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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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Novel KCNQ4 variants in different functional domains confer genotype- and mechanism-based therapeutics in patients with nonsyndromic hearing loss. Exp Mol Med 2021; 53:1192-1204. [PMID: 34316018 PMCID: PMC8333092 DOI: 10.1038/s12276-021-00653-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 05/13/2021] [Accepted: 06/09/2021] [Indexed: 02/07/2023] Open
Abstract
Loss-of-function variant in the gene encoding the KCNQ4 potassium channel causes autosomal dominant nonsyndromic hearing loss (DFNA2), and no effective pharmacotherapeutics have been developed to reverse channel activity impairment. Phosphatidylinositol 4,5-bisphosphate (PIP2), an obligatory phospholipid for maintaining KCNQ channel activity, confers differential pharmacological sensitivity of channels to KCNQ openers. Through whole-exome sequencing of DFNA2 families, we identified three novel KCNQ4 variants related to diverse auditory phenotypes in the proximal C-terminus (p.Arg331Gln), the C-terminus of the S6 segment (p.Gly319Asp), and the pore region (p.Ala271_Asp272del). Potassium currents in HEK293T cells expressing each KCNQ4 variant were recorded by patch-clamp, and functional recovery by PIP2 expression or KCNQ openers was examined. In the homomeric expression setting, the three novel KCNQ4 mutant proteins lost conductance and were unresponsive to KCNQ openers or PIP2 expression. Loss of p.Arg331Gln conductance was slightly restored by a tandem concatemer channel (WT-p.R331Q), and increased PIP2 expression further increased the concatemer current to the level of the WT channel. Strikingly, an impaired homomeric p.Gly319Asp channel exhibited hyperactivity when a concatemer (WT-p.G319D), with a negative shift in the voltage dependence of activation. Correspondingly, a KCNQ inhibitor and chelation of PIP2 effectively downregulated the hyperactive WT-p.G319D concatemer channel. Conversely, the pore-region variant (p.Ala271_Asp272del) was nonrescuable under any condition. Collectively, these novel KCNQ4 variants may constitute therapeutic targets that can be manipulated by the PIP2 level and KCNQ-regulating drugs under the physiological context of heterozygous expression. Our research contributes to the establishment of a genotype/mechanism-based therapeutic portfolio for DFNA2.
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Rashid MH. Molecular simulation of the Kv7.4[ΔS269] mutant channel reveals that ion conduction in the cavity is perturbed due to hydrophobic gating. Biochem Biophys Rep 2020; 25:100879. [PMID: 33367117 PMCID: PMC7749434 DOI: 10.1016/j.bbrep.2020.100879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Revised: 11/19/2020] [Accepted: 12/09/2020] [Indexed: 12/05/2022] Open
Abstract
Mutations in the voltage-gated potassium channel Kv7.4 (encoded as KCNQ4) lead to the early onset of non-syndromic hearing loss, which is significant during language acquisition. The deletion of the S269 pore residue (genetic Δ mutation) in Kv7.4 has been reported to be associated with hearing loss. So far, there is no mechanistic understanding of how this mutation modulates channel function. To understand the role of S269 in ion conduction, we performed molecular dynamics simulations for both wild type and ΔS269 mutant channels. Simulations indicate that the ΔS269 mutation suppresses the fluctuations in the neighboring Y269 residue and thereby consolidates the ring formed by I307 and F310 residues in the adjacent S6 helixes in the cavity region. We show that the long side chains of I307 near the entrance to the cavity form a hydrophobic gate. Comparison of the free energy profiles of a cavity ion in Kv7.4 and Kv7.4[ΔS269] channels reveals a sizable energy barrier in the latter case, which suppresses ion conduction. Thus the simulation studies reveal that the hydrophobic gate resulting from the ΔS269 mutation appears to be responsible for sensorineural hearing loss. DeltaS269 mutation in the Kv7.4 channel is associated with hearing loss (SNHL). The mutation effects on channel function are studied via MD simulations. DeltaS269 mutation imposes a constriction at the cavity to suppress K+ conductance. Understanding the mutation effects on channel function will help to treat SNHL.
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Affiliation(s)
- Md Harunur Rashid
- School of Engineering, RMIT University, Melbourne, Victoria, 3001, Australia
- Department of Mathematics and Physics, North South University, Bashundhara, Dhaka, 1229, Bangladesh
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Walls WD, Moteki H, Thomas TR, Nishio SY, Yoshimura H, Iwasa Y, Frees KL, Nishimura CJ, Azaiez H, Booth KT, Marini RJ, Kolbe DL, Weaver AM, Schaefer AM, Wang K, Braun TA, Usami SI, Barr-Gillespie PG, Richardson GP, Smith RJ, Casavant TL. A comparative analysis of genetic hearing loss phenotypes in European/American and Japanese populations. Hum Genet 2020; 139:1315-1323. [PMID: 32382995 DOI: 10.1007/s00439-020-02174-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 04/29/2020] [Indexed: 01/04/2023]
Abstract
We present detailed comparative analyses to assess population-level differences in patterns of genetic deafness between European/American and Japanese cohorts with non-syndromic hearing loss. One thousand eighty-three audiometric test results (921 European/American and 162 Japanese) from members of 168 families (48 European/American and 120 Japanese) with non-syndromic hearing loss secondary to pathogenic variants in one of three genes (KCNQ4, TECTA, WFS1) were studied. Audioprofile characteristics, specific mutation types, and protein domains were considered in the comparative analyses. Our findings support differences in audioprofiles driven by both mutation type (non-truncating vs. truncating) and ethnic background. The former finding confirms data that ascribe a phenotypic consequence to different mutation types in KCNQ4; the latter finding suggests that there are ethnic-specific effects (genetic and/or environmental) that impact gene-specific audioprofiles for TECTA and WFS1. Identifying the drivers of ethnic differences will refine our understanding of phenotype-genotype relationships and the biology of hearing and deafness.
