Characterization of Takusan, a Novel Gene Family that Regulates Synaptic Activity

We have characterized a rodent-specific gene family designated α-takusan (meaning “many” in Japanese). We initially identified a member of the family whose expression is upregulated in mice lacking the NMDAR subunit NR3A. We then isolated cDNAs encoding 46 α-takusan variants from mouse brains. Most variants share a ~130-aa long sequence, which contains the previously identified DUF622 (domain of unknown function 622) and is predicted to form coiled-coil structures. Single-cell PCR analyses indicate one neuron can express multiple α-takusan variants, and particular variants may predominate in certain cell types. Forced expression in cultured hippocampal neurons of two variants, α1 or α2, which bind either directly or indirectly to PSD-95, leads to an increase in PSD-95 clustering, dendritic-spine density, GluR1 surface expression, and AMPAR activity. Conversely, treating cultured neurons with RNAi targeting α-takusan variants resulted in the opposite phenotype. Hence, α-takusan represents a novel gene family that regulates synaptic activity.