The SLITRK family of integral membrane proteins consists of at least 6 members (SLITRK1-6). They are named for the presence of two leucine-rich repeats (LRR) in the extracellular domain similar to those found in the Slit family, and a C-terminal domain with homology to Trk tyrosine kinase receptors. SLITRKs are expressed mainly in the brain, but may also show differential expression in other normal tissues and nervous system-derived tumors. Functionally, SLITRKs may modulate neurite outgrowth, and sequence variants of SLITRK1 have been linked to Tourette's syndrome.