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Yu X, Li S, Ding Y. Maternally transmitted nonsyndromic hearing impairment may be associated with mitochondrial tRNA Ala 5601C>T and tRNA Leu(CUN) 12311T>C mutations. J Clin Lab Anal 2022; 36:e24298. [PMID: 35218233 PMCID: PMC8993639 DOI: 10.1002/jcla.24298] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/31/2022] [Accepted: 02/08/2022] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Sequence alternations in mitochondrial genomes, especially in genes encoding mitochondrial tRNA (mt-tRNA), were the important contributors to nonsyndromic hearing loss (NSHL); however, the molecular mechanisms remained largely undetermined. METHODS A maternally transmitted Chinese pedigree with NSHL underwent clinical, genetic, and biochemical assessment. PCR and direct sequence analyses were performed to detect mitochondrial DNA (mtDNA), GJB2, and SLC26A4 gene mutations from matrilineal relatives of this family. Mitochondrial functions including mitochondrial membrane potential (MMP), ATP, and ROS were evaluated in polymononuclear leukocytes (PMNs) derived from three deaf patients and three controls from this pedigree. RESULTS Four of nine matrilineal relatives developed hearing loss at the variable age of onset. Two putative pathogenic mutations, m.5601C>T in tRNAAla and m.12311T>C in tRNALeu(CUN) , were identified via PCR-Sanger sequencing, as well as 34 variants that belonged to mtDNA haplogroup G2b2. Intriguingly, m.5601C>T mutation resided at very conserved nucleotide in the TψC loop of tRNAAla (position 59), while the T-to-C substitution at position 12311 located at position 48 in the variable stem of tRNALeu(CUN) and was believed to alter the aminoacylation and the steady-state level of tRNA. Biochemical analysis revealed the impairment of mitochondrial functions including the significant reductions of ATP and MMP, whereas markedly increased ROS levels were found in PMNs derived from NSHL patients with m.5601C>T and m.12311T>C mutations. However, we did not detect any mutations in GJB2 and SLC26A4 genes. CONCLUSION Our data indicated that mt-tRNAAla m.5601C>T and tRNALeu(CUN) 12311T>C mutations were associated with NSHL.
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Affiliation(s)
- Xuejiao Yu
- Department of Clinical LaboratoryQuzhou People's Hospitalthe Quzhou Affiliated Hospital of Wenzhou Medical UniversityQuzhouChina
| | - Sheng Li
- Department of OtolaryngologyQuzhou People's Hospitalthe Quzhou Affiliated Hospital of Wenzhou Medical UniversityQuzhouChina
| | - Yu Ding
- Central LaboratoryHangzhou First People’s HospitalZhejiang University School of MedicineHangzhouChina
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Ding Y, Teng YS, Zhuo GC, Xia BH, Leng JH. The Mitochondrial tRNAHis G12192A Mutation May Modulate the Clinical Expression of Deafness-Associated tRNAThr G15927A Mutation in a Chinese Pedigree. Curr Mol Med 2020; 19:136-146. [PMID: 30854964 DOI: 10.2174/1566524019666190308121552] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 03/02/2019] [Accepted: 03/04/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND Mutations in mitochondrial tRNA (mt-tRNA) genes have been found to be associated with both syndromic and non-syndromic hearing impairment. However, the pathophysiology underlying mt-tRNA mutations in clinical expression of hearing loss remains poorly understood. OBJECTIVE The aim of this study was to explore the potential association between mttRNA mutations and hearing loss. METHODS AND RESULTS We reported here the molecular features of a pedigree with maternally transmitted non-syndromic hearing loss. Among 12 matrilineal relatives, five of them suffered variable degree of hearing impairment, but none of them had any medical history of using aminoglycosides antibiotics (AmAn). Genetic screening of the complete mitochondrial genomes from the matrilineal relatives identified the coexistence of mt-tRNAHis G12192A and mt-tRNAThr G15927A mutations, together with a set of polymorphisms belonging to human mitochondrial haplogroup B5b1b. Interestingly, the G12192A mutation occurred 2-bp from the 3' end of the TψC loop of mt-tRNAHis, which was evolutionarily conserved from various species. In addition, the well-known G15927A mutation, which disrupted the highly conserved C-G base-pairing at the anticodon stem of mt-tRNAThr, may lead to the failure in mt-tRNA metabolism. Furthermore, a significant decreased in ATP production and an increased ROS generation were observed in polymononuclear leukocytes (PMNs) which were isolated from the deaf patients carrying these mt-tRNA mutations, suggested that the G12192A and G15927A mutations may cause mitochondrial dysfunction that was responsible for deafness. However, the absence of any functional mutations/variants in GJB2, GJB3, GJB6 and TRMU genes suggested that the nuclear genes may not play important roles in the clinical expression of non-syndromic hearing loss in this family. CONCLUSION Our data indicated that mt-tRNAHis G12192A mutation may increase the penetrance and expressivity of deafness-associated m-tRNAThr G15927A mutation in this family.
