CRMPs (collapsin response mediator proteins)/ULIPs (unc-33-like proteins) are a family of intracytoplasmic proteins that are expressed mainly in the brain. The involvement of CRMP/ULIP members in neuronal differentiation, growth cone motility and axonal collapse has been suggested. We recently found that a member of this family, CRMP3/ULIP4, corresponds to POP66 (paraneoplastic oligodendrocyte protein of 66 kDa), a protein which may be associated with auto-immune induced-neuronal degeneration in paraneoplastic neurological syndromes. However, the physiological functions of these proteins remain to be elucidated. Further studies, including the generation of cell lines and of animals with modified/disrupted CRMP/ULIP gene expression, are necessary to explore the functions of this protein. We have cloned and determined the organization and chromosomal localization of the mouse gene encoding CRMP3/ULIP4. The gene is composed of 14 exons and spans more than 20 kb. We assigned the mouse CRMP3/ULIP4 gene to the distal end of chromosome 7. In mouse brain, in situ hybridization showed that CRMP3/ULIP4 mRNA is expressed mainly in the dentate gyrus of hippocampus, in the granular layers of cerebellum and in the inferior olive of the pons, the nucleus which controls movement and posture, and adjusts the major output of descending motor system.