Effects of methylmercury on retinoic acid-induced neuroectodermal derivatives of embryonal carcinoma cells

Immunofluorescence staining with antibodies to tubulin, neurofilaments and glial filaments was used to study the effects of methylmercury on the differentiation of retinoic acid-induced embryonal carcinoma cells into neurons and astroglia and on the cytoskeleton of these neuroectodermal derivatives. Methylmercury did not prevent undifferentiated embryonal carcinoma cells from developing into neurons and glia. Treatment of committed embryonal carcinoma cells with methylmercury doses exceeding 1 microM resulted in the formation of neurons with abnormal morphologies. In differentiated cultures, microtubules were the first cytoskeletal element to be affected. Their disassembly was time- and concentration-dependent. Microtubules in glial cells and in neuronal perikarya were more sensitive than those in neuronal processes. Neurofilaments and glial filaments appeared relatively insensitive to methylmercury treatment but showed reorganization after complete disassembly of the microtubules. The data demonstrate 1) the sensitivity of microtubules of both neurons and glia to methylmercury-induced depolymerization, and 2) the heterogeneous response of neuronal microtubules to methylmercury, presumably reflecting posttranslational modifications of different subpopulations of microtubules in the perikarya and neurite.