Abstract
Purpose: :
A 5–bp deletion in the human ELOVL4 gene is a genetic basis of hereditary dominant Stargardt–3 macular dystrophy (STGD3). To study the molecular basis of the resulting human pathology, we have generated Stgd3 gene–knockin mice that carry the corresponding deletion mutation in the mouse Elovl4 gene.
Methods: :
An 11–kb gene knockin construct containing exon 6 of the mouse Elovl4 gene with the Stgd–3 mutation was electroporated into 129SvEv mouse ES cells. Recombined clones were selected and used to generate Stgd3 gene–knockin mice. Resulting chimeric males were bred with 129 SvEs females and their offspring crossed with Cre–transgenic mice to delete a Neo cassette used for recombined clone selection. Stgd3 mice were characterized for Elovl4 gene organization by Southern blot analysis, for Elovl4 mRNA expression by S1–nuclease protection assay, for lipofuscin accumulation in the retina, and for retinal morphology and electrophysiology.
Results: :
We have generated Stgd3 mice that carry a human STGD3 mutation in the mouse Elovl4 gene. Replacement of both Elovl4 alleles with the mutant allele causes embryonic lethality. In contrast, mice carrying one defective allele are born at a proper Mendelian ratio and develop normally. The mutation does not affect Elovl4 mRNA stability. Heterozygous retinas express equal amounts of both, wt and mutant, Elovl4 mRNAs and the amount of wt mRNA is a half of that present in the wt retina. Heterozygous retinas of mice have normal lipofuscin content, morphology and electrophysiology up to six months of age.
Conclusions: :
The Stgd3 mutation causes embryonic lethality in homozygous mice but no retinal pathology in heterozygous mice up to six months of age.
Keywords: transgenics/knock-outs • retinal degenerations: hereditary • proteins encoded by disease genes