Coordination of dorsoventral axis formation by multiple heparan sulfate proteoglycans

Abstract

Heparan sulfate proteoglycans are essential mediators of multiple cell‐cell signaling pathways during embryonic development. To better understand how glypicans (GPCs) ‐ a membrane anchored subfamily of heparan sulfate core proteins ‐ function in zebrafish development, we used antisense morpholinos to individually and specifically knock down the expression of all ten GPC genes in zebrafish. Knockdown of GPC2, GPC6a, or GPC6b uniquely resulted in strong dorsoventral phenotypes between gastrulation and 24hpf. To better understand the molecular pathways in which GPCs are involved, we used a candidate gene approach to study changes in transcription of BMP, Wnt and FGF target genes because these cell‐cell signaling pathways are known to regulate dorsoventral patterning. We identified gene expression patterns that were different between each GPC knockdown, with GPC2 having a distinct affect on FGF target genes. These results were confirmed using several complimentary approaches, suggesting that GPC2, GPC6a, and GPC6b regulate distinct steps in dorsoventral patterning, an observation that adds a new dimension to our understanding of how proteoglycans work together to mediate early development.