The role of Shh transcription activator Gli2 in chick cloacal development

• Published in: Developmental biology 2007-03, Vol.303 (2), p.448-460
• Main Authors: Liu, Guodong, Moro, Anne, Zhang, Jennifer J.R., Cheng, Wei, Qiu, Wei, Kim, Peter C.W.
• Format: Article
• Language: English
• Subjects: Animals; Animals, Genetically Modified; Apoptosis; Base Sequence; Cell Cycle; Cell Differentiation; Cell Proliferation; Chick embryo; Chick Embryo - embryology; Chick Embryo - physiology; Cloaca; Cloaca - embryology; DNA Primers - genetics; Endoderm - cytology; Gene Expression Regulation, Developmental; Gli2; Hedgehog Proteins - genetics; Hedgehog Proteins - physiology; Hindgut; Kruppel-Like Transcription Factors - genetics; Kruppel-Like Transcription Factors - physiology; Mesoderm - cytology; p63; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Shh pathway; Signal Transduction; Trans-Activators - genetics; Trans-Activators - physiology; Zinc Finger Protein Gli2
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/j.ydbio.2006.10.051

Patterning and differentiation along the dorsal–ventral (D–V) axis lead to cloacal partitioning into ventral urinary and dorsal alimentary tracts in most mammals, but not birds and fish. We previously reported that the major activator of Sonic hedgehog (Shh) signaling transcription factor Gli2 plays an essential role in cloacal partitioning along the D–V axis in a mouse model. Here, we report that chick cloacal patterning and differentiation is along the anterior–posterior axis. During chick cloacal formation, Shh is expressed strongly in hindgut endoderm; Gli2 is very weakly detected in the surrounding hindgut mesoderm. In the mesoderm of the cloacal region, the over-expression of the constitutively active form of mouse Gli2 has been shown to: not induce cloacal partitioning along the D–V axis; induce expression of Ptch1, Gli2, bmp4, wnt5a, and hoxd-13, which have been previously shown to play a role in hindgut patterning; increase cell proliferation; and reduce apoptosis. Interestingly, p63 expression in the cloacal endoderm is also up-regulated, suggesting an interaction between the Shh and p63 pathways. In conclusion, Gli2 alone is insufficient to induce partitioning along the D–V axis in the chick embryo. However, Gli2 regulates both epithelial and mesenchymal cell proliferation and apoptosis during cloacal development.