INVOLVEMENT OF DNASE-II IN NUCLEAR DEGENERATION DURING LENS CELL-DIFFERENTIATION

The characterization of DNase II and DNase I activity was undertaken t o discriminate their different roles in physiological nuclear degradat ion during lens fiber cell differentiation. The activity of both nucle ases determined in a new assay allows to discriminate DNase II from DN ase I in the same extract, In fibers, both types of nuclease activitie s are found and appear higher than in epithelial cells. Specific polyc lonal antibodies directed against these two nucleases reveal by Wester n blot analysis the presence of various DNase isoforms, DNase II like- nuclease, present in fibers, is represented by three major bands (60, 23, and 18 kDa), which are not detected, at least for two of them (60 and 23 kDa), in epithelial cells, DNase I like nuclease pattern in fib er cells shows a single 32-kDa band, while several bands can be detect ed in epithelial cells, Immunocytochemistry studies show both nuclease s present in lens cell sections, DNase II is, as usual, in cytoplasm o f epithelial cells, but it appears strikingly concentrated in the nucl ei of fibers, DNase I is always concentrated in nuclei of epithelial a nd fiber cells, DNA degradation observed in agarose gels shows that DN ase II-activating medium cleaves the DNA from fiber cells more efficie ntly than DNase I-activating buffer, In addition, DNase II antibody is able to prevent this degradation, These results suggest a specific in volvement of DNase II in nuclear degradation during lens cell differen tiation.