Mitochondrial transfer RNA mutations and male infertility

Background: Mitochondrial DNA (MtDNA) mutations affecting flagellar movement are often causes of sperm dysmotility. Among these mutations, mitochondrial transfer RNA (mt-tRNA) is the hot spot. However, the role of mt-tRNA mutations in male infertility remains heated debates. Purpose: To evaluate the roles of mt-tRNA mutations in male infertility. Methods: To address this problem, we reassessed 5 recent reported mutations: tRNAHis C12187A, tRNAThr G15928A, tRNAArg T10463C, tRNALys A8312G and tRNAAsp T7572C, in clinical expression of asthenozoospermia. We first performed database searches for these mutations; in addition, the phylogenetic approach was performed to determine the Conservation Index (CI) of these mutations between different species. We also used the bioinformatics tool to predict the secondary structure of mttRNAs with and without these mutations. In addition, the pathogenicity scoring system was used to assess the status of each mt-tRNA mutation. Results: We found that only tRNALys A8312G mutation could be regarded as "possibly pathogenic", whereas other mutations should be classified as "neutral polymorphisms". Conclusions: This is the first report dealing with the association between mt-tRNA mutations and male infertility, thus, our study provided novel insight into the molecular basis underlying mt-tRNA mutations in male infertility.