Evaluation of lens epithelial cell differentiation by quantitation of MP26 mRNA relative to γ-crystallin mRNA in initiation of galactose cataracts in the rat

It is well established that in response to feeding of galactose to four-week-old rats cataracts develop (Unakar, Genyea, Reddan & Reddy, Exp. Eye Res. 26, 123–133, 1978). Initiation of cataracts leads to epithelial cell proliferation. In the lens, the main intrinsic membrane protein, MP26, is recognized as a fiber cell-specific gene product, and γ-crystallin is found in terminally differentiated fiber cells. By Northern blot analysis we quantitated the MP26 and γ-crystallin mRNAs found in the lens at various times spanning from 0 to 96 hr on galactose. We find that by 24 hr, MP26 mRNA, as well as γ-crystallin mRNA, increased significantly above the zero time levels. The data was also confirmed by in situ hybridization of various lens sections to both γ-crystallin and MP26 35S-labeled antisense RNA probes. As expected, at later periods beyond 24 hr, the levels of γ-crystallin and MP26 mRNAs dropped to below the control levels. The initial increase in MP26 and γ-crystallin mRNAs lead us to conclude that initiation of galactose cataracts appears to support, although for a short time period, both epithelial cell elongation and fiber cell differentiation.