Reduced levels of γ-crystallin transcripts during embryonic development of murine Cat2 ^nop mutant lenses

Abstract

• Background: From previous experiments it is known that the murine dominant cataract mutants carrying the gene Cat2 have a decreased content of γ-crystallin-specific transcripts in the juvenile lenses, when the cataract is completely expressed. Moreover, the mutant locus has been mapped recently to chromosome 1, closely linked to the γE-crystallin gene (map distance 0.3±0.3 cM). In the present paper we describe the phenotypic changes and the γ-crystallin expression in embryonic lenses of the Cat2 ^nop mutants as an example for the Cat2 allelic series. •. Methods: The technique of in situ hybridization was applied using a probe from the murine γD-crystallin gene, and, for control, from the murine αA-crystallin gene. Simultaneously, a series of lens sections was examined histologically. • Results: The presence of γ-crystallin mRNA was demonstrated from embryonic day 13.5 (E13.5) onward, but in the mutants to a lower extent than in the wild-type lenses. However, the first morphological abnormality in the mutant lenses was observed as swelling of lens fibers at day E15.5. Progressive degeneration of the lens core followed, leading to a cataracta immatura. • Conclusion: The reduced level of γ-crystallin transcripts is the first alteration observable during the embryonic development of the Cat2 mutant lenses; it precedes the morphological changes. This result represents an additional line of argument that the γ-crystallin genes may be the target of the mutation in the Cat2 mice.