Differential expression of laminin isoforms and α6‐β4 integrin subunits in the developing human and mouse intestine

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Abstract
The intestinal tissue is characterized by important morphogenetic movements during development as well as by a continuous dynamic crypt to villus epithelial cell migration leading to differentiation of specialized cells. In this study, we have examined the spatio-temporal distribution of laminin A and M chains as well as of α6 and β4 integrin subunits in adult and developing human and mouse intestine by indirect immunofluorescence. Selective expression of the constituent polypeptides 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 lining 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 found in the adult mouse intestine, since both M and A chains were found in the crypts. During mouse intestinal development the delayed expression 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 α6 and β4 subunits was not coordinated. In both species the α6 expression preceded that of β4. Furthermore, while β4 staining in adult mouse intestine was detected at the basal surface of all cells lining the cryptvillus, that of α6 was mainly confined to the crypt cell compartment. An overall similarity of location between α6 integrin subunit and laminin A chain at the epithelial/stromal interface was noted. These data indicate that the spatial and temporal distribution of laminin variants in the developing intestine may be characteristic for each species and that interactions of laminin variants with particular receptors may be important for induction and/or maintenance of differentiated cells.

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