Meeting Abstract

135.3  Monday, Jan. 7  Planar polarity controls cartilage morphogenesis during vertebrate jaw development LE PABIC, P*; NG, CL; SCHILLING, TF; Univ. of California, Irvine; Univ. of California, Irvine; Univ. of California, Irvine plepabic@uci.edu

Little is known about the mechanisms of cell-cell communication necessary to assemble skeletal elements of appropriate size and shape. Skeletal progenitors may behave as coherent units by communicating via the planar cell polarity (PCP) pathway – a signaling system best known for its role in propagating consistent hair orientation across mammalian skin and insect cuticle. We find that cartilage of the jaw and in fact all pharyngeal cartilages in larval teleosts are polarized and that this polarity is conserved across vertebrate taxa. In Drosophila, two sets of factors control PCP independently: the Fat and the non-canonical Wnt signaling systems. While a requirement for components of the non-canonical Wnt system has been recently demonstrated in regulating the oriented divisions and intercalations of chondrocytes in the growth plates of long bones, a role for the Fat system in skeletal development has not been reported. We find that loss of several Fat-pathway orthologues in zebrafish disrupts chondrocyte polarity and stacking – two PCP-regulated behaviors in other contexts such as gastrulation. Furthermore, Fat signaling appears to link polarity with the onset of sox9 and col2 expression necessary for cartilage differentiation. Consistent with a role for Fat in cartilage PCP, mosaic studies demonstrate that requirements for Fat are non-cell autonomous. These results provide genetic evidence that skeletal morphogenesis and differentiation are controlled through a conserved Fat signaling pathway, and suggest that this mechanism of cell-cell communication is important for determining skeletal element size and shape.