DIFFERENTIAL EXPRESSION OF LAMININ ISOFORMS AND ALPHA-6-BETA-4 INTEGRIN SUBUNITS IN THE DEVELOPING HUMAN AND MOUSE INTESTINE

The intestinal tissue is characterized by important morphogenetic move ments during development as well as by a continuous dynamic crypt to v illus epithelial cell migration leading to differentiation of speciali zed cells. In this study, we have examined the spatio-temporal distrib ution of laminin A and M chains as well as of alpha 6 and beta 4 integ rin subunits in adult and developing human and mouse intestine by indi rect immunofluorescence. Selective expression of the constituent polyp eptides of laminin isoforms (A and M chains) was demonstrated. In the mature human intestine, A and M chains were found to be complementary, the M chain being restricted to the base of crypts and the A chain li ning the villus basement membrane. In the developing human intestine, M chain expression was delayed as compared to that of A chain; as soon as the M chain was visualized, it exhibited the typical localization in the crypt basement membrane. A somewhat different situation was fou nd in the adult mouse intestine, since both M and A chains were found in the crypts. During mouse intestinal development the delayed express ion of the M chain as compared to that of the A chain was also obvious . The absence of M chain expression in mutant dy mouse did not impair intestinal morphogenesis nor cell. differentiation. The expression of alpha 6 and beta 4 subunits was not coordinated. In both species the a lpha 6 expression preceded that of beta 4. Furthermore, while beta 4 s taining in adult mouse intestine was detected at the basal surface of all cells lining the crypt-villus, that of alpha 6 was mainly confined to the crypt cell compartment. An overall similarity of location betw een alpha 6 integrin subunit and laminin A chain at the epithelial/str omal interface was noted. These data indicate that the spatial and tem poral distribution of laminin variants in the developing intestine may be characteristic for each species and that interactions of laminin v ariants with particular receptors may be important for induction and/o r maintenance of differentiated cells. (C) 1994 Wiley-Liss, Inc.