Expression of RBMX after spinal cord injury in rats.

RBMX (RNA-binding motif gene, X chromosome) is a heterogeneous nuclear ribonucleoprotein that associates with the spliceosome, binds RNA, and influences alternative splicing. The gene encoding RBMX is located on chromosome Xq26 and is ubiquitously expressed. However, its expression and function in spinal cord injury are still unclear. In this study, we performed an acute spinal cord contusion injury (SCI) model in adult rats and investigated the dynamic changes of RBMX expression in spinal cord. Western blot and immunohistochemistry analysis revealed that RBMX was present in normal spinal cord. It gradually increased, reached a peak at 1 day, and then declined to basal levels at 14 days after spinal cord injury. Double immunofluorescence staining showed that RBMX immunoreactivity was found in neurons and astrocytes, but not in microglia. Interestingly, RBMX expression was increased predominantly in neurons and astrocytes. Moreover, colocalization of RBMX/proliferating cell nuclear antigen (PCNA) and RBMX/active caspase-3 was detected in GFAP and NeuN, respectively. We also examined the expression profiles of active caspase-3, bcl-2, Bax, and PCNA, whose changes were correlated with the expression profiles of RBMX. In conclusion, this is the first description of RBMX expression in spinal cord injury. Our results suggested that RBMX might play crucial roles in CNS pathophysiology after SCI.