Search

The 1555A→G mutation in mitochondrial 12S rRNA has been associated with aminoglycoside-induced and non-syndromic deafness in many individuals worldwide. Mitochondrial genetic modifiers are proposed to influence the phenotypic expression of m.1555A→G mutation. Here, we report that a deafness-susceptibility allele (m.4317A→G) in the tRNAIle gene modulates the phenotype expression of m.1555A→G mutation. Strikingly, a large Han Chinese pedigree carrying both m.4317A→G and m.1555A→G mutations exhibited much higher penetrance of deafness than those carrying only the m.1555A→G mutation. The m.4317A→G mutation affected a highly conserved adenine at position 59 in the T-loop of tRNAIle. We therefore hypothesized that the m.4317A→G mutation alters both structure and function of tRNAIle. Using lymphoblastoid cell lines derived from members of Chinese families (three carrying both m.1555A→G and m.4317A→G mutations, three harboring only m.1555A→G mutation, and three controls lacking these mutations), we found that the cell lines bearing both m.4317A→G and m.1555A→G mutations exhibited more severe mitochondrial dysfunctions than those carrying only the m.1555A→G mutation. We also found that the m.4317A→G mutation perturbed the conformation, stability, and aminoacylation efficiency of tRNAIle. These m.4317A→G mutation-induced alterations in tRNAIle structure and function aggravated the defective mitochondrial translation and respiratory phenotypes associated with the m.1555A→G mutation. Furthermore, mutant cell lines bearing both m.4317A→G and m.1555A→G mutations exhibited greater reductions in the mitochondrial ATP levels and membrane potentials and increasing production of reactive oxygen species than those carrying only the m.1555A→G mutation. Our findings provide new insights into the pathophysiology of maternally inherited deafness arising from the synergy between mitochondrial 12S rRNA and tRNA mutations.

Purpose To assess the efficacy and safety of bupivacaine compared with lidocaine in local anesthesia of nasopharynx through meta-analysis. Methods A number of medical literature data bases were searched electronically. Relevant journals and references of included studies were manually searched. Two reviewers independently performed data extraction and quality assessment. Results Four studies were included. Visual analog scale (VAS) scores, acceptable discomfort, and bleeding scores were analyzed for bupivacaine versus lidocaine. When considering the VAS scores, bupivacaine as a local anesthetic agent was better than lidocaine in controlling the pain of postoperative patients (p < 0.00001). From VAS scores of patients for transnasal fiberoptic nasopharyngolaryngoscopic examination that was performed to evaluate upper airway structures, lidocaine was found to be better at pain management in patients who underwent transnasal endoscopic examination (p < 0.00001). However, when analyzing the acceptable discomfort of patients who underwent upper gastrointestinal endoscopy, which serves as a valuable tool to evaluate upper gastrointestinal structures, the patients in the bupivacaine group demonstrated a higher acceptable discomfort than the patients in the lidocaine group (p = 0.008). With regard to the bleeding scores of the patients with nasal surgery, lidocaine was better at bleeding in postoperative patients compared with bupivacaine (p = 0.0007). These results indicated that bupivacaine showed better pain control of postoperative patients and acceptable discomfort in patients with upper gastrointestinal endoscopy. Lidocaine had a significantly increased ability the pain of patients with transnasal fiberoptic nasopharyngolaryngoscopic examination and bleeding in postoperative patients. No systemic adverse events were reported. Conclusion Bupivacaine was found to have better promotion to pain control than did lidocaine for the patients after nasal surgery. Lidocaine had a significantly increased inhibition of bleeding in these postoperative patients; however, the efficacy between bupivacaine and lidocaine was unclear for the patients who had transnasal endoscopic examinations.

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.

