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Homma K. The Pathological Mechanisms of Hearing Loss Caused by KCNQ1 and KCNQ4 Variants. Biomedicines 2022; 10:biomedicines10092254. [PMID: 36140355 PMCID: PMC9496569 DOI: 10.3390/biomedicines10092254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/08/2022] [Accepted: 09/09/2022] [Indexed: 11/29/2022] Open
Abstract
Deafness-associated genes KCNQ1 (also associated with heart diseases) and KCNQ4 (only associated with hearing loss) encode the homotetrameric voltage-gated potassium ion channels Kv7.1 and Kv7.4, respectively. To date, over 700 KCNQ1 and over 70 KCNQ4 variants have been identified in patients. The vast majority of these variants are inherited dominantly, and their pathogenicity is often explained by dominant-negative inhibition or haploinsufficiency. Our recent study unexpectedly identified cell-death-inducing cytotoxicity in several Kv7.1 and Kv7.4 variants. Elucidation of this cytotoxicity mechanism and identification of its modifiers (drugs) have great potential for aiding the development of a novel pharmacological strategy against many pathogenic KCNQ variants. The purpose of this review is to disseminate this emerging pathological role of Kv7 variants and to underscore the importance of experimentally characterizing disease-associated variants.
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Affiliation(s)
- Kazuaki Homma
- Department of Otolaryngology-Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; ; Tel.: +1-312-503-5344
- The Hugh Knowles Center for Clinical and Basic Science in Hearing and Its Disorders, Northwestern University, Evanston, IL 60608, USA
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Unraveling the genetic complexities of combined retinal dystrophy and hearing impairment. Hum Genet 2021; 141:785-803. [PMID: 34148116 PMCID: PMC9035000 DOI: 10.1007/s00439-021-02303-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 06/15/2021] [Indexed: 12/11/2022]
Abstract
Usher syndrome, the most prevalent cause of combined hereditary vision and hearing impairment, is clinically and genetically heterogeneous. Moreover, several conditions with phenotypes overlapping Usher syndrome have been described. This makes the molecular diagnosis of hereditary deaf–blindness challenging. Here, we performed exome sequencing and analysis on 7 Mexican and 52 Iranian probands with combined retinal degeneration and hearing impairment (without intellectual disability). Clinical assessment involved ophthalmological examination and hearing loss questionnaire. Usher syndrome, most frequently due to biallelic variants in MYO7A (USH1B in 16 probands), USH2A (17 probands), and ADGRV1 (USH2C in 7 probands), was diagnosed in 44 of 59 (75%) unrelated probands. Almost half of the identified variants were novel. Nine of 59 (15%) probands displayed other genetic entities with dual sensory impairment, including Alström syndrome (3 patients), cone-rod dystrophy and hearing loss 1 (2 probands), and Heimler syndrome (1 patient). Unexpected findings included one proband each with Scheie syndrome, coenzyme Q10 deficiency, and pseudoxanthoma elasticum. In four probands, including three Usher cases, dual sensory impairment was either modified/aggravated or caused by variants in distinct genes associated with retinal degeneration and/or hearing loss. The overall diagnostic yield of whole exome analysis in our deaf–blind cohort was 92%. Two (3%) probands were partially solved and only 3 (5%) remained without any molecular diagnosis. In many cases, the molecular diagnosis is important to guide genetic counseling, to support prognostic outcomes and decisions with currently available and evolving treatment modalities.
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Amirian A, Zafari Z, Karimipoor M, Kordafshari A, Dalili M, Saber S, Fazelifar AF, Zeinali S. Identification of a Novel KCNQ1 Frameshift Mutation and Review of the Literature among Iranian Long QT Families. IRANIAN BIOMEDICAL JOURNAL 2019; 23. [PMID: 30797226 PMCID: PMC6462296 DOI: 10.29252/.23.3.228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Background Long QT syndrome (LQTS) is characterized by the prolongation of QT interval, which results in syncope and sudden cardiac death in young people. KCNQ1 is the most common gene responsible for this syndrome. Methods Molecular investigation was performed by DNA Sanger sequencing in Iranian families with a history of syncope. In silico examinations were performed for predicting the pathogenicity of the novel variant. Results A novel homozygous KCNQ1 frameshift mutation, c.1426_1429delATGC (M476Pfs*4), was identified, and then the current literatures of five patients were reviewed regarding the LQTS. Conclusion The novel frameshift mutation has been reported for the first time among the Iranian population. Our finding along with the case series study of LQTS patients illustrates the importance of genetic and case series in precise detection of the frequency of LQTS carriers.
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Affiliation(s)
- Azam Amirian
- Department of Molecular Medicine, Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Zahra Zafari
- Department of Molecular Medicine, Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran,Department of Biology, Shahed University, Tehran, Iran
| | - Morteza Karimipoor
- Department of Molecular Medicine, Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Alireza Kordafshari
- Department of Molecular Medicine, Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Mohammad Dalili
- Cardiac Electrophysiology Research Center, Rajaie Cardiovascular Medical, and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Siamak Saber
- Cardiac Electrophysiology Research Center, Rajaie Cardiovascular Medical, and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Amir Farjam Fazelifar
- Cardiac Electrophysiology Research Center, Rajaie Cardiovascular Medical, and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Sirous Zeinali
- Department of Molecular Medicine, Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran,Medical Genetics Laboratory, Kawsar Human Genetics Research Center, No. 41 Majlesi St., Vali Asr St., Tehran, Iran,Corresponding Authors: Sirous Zeinali Department of Molecular Medicine, Biotechnology Research Center, Pasteur Institute of Iran, Tehran, P. O. Box: 1316943551, Iran; Tel.: (+98-21) 66969293; E-mail:
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