Novel OPA1 mutations identified in Japanese pedigrees with optic atrophy.
OBJECTIVE
To determine whether mutations in the OPA1 gene were present in two Japanese families with optic atrophy.


METHODS
Thirty exons and their boundaries of the OPA1 gene were amplified by PCR with genomic DNA as templates and directly sequenced. The detected sequence changes were confirmed to be mutations by examining whether they were present in normal control individuals. A splicing mutation was characterized by RT-PCR of total RNA of leukocytes obtained from patients and one normal individual. The mutant transcripts resulting from the splicing mutation were further confirmed and quantified by sequencing and identifying the denatured RT-PCR products by polyacrylamide electrophoresis.


RESULTS
One novel splicing mutation of c.871-1G>T and one novel insertion mutation of c.579_580insTT (p.R194fsX228) were identified from two familial cases, respectively. Both mutations segregated within the family heterozygously and were not found in the 189 control individuals examined. Two mutant transcripts resulted from the splicing mutation were identified through amplified OPA1 cDNA prepared from the RNA of leukocytes of the patients. One had a 21 bp deletion at the beginning of the exon 9 leading to a 7 amino acid in-frame deletion of the protein. The expression level of this mutant transcript was similar to the transcript from the wild type allele of the patient. The other mutation was a 114 bp deletion, leading to a 38 amino acid in-frame deletion that skipped all of exon 9, and the expression of this mutant transcript was much lower than the 21 bp deletion.


CONCLUSIONS
The predicted consequence of both mutations is the loss of GTPase activity. Our findings further establish the involvement of OPA1 mutation in Japanese patients with optic atrophy and serve as supportive evidence that haploinsufficiency of the OPA1 gene is the cause of the optic atrophy.
Qin
Minghui
M
Division of Genome Analysis, Research Center for Genetic Information, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
Kondo
Hiroyuki
H
Uno
Hideaki
H
Fujiwara
Eriko
E
Uchio
Eiichi
E
Tahira
Tomoko
T
Hayashi
Kenshi
K
D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D044466:Asian People / Q000235:genetics*; D001483:Base Sequence; D004251:DNA Transposable Elements; D004274:DNA, Recombinant; D005260:Female; D020558:GTP Phosphohydrolases / Q000235:genetics*; D017353:Gene Deletion; D006151:Guanosine; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D015418:Optic Atrophies, Hereditary / Q000235:genetics*; D010375:Pedigree; D013941:Thymine
D004251:DNA Transposable Elements; D004274:DNA, Recombinant; D006151:Guanosine; D020558:GTP Phosphohydrolases; C415198:OPA1 protein, human; D013941:Thymine