Slit2 is a 180­210kD secreted member of the SLIT family of proteins. It is expressed in select sites in the embryo (via glia, motoneurons and posterior sclerotome mesoderm), and found in discrete adult cell types such as preosteoblasts, monocytes, granulose lutein cells, and likely keratinocytes. Slit2 binds to multiple receptors, including ROBO­1 thru ­4, laminin­1, Dan, Gremlin and netrin­1. Depending upon the target, Slit2 can promote a number of diverse effects, including both growth cone collapse and outgrowth, inhibition of dendritic cell migration, and axon repulsion. Mature mouse Slit2 is 1496 amino acids (aa) in length (aa26­1521). It contains multiple intermingled domains, including nine EGF­like domains, 20 Leu­rich repeats (LRRs), one laminin G­like and CTCK (C­terminal Cys knot­like) domain, and eight total C­ plus N­terminal LRRs. There are two potential isoform splice variants. One contains a four aa insertion after Ser258, while another possesses the same insertion after Ser258 coupled to both an eight aa insertion after Ser479 and a nine aa insertion after Thr1021. Slit2 apparently undergoes proteolytic cleavage after Arg1113. This generates a 140­150kD N­terminal protein, and a 55­60kD C­terminal fragment. This processing does not inactivate Slit2. Rather, it creates molecules with distinct activities. For example, the N­terminal fragment will bind ROBO­1 and repel motor axon migration, while the C­terminal fragment won't bind ROBO­1, but will bind glypican­1 and promote motor axon migration. Over aa 26­900, mouse SLIT2 shares 99% and 97%aa sequence identity with rat and human Slit2, respectively.