Precise orchestration of palate formation involves the complex interaction of signalling cascades and transcriptional networks in the developing craniofacial region. Pax9 and Osr2 have previously been implicated in palate formation, but little is known about how these molecular components interact within the greater regulatory network. Now, on , Rulang Jiang and colleagues report a crucial role for Pax9 in patterning the anterior-posterior axis as well as outgrowth of the developing palatal shelves. The authors show that Pax9 regulates mesenchyme-epithelium interactions during pattern formation and that the expression of several key genes involved in palate development, such as Shh, Bmp4, Fgf10, Msx1 and Osr2, is reduced in Pax9 mutant mice. Interestingly, expression of Osr2 from the Pax9 locus was able to rescue the posterior, but not anterior, palate formation defect in the absence of Pax9 function. These data place Pax9 upstream of transcription factor Osr2 and signalling molecules Bmp4, Fgf10 and Shh in the molecular network that regulates palate development.
