Figure 9.
Figure 9. Summary diagram. The relative levels of GnT1IP-L and GlcNAcT-I transcripts in germ cells vary during spermatogenesis as indicated (Chalmel et al., 2007; Fig. 8), and the N-glycans on germ cells vary as shown by changes in lectin binding (Jones et al., 1992). In spermatogonia, negligible levels of the new GlcNAcT-I inhibitor GnT1IP-L described herein, and high GlcNAcT-I leads to the synthesis of complex N-glycans. In spermatocytes, increased expression of GnT1IP-L accompanied by down-regulation of GlcNAcT-I leads to the expression of high mannose N-glycans on germ cell glycoproteins. This change in N-glycans is predicted to enhance the binding of spermatocytes to Sertoli cells (Fig. 8). At later stages of spermatogenesis GnT1IP-L expression levels decrease while GlcNAcT-I levels increase, and spermatids express complex N-glycans and have reduced binding to Sertoli cells.

Summary diagram. The relative levels of GnT1IP-L and GlcNAcT-I transcripts in germ cells vary during spermatogenesis as indicated (Chalmel et al., 2007; Fig. 8), and the N-glycans on germ cells vary as shown by changes in lectin binding (Jones et al., 1992). In spermatogonia, negligible levels of the new GlcNAcT-I inhibitor GnT1IP-L described herein, and high GlcNAcT-I leads to the synthesis of complex N-glycans. In spermatocytes, increased expression of GnT1IP-L accompanied by down-regulation of GlcNAcT-I leads to the expression of high mannose N-glycans on germ cell glycoproteins. This change in N-glycans is predicted to enhance the binding of spermatocytes to Sertoli cells (Fig. 8). At later stages of spermatogenesis GnT1IP-L expression levels decrease while GlcNAcT-I levels increase, and spermatids express complex N-glycans and have reduced binding to Sertoli cells.

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