摘要：

Sonic hedgehog (Shh) signaling patterns many vertebrate tissues. shh mutations dramatically affect ventral forebrain and floor plate but produce minor defects in . have two mammalian Shh orthologs, sonic hedgehog and tiggy-winkle hedgehog, and another gene, hedgehog, that could have overlapping functions. To examine the role of Hedgehog signaling in , we have characterized slow muscle omitted (smu) mutants. We show that smu encodes a ortholog of Smoothened that transduces Hedgehog signals. smoothened is expressed maternally and zygotically and supports specification of motoneurons, pituitary cells and ventral forebrain. We propose that smoothened is required for induction of lateral floor plate and a subpopulation of hypothalamic cells and for maintenance of medial floor plate and hypothalamic cells.

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