Neurofilament and neural cell adhesion molecule immunocytochemistry of Huntington's disease striatum

We examined normal and Huntington's disease (HD) human striatum with specific monoclonal antibodies to nonphosphorylated (SMI 32) and phosphorylated (SMI 31) neurofilament and neural cell adhesion molecule (NCAM). SMI 32 identifies medium-sized neuronal perikarya and dendrites in normal striatum. Axons are not immunoreactive. In high-grade HD striatum (grades 3 and 4) SMI 32 neurons are morphologically abnormal and significantly depleted. Dendritic arbors are intensely immunoreactive, tortuous, and fragmented, especially in the subependymal zone. Proliferative SMI 32-positive sprout-like structures and axon-like processes are seen. SMI 31 normally stains a fine meshwork of axon-like processes that become intensely immunoreactive, condensed, convoluted, and fragmented in HD. NCAM staining is minimal in normal striatum, but, in HD striatum, many dot- and thread-like structures are found, especially in the subependymal region. The abnormalities revealed by SMI 31, SMI 32, and NCAM suggest that neurofilament phosphorylation is altered and growth related proteins are reexpressed in HD. Dephosphorylation and destabilization of the cytoskeleton may contribute to neuronal injury and death in HD.