Involvement of DNase II-like acid DNase in the cataract formation of the UPL rat and the Shumiya cataract rat

The loss of organelles and DNA is important to ensure transparency of the lenses, and DNase II-like acid DNase (also called DNase IIbeta, DLAD) is related to the loss of organelles and DNA in the lenses. We investigated the relation between the degradation of DNA and DLAD mRNA expression in the lenses of two hereditary cataract rats, the UPL rat (UPLR) and the Shumiya cataract rat (SCR), during cataract development. Undigested DNA was detected in the lens cortexes of normal UPLRs and SCRs, and undigested DNA was degraded in the lens nuclei of normal UPLRs and SCRs. DLAD does not affect common cataract formation, since DLAD mRNA expression levels in the lenses of cataractous SCRs were not changed with an increase in age, and undigested DNA was degraded in the lens nuclei of cataractous SCRs. On the other hand, an accumulation of undigested DNA was found in the lens nuclei of cataractous UPLRs at 46 and 53 d of age with opaque lenses, and the decrease in DLAD mRNA expression levels occurred prior to the accumulation of undigested DNA in the lens nuclei. It is possible that UPLRs are a good model for cataract caused by a decrease of DNA degradation in the lenses.