Expression pattern of Hh genes in the developing cloaca. In situ hybridisation stains in WT embryos. (A-C) Transcripts for shha are detected at low levels in the posterior gut endoderm and persist until at least 120 hpf. (D-F) ihha is expressed in the proctodeum from 24 hpf and is expressed in the posterior gastrointestinal tract and proctodeum until at least 120 hpf. (G-H) Before 48 hpf ptc1 transcripts are not up-regulated in the area surrounding the posterior gut, but later ptc1 is expressed at higher levels in the mesodermal layer that surrounds the Hh expressing endoderm. (J-L) At 24 hpf gli2a is expressed in a diffuse pattern around the developing posterior gut, around 48 hpf gli2a expression in the developing posterior gut is at its strongest, with low-level expression on the posterior edge of the pronephric ducts, but not within them. By 72 hpf gli2a is expressed in cells surrounding the anal sphincter, and weakly in a large diffuse area around the urorectal opening. gli2a expression is not detectable in the urorectal region after 96 hpf.
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