title: The role of Shh transcription activator Gli2 in chick cloacal development.
abstract: 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.
authors.affiliation: Department of Surgery, Programs of Infection, Immunity, Injury and Repair, The Hospital for Sick Children, 555 University Ave, Suite 1526, Toronto, Ontario, Canada M5G 1X8.
authors.forename: Guodong
authors.initials: G
authors.lastname: Liu
authors.forename: Anne
authors.initials: A
authors.lastname: Moro
authors.forename: Jennifer J R
authors.initials: JJ
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Cheng
authors.forename: Wei
authors.initials: W
authors.lastname: Qiu
authors.forename: Peter C W
authors.initials: PC
authors.lastname: Kim
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017209:Apoptosis; D001483:Base Sequence; D002453:Cell Cycle; D002454:Cell Differentiation; D049109:Cell Proliferation; D002642:Chick Embryo / Q000196:embryology* / Q000502:physiology; D002988:Cloaca / Q000196:embryology*; D017931:DNA Primers / Q000235:genetics; D004707:Endoderm / Q000166:cytology; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000235:genetics / Q000502:physiology; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000502:physiology*; D008648:Mesoderm / Q000166:cytology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology; D000075746:Zinc Finger Protein Gli2
chemical_list: D017931:DNA Primers; C000618551:Gli2 protein, mouse; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D000075746:Zinc Finger Protein Gli2