Along with the positively regulated genes, there were also genes found which were negatively regulated. An example of such a gene is the pax3 gene. It was found via microarray that the expression of pax3 was lowered in the embryos which had been injected with Shh mRNA, and expression was slightly higher in the smu(smo) mutants. pax3 is involved in many different developmental processes in the brain, including closing of the neural tube and differentiation of various cell types. The researchers examined the promoter of pax3 and discovered that it contains Gli binding sites. This suggests that Hh and Gli act to reduce the transcription of pax3 by Gli binding at the promoter, and therefore reduce the expression of pax3.
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