The genetic causes of premature ovarian failure (POF) are highly heterogeneous, and causative mutations have been identified in more than ten genes so far. In two families affected by POF accompanied by hearing loss (together, these symptoms compose Perrault syndrome), exome sequencing revealed mutations in LARS2, encoding mitochondrial leucyl-tRNA synthetase: homozygous c.1565C>A (p.Thr522Asn) in a consanguineous Palestinian family and compound heterozygous c.1077delT and c.1886C>T (p.Thr629Met) in a nonconsanguineous Slovenian family. LARS2 c.1077delT leads to a frameshift at codon 360 of the 901 residue protein. LARS2 p.Thr522Asn occurs in the LARS2 catalytic domain at a site conserved from bacteria through mammals. LARS2 p.Thr629Met occurs in the LARS2 leucine-specific domain, which is adjacent to a catalytic loop critical in all species but for which primary sequence is not well conserved. A recently developed method of detecting remote homologies revealed threonine at this site in consensus sequences derived from multiple-species alignments seeded by human and E. coli residues at this region. Yeast complementation indicated that LARS2 c.1077delT is nonfunctional and that LARS2 p.Thr522Asn is partially functional. LARS2 p.Thr629Met was functional in this assay but might be insufficient as a heterozygote with the fully nonfunctional LARS2 c.1077delT allele. A known C. elegans strain with the protein-truncating alteration LARS-2 p.Trp247Ter was confirmed to be sterile. After HARS2, LARS2 is the second gene encoding mitochondrial tRNA synthetase to be found to harbor mutations leading to Perrault syndrome, further supporting a critical role for mitochondria in the maintenance of ovarian function and hearing.
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