Localization of B-DNA and Z-DNA in terminally differentiating fiber cells in the adult lens

We examined histochemically and immunohistochemically the distribution of B- and Z-DNA in the epithelium and terminally differentiating dog lens fiber cells. On the basis of anti-DNA antibody reactivity, qualitative and quantitative data on B- and Z-DNA in cells were determined. Anti-B-DNA immunoreactivity gradually declined throughout nucleated fibers, with a precipitous decrease at ~90 μm. Anti-Z-DNA antibody binding decreased with a sudden loss of immunoreactivity at ~90 μm. The pattern of anti-B- and Z- DNA staining correlates with the loss of α-crystallin immunoreactivity, the major lens crystallin, and decreased eosin staining of proteins. Germinative zone cell nuclei showed the highest DNA probe binding values, followed by the superficial fibers, central zone, middle fibers, and deep fibers. The presence of single-stranded (ss)DNA in deeper fibers was detected by antiss- DNA antibodies. This is indicative of DNA degradation. These observations suggest that a dramatic reorganization of lens fiber cells' supramolecular order occurs at ~90 μm, the phase transition zone.