UDP-N-acetylglucosamine:alpha-3-D-mannoside
beta-1,2-N-acetylglucosaminyltransferase I (GnT I) is a key enzyme in the synthesis of hybrid and complex N-glycans. Disruption of the GnT I gene in the mouse results in arrest of embryogenesis. Defects in the synthesis of complex N-glycans have been shown to be associated with several human congenital diseases. We are investigating the role of complex N-glycans in C. elegans . Three C. elegans genes homologous to mammalian GnT I have been identified by searching the genome databases. They are designated
gly-12,
gly-13 and
gly-14 . cDNAs encoding these predicted genes have been cloned and their expression patterns determined. Both
gly-12 and
gly-14 encode active enzymes while
gly-13 does not, towards the substrate tested [Chen et al ., 1999]. To better understand its biological function, we wanted to isolate a GnT I null mutant. We screened worms that were UV irradiated in the presence of trimethylpsoralen(TMP) and isolated a mutant with a 1.6kb deletion of
gly-12 . The deletion covers from intron 6 to exon 12, a DNA fragment encoding most of the GnT I C-terminal catalytic domain. The mutants have no obvious phenotypic defects. A Tc1 insertion has been detected within intron 9 of
gly-14 . Screening for Tc1 derived deletions is under way. We will create double mutants that lack both
gly-12 and
gly-14 to test the redundancy of these two GnT I genes. Chen, S., Zhou, S., Sarkar, M., Spence, A. M., and Schachter, H. (1999) J. Biol. Chem. 274 , 288-297.