Project description:In this study, we have investigated the molecular basis of Shh signalling during development of the secondary palate and how CNCC patterning and fate is influenced by the Shh signalling network. Using a gain-of-function mouse model to activate Smoothened (R26SmoM2) signalling in the palatal mesenchyme (Osr2-IresCre), we demonstrate ectopic Hh-Smo signalling results in fully penetrant cleft palate, disrupted oral-nasal patterning and defective palatine bone formation. We show that a series of Fox transcription factors, including the novel direct target Foxl1, function downstream of Hh signalling in the secondary palate. Furthermore, we demonstrate that Wnt/BMP antagonists, in particular Sostdc1, are positively regulated by Hh signalling, concomitant with down-regulation of key regulators of osteogenesis and BMP signalling effectors. Microarray analysis was performed on excised palatal shelves from Osr2-IresCre+/- (wild-type) and Osr2-IresCre;Smo+/M2 (mutant) embryos at embryonic day (E)13.5. Osr2-IresCre (PMID:17941042) and R26SmoM2 (PMID:15107405) mice have been described previously.