Mouse zygotes express endogenous lectins

Cell interactions during mouse development have been shown to involve carbohydrate‐containing macromolecules (glycoconjugates). We have therefore used a series of fluorescein‐labelled synthetic glycoproteins to determine if mouse oocytes and zygotes also express sugar binding molecules (endogenous lectins) which might participate in such interactions. Unfertilised secondary oocytes did not express endogenous lectins at 4°C but a low level of expression of fucose, mannose, and galactose‐binding activity could be detected at 37°C. In contrast, the zygote clearly expressed three classes of endogenous lectins, with preferential binding for i) fucose or mannose, ii) glucose or galactose, and iii) lactose. The expression of these lectins was much reduced at 4°C and maximal binding at 37°C was achieved only after 2 h incubation. We therefore conclude that a low level of endogenous lectin expression in the mouse oocyte is greatly enhanced after fertilisation and that, at both stages, expression, or the detection of expression, is markedly temperature dependent.