The 1555A→G mutation in mitochondrial 12S rRNA has been associated with aminoglycoside-induced and non-syndromic deafness in many individuals worldwide. Mitochondrial genetic modifiers are proposed to influence the phenotypic expression of m.1555A→G mutation. Here, we report that a deafness-susceptibility allele (m.4317A→G) in the tRNA(Ile) gene modulates the phenotype expression of m.1555A→G mutation. Strikingly, a large Han Chinese pedigree carrying both m.4317A→G and m.1555A→G mutations exhibited much higher penetrance of deafness than those carrying only the m.1555A→G mutation. The m.4317A→G mutation affected a highly conserved adenine at position 59 in the T-loop of tRNA(Ile). We therefore hypothesized that the m.4317A→G mutation alters both structure and function of tRNA(Ile). Using lymphoblastoid cell lines derived from members of Chinese families (three carrying both m.1555A→G and m.4317A→G mutations, three harboring only m.1555A→G mutation, and three controls lacking these mutations), we found that the cell lines bearing both m.4317A→G and m.1555A→G mutations exhibited more severe mitochondrial dysfunctions than those carrying only the m.1555A→G mutation. We also found that the m.4317A→G mutation perturbed the conformation, stability, and aminoacylation efficiency of tRNA(Ile). These m.4317A→G mutation-induced alterations in tRNA(Ile) structure and function aggravated the defective mitochondrial translation and respiratory phenotypes associated with the m.1555A→G mutation. Furthermore, mutant cell lines bearing both m.4317A→G and m.1555A→G mutations exhibited greater reductions in the mitochondrial ATP levels and membrane potentials and increasing production of reactive oxygen species than those carrying only the m.1555A→G mutation. Our findings provide new insights into the pathophysiology of maternally inherited deafness arising from the synergy between mitochondrial 12S rRNA and tRNA mutations.

Purpose To investigate the prevalence and spectrum of mitochondrial ND4 mutations in subjects with Leber's hereditary optic neuropathy (LHON). Methods A cohort of 1281 Chinese Han probands and 478 control subjects underwent clinical and genetic evaluation, and sequence analysis of mitochondrial (mt) DNA, as well as enzymatic assay of NADH:ubiquinone oxidoreductase. Results In this cohort, 503 probands had a family history of optic neuropathy and 778 subjects were sporadic cases. Mutational analysis of ND4 gene identified 149 (102 known and 47 novel) variants. The prevalence of known m.11778G>A mutation was 35.36%. Furthermore, we identified the known m.11696G>A and m.11253T>C mutations and five novel putative LHON-associated mutations. These mutations accounted for 2.74% of cases of LHON subjects. By enzymatic assay, we showed a mild decrease in the activity of NADH:ubiquinone oxidoreductase in mutant cell lines carrying only one putative mtDNA mutation. The low penetrance of optic neuropathy and mild biochemical defects in these pedigrees carrying only m.11696G>A mutation and one putative LHON-associated mutation suggested that the mutation(s) is(are) necessary but is(are) itself(themselves) insufficient to produce a visual failure. Moreover, mtDNAs in 169 probands carrying the LHON-associated mutation(s) were widely dispersed among 13 Eastern Asian haplogroups. In particular, the frequencies of haplogroups D, M8, M10, M11, and H in probands carrying the LHON-associated mtDNA mutation(s) were higher than those in Chinese controls. Conclusions These results suggested that the ND4 gene is the hot spot for mutations associated with LHON. Thus, these findings may provide valuable information for the further understanding of pathogenic mechanism of LHON.

To identify secondary mutations associated with deafness in a Chinese family affected with deafness.The family has been subjected to clinical and molecular analyses, in addition with measurement of reactive oxygen species and doubling time after establishment of immortalized lymphocyte cell lines.The results showed that the hearing loss level and audiometric configuration were discrepant among the family members with maternally transmitted hearing loss. The penetrance of hearing loss in this family was respectively 66.7% and 44.4% when aminoglycoside-induced hearing loss was included or excluded. Analysis of whole mitochondrial genome has found 33 variants as previously reported polymorphisms, except for a 12s rRNA A1555G mutation and a tRNA(Thr)T15943C mutation. Haplotype evolutionary tree has verified that this family belonged to East-Asian haplogroup F. 15943 position was located on the T-stem of the tRNA(Thr), which has destroyed the extremely conserved T-A base pair when T changed to C at this position. However, functional experiments indicated that the population doubling time in special galactose and glucose were longer, whilst the level of reactive oxygen species has increased. Compared with the control cell line groups and a family only carrying the 12s rRNA A1555G mutation, all of the three groups belonged to the same haplogroup.Mitochondrial tRNA(Thr)T15943C mutation may act as a potential modifying factor and interact with 12s rRNA A1555G mutation, and thereby enhance the penetrance and expression of deafness.

