Shh and Ptch Expression in Mouse Embryonic Craniofacial Development

Volume 11, Number 1, 2008 Hedgehog (HH) proteins, a family of secreted molecules first identified by a genetic screen in Drosophila, are involved in many patterning processes during development. Sonic hedgehog (SHH) is the most broadly expressed member of three mammalian HH homologues and is probably responsible for the major effects of this signalling pathway. Genes in the Shh signalling pathway include Shh, patched (Ptch), patched2 (Ptch2), smoothened (Smo), Gli1, Gli2, and Gli3. PTCH, the putative 12-pass transmembrane receptor for SHH, normally acts to inhibit SHH signalling by repressing the signalling activity of a seven-pass transmembrane protein, Smoothened (SMO). This inhibition is relieved when SHH binds to PTCH, possibly through changes in distribution or concentration of a small molecule1 and allows a zinc-finger-type transcription factor GLI to enter the nucleus, where it regulates transcription. Compared with many reports about the expression of Shh and Ptch in the brain and limb2–5, there are few studies focusing on expression patterns in the oral maxillofacial region6,7. Many studies indicate that Shh and Ptch play key roles in embryonic craniofacial development, but few studies address the particular expression of Shh and Ptch in the craniofacial region, and their functions in development remain unclear. In this study we use wholemount and section in-situ hybridization (ISH), immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) to study the gene expression patterns of the Shh signalling pathway during mouse embryonic craniofacial development. Objective: To evaluate the particular expression of Shh and its receptor patched (Ptch) involved in mouse embryonic craniofacial development. Methods: The expression patterns of Shh pathway genes during murine embryonic craniofacial development were investigated by applying in-situ hybridization studies of whole-mount and sections, immunohistochemistry, and reverse transcription polymerase chain reaction analysis. Results: Shh was expressed in the mouse embryo at 11 and 12.5 days postcoitum (dpc); Ptch was expressed at 11, 12.5, and 14.5 dpc, but expression patterns were different. SHH protein could also be detected at 11, 12.5, and 14.5 dpc, confirming the gene expression studies. Conclusion: Shh and Ptch expression patterns are characterized. The data suggest that Shh and Ptch are involved during craniofacial development and their roles may vary.