Nuclear endogenous Ca2+-dependent endodeoxyribonuclease in differentiating chick embryonic lens fibers

During terminal differentiation of lens epithelial cells into fiber cells, nuclei become pycnotic and DNA degradation occurs. We investigated the putative role in this process of an endogenous DNAase. After incubation of isolated nuclei of both cell types at 37 degrees C, DNAase activity was revealed by DNA size analysis on 0.3-1% neutral and alkaline agarose, one- and two-dimensional gels. This DNAase activity is more prominent in lens fiber nuclei than in epithelial nuclei at all the embryonic stages probably because of a preexisting higher concentration of divalent cations in the former. This activity is calcium or magnesium dependent in both types of nuclei.