D. Chui et al., ALPHA-MANNOSIDASE-II DEFICIENCY RESULTS IN DYSERYTHROPOIESIS AND UNVEILS AN ALTERNATE PATHWAY IN OLIGOSACCHARIDE BIOSYNTHESIS, Cell, 90(1), 1997, pp. 157-167
Alpha-mannosidase-II (alpha M-II) catalyzes the first committed step i
n the biosynthesis of complex asparagine-linked (N-linked) oligosaccha
rides (N-glycans). Genetic deficiency of alpha M-II should abolish com
plex N-glycan production as reportedly does inhibition of alpha M-II b
y swainsonine. We find that mice lacking a functional alpha M-II gene
develop a dyserythropoietic anemia concurrent with loss of erythrocyte
complex N-glycans. Unexpectedly, nonerythroid cell types continued to
produce complex N-glycans by an alternate pathway comprising a distin
ct alpha-mannosidase. These studies reveal cell-type-specific variatio
ns in N-linked oligosaccharide biosynthesis and an essential role for
alpha M-II in the formation of erythroid complex N-glycans. alpha M-II
deficiency elicits a phenotype in mice that correlates with human con
genital dyserythropoietic anemia type II.