To investigate the correlation between nonsyndromic deafness and mitochondrial 12s rRNA A839G mutation.According to the clinical manifestations of mitochondrial DNA sequencing and analysis to find and determine family containing mitochondrial 12s rRNA A839G mutation. Harvested its family members blood and transferred their lymphocytes into lymphoblastoid cell lines, followed by cells cultured, cell doubling experiment, susceptibility testing, cellular oxygen consumption rate experiment, ROS and mitochondrial membrane potential experimental tests were progressed to explore the correlation between the A839G mutation and nonsyndromic deafness.The mitochondrial 12s rRNA A839G mutation pedigrees were determined through the full sequence detections of the Mitochondrial DNA, further phylogenetic analysis showed that 839 point conservative index (CI) up to 78.6%; in RPMI-galactose medium containing A839G gene mutant cell line, the doubling time was significantly longer than the control group, and the difference was significant (P = 0.033). The effect to cell lines containing the A839G mutation of aminoglycoside drugs was not obvious. When compared with the control group, cell lines containing the A839G mutation significantly reduced cellular oxygen consumption rate(P = 0.033); compared with the control group, the ROS levels of cell lines containing the A839G mutation appeared more substantial elevated with significan difference (P0.01). The mitochondrial membrane potential of cells of experimental group was significantly reduced than the control group.The present study proved that the mitochondria 12s rRNA A839G mutations affect the function of the mitochondrial respiratory chain at the cell level, which might reduce the growth rate of the mutant cell lines, result in hearing.

Mutations in Gap Junction Beta 2 (GJB2) have been reported to be a major cause of non-syndromic hearing loss in many populations worldwide. The spectrums and frequencies of GJB2 variants vary substantially among different ethnic groups, and the genotypes among these populations remain poorly understood. In the present study, we carried out a systematic and extended mutational screening of GJB2 gene in 1067 Han Chinese subjects with non-syndromic hearing loss, and the resultant GJB2 variants were evaluated by phylogenetic, structural and bioinformatic analysis. A total of 25 (23 known and 2 novel) GJB2 variants were identified, including 6 frameshift mutations, 1 nonsense mutation, 16 missense mutations and 2 silent mutations. In this cohort, c.235delC is the most frequently observed pathogenic mutation. The phylogenetic, structural and bioinformatic analysis showed that 2 novel variants c.127G>T (p.V43L), c.293G>C (p.R98P) and 2 known variants c. 107T>C (p.L36P) and c.187G>T (p.V63L) are localized at highly conserved amino acids. In addition, these 4 mutations are absent in 203 healthy individuals, therefore, they are probably the most likely candidate pathogenic mutations. In addition, 66 (24 novel and 42 known) genotypes were identified, including 6 homozygotes, 20 compound heterozygotes, 18 single heterozygotes, 21 genotypes harboring only polymorphism(s) and the wild type genotype. Among these, 153 (14.34%) subjects were homozygous for pathogenic mutations, 63 (5.91%) were compound heterozygotes, and 157 (14.71%) carried single heterozygous mutation. Furthermore, 65.28% (141/216) of these cases with two pathogenic mutations exhibited profound hearing loss. These data suggested that mutations in GJB2 gene are responsible for approximately 34.96% of non-syndromic hearing loss in Han Chinese population from Zhejiang Province in eastern China. In addition, our results also strongly supported the idea that other factors such as alterations in regulatory regions, additional genes, and environmental factors may contribute to the clinical manifestation of deafness.