Morphological study on rupture of posterior capsule in RLC mouse lens

A novel spontaneous mutation of BCAR3 results in extrusion cataracts in CF#1 mouse strain

A substrain of mice originating from the CF#1 strain (an outbred colony) reared at Osaka Prefecture University (CF#1/lr mice) develops cataracts beginning at 4 weeks of age. Affected mice were fully viable and fertile and developed cataracts by 14 weeks of age. Histologically, CF#1/lr mice showed vacuolation of the lens cortex, swollen lens fibers, lens rupture and nuclear extrusion. To elucidate the mode of inheritance, we analyzed heterozygous mutant hybrids generated from CF#1/lr mice and wild-type BALB/c mice. None of the heterozygous mutants were affected, and the ratio of affected to unaffected mice was 1:3 among the offspring of the heterozygous mutants. For the initial genome-wide screening and further mapping, we used affected progeny of CF#1/lr × (CF#1/lr × BALB/c) mice. We concluded that the cataracts in CF#1/lr mice are inherited through an autosomal recessive mutation and that the mutant gene is located on mouse chromosome 3 between D3Mit79 and D3Mit216. In this region, we identified 8 genes associated with ocular disease. All 8 genes were sequenced and a novel point mutation (1 bp insertion of cytosine) in exon 7 of the Bcar3 gene was identified. This mutation produced a premature stop codon and a truncated protein. In conclusion, we have identified the first spontaneous mutation in the Bcar3 gene associated with lens extrusion cataracts. This novel cataract model may provide further knowledge of the molecular biology of cataractogenesis and the function of the BCAR3 protein.

Novel cataract mouse model using ddY strain: hereditary and histological characteristics

A novel cataract model was identified in the ddY strain (outbred colony) reared at Osaka Prefecture University. Opacity appeared as a white pinpoint focus in the unpigmented eyes of cataract mice at 6 weeks of age. All mice, fully viable and fertile, were bilaterally affected by the time they were 10 weeks of age. There were no gender differences in the incidence of cataracts. Histologically, 5-month-old cataract mice showed vacuolation of epithelial cells, disruption of lens fibers, and dislocation of the lens nucleus to the posterior lens cortex. To elucidate the mode of inheritance, heterozygous mutant hybrids between cataract mice and wild-type ddY mice, as well as offspring between the heterozygous mutants, were analyzed. No affected mice were observed among the heterozygous mutants, and the ratio of affected to unaffected mice was 1:3 among offspring between heterozygous mutants. For linkage analysis, we produced backcross progeny [cataract mouse x (cataract mouse x MSM/Ms mouse)], and concluded that the cataracts are inherited by an autosomal recessive gene. Moreover, the locus of the cataract gene, mct, was mapped to the 3.91 cM region encompassed by D2Mit467 and D2Mit320 on mouse chromosome 2 by linkage analysis. Thus, the present cataract mice represent a novel cataract mouse model, and have been designated Morioka cataract (MCT) mice.

Mutation of Dock5, a member of the guanine exchange factor Dock180 superfamily, in the rupture of lens cataract mouse

Rupture of lens cataract (RLC) in the mouse is a spontaneous mutation inherited by a single autosomal recessive gene mapped on chromosome 14. Fine mapping of the mutant locus revealed a nucleotide deletion of 27-bp at the end of 15th exon of Dock5 (Dedicator of cytokinesis-5), a member of the Dock gene superfamily. Since the deletion occurred in-frame, the RLC-DOCK5 protein had a deletion of 9 amino acids (a.a. 506-514) in the DHR1 (DOCK homology region-1) domain that is essential for DOCK5, a GTP-exchanger for Rac1. Although Dock5 mRNA was intensely expressed equally in mutant and wild-type lenses, DOCK5 protein was hardly detectable in the mutant lens. In contrast, expression of Dock180, another member of Dock subfamily A, was not affected in RLC. Immunohistochemically, DOCK5 was stained intensely in the cytoplasm of the anterior epithelial cells and weakly in lens fiber of the wild type lenses, but little in RLC lens. These observations suggest that the mutation may somehow destabilize DOCK5 protein. We propose to designate the mutant allele of rlc as Dock5rlc. Relevance of the signaling pathway involving DOCK5-RAC1 in maintenance of lens integrity of growing lens is discussed.

Canine cataracts, diabetes mellitus and spontaneous lens capsule rupture: a retrospective study of 18 dogs

OBJECTIVE

To describe the clinical presentation and surgical outcome of diabetic canine patients with cataracts and preoperative spontaneous lens capsule rupture.

ANIMALS STUDIED

A total of 20 dogs and 40 eyes were included in the retrospective evaluation. The patients' ages ranged from 5 to 14 years (mean 8.5 years).

RESULTS

All dogs had clinical diabetes mellitus, with the duration since diagnosis ranging from 30 to 240 days (mean 123 days). Cataracts were bilateral and noted to have been present for 14-112 days (mean 39 days). Of the 40 eyes affected with cataracts, 30 had a spontaneous rupture of the lens capsule prior to surgery. The capsular rupture was diagnosed on clinical examination in 28/30 eyes and was noted intraoperatively in 2/30. The location of the capsular rupture was equatorial in 29/30 and posterior in 1/30 eyes. Surgery was performed in 38/40 eyes, with one case lost to follow-up without surgical intervention. Prior to surgery, routine diagnostic ophthalmic examination, ocular ultrasound, electroretinography, and systemic evaluation were performed in all dogs. Surgical procedures included phacoemulsification in 28/40 eyes, with IOL placement performed in 20/28 eyes. Intrascleral prosthesis placement or enucleation was performed in 8/40 and 2/40 eyes, respectively, due to a significantly reduced ERG or secondary glaucoma.

CONCLUSIONS

The duration of clinical follow-up (19/20 dogs) ranged from 1 to 36 months (mean 12.9 months). All eyes that had cataract surgery with or without IOL placement were sighted at the time of the last follow-up examination. Spontaneous lens capsule rupture associated with diabetes mellitus, cataract and rapid lens intumescence occurs in the dog. Early surgical intervention, prior to secondary complications of glaucoma and loss of retinal function, is associated with a favorable outcome.