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Affiliation(s)
- W Daniel Walls
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Hideaki Moteki
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Nagano, 390-8621, Japan
| | - Taylor R Thomas
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Shin-Ya Nishio
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Nagano, 390-8621, Japan
| | - Hidekane Yoshimura
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Nagano, 390-8621, Japan
| | - Yoichiro Iwasa
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Nagano, 390-8621, Japan
| | - Kathy L Frees
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Carla J Nishimura
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Hela Azaiez
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Kevin T Booth
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA.,Department of Neurobiology, Harvard Medical School, Boston, MA, 02215, USA
| | - Robert J Marini
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Diana L Kolbe
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA
| | - A Monique Weaver
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Amanda M Schaefer
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Kai Wang
- Department of Biostatistics, University of Iowa, Iowa City, IA, 52242, USA
| | - Terry A Braun
- Department of Biomedical Engineering, University of Iowa, Iowa City, IA, 52242, USA
| | - Shin-Ichi Usami
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Nagano, 390-8621, Japan
| | | | - Guy P Richardson
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, UK
| | - Richard J Smith
- Molecular Otolaryngology and Renal Research Labs, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA. .,Interdepartmental Ph.D. Program in Genetics, University of Iowa, Iowa City, IA, 52242, USA. .,Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA.
| | - Thomas L Casavant
- Department of Biomedical Engineering, University of Iowa, Iowa City, IA, 52242, USA.,Center for Bioinformatics and Computational Biology, University of Iowa, Iowa City, IA, 52242, USA.,Department of Electrical and Computer Engineering, University of Iowa, Iowa City, IA, 52242, USA
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Molecular basis and restoration of function deficiencies of Kv7.4 variants associated with inherited hearing loss. Hear Res 2020; 388:107884. [PMID: 31995783 DOI: 10.1016/j.heares.2020.107884] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Revised: 12/12/2019] [Accepted: 12/31/2019] [Indexed: 11/20/2022]
Abstract
Deafness non-syndromic autosomal dominant 2 (DFNA2) is characterized by symmetric, predominantly high-frequency sensorineural hearing loss that is progressive across all frequencies. The disease is associated with variants of a potassium voltage-gated channel subfamily Q member 4 gene, KCNQ4 (Kv7.4). Here, we studied nine recently identified Kv7.4 variants in DFNA2 pedigrees, including V230E, E260K, D262V, Y270H, W275R, G287R, P291L, P291S and S680F. We proved that the variant S680F did not alter the channel function while the other eight variants resulted in function deficiencies. We further proved that the two variants E260K and P291S showed reduced cell membrane expressions while the other seven variants showed moderate cell surface expressions. Thus, trafficking deficiency is not a common mechanism underlying channel dysfunction. Next, we studied two variants, V230E and G287R, using molecular dynamics simulation. We showed that V230E stabilized Kv7.4 channel in the closed state by forming an additional hydrogen bond with a basic residue K325, while G287R distorted the selectivity filter and blocked the pore region of Kv7.4 channel. Moreover, by co-expressing wild-type (WT) and variant proteins in vitro, we demonstrated that the heterogeneous Kv7.4 channel currents were reduced compared to the WT channel currents and the reduction could be rescued by a Kv7.4 opener retigabine. Our study provided the underlying mechanisms and suggested a potential alternative therapeutic approach for DFNA2.
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Uwineza A, Caberg JH, Hitayezu J, Hellin AC, Jamar M, Dideberg V, Rusingiza EK, Bours V, Mutesa L. Array-CGH analysis in Rwandan patients presenting development delay/intellectual disability with multiple congenital anomalies. BMC MEDICAL GENETICS 2014; 15:79. [PMID: 25016475 PMCID: PMC4123504 DOI: 10.1186/1471-2350-15-79] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Accepted: 07/08/2014] [Indexed: 01/08/2023]
Abstract
Background Array-CGH is considered as the first-tier investigation used to identify copy number variations. Right now, there is no available data about the genetic etiology of patients with development delay/intellectual disability and congenital malformation in East Africa. Methods Array comparative genomic hybridization was performed in 50 Rwandan patients with development delay/intellectual disability and multiple congenital abnormalities, using the Agilent’s 180 K microarray platform. Results Fourteen patients (28%) had a global development delay whereas 36 (72%) patients presented intellectual disability. All patients presented multiple congenital abnormalities. Clinically significant copy number variations were found in 13 patients (26%). Size of CNVs ranged from 0,9 Mb to 34 Mb. Six patients had CNVs associated with known syndromes, whereas 7 patients presented rare genomic imbalances. Conclusion This study showed that CNVs are present in African population and show the importance to implement genetic testing in East-African countries.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Leon Mutesa
- Center for Medical Genetics, College of Medicine and Health Sciences, University of Rwanda, Huye, Rwanda.
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