Abnormal HNK-1 expression in the cerebellum of an N-CAM null mouse.

Human natural killer antigen-1 (HNK-1) is a carbohydrate epitope associated with sulfoglucuronylglycolipids and glycoproteins. Biochemical analyses have demonstrated associations between the HNK-1 epitope and isoforms of the neural cell adhesion molecule (N-CAM) family. In the cerebellum, HNK-1 is prominently expressed in Purkinje cell dendrites and Golgi cells. Purkinje cell expression of HNK-1 reveals an array of parasagittal stripes and transverse zones. Interestingly, the parasagittal expression pattern of HNK-1 is different from those reported with several other markers such as zebrin II/aldolase C and the small heat shock protein HSP25. N-CAM null knockout mice were used to explore the possible role of the HNK-1/N-CAM interaction during the topographical organization of the cerebellar cortex. N-CAM null mice have no N-CAM immunoreactivity but otherwise the cerebellum appears morphologically normal. Further, in the N-CAM null HNK-1 immunoreactivity is abolished from Purkinje cell dendrites but is retained on Golgi cells and neurons of the cerebellar nuclei. Despite the absence of N-CAM/HNK-1, parasagittal stripes and transverse zones in the cerebellum as revealed by using zebrin II immunocytochemistry appear normal.