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Abstract
Hearing loss (HL) is an etiologically heterogeneous disorder that affects around 5% of the world's population. There has been an exponential increase in the identification of genes and variants responsible for hereditary HL over recent years. Iran, a country located in the Middle East, has a high prevalence of consanguineous marriages, so heterogeneous diseases such as HL are more common. Comprehensive studies using different strategies from linkage analysis to next-generation sequencing, especially exome-sequencing, have achieved significant success in identifying possible pathogens in deaf Iranian families. About 12% of non-syndromic autosomal recessive HL genes investigated to date, were first identified in families from Iran. Variations of 56 genes have been observed in families with NSHL in Iran. Variants in GJB2, SLC26A4, MYO15A, MYO7A, CDH23, and TMC1 account for 16.5%, 16.25%, 13.5%, 9.35%, 6.9% and 4.92%, cases of NSHL, respectively. In summary, there are also different diagnostic rates between studies conducted in Iran. In the comprehensive investigations conducted by the Genetic Research Center of the University of Social Welfare and Rehabilitation Sciences over the past 20 years, the overall diagnosis rate is about 80% while there are other studies with lower diagnostic rates which could reflect differences in project designs, sampling, and accuracy and validity of the methods used. Furthermore, there are several syndromic HHLs in Iran including, Waardenburg syndrome, BOR syndrome, Brown-Vialetto-Van Laere syndrome, Wolfram syndrome, among which Pendred and Usher syndromes are well-studied. These results are of importance for further investigation and elucidation of the molecular basis of HHL in Iran.
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Mohseni M, Babanejad M, Booth KT, Jamali P, Jalalvand K, Davarnia B, Ardalani F, Khoshaeen A, Arzhangi S, Ghodratpour F, Beheshtian M, Jahanshad F, Otukesh H, Bahrami F, Seifati SM, Bazazzadegan N, Habibi F, Behravan H, Mirzaei S, Keshavarzi F, Nikzat N, Mehrjoo Z, Thiele H, Nothnagel M, Azaiez H, Smith RJ, Kahrizi K, Najmabadi H. Exome sequencing utility in defining the genetic landscape of hearing loss and novel-gene discovery in Iran. Clin Genet 2021; 100:59-78. [PMID: 33713422 PMCID: PMC8195868 DOI: 10.1111/cge.13956] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 03/03/2021] [Accepted: 03/08/2021] [Indexed: 12/22/2022]
Abstract
Hearing loss (HL) is one of the most common sensory defects affecting more than 466 million individuals worldwide. It is clinically and genetically heterogeneous with over 120 genes causing non-syndromic HL identified to date. Here, we performed exome sequencing (ES) on a cohort of Iranian families with no disease-causing variants in known deafness-associated genes after screening with a targeted gene panel. We identified likely causal variants in 20 out of 71 families screened. Fifteen families segregated variants in known deafness-associated genes. Eight families segregated variants in novel candidate genes for HL: DBH, TOP3A, COX18, USP31, TCF19, SCP2, TENM1, and CARMIL1. In the three of these families, intrafamilial locus heterogeneity was observed with variants in both known and novel candidate genes. In aggregate, we were able to identify the underlying genetic cause of HL in nearly 30% of our study cohort using ES. This study corroborates the observation that high-throughput DNA sequencing in populations with high rates of consanguineous marriages represents a more appropriate strategy to elucidate the genetic etiology of heterogeneous conditions such as HL.
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Affiliation(s)
- Marzieh Mohseni
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Mojgan Babanejad
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Kevin T Booth
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
- Harvard Medical School, Department of Neurobiology, Boston, Massachusetts, USA
| | - Payman Jamali
- Shahrood Genetic Counseling Center, Welfare Organization, Semnan, Iran
| | - Khadijeh Jalalvand
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Behzad Davarnia
- Department of Anatomy and Pathology, Ardabil University of Medical Sciences, Ardabil, Iran
| | - Fariba Ardalani
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | | | - Sanaz Arzhangi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Fatemeh Ghodratpour
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Maryam Beheshtian
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | | | - Hasan Otukesh
- Department of Pediatric Neurology, Iran University of Medical Sciences, Tehran, Iran
| | - Fatemeh Bahrami
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Seyed Morteza Seifati
- Medical Biotechnology Research Center, Islamic Azad University, Ashkezar, Yazd, Iran
| | - Niloofar Bazazzadegan
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Farkhondeh Habibi
- Genetic Counseling Center of Welfare Organization, Rasht, Guilan, Iran
| | - Hanieh Behravan
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Sepide Mirzaei
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Fatemeh Keshavarzi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Nooshin Nikzat
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Zohreh Mehrjoo
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Holger Thiele
- Cologne Center for Genomics (CCG), University of Cologne, Cologne, Germany
| | - Michael Nothnagel
- Cologne Center for Genomics (CCG), University of Cologne, Cologne, Germany
- University Hospital Cologne, Cologne, Germany
| | - Hela Azaiez
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Richard J Smith
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Kimia Kahrizi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Hossein Najmabadi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
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