The developmental expression of two Xenopus laevis steel homologues, Xsl-1 and Xsl-2.

We have investigated the expression patterns of two Xenopus laevis genes with similarity to mouse steel (sl) using whole-mount in situ hybridization. Areas of overlapping expression include the epidermis, stomodeum, proctodeum, and otic placodes. Xsl-1 is specifically expressed in the pronephros, neural tube, gil arches, and a superficial region of the somite, while Xsl-2 is in the ganglion and facial nerve projecting to visceral arch 3, the mandibular arch, and the clefts of anterior somites. Thus, both transcripts exhibit partially overlapping expression patterns, but their tissue distribution differs significantly from that of sl expression in the mouse and chicken.