along with a new 'Disease Cause Modifier' class.…”

Enhancing Genetic Medicine: Rapid and Cost-Effective Molecular Diagnosis for a GJB2 Founder Mutation for Hearing Impairment in Ghana

“…Globally, the most prevailing sensorineural disorder is hearing impairment (HI) [1], which accounts for about 466 million people worldwide [2]. According to the World Health Organization fact sheet, an estimate of 900 million people will be living with the condition by the year 2050 [2].…”

“…According to the World Health Organization fact sheet, an estimate of 900 million people will be living with the condition by the year 2050 [2]. Over 119 genes [3] with more than 1000 mutations have been associated with hearing impairment of varied degrees in different populations [1]. Gap-junction protein β 2 (GJB2) and gap-junction protein β 6 (GJB6) are the most common genes associated with the condition globally, with high prevalence reported in the European and Asian populations.…”