Identification of mRNAs localizing in the postsynaptic region.

Local protein synthesis using mRNAs readily distributed in the dendrites is believed to play an important role in maintaining the already expressed synaptic plasticity. To find proteins translated in the postsynaptic region, such as neuronal dendrites, we tried to identify the mRNAs associated with the postsynaptic density (PSD) fraction prepared from a rat's forebrain. The PSD-associated mRNAs were amplified by reverse transcriptase-based polymerase chain reaction (RT-PCR), separated by polyacrylamide gel electrophoresis, and sequenced. The database search revealed, among 130 mRNAs sequenced, 17 known and 108 unknown sequences, while five mRNAs were too short for the search. Of the mRNAs with unknown sequences, we selected 33 genes with a length longer than 150 bases, performed in situ hybridization, and found that at least 12 mRNA types were localized in the dendrites. These results suggest that a large number of mRNAs localize around the postsynaptic area of the neuronal cells in the central nervous system. In addition, our method proved efficient in identifying collectively the mRNAs localizing in the dendrites.