TYPE-II CYTOKERATIN EXPRESSION IN ADULT VERTEBRATE SPINAL-CORD

The phylogenetic evolution of the expression of type II cytokeratins ( CKs) in the spinal cord of different adult vertebrates has been studie d using an anti-CK immunohistochemical technique, Type II CK expressio n was stronger in lower vertebrates, specially anuran amphibians, than in higher vertebrates, No CK expression was found either in reptiles or birds, hut a weak expression was demonstrated in mammals. The main neuroectodermal cell implicated in CK expression was the ependymocyte; some CK-positive radial astrocytes were also found in amphibians and fish, but neither CK-positive astrocytes nor neurons were observed in any vertebrate group. The functional significance of CK expression in the vertebrate spinal cord is not known, CKs do not have a consistent pattern of expression amongst vertebrates; however, the most common si te is the ependyma.