Novel OPA1 mutations identified in Japanese pedigrees withoptic atrophy

[摘要] Purpose: To determine whether mutations in the OPA1 gene werepresent in two Japanese families with optic atrophy.Methods: Thirty exons and their boundaries of the OPA1 gene wereamplified by PCR with genomic DNA as templates and directly sequenced.The detected sequence changes were confirmed to be mutations byexamining whether they were present in normal control individuals. Asplicing mutation was characterized by RT-PCR of total RNA of leukocytesobtained from patients and one normal individual. The mutant transcriptsresulting from the splicing mutation were further confirmed andquantified by sequencing and identifying the denatured RT-PCR productsby polyacrylamide electrophoresis.Results: One novel splicing mutation of c.871-1G>T and one novelinsertion mutation of c.579_580insTT (p.R194fsX228) were identified fromtwo familial cases, respectively. Both mutations segregated within thefamily heterozygously and were not found in the 189 control individualsexamined. Two mutant transcripts resulted from the splicing mutationwere identified through amplified OPA1 cDNA prepared from the RNA ofleukocytes of the patients. One had a 21 bp deletion at the beginning ofthe exon 9 leading to a 7 amino acid in-frame deletion of the protein.The expression level of this mutant transcript was similar to thetranscript from the wild type allele of the patient. The other mutationwas a 114 bp deletion, leading to a 38 amino acid in-frame deletion thatskipped all of exon 9, and the expression of this mutant transcript wasmuch lower than the 21 bp deletion.Conclusions: The predicted consequence of both mutations is the lossof GTPase activity. Our findings further establish the involvement ofOPA1 mutation in Japanese patients with optic atrophy and serve assupportive evidence that haploinsufficiency of the OPA1 gene is thecause of the optic atrophy.

[学科分类] 生物化学/生物物理