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Affiliation(s)
- Yu Ding
- Central Laboratory, Hangzhou First People's Hospital, Zhejiang University, School of Medicine, Hangzhou, China
| | - Yao-Shu Teng
- Department of Otolaryngology, Hangzhou First People's Hospital, Zhejiang University, School of Medicine, Hangzhou, China
| | - Guang-Chao Zhuo
- Central Laboratory, Hangzhou First People's Hospital, Zhejiang University, School of Medicine, Hangzhou, China
| | - Bo-Hou Xia
- Department of Pharmacy, Hunan Chinese Medical University, Changsha, China
| | - Jian-Hang Leng
- Central Laboratory, Hangzhou First People's Hospital, Zhejiang University, School of Medicine, Hangzhou, China
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Peng W, Zhong Y, Zhao X, Yuan J. Low penetrance of hearing loss in two Chinese families carrying the mitochondrial tRNASer(UCN) mutations. Mol Med Rep 2020; 22:77-86. [PMID: 32377700 PMCID: PMC7248462 DOI: 10.3892/mmr.2020.11100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2019] [Accepted: 02/20/2020] [Indexed: 01/07/2023] Open
Abstract
Mutations in mitochondrial DNA (mtDNA), especially in mitochondrial 12S rRNA and transfer RNA(tRNA)Ser(UCN) genes, are important causes of non-syndromic hearing loss. However, the molecular mechanism underlying mt-tRNA mutations in clinical hearing impairment are not fully understood. The present study assessed the molecular characterization of two Chinese families with non-syndromic hearing loss, who both exhibited very low penetrance of deafness (9.1 and 12.5% for Family 1 and 2, respectively). Mutational analysis of the complete mtDNA genes identified the presence of cytochrome c oxidase 1/tRNASer(UCN) G7444A and tRNASer(UCN) C7492T mutations, together with polymorphisms belonging to human mitochondrial haplogroup D4 and G2b, respectively. Moreover, the G7444A and C7492T mutations occurred at highly conserved tRNASer(UCN) nucleotides and may cause tRNA metabolism failure, which is involved in mitochondrial translation defects. Therefore, the G7444A and C7492T mutations may lead to the mitochondrial dysfunction that responsible for deafness. However, the absence of any functional variants in Gap junction β-2, Solute Carrier Family 26 Member 4 and TRNA 5-methylaminomethyl-2-thiouridylate methyltransferase suggested that nuclear genes may not play active roles in the occurrence of deafness. In the present study, the observed incomplete penetrance of hearing loss and mild mitochondrial dysfunction indicated that mtDNA G7444A and C7492T mutations are insufficient to produce the deafness phenotype. Therefore, other risk factors such as environmental factors and epigenetic regulation may be involved in the pathogenesis of hearing loss in the families recruited in the present study.
