Regulation ofnetrin-1aExpression by Hedgehog Proteins
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文摘
Netrins,a family of growth cone guidance molecules, are expressed both in the ventral neural tube and in subsets of mesodermal cells. In an effort to better understand the regulation ofnetrins,we examined the expression ofnetrin-1ain mutantcyclops, no tail,andfloating headzebrafish embryos, in which axial midline structures are perturbed.Netrin-1aexpression requires signals present in notochord and floor plate cells. In the myotome, but not the neural tube,netrin-1aexpression requiressonic hedgehog.In embryos lackingsonic hedgehog,thesonic-youlocus,netrin-1aexpression is reduced or absent in the myotomes but present in the neural tube. Embryos lackingsonic hedgehogexpresstiggy-winkle hedgehogin the floor plate, suggesting that, in the neural tube,tiggy-winkle hedgehogcan compensate for the lack ofsonic hedgehogin inducingnetrin-1aexpression. Ectopic expression ofsonic hedgehog, tiggy-winkle hedgehog,orechidna hedgehoginduces ectopicnetrin-1aexpression in the neural tube, and ectopic expression ofsonic hedgehogortiggy-winkle hedgehog,but notechidna hedgehog,induces ectopicnetrin-1aexpression in somites. These data demonstrate that in vertebratesnetrinexpression is regulated by Hedgehog signaling.