Differential expression of the integrins α6Aβ4 and α6Bβ4 along the crypt-villus axis in the human small intestine

The integrin alpha 6 subunit exists as two different variants, termed alpha 6A and alpha 6B. These two variants have been shown to harbor potentially distinct biochemical properties but little is known about their cellular function. The aim of this work was to characterize the expression of the integrin alpha 6A and B variants in relation to cell proliferation and differentiation in the human small intestinal epithelium. The results showed distinct expression patterns for the two variants along the crypt-villus axis. Indeed, proliferative cells of the crypt were found to predominantly express alpha 6A, while differentiated enterocytes and Paneth cells expressed the alpha 6B variant. A similar relationship was observed in intestinal cell models by competitive RT-PCR. Further studies in the Caco-2 cell model showed that manipulating the cellular balance of the two alpha 6 variants can influence transcriptional activities related to cell proliferation but not differentiation. This suggests that differential expression of the alpha 6 subunits is involved in the intestinal epithelial cell renewal process. Further studies will be needed to substantiate this hypothesis.