Abstract
Purpose: :
Lens opacity 13 (lop13) is a novel congenital autosomal recessive cataract locus that arose spontaneously in the 129/sv-ter strain. The goal of this study is to identify the gene harboring the mutation responsible for the lop13 phenotype and establish mouse/human homology for the lop13 locus.
Methods: :
For histopathology eyes were collected from 3 weeks old mice, serially sectioned and stained with H&E, trichrome, and alcian blue PAS. For genetic analysis lop13 mice were outcrossed to wild type C3A.BLiA-Pde6b+/J. The F1 mice were backcrossed to lop 13 and 144 F2 progeny were generated. At weaning the progeny were evaluated with a slit lamp following mydriasis with 1% atropine. After noting the phenotype, the progeny were euthanized and tissues were collected. Genomic DNA was isolated from collected spleens. Microsatellite markers were selected to evenly cover the mouse genome. Genotypes were determined by PCR amplification of genomic DNA and alleles were scored.
Results: :
At weaning lop13 mice exhibit mature cortical nuclear cataracts and lenticonus. Histological analysis also identified an abnormal lid development with an abnormally positioned sebaceous gland deep in the dermis. Some lop13 mice exhibit eyelid fissures. Linkage analysis mapped lop13 locus to mouse chromosome 15. The linkage map established the lop13 critical to be between microsatellite markers D15Mit118 and D15Mit33 a region of 1.4 Mb. Evaluation of the candidate genes identified Arg1038Cys substitution in the Srebp-2 gene.
Conclusions: :
The lop13 mouse results from a mutation in a gene essential for the normal transparency of the lens. The linkage analysis mapped the lop13 locus to mouse chromosome 15 and identified a mutation in the Srebp-2 gene. The Srebp-2 gene is involved in the cholesterol metabolism. Evaluation of the molecular mechanism of Srebp-2 in maintenance of the normal transparency of the lens is currently in progress.
Keywords: genetics • cataract • linkage analysis