https://orcid.org/0000-0003-1246-2563
Abstract
Purpose
This study aimed to examine the frequencies of mt-tRNAGlu variants in 180 pediatric patients with non-syndromic hearing loss (NSHL) and 100 controls.
Methods
Sanger sequencing was performed to screen for mt-tRNAGlu variants. These mitochondrial DNA (mtDNA) pathogenic mutations were further assessed using phylogenetic conservation and haplogroup analyses. We also traced the origins of the family history of probands carrying potential pathogenic mtDNA mutations. Mitochondrial functions including mtDNA content, ATP and reactive oxygen species (ROS) were examined in cells derived from patients carrying the mt-tRNAGlu A14692G and CO1/tRNASer(UCN) G7444A variants and controls.
Results
We identified four possible pathogenic variants: m.T14709C, m.A14683G, m.A14692G and m.A14693G, which were found in NSHL patients but not in controls. Genetic counseling suggested that one child with the m.A14692G variant had a family history of NSHL. Sequence analysis of mtDNA suggested the presence of the CO1/tRNASer(UCN) G7444A and mt-tRNAGlu A14692G variants. Molecular analysis suggested that, compared with the controls, patients with these variants exhibited much lower mtDNA copy numbers, ATP production, whereas ROS levels increased (p<0.05 for all), suggesting that the m.A14692G and m.G7444A variants led to mitochondrial dysfunction.
Conclusion
mt-tRNAGlu variants are important risk factors for NSHL.
Plain Language Summary
The main aim of our study was to explore the association between the mt-tRNAGlu variants and hearing loss. We found that m.T14709C, m.A14683G, m.A14692G and m.A14693G variants were associated with hearing impairments, these variants localized at extremely conserved nucleotides of mt-tRNAGlu and may result a failure in tRNA metabolism, furthermore, patients with mt-tRNAGlu variants exhibited much lower levels of mtDNA copy number, ATP as compared with controls, whereas ROS increased. As a result, mt-tRNAGlu variants may serve as biomarkers for mitochondrial deafness, and screening for tRNAGlu variants is recommended for early detection and diagnosis of mitochondrial deafness.
Abbreviations
mtDNA, mitochondrial DNA; NSHL, non-syndromic hearing loss; ROS, reactive oxygen species; OXPHOS, oxidative phosphorylation; AINSHL, aminoglycoside-induced and non-syndromic hearing loss; mt-tRNA, mitochondrial tRNA; PTA, pure-tone audiometry; dB, decibels; rCRS, revised Cambridge reference sequences; CI, conservation index; DCFH, 2,7-dichlorodihydrofluorescein; MIDD, maternally inherited diabetes and deafness.
Data Sharing Statement
The datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request (Yu Ding: [email protected]).
Ethics Approval and Consent to Participate
This study was approved by the Ethics Committees of Hangzhou First People’s Hospital (Approval No: 2020-285-01) and Quzhou People’s Hospital (Approval No: 2021-028). Prior to the commencement of the research, our team obtained written informed consent from each patient.
Consent for Publication
Each participant provided their consent for publication.
Acknowledgment
We thank the members of the Department of Clinical Laboratory, Quzhou People’s Hospital for their discussion.
Author Contributions
All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.
Disclosure
The authors declare that they have no competing interests in this work.