DISTRIBUTION OF BASEMENT-MEMBRANE COMPONENTS IN THE MOUSE PRIMARY PALATE

Laminin, type IV collagen, and fibronectin are major components of the basement membrane of epithelial tissues. The purpose of this study wa s to characterize their distributions as the epithelial seam of the pr imary palate is disrupted and the mesenchymal bridge forms and enlarge s. The distributions of these molecules were studied with indirect imm unofluorescence in day 11 (9-20 tail somites), noncleft CD1 mice. Duri ng epithelial seam formation at 9-11 tail somites (TS), all three mole cules were intensely localized in the basement membrane of the seam an d adjacent stomodeal and nasal epithelia. During epithelial seam repla cement by mesenchymal tissues at 12-18 TS, basement membrane component s were first fragmented along the seam, then absent at the site of the mesenchymal bridge. At 19-20 TS, basement membrane components were in tact around the margins of the primary palate. These results show that disruption of basement membrane components occurs rapidly and simulta neously with mesenchymal bridge formation in the primary palate.