IN-VIVO OVEREXPRESSION OF CORE2 N-ACETYLGLUCOSAMINYLTRANSFERASE PREVENTS REPOPULATION OF THE BONE-MARROW WITH COLONY-FORMING CELLS BUT FAILS TO AFFECT NORMAL T-CELL DEVELOPMENT

UDP-GlcNAc:Gal beta 1 --> 3GalNAc-R beta 1 --> 6N-acetylglucosaminyltr ansferase (Core2 N-acetyl-glucosaminyltransferase, C2GnT; EC 2.4.1.102 ) forms beta 1 --> 6N-acetyl-glucosaminyl linkages in O-glycoproteins and creates branches for the addition of N-acetyl-lactosamine antennae . Changes in C2GnT activity have been associated with immune disorders , malignancies, and T-cell ontogeny. In this study, we used SCID (seve re combined immune deficiency) mice to determine the effects of C2GnT overexpression on hemopoiesis, and in particular, on thymocyte develop ment. BALB/c bone marrow cells transfected with C2GnT using the retrov iral murine stem cell vector were used to repopulate SCID mice. Mice w ere analysed 3 weeks to 3 months after bone marrow transfer. Elevated levels of C2GnT activity in bone marrow, spleen, and thymus from mice repopulated with C2Gnt transfected bone marrow cells indicated that C2 GnT was overexpressed in recipient mice. In C2GnT repopulated mice, up to 50% of T cells showed an increase in CD43 130-kDa expression, comp ared with T cells from control animals, indicative of an elevated C2Gn T activity in these cells. Furthermore, T-cell subset numbers appeared to be normal, suggesting that C2GnT overexpression did not alter T-ce ll ontogeny. Interestingly, C2GnT overexpression negatively affected t he repopulation of myeloid cells. Only insignificant numbers of interl eukin-3/granulocyte-macrophage colony stimulating factor (IL-3/GM-CSF) responsive bone marrow cells were found to be retrovirally transfecte d in C2GnT repopulated mice, whereas up to 50% of IL-3/GM-CSF responsi ve bone marrow cells were found to be retrovirally transfected in corr esponding controls. These data indicate that in vivo overexpression of C2GnT negatively interferes with the myeloid differentiation pathway but does not affect T-cell development. (C) 1998 Wiley-Liss, Inc.