Different expression patterns of Gli1–3 in mouse embryonic maxillofacial development

The Sonic hedgehog (SHH) signaling pathway plays many key roles in the development of Drosophila and vertebrate embryos, including regulating craniofacial development. The GLI family of transcription factors (GLI1, 2, and 3) mediates the SHH morphogenetic signal by regulating the expression of downstream target genes. Signaling aberrations seriously affect vertebrate development. To better understand the regulation of GLI transcription factors, we investigated the expression patterns of Gli1–3 during murine embryonic craniofacial development using in situ hybridization with whole-mounts and sections and quantitative real-time PCR. We found that Gli1 expression was mostly detected in the mesenchyme in embryonic dermis, and strongly detected in embryonic oral mucosa at late stages of face development. Gli2 was strong in mesenchyme, both in dermis and oral mucosa. Gli3 expression was detected fainter in the epithelium than the mesenchyme at 11 days post-coitum (dpc), but at 14.5 dpc, expression was stronger in the epithelium. Of the three genes, Gli1 expression was highest in early stages of face development, Gli3 expression was highest in the second half of facial development (and remained stable thereafter), whereas Gli2 expression remained low throughout facial development. The present findings suggest that Gli1–3 may play different roles during facial development.