Abstract
Dendritic spines are multiple functional units that receive most excitatory inputs in central nervous system. Modification of dendritic spine number is associated with several neurological diseases and synaptic plasticity. Spikar is a novel molecule which was isolated as a drebrin-binding protein using yeast two hybrid screening. In rat primary cultured hippocampal neurons, GFP-Spikar was localized primarily in nucleus and dendritic spines, and lesser amounts in soma, dendritic shafts, and axons. In this study, we investigated the role of Spikar in cultured hippocampal neurons during development. Hippocampal neurons were transfected with a Spikar-shRNA expression vector or an empty vector as a control at several developmental stages. The Spikar-shRNA expression vector caused 60-90% knock down (KD) of endogenous Spikar. In early stage of development, Spikar KD did not affect the density of dendritic protrusions. In contrast, at a stage of synapse formation, Spikar KD reduced spine density without changing filopodia density. In more mature stage when majority of dendritic protrusions are dendritic spines, Spikar KD reduced spine density as well. These results suggest that Spikar plays a role in the maintenance of dendritic spines without affecting the filopodia formation. [J Physiol Sci. 2006;56 Suppl:S105]
