FAC1 expression and localization in motor neurons of developing, adult, and amyotrophic lateral sclerosis spinal cord.

In this study we report the localization and expression of FAC1 protein in developing, normal adult and amyotrophic lateral sclerosis (ALS) lumbar spinal cord. High levels of FAC1 protein were detected in cells throughout all areas (gray and white matter) of the developing lumbar spinal cord. FAC1 protein was localized predominately in nuclei and the cell body of motor neurons during early stages of spinal cord development. In contrast, low levels of FAC1 protein were observed in the adult lumbar spinal cord, localized only in the cell body of large alpha motor neurons found in lamina IX. Interestingly, FAC1 protein expression was elevated in surviving motor neurons of ALS spinal cord compared to the controls and was located both in the nucleus and throughout the cytoplasm of motor neurons. FAC1 protein was also observed in white matter cells and fibers in ALS spinal cord. In support of the immunocytochemical results, in situ hybridization studies demonstrated that FAC1 mRNA is also elevated in ALS spinal cord motor neurons. These data describe the developmental regulation of FAC1 protein in the spinal cord by immunocytochemical techniques and provide evidence that this protein is reexpressed in ALS motor neurons.