Distribution of striatin, a newly identified calmodulin-binding protein in the rat brain: an in situ hybridization and immunocytochemical study.

Striatin, a 110-kDa protein, is the first member of the tryptophane-aspartate repeat protein family known to bind calmodulin in the presence of Ca2+. We examined the distribution of striatin and its mRNA in the rat central nervous system (CNS) by using immunocytochemistry and in situ hybridization, respectively. Striatin immunostaining and mRNA labeling patterns are generally concordant. Regions showing the most intense staining are the dorsal striatum, nucleus accumbens (anterior and shell parts), olfactory tubercle, red nucleus, subthalamic nucleus, cranial nerve motor nuclei, and layer IX of the spinal cord (motoneurons). Low levels of both striatin and its mRNA are detected in the cerebral cortex, thalamus, septum, amygdala, hippocampus, midbrain and cerebellum. Striatin-immunoreactive neuronal processes are found predominantly in the structures containing striatin-positive neurons, suggesting that these labeled processes represent dendritic arborization rather than axonal processes. Except for the medial forebrain bundle, all axonal fiber tracts examined are devoid of striatin immunolabeling. These data show that the somatodendritic localization of striatin, previously described in the striatum, may be a main feature of the subcellular distribution of this protein throughout the CNS. Although widely distributed in neurons throughout the rat CNS, striatin is expressed prominently in the structures belonging to the motor system, suggesting that this protein may play a preponderant role in motor control.