EFFECTS OF METHIONINE ON THE CYTOPLASMIC DISTRIBUTION OF ACTIN AND TUBULIN DURING NEURAL-TUBE CLOSURE IN RAT EMBRYOS

Research has previously shown that, without methionine supplements, ne ural tube proteins of rat embryos cultured on bovine sera were hypomet hylated and neural tubes failed to close, In the present study, to ide ntify the proteins that became methylated during neurulation, rat embr yos were first cultured on methionine-deficient bovine serum for 40 hr , then incubated with puromycin for 1 hr, and, finally, incubated with [methyl-C-14] methionine and puromycin for 5 hr. On the basis of mole cular weights, isoelectric points, and Western immunoblots, the methyl -C-14-labeled proteins,were identified as actin, alpha beta-tubulin, a nd neurofilament L. Indirect immunofluorescence studies indicated that without the addition of methionine to the culture, localization of ac tin and alpha beta-tubulin in the basal cytoplasm did not occur and th ese neuroepithelial cells lost their columnar morphology.