RESTRICTED DISTRIBUTION OF INTEGRIN BETA-6 MESSENGER-RNA IN PRIMATE EPITHELIAL TISSUES

Integrins are cell adhesion receptors that mediate cell-extracellular matrix and cell-cell interactions. Each integrin consists of two glyco protein subunits (alpha and beta). We have previously described a nove l integrin beta-subunit, beta6, which is expressed in cultured epithel ial cells. Beta6 can associate with alphav to form the fibronectin-bin ding heterodimer alphavbeta6. Here we report the tissue distribution o f beta6 integrin mRNA determined by in situ hybridization of a beta6 c RNA probe with representative frozen tissue sections from a rhesus mon key tissue bank. We detected beta6 mRNA exclusively in epithelial cell s. However, beta6 mRNA expression varied greatly among different epith elia. High levels of beta6 mRNA were found only in two very specialize d epithelial cell types: a portion of the kidney tubule epithelium, te rmed macula densa, and the endometrial epithelium of secretory phase u terus. In the endometrium, beta6 expression was highest in the differe ntiated epithelium of functional layer glands, suggesting that beta6 e xpression can be regulated in a differentiation-dependent manner. Beta 6 expression may also depend on the stage in the estrous cycle, since we found much lower beta6 mRNA levels in a specimen of proliferative p hase endometrium. Epithelium in several other tissues, including saliv ary gland ducts, gall bladder, and epididymis, contained detectable le vels of beta6 mRNA, albeit much lower than in macula densa and endomet rium. In other epithelia, including skin and lung, beta6 mRNA was unde tectable. Taken together, these results suggest that in normal adult p rimates beta6 expression is regulated in a cell type-specific manner, restricted to a few epithelial tissues.