alpha-Dystroglycan (alpha-DG) plays crucial roles in maintaining the stability of cells. We demonstrated previously that the N-terminal domain of alpha-DG (alpha-DG-N) is secreted by cultured cells into the culture medium. In the present study, to clarify its function in vivo, we generated a monoclonal antibody against alpha-DG-N and investigated the secretion of alpha-DG-N in human cerebrospinal fluid (CSF). Interestingly, we found that a considerable amount of alpha-DG-N was present in CSF. alpha-DG-N in CSF was a sialylated glycoprotein with both N- and O-linked glycan. These observations suggest that secreted alpha-DG-N may be transported via CSF and have yet unidentified effects on the nervous system. (C) 2011 Elsevier Inc. All rights reserved.