DIFFERENTIAL DISTRIBUTION OF GLUTAMYLATED TUBULIN DURING SPERMATOGENESIS IN MAMMALIAN TESTIS

The distribution of glutamylated tubulin has been analyzed in mammalia n testis using the specific mAb GT335 by immunoelectron microscopy and immunoblotting. In spermatozoa of various species, immunogord labelin g showed the pres ence of glutamylated tubulin in all of the microtubu les of axoneme and centrioles, whereas the microtubule network of the spermatid manchette was unlabeled. In earlier germ cells, centriole wa s the only microtubule structure to be labeled. A similar distribution was observed using the anti-acetylated tubulin antibody (6-11B-l), co nfirming previous results of Hermo et al. [Anat. Rec. 229:31-50, 1991] . However, among testicular somatic cells, microtubules of some Sertol i cell branches were not acetylated but glutamylated. 2-D PAGE of mous e and hamster sperm extracts showed a high level of alpha and beta-tub ulin heterogeneity, comparable to that found in brain. Immunoblotting with GT335 revealed a large amount of glutamylated tubulin resolved in to numerous alpha as well as beta-tubulin isoforms. This suggests that the major testis-specific tubulin isotypes (m alpha 3/7 and m beta 3) are also glutamylatable. These results show a subcellular sorting of posttranslationally modified tubulin isoforms in spermatids, glutamyla tion being associated with the most stable microtubule structures. (C) 1994 Wiley-Liss, Inc.