Loxl3 Affects Palatal Shelf Elevation by Regulating Cell Proliferation and Collagen Deposition.

Cleft palate is one of the most common congenital abnormalities and one of the main symptoms of Stickler syndrome. Secondary palate development is a complex multi-step process that involves raising the palatal frame from a vertical to a horizontal position. Lysyl oxidase-like 3 (LOXL3), a member of the lysyl oxidase family responsible for the crosslinking in collagen, is also one of the mutated genes detected in Stickler syndrome. Loss of Loxl3 causes delayed palatal shelf elevation, which in turn resulted in cleft palate. However, the precise mechanisms of palatal shelf delayed elevation remain unclear. In this study, we deeply investigated the mechanism of Loxl3 induced delayed elevation in palatal shelves. We found that Loxl3 deficiency caused reduced cell proliferation in both medial and posterior palatal mesenchyme through BrdU labeling and Western blot analysis (p < 0.05, p < 0.01), decreased migration of palatal mesenchymal cells through cell scratch assay (p < 0.05), and decreased expression of genes associated with proliferation through Western blot analysis (p < 0.05, p < 0.01) at E14. We found that the specific deletion of Loxl3 in the palatal mesenchyme resulted in delayed elevation but normal fusion of palatal shelves, also reduced cell proliferation and collagen fibers deposition in medial palatal mesenchyme through BrdU labeling and histological analysis (p < 0.05, p < 0.01). Thus, our data suggest that Loxl3 regulates cell proliferation and collagen fibers deposition in the palatal mesenchyme, thus controlling palatal shelf elevation.