Enhanced expression of collapsin response mediator protein 4 in spinal cords of rat fetuses with spina bifida aperta

Neural tube defects (NTDs) are severe congenital malformations that result from incomplete neurulation of the central nervous system. While collapsin response mediator protein 4 (CRMP-4) plays a critical role in the regulation of neurulation, information regarding the temporal expression of CRMP-4 during embryonic development of the spinal cord has yet to be reported. We therefore investigated the expression pattern of CRMP-4 in fetal spinal cords of healthy rats and of rats with spina bifida from prenatal day (E) 11 to postnatal day 1 (P0). Specifically, the mRNA and protein levels of CRMP-4 were measured in spinal cord tissues harvested from healthy and all-trans retinoic acid (atRA)-induced spina bifida rat fetuses. For these experiments, spina bifida was induced at discrete stages of neural development, including at E11, E12, E13, E15, E17, and P0. Expression of CRMP-4 mRNA and protein was detected in the spinal cords of both normal fetuses and fetuses with spina bifida as early as E11 and E12, respectively. The expression levels then gradually increased throughout embryonic development and peaked at E15 and P0, respectively. Notably, both the protein and mRNA levels of CRMP-4 were significantly enhanced in the spinal cords of fetuses with spina bifida, compared to the levels detected in healthy fetuses. Furthermore, the expression of CRMP-4 was time-dependent and occurred at a distinct stage of normal embryonic development. Lastly, CRMP-4 was overexpressed at both the mRNA and protein levels in the spinal cord tissue of fetuses with spina bifida, suggesting that CRMP-4 may contribute to the pathogenesis of this disease by regulating neurite outgrowth and neuronal apoptosis.