Postnatal alteration of collapsin response mediator protein 4 mRNA expression in the mouse brain

Collapsin response mediator protein 4 (CRMP4) is a molecular marker for immature neurons but only limited information is available on the spatiotemporal gene expression changes of Crmp4 in the developing rodent. In the present study, the variation of CRMP4 mRNA expression in the mouse brain was investigated from postnatal day (PD) 0 (the day of birth) to adulthood by in situ hybridization. The hybridization signals were broadly detected on PD0 and regional changes in expression during development were noted. Expression patterns of CRMP4 mRNA were classified into the following three types: (i) signals that were strongest on PD0 or PD7, weak or undetectable on PD14, and absent in adulthood: this pattern was observed in most brain areas; (ii) signals that were first detected on PD0 or PD7 and persisted into adulthood: this pattern was seen in the dentate gyrus and subventricular zone of the olfactory bulb (OB); and (iii) signals that were strongest on PD0 and decreased gradually with age but were still detectable in adulthood: this pattern was identified for the first time in the mitral cell layer of the OB. Analysis using quantitative real-time RT-PCR confirmed higher expression of CRMP4 mRNA in the OB than in other adult brain regions. The persistence of CRMP4 mRNA in the adult OB, including the mitral cell layer, suggests the possibility of both neurogenetic and non-neurogenetic functional roles of CRMP4 in this region.