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M. Votruba, G. Smith, V. Davies; Homozygous Protein–Truncating Missense Mutation in Mouse Opa1 GTPase Leads to Embryonic Lethality . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4590.
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© ARVO (1962-2015); The Authors (2016-present)
We aimed to generate a mouse model of human autosomal dominant optic atrophy which is caused by heterozygous mutation in the OPA1 gene (human 3q28/ mouse chromosome 16), and leads to blindness through the loss of retinal ganglion cells (RGCs).
An ENU mutagenised DNA archive from C3H mice was screened using heteroduplex temperature gradient capillary electrophoresis for mutations in mouse opa1. A heterozygous missense mutation in exon 8 coding for a C to T transition at 1051bp was detected. This mutation is predicted to result in protein truncation (Gln 285 to Stop: Q285X), resembling human disease causing mutations at aa 290: R290W and R290Q (c.868C>T and c.869G>T). Sperm were used (IVF with C57Bl/6) to generate heterozygous F1 hybrid founders. PCR genotyping, excluding rd1 (pdeB), and opa1 allele–specific genotyping were used to direct breeding with WT C57Bl/6.
At F3 no opa1–/– homozygous animals have been detected, and together with smaller than expected litter size this is evidence for opa–/– being embryonic lethal. Examination of embryos shows early embryonic lethality. No gross systemic or neurological anomalies were identified when F2 opa1+/– and WT litter mates were screened using the SHIRPA test or on histology. No significant retinal pathology was identified by dilated fundal examination or on H& E retinal RGC counts. However, anti–opa1 antibody staining of retina revealed a reduction in opa1 expression. Functional visual phenotyping, using the optokinetic response, failed to highlight a significant difference between 6 month old opa1+/– and WT littermates, but large differences within the opa1+/– visual acuity scores suggest variable expression.
Our finding of opa1–/– embryonic lethality suggests a vital early developmental role for opa1 and suggests that the GTPase and dynamin–central regions are of key importance to the protein function. The absence of a gross retinal phenotype at 6 months of age, highlights the need to age this model for a retinal phenotype to manifest, mirroring the heterogeneous nature of this human condition.
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