Craniofacial skeletal defects of adult zebrafish Glypican 4 (knypek) mutants

Abstract

The heparan sulfate proteoglycan Glypican 4 (Gpc4) is part of the Wnt/planar cell polarity pathway, which is required for convergence and extension during zebrafish gastrulation. To observe Glypican 4-deficient phenotypes at later stages, we rescued gpc4 2/2 (knypek) homozygotes and raised them for more than one year. Adult mutants showed diverse cranial malformations of both dermal and endochondral bones, ranging from shortening of the rostral-most skull to loss of the symplectic. Additionally, the adult palatoquadrate cartilage was disorganized, with abnormal chondrocyte orientation. To understand how the palatoquadrate cartilage normally develops, we examined a juvenile series of wild type and mutant specimens. This identified two novel domains of elongated chondrocytes in the larval palatoquadrate, which normally form prior to endochondral ossification. In contrast, gpc4 2/2 larvae never form these domains, suggesting a failure of chondrocyte orientation, though not differentiation. Our findings implicate Gpc4 in the regulation of zebrafish cartilage and bone morphogenesis.

Distinct requirements for wnt9a and irf6 in extension and integration mechanisms during zebrafish palate morphogenesis

“…2A,B). Likewise, Wnt regulation of the convergence extension process during zebrafish embryogenesis has been described, where disruption of Wnt/planar cell polarity in the zebrafish gpc4 mutant also resulted in foreshortened ethmoid plate (Verkade and Heath, 2008;LeClair et al, 2009).…”

Muscle contraction controls skeletal morphogenesis through regulation of chondrocyte convergent extension

“…During this process, mesenchymal cells condense and differentiate to chondrocytes, which proliferate to form a cartilaginous anlage that is later replaced by bone (Provot and Schipani, 2005). During endochondral ossification, the mediolateral intercalation of chondrocytes into columns is an important module that facilitates elongation and contributes to bone morphology (Ahrens et al, 2009;Aszodi et al, 2003;Bengtsson et al, 2005;Clement et al, 2008;Dodds, 1930;Gao et al, 2011;Keller et al, 2000;Kimmel et al, 1998;LeClair et al, 2009;Li and Dudley, 2009;Sarmah et al, 2010;Yang et al, 2003). Cell intercalation is a morphogenetic process, which occurs in epithelial or mesenchymal cells and leads to tissue narrowing, known as convergence, and its elongation, or extension.…”

On the Roles and Regulation of Chondroitin Sulfate and Heparan Sulfate in Zebrafish Pharyngeal Cartilage Morphogenesis

“…A number of genes involved in PG biosynthesis have been shown to be crucial for the development of the jaw and the pharyngeal arches in zebrafish, including glypican 4 (gpc4/knypek) (9,10), UDP-glucuronic acid decarboxylase 1 (uxs1) (11,12), exostosin 2 (ext2/dackel) (12)(13)(14)(15), exostoses (multiple)-like 3 (extl3/boxer) (15), udp-glucose dehydrogenase (ugdh/jekyll) (16,17), and solute carrier family 35, member B2 (slc35b2/ pincher, reported as papst1) (13). From previous studies of these genes, it stands relatively clear that PGs are required for the intercalation of chondrocytes during the formation of rodlike cartilage structures.…”