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Abnormal eye development associated with Cat4a, a dominant mouse cataract mutation on chromosome 8
P A Grimes1, B Koeberlein, J Favor
1Department of Ophthalmology and Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia 19104-6075, USA.
Investigative Ophthalmology & Visual Science
|September 4, 1998
Summary
The Cat4a mutation in mice causes eye developmental defects, including corneal opacity and cataracts in heterozygotes and microphthalmia in homozygotes due to failed lens separation from ectoderm.
Area of Science:
- Developmental biology
- Genetics
- Ophthalmology
Background:
- The Cat4a mutation is one of four alleles at the mouse Cat4 locus.
- It affects ocular development, causing central corneal opacity and anterior polar cataract in heterozygotes, and microphthalmia in homozygotes.
- The Cat4 locus is on chromosome 8.
Purpose of the Study:
- To investigate the ocular development of Cat4a mutant mice.
- To characterize the specific defects in eye morphogenesis caused by the Cat4a mutation.
Main Methods:
- Examined serial sections of eyes from wild-type, heterozygous, and homozygous littermates using light microscopy from embryonic day 11 to postnatal day 1.
- Histologically evaluated eyes of adult heterozygous and homozygous mice.
Main Results:
- The earliest defect observed was the failure of the lens vesicle to separate from the surface ectoderm.
- Heterozygotes showed persistent lens-cornea connection, leading to central corneal stroma/endothelium defects and anterior polar cataracts.
- Homozygotes exhibited aborted lens development, optic fissure closure failure, impaired eye cup growth, microphthalmia, poorly developed cornea, absent anterior chamber/vitreous compartment, folded retina, and degenerated lens remnants.
Conclusions:
- A developmental defect in lens vesicle and surface ectoderm separation, caused by the Cat4a mutation, underlies the observed ocular abnormalities.
- Homozygous Cat4a mutations severely impact subsequent lens and eye morphogenesis.
- Cat4a shares phenotypic similarities with other mutations like Small eye (Pax6 gene), suggesting Cat4 may be part of a conserved gene cascade regulating eye development.