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Affiliation(s)
- Wei Peng
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
| | - Yi Zhong
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
| | - Xueyan Zhao
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
| | - Jie Yuan
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
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Subathra M, Ramesh A, Selvakumari M, Karthikeyen NP, Srisailapathy CRS. Genetic Epidemiology of Mitochondrial Pathogenic Variants Causing Nonsyndromic Hearing Loss in a Large Cohort of South Indian Hearing Impaired Individuals. Ann Hum Genet 2017; 80:257-73. [PMID: 27530448 DOI: 10.1111/ahg.12161] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 05/16/2016] [Indexed: 01/28/2023]
Abstract
Mitochondria play a critical role in the generation of metabolic energy in the form of ATP. Tissues and organs that are highly dependent on aerobic metabolism are involved in mitochondrial disorders including nonsyndromic hearing loss (NSHL). Seven pathogenic variants leading to NSHL have so far been reported on two mitochondrial genes: MT-RNR1 encoding 12SrRNA and MT-TS1 encoding tRNA for Ser((UCN)) . We screened 729 prelingual NSHL subjects to determine the prevalence of MT-RNR1 variants at position m.961, m.1555A>G and m.1494C>T, and MT-TS1 m.7445A>G, m.7472insC m.7510T>C and m.7511T>C variants. Mitochondrial pathogenic variants were found in eight probands (1.1%). Five of them were found to have the m.1555A>G variant, two others had m.7472insC and one proband had m.7444G>A. The extended relatives of these probands showed variable degrees of hearing loss and age at onset. This study shows that mitochondrial pathogenic alleles contribute to about 1% prelingual hearing loss. This study will henceforth provide the reference for the prevalence of mitochondrial pathogenic alleles in the South Indian population, which to date has not been estimated. The m.1555A>G variant is a primary predisposing genetic factor for the development of hearing loss. Our study strongly suggests that mitochondrial genotyping should be considered for all hearing impaired individuals and particularly in families where transmission is compatible with maternal inheritance, after ruling out the most common variants.
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Affiliation(s)
- Mahalingam Subathra
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, India
| | - Arabandi Ramesh
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, India
| | - Mathiyalagan Selvakumari
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, India
| | - N P Karthikeyen
- DOAST (Doctrine Oriented Art of Symbiotic Treatment) Hearing Care Center and Integrated Therapy Center for Autism, Anna Nagar West, Chennai, India
| | - C R Srikumari Srisailapathy
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai, India
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Tang X, Zheng J, Ying Z, Cai Z, Gao Y, He Z, Yu H, Yao J, Yang Y, Wang H, Chen Y, Guan MX. Mitochondrial tRNA(Ser(UCN)) variants in 2651 Han Chinese subjects with hearing loss. Mitochondrion 2015; 23:17-24. [PMID: 25968158 DOI: 10.1016/j.mito.2015.05.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 04/14/2015] [Accepted: 05/04/2015] [Indexed: 12/17/2022]
Abstract
Mutations in the mitochondrial DNA have been associated with hearing loss. However, the prevalence and spectrum of mitochondrial tRNA mutations in hearing-impaired subjects are poorly understood. In this report, we have investigated the prevalence and spectrum of mitochondrial tRNA(Ser(UCN)) mutations in a large cohort of 2651 Han Chinese subjects with hearing loss. The clinical evaluation showed that 744 subjects (432 males and 312 females) had a history of exposure to aminoglycosides and other probands exhibited nonsyndromic hearing loss. Mutational analysis of tRNA(Ser(UCN)) gene identified 9 (8 known and 1 novel) variants. The prevalence of the known deafness-associated 7511T>C, 7505T>C and 7445A>C mutations was 0.04%, 0.04% and 0.04%, respectively. Other variants were evaluated by the evolutionary conservation, allelic frequency of Chinese controls, potential structural and functional alterations and pedigree analysis. Three variants were polymorphisms, while the 7444G>A, 7471DelG and 7496A>G variants were putative deafness-associated mutations. These putative deafness-associated variants accounted for 0.68% cases of hearing-impaired subjects in this cohort. The low penetrance of hearing loss in pedigrees carrying one of these putative deafness-associated mutations indicated that the mutation(s) is necessary but itself insufficient to produce a clinical phenotype. Other genetic or environmental factor(s) may influence the phenotypic manifestation of these tRNA(Ser(UCN)) mutations. Moreover, mtDNAs in 20 probands carrying one of the putative deafness-associated mutations were widely dispersed among 8 Eastern Asian haplogroups. In particular, the occurrences of haplogroups D4a, M22, and H2 in patients carrying the deafness-associated variants were higher than those in Chinese controls. These data further support that the mitochondrial tRNA(Ser(UCN)) gene is the hot spot for mutations associated with hearing loss. Thus, our findings may provide valuable information for the further understanding of pathophysiology and management of hearing loss.
