Expression of glycylated tubulin during the differentiation of spermatozoain mammals

Using quantitative immunogold analyses of tubulin isoforms we previously de monstrated a unique differential expression of glutamylated tubulin in the flagellum of mouse and man spermatozoa [Fouquet et al., 1997: Tissue Cell 2 9:573-583]. We have performed similar analyses far glycylated tubulin using two monoclonal antibodies, TAP 952 and AXO 49, directed to mono- and polyg lycylated tubulin respectively. Glycylated tubulin was not found in centrio les and cytoplasmic microtubules (manchette) of germ cells. In mouse and ma n, axonemal tubulin was first monoglycylated and uniformly distributed in a ll doublets at all levels of the flagellum in elongating spermatids. In hum an mature spermatozoa axonemal microtubules were enriched in monoglycylated tubulin from the base to the tip of the flagellum. In mouse sperm flagellu m a similar gradient of monoglycylated tubulin was also observed in additio n to an opposite gradient of polyglycylated tubulin. In both species, monog lycylated tubulin labeling predominated in doublets 3-8 whereas glutamylate d tubulin labeling [Fouquet et al., 1997] predominated in doublets 1-5-6. T hese differential labelings were suppressed after motility inhibition of mo use spermatozoa by sodium azide treatment and in non-motile human spermatoz oa lacking dynein arms. The unique distribution of these tubulin isoforms a nd the known inhibition of motility induced by their specific antibodies ar e consistent with a complementary role of tubulin glycylation and glutamyla tion in the regulation of flagellar beating in mammalian spermatozoa. (C) 1 998 Wiley-Liss, Inc.