Wwp2 is essential for palatogenesis mediated by the interaction between Sox9 and mediator subunit 25

Abstract

Sox9 is a direct transcriptional activator of cartilage-specific extracellular matrix genes and has essential roles in chondrogenesis. Mutations in or around the SOX9 gene cause campomelic dysplasia or Pierre Robin Sequence. However, Sox9-dependent transcriptional control in chondrogenesis remains largely unknown. Here we identify Wwp2 as a direct target of Sox9. Wwp2 interacts physically with Sox9 and is associated with Sox9 transcriptional activity via its nuclear translocation. A yeast two-hybrid screen using a cDNA library reveals that Wwp2 interacts with Med25, a component of the Mediator complex. The positive regulation of Sox9 transcriptional activity by Wwp2 is mediated by the binding between Sox9 and Med25. In zebrafish, morpholino-mediated knockdown of either wwp2 or med25 induces palatal malformation, which is comparable to that in sox9 mutants. These results provide evidence that the regulatory interaction between Sox9, Wwp2 and Med25 defines the Sox9 transcriptional mechanisms of chondrogenesis in the forming palate.

The transcription factor Foxc1 is necessary for Ihh–Gli2-regulated endochondral ossification

“…Moreover, several reports have indicated that the combination of tissue-specific reporter mice and FACS-assisted microarray profiling is a useful tool in gene screening. For example, Nakamura et al 50 identified Wwp2 as a Sox9 target gene in chondrocytes using Sox9-3 0 EGFP knock-in mice, while Ieda et al 51 identified three transcription factors that enable the direct reprogramming of dermal fibroblasts into functional cardiomyocytes using the aMHC promoter. Although we focused on Foxc1 in this study, other genes identified by microarray analysis might play important roles in endochondral ossification.…”

The Mediator complex: a master coordinator of transcription and cell lineage development

“…It has been shown that MED12 functions as a co-factor of Sox9 and plays an important role in craniofacial chondrogenesis/endochondral bone formation during zebrafish development (Zhou et al, 2002). Recently, MED25 was found to be another direct target of Sox9, and morpholino-mediated knockdown of Med25 in zebrafish resulted in palatal malformation similar to that observed in sox9 mutants (Nakamura et al, 2011). Med31 mutant mice exhibit normal limb bud patterning but experience delayed chondrogenesis due to a lack of Col2a1 and Sox9 expression (Risley et al, 2010).…”

Palatogenesis: morphogenetic and molecular mechanisms of secondary palate development

“…In addition, the chick is a classical experimental embryology model system in which palate morphogenesis has been characterized (Ferguson, 1988). More recently, several studies have used the morpholino knockdown approach in zebrafish to assess gene function in palate development (Ghassibe-Sabbagh et al, 2011;Nakamura et al, 2011;Swartz et al, 2011). It is therefore important to understand the extent to which mechanisms for palatogenesis are conserved across these species.…”