The differentiation process of intestinal epithelial cells is associated with the appearance of statin, a non-proliferation-specific nuclear protein.

The expression of statin, a 57,000 Mr nuclear protein specifically present in non-proliferating cultured fibroblasts, was studied in vivo in the differentiating epithelial cells of the rat intestine. Using immunofluorescence microscopy we found that undifferentiated, proliferating crypt enterocytes are statin negative, whereas the differentiated non-proliferating villus enterocytes are statin positive. The epithelial cells of the intestine were isolated according to different stages of differentiation and the expression of statin was studied biochemically by immunoblotting assays. The prominent band (57,000 Mr) was present in abundance in villus cell fractions but undetectable in crypt cell fractions. These findings were also confirmed by immunofluorescence microscopy on individual intestinal epithelial cells of the different isolated fractions. The results presented here, which are similar to observations made in cell cultures, suggest that statin is a unique protein associated with the non-proliferative state of differentiated cells in tissue.