Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 49 11 2020 10 27 2128 2135 Farnoush ALIAZAMI Department of Genetics, Tehran Medical Branch, Islamic Azad University, Tehran, Iran AND Applied Biotechnology Research Center, Tehran Medical Branch, Islamic Azad University, Tehran, Iran Dariush D. FARHUD School of Public Health, Tehran University of Medical Sciences, Tehran, Iran AND Department of Basic Sciences, Iranian Academy of Medical Sciences, Tehran, Iran Marjan ZARIF-YEGANEH Cellular and Molecular Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Siamak SALEHI Institute of Liver Studies, King's College Hospital, London, United Kingdom Azam HOSSEINIPOUR Department of Exceptional Children, Ministry of Education and Training of the Islamic Republic of Iran, Tehran, Iran Roxana SASANFAR Psychiatric and Neurodevelopmental Genetic Unit, Massachusetts General Hospital, Harvard Medical School, Boston, USA Maryam Eslami Department of Genetics, Tehran Medical Branch, Islamic Azad University, Tehran, Iran AND Applied Biotechnology Research Center, Tehran Medical Branch, Islamic Azad University, Tehran, Iran 2019 12 02 2020 06 24 Background: Hearing loss (HL) is one of the most common heterogeneous congenital disabilities worldwide. Gap junction protein β-3 (GJB3) gene encodes Connexin31 protein (Cx31). The hereditary type of hearing impairment in this gene are known to cause both autosomal recessive and autosomal dominant form. In addition, GJB3 mutations have been involved in sensorineural deafness, erythrokeratodermia variabilis (EKV), and neuropathy diseases. We aimed to investigate GJB3 mutations in people suffering from HL among three different ethnicities of Iranian population (Baloch, Kurd, and Turkmen). Methods: In this descriptive study, 50 GJB2-negative non-syndromic hearing loss (NSHL) Iranian individuals from 3 ethnic groups of Baloch (n=17), Kurd (n =15) and Turkmen (n=18) were enrolled.  DNA extractions, PCR, and mutation detection was carried out for the two large deletions of the GJB6, del (GJB6 -D13S1830,) and del (GJB6 -D13S1854) followed by direct DNA sequencing method for the GJB3. Results: DNA sequencing of GJB3 was shown a missense heterozygous mutation rs199689484 (NM_024009.3) GJB3: c.340G>A (p.Ala114Thr) in a Baloch patient, and a polymorphism rs35983826 (NM_024009.3) GJB3: c.798C>T (p.Asn266=) in a Turkman patient, in coding region of the GJB3. We did not detect del (GJB6 -D13S1830) and del (GJB6 -D13S1854) among these three ethnicities in Iran. Conclusion: Deafness is a heterogeneous disorder. Specific genes and mutations contribute to hearing loss that varies from locus to locus as well as from population to population. https://ijph.tums.ac.ir/index.php/ijph/article/view/19049 https://ijph.tums.ac.ir/index.php/ijph/article/download/19049/7040