MOLUCCELLA LAEVIS LECTIN, A MARKER FOR CELLULAR-DIFFERENTIATION PROGRAMS IN MOUSE GUT EPITHELIUM

We have assembled a system for testing the hypothesis that changes in glycoconjugate production represent markers for defining developmental , spatial, and environmental influences on the proliferation and diffe rentiation programs of various mouse gut epithelial cell lineages. Mul tilabel immunohistochemical methods were used to survey the interactio ns of purified lectins with 1) normal fetal, neonatal, and adult FVB/N mouse gut, 2) gastric and intestinal isografts harvested at various d evelopmental stages, and 3) transgenic mouse models of intestinal epit helial cell hyperplasia, dysplasia, and/or neoplasia. As a demonstrati on of the system's utility, we used the recently purified, alpha-N-ace tyl-D-galactosamine-specific, Moluccella laevis lectin (MLL). In the a dult FVB/N mouse stomach, MLL only recognizes glycoconjugates produced by a population of nonproliferating neck and prezymogenic cells that occupy a pivotal point in the complex, migration-associated differenti ation program of the zymogenic cell lineage. In the developing FVB/N s tomach, MLL binds to members of the zymogenic and pit lineages even be fore morphogenesis of gastric units is completed. Expression of MLL ep itopes in pit cells is restricted to the period before the gastric epi thelium has completed its morphoregulatory program. Analysis of gastri c isografts indicates that these lineage- and developmental stage-spec ific patterns of glycoconjugate accumulation are not influenced by nor mal luminal contents. In the adult FVB/N intestine, MLL binding can be used to operationally define variations in the differentiation progra ms of 1) members of the enteroendocrine and goblet cell lineages durin g their migration along the crypt-to-villus axis and 2) cells comprisi ng the follicle-associated epithelium overlying Peyer's patches. Accum ulation of MLL epitopes in villus-associated enterocytes does not appe ar to be affected when these cells are induced to reenter the cell cyc le by simian virus 40 large T antigen (SV40 TAg). MLL reactivity is no t diminished when enterocytes begin to dedifferentiate as a result of production of SV40 TAg, human K-ras(Val12), and a dominant negative hu man p53 mutant. The lack of change in MLL binding properties may refle ct the brief residence time of enterocytes on the villus. These result s indicate that glycoconjugate production represents a very useful too l for studying gut epithelial cell biology. Preliminary studies sugges t that this is also true in the human gut.