الفهرس 
Introduction and aim of the work
A brief review of hearing mechanismOnly 14 pages are availabe for public view
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Abstract
Hearing loss (HL) is the most common birth defect in developed countries and the most prevalent sensorineural disorder. HL is an etiologically heterogeneous pathology caused by different genetic and environmental factors with half of the cases estimated to be genetic. Hereditary hearing loss may be either syndromic (SHL), i. e. associated with other disorders or non-syndromic (NSHL). Nonsyndromic hearing loss represents about 70% of cases of genetic hearing loss. The inheritance pattern among the disorders with prelingual nonsyndromic hearing loss is 80% autosomal recessive, 20% autosomal dominant, and 1%-1.5% X-linked, mitochondrial or other.
The prevalence of HL is high in Egypt; it is 13.8 % in the age group between 0-14 years. Genetic hearing loss is found in almost 50% of the cases of pediatric hearing loss in Egypt. Nonsyndromic hereditary hearing loss is characterized by extreme genetic heterogeneity. More than 6,000 causative variants have been identified in more than 110 genes. To my knowledge, there has been no study conducted before about the genetic causes of nonsyndromic hearing loss in the Egyptian population. Detection of genes implicated in NSHL will result in early diagnosis of HL and help to predict the progression of the disease. It will also help to prescribe the optimal rehabilitation for a child’s development.
To identify the genes responsible for hereditary nonsyndromic hearing loss in the Egyptian population, blood samples from 139 subjects representing 37 Egyptian families with nonsyndromic hearing loss were collected. A DNA sample from one affected member of each family was subjected to targeted enrichment of 94 genes or the whole exome and subsequently to massively parallel sequencing.
In 28 out of 37 families, a causative variant could be detected. The causative variants were found in 18 different genes. The majority of these variants (13/24) is novel. The most frequently mutated genes in the analyzed 37 families are SLC26A4 (13.5%) and GJB2 (10.8%), followed by MYO15A (8.1%) and MYO7A (5.4%).
The presumed genetic origin of hearing loss in the nine remaining families could not be identified. In view of the extreme genetic heterogeneity, it is likely that novel HL genes are involved in these families. More blood samples and a more comprehensive analysis approach may be necessary to elucidate the molecular genetic cause in the remaining families.
from the results of this study I conclude that designing a gene panel that includes all known HL genes, at least those associated with nonsyndromic hearing loss in Egyptian families, and applying this technique in a genetic screening of newborns will be very helpful in early diagnosis and efficient management of children suffering from NSHL.