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Affiliation(s)
- Xiaowen Tang
- Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Jing Zheng
- Institute of Genetics, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Zhengbiao Ying
- Department of Otolaryngology, Wenling People's Hospital, Wenzhou Medical University, Wenling, Zhejiang, China
| | - Zhaoyang Cai
- Department of Otolaryngology, Wenling People's Hospital, Wenzhou Medical University, Wenling, Zhejiang, China
| | - Yinglong Gao
- Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zheyun He
- Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Han Yu
- Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Juan Yao
- Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yaling Yang
- Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Hui Wang
- Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Ye Chen
- Institute of Genetics, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Min-Xin Guan
- Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China; Institute of Genetics, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
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Levin L, Blumberg A, Barshad G, Mishmar D. Mito-nuclear co-evolution: the positive and negative sides of functional ancient mutations. Front Genet 2014; 5:448. [PMID: 25566330 PMCID: PMC4274989 DOI: 10.3389/fgene.2014.00448] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 12/08/2014] [Indexed: 12/31/2022] Open
Abstract
Most cell functions are carried out by interacting factors, thus underlying the functional importance of genetic interactions between genes, termed epistasis. Epistasis could be under strong selective pressures especially in conditions where the mutation rate of one of the interacting partners notably differs from the other. Accordingly, the order of magnitude higher mitochondrial DNA (mtDNA) mutation rate as compared to the nuclear DNA (nDNA) of all tested animals, should influence systems involving mitochondrial-nuclear (mito-nuclear) interactions. Such is the case of the energy producing oxidative phosphorylation (OXPHOS) and mitochondrial translational machineries which are comprised of factors encoded by both the mtDNA and the nDNA. Additionally, the mitochondrial RNA transcription and mtDNA replication systems are operated by nDNA-encoded proteins that bind mtDNA regulatory elements. As these systems are central to cell life there is strong selection toward mito-nuclear co-evolution to maintain their function. However, it is unclear whether (A) mito-nuclear co-evolution befalls only to retain mitochondrial functions during evolution or, also, (B) serves as an adaptive tool to adjust for the evolving energetic demands as species' complexity increases. As the first step to answer these questions we discuss evidence of both negative and adaptive (positive) selection acting on the mtDNA and nDNA-encoded genes and the effect of both types of selection on mito-nuclear interacting factors. Emphasis is given to the crucial role of recurrent ancient (nodal) mutations in such selective events. We apply this point-of-view to the three available types of mito-nuclear co-evolution: protein-protein (within the OXPHOS system), protein-RNA (mainly within the mitochondrial ribosome), and protein-DNA (at the mitochondrial replication and transcription machineries).
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Affiliation(s)
- Liron Levin
- Department of Life Sciences, Ben-Gurion University of the Negev Beersheba, Israel
| | - Amit Blumberg
- Department of Life Sciences, Ben-Gurion University of the Negev Beersheba, Israel
| | - Gilad Barshad
- Department of Life Sciences, Ben-Gurion University of the Negev Beersheba, Israel
| | - Dan Mishmar
- Department of Life Sciences, Ben-Gurion University of the Negev Beersheba, Israel
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Soini HK, Moilanen JS, Vilmi-Kerälä T, Finnilä S, Majamaa K. Mitochondrial DNA variant m.15218A > G in Finnish epilepsy patients who have maternal relatives with epilepsy, sensorineural hearing impairment or diabetes mellitus. BMC MEDICAL GENETICS 2013; 14:73. [PMID: 23870133 PMCID: PMC3726289 DOI: 10.1186/1471-2350-14-73] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 07/17/2013] [Indexed: 01/04/2023]
Abstract
BACKGROUND Mitochondrial diseases caused by mutations in mitochondrial DNA (mtDNA) affect tissues with high energy demand. Epilepsy is one of the manifestations of mitochondrial dysfunction when the brain is affected. We have studied here 79 Finnish patients with epilepsy and who have maternal first- or second-degree relatives with epilepsy, sensorineural hearing impairment or diabetes mellitus. METHODS The entire mtDNA was studied by using conformation sensitive gel electrophoresis and PCR fragments that differed in mobility were directly sequenced. RESULTS We found a common nonsynonymous variant m.15218A > G (p.T158A, MTCYB) that occurs in haplogroup U5a1 to be more frequent in patients with epilepsy. The m.15218A > G variant was present in five patients with epilepsy and in four out of 403 population controls (p = 0.0077). This variant was present in two branches in the phylogenetic network constructed on the basis of mtDNA variation among the patients. Three algorithms predicted that m.15218A > G is damaging in effect. CONCLUSIONS We suggest that the m.15218A > G variant is mildly deleterious and that mtDNA involvement should be considered in patients with epilepsy and who have a maternal history of epilepsy, sensorineural hearing impairment or diabetes mellitus.
