Expression of slit-2 and slit-3 during chick development

The Drosophila and vertebrate slit proteins have been characterized as secr eted chemorepellents recognized by the robo receptor proteins that function principally for the guidance of neuronal axons and neurons. slit genes are also expressed in the limb. To provide a basis for the determination of sl it functions in the limb we have isolated and characterized the expression of chick slit-2 and slit-3 in the developing limb and other tissues of the chick embryo. Both genes share similar expression profiles in the chick emb ryo when compared to that of their mammalian homologues, particularly in th e neural tube. In the limb, their expression patterns suggest their involve ment in many aspects of limb development. In the early limb bud, slit-2 is expressed in the peripheral mesenchyme and invading muscle precursors, whil e slit-3 expression is restricted to the future chondrogenic core of the li mb bud. At later stages, both slit genes are expressed in interdigital mese nchyme, in inner periosteal cells, and in mesenchyme immediately radial to the periosteum and under the epidermis. slit-3 is also expressed in prolife rating chondrocytes during cartilage development, while slit-2 is expressed in later muscle masses and peripherally to joints in the autopod. (C) 2001 Wiley-Liss, Inc.