Identifying synaptically enriched mRNA by using next generation sequencing

Preparation of Synaptosomes by density gradient and compare synaptically enriched mRNA to total homogenate transcriptome In brief, mouse brains were homogenized in 5 ml homogenization buffer (0.32 M sucrose, 1 mM EDTA pH 7.4, 1 mM dithiothreitol, phenylmethanesulfonyl fluoride solution (Sigma, 93482-50ML-F), complete mini-protease inhibitor (Roche Diagnostics) for 10 sec using a polytron. The homogenate was centrifuged at 1,000g for 10 min at 4 °C yielding the nuclear fraction (Nuc) and the supernatant (Sup). The supernatant was centrifuged at 31,000g for 5 min at 4°C using a discontinuous Percoll gradient. The layer between 3% and 10% of Percoll were collected, washed in 30 ml of homogenization buffer and further centrifuged at 22,000 × g for 15 min at 4°CT. The pellet was resuspended in in EBC buffer (50 mM Tris-HCl pH 8.0, 120 mM NaCl and 0.5% NP-40) containing complete mini-protease inhibitor (Roche Diagnostics) and phosphatase inhibitor cocktail 1 and 2 (Sigma–Aldrich)) for Western blot analysis or lysis buffer for RNA extraction (GenElute Mammalian Total RNA Miniprep Kit, Sigma).