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Affiliation(s)
- Heidi K Soini
- Department of Neurology, Oulu University Hospital, P.O. Box 20, Oulu FI-90029, OYS, Finland
- Department of Clinical Medicine, Neurology, University of Oulu, P.O. Box 5000, FI-90014, Oulu, Finland
- Clinical Research Center, Oulu University Hospital, P.O. Box 5000, FI-90014, Oulu, Finland
| | - Jukka S Moilanen
- Department of Clinical Genetics, Oulu University Hospital and University of Oulu P.O. Box 23, FI-90029, OYS, Oulu, Finland
| | - Tiina Vilmi-Kerälä
- Department of Neurology, Oulu University Hospital, P.O. Box 20, Oulu FI-90029, OYS, Finland
- Department of Clinical Medicine, Neurology, University of Oulu, P.O. Box 5000, FI-90014, Oulu, Finland
- Clinical Research Center, Oulu University Hospital, P.O. Box 5000, FI-90014, Oulu, Finland
| | - Saara Finnilä
- Department of Neurology, Oulu University Hospital, P.O. Box 20, Oulu FI-90029, OYS, Finland
- Department of Clinical Medicine, Neurology, University of Oulu, P.O. Box 5000, FI-90014, Oulu, Finland
- Clinical Research Center, Oulu University Hospital, P.O. Box 5000, FI-90014, Oulu, Finland
| | - Kari Majamaa
- Department of Neurology, Oulu University Hospital, P.O. Box 20, Oulu FI-90029, OYS, Finland
- Department of Clinical Medicine, Neurology, University of Oulu, P.O. Box 5000, FI-90014, Oulu, Finland
- Clinical Research Center, Oulu University Hospital, P.O. Box 5000, FI-90014, Oulu, Finland
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Rydzanicz M, Cywińska K, Wróbel M, Pollak A, Gawęcki W, Wojsyk-Banaszak I, Lechowicz U, Mueller-Malesińska M, Ołdak M, Płoski R, Skarżyński H, Szyfter K, Szyfter W. The contribution of the mitochondrial COI/tRNA(Ser(UCN)) gene mutations to non-syndromic and aminoglycoside-induced hearing loss in Polish patients. Mol Genet Metab 2011; 104:153-9. [PMID: 21621438 DOI: 10.1016/j.ymgme.2011.05.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Revised: 05/08/2011] [Accepted: 05/08/2011] [Indexed: 11/17/2022]
Abstract
Mutations in mitochondrial DNA have been implicated in both, non-syndromic and aminoglycoside-induced hearing loss. In the present study, we have performed the systematic mutation screening of the COI/tRNA(Ser(UCN)) genes in 250 unrelated Polish subjects with hearing impairment. Three different homoplasmic sequence variants were identified, including one common polymorphism m.7476 C>T in tRNA(Ser(UCN)) and two mutations, m.7444 G>A and m.7445 A>G localized in the COI/precursor of tRNA(Ser(UCN)). The incidence of m.7444 G>A substitution was estimated at 1.6% (4/250), however variable penetrance of hearing loss, age of onset and hearing thresholds among m.7444 G>A carriers was observed. Two subjects had the positive history of aminoglycoside exposure and one of them harbored both m.7444 G>A and 12S rRNA m.1555 A>G mutations. Those suggest that m.7444 G>A itself is not sufficient to produce a clinical phenotype and additional modifier factors are required for pathogenic manifestation of m.7444 G>A substitution. Moreover, we have described the first Polish family with non-syndromic hearing loss, harboring m.7445 A>G mutation. The penetrance of hearing loss in this pedigree was 58% when aminoglycoside-induced hearing impairment was included, and 8% when ototoxic effect was excluded. This finding strongly suggests the possible role of m.7445 A>G in susceptibility to aminoglycoside induced-hearing loss.
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Affiliation(s)
- Małgorzata Rydzanicz
- Institute of Human Genetics, Polish Academy of Sciences, Strzeszyńska 32, 60-479 Poznań, Poland.
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