The in vivo role of alpha-mannosidase IIx and its role in processing of N-glycans in spermatogenesis.

The surfaces of mammalian cells are covered by a variety of carbohydrates linked to proteins and lipids. N-glycans are commonly found carbohydrates in plasma membrane proteins. The structure and biosynthetic pathway of N-glycans have been analyzed extensively. However, functional analysis of cell surface N-glycans is just under way with recent studies of targeted disruption of genes involved in N-glycan synthesis. This review briefly introduces the potential role of processing alpha-mannosidases in N-glycan biosynthesis and recent findings derived from the alpha-mannosidase IIx (MX) gene knockout mouse, which shows male infertility. Thus, the MX gene knockout experiment unveiled a novel function of specific N-glycan, which is N-acetylglucosamine-terminated and fucosylated triantennary structure, in the adhesion between germ cells and Sertoli cells. Analysis of the MX gene knockout mouse is a good example of a multidisciplinary approach leading to a novel discovery in the emerging field of glycobiology.