GSM5522899: SM-GE5PH_S319_E1-50; Mus musculus; RNA-Seq
We isolated single cells and nuclei as previously described (Tasic et al., 2016, Bakken et al., 2018) with modifications. We updated our ACSF formulation to consist of CaCl2 (0.5 mM), glucose (25 mM), HCl (96 mM), HEPES (20 mM), MgSO4 (10 mM), NaH2PO4 (1.25 mM), myo-inositol (3 mM), N-acetylcysteine (12 mM), NMDG (96 mM), KCl (2.5 mM), NaHCO3 (25 mM), sodium L-ascorbate (5 mM), sodium pyruvate (3 mM), taurine (0.01 mM), thiourea (2 mM), and bubbled with carbogