UDPgalactose inhibits blastocyst formation in the mouse. Implications for the mode of action of T/t-complex mutations.

The effect of UDPgalactose on normal mouse blastocyst formation has been examined. In the presence of 10 mM UDP galactose, only 37% of the morulae differentiated into blastocysts, while 92% formed blastocysts in the absence of UDPgalactose. Identical concentrations of galactose and UDPglucose were ineffective in disturbing morulae development. The presence of anti-F9 antiserum (1/11 final dilution) protected approximately 76% of the morulae from the effects of UDPgalactose. The same anti-F9 antiserum offered no protective value when all of its anti-F9 activity was removed by prior absorption with F9 cells. These results suggest that the function of the F9 antigen, crucial for blastocyst formation, may be integrated with galactosyltransferase activity.