Expression of collapsin response mediator protein-4 (CRMP-4) in plastic brain areas of adult songbird brain

Collapsin response mediator protein-4 (CRMP-4), a member of CRMP family, is involved in neuronal differentiation and regulation of synaptic rearrangement. Neurite growth and axonal reorganization still continue in the adult songbird brain. It is probable for CRMP-4 to play an important role during these processes. To address this issue, we first obtained CRMP-4 cDNA from the brain of songbird (Lonchura striata) by use of RT-PCR and 3' rapid amplification of cDNA ends (3'RACE). We then examined the expression of CRMP-4 mRNA and protein in some plastic brain regions, including the hippocampus, song control nuclei and the cerebellum. Double immunohistochemistry was employed to identify the phenotypes of CRMP-4 expressing cells. The results indicated that: 1) a cloned fragment of CRMP-4 cDNA (798bp) showed high similarity with those comparable cDNA of reported species, confirming the evolutionary conservation of CRMP-4 sequence; 2) both CRMP-4 mRNA and protein were found to be dominantly located in the hippocampus, song control nuclei and the cerebellum among the whole brain; 3) some CRMP-4 positive cells were also labeled by the antibody for HuD (immature neurons), but not for NeuN (mature neurons), and GFAP (astrocytes). The presence of CRMP-4 in the plastic regions suggests that CRMP-4 might be concerned with the neural plasticity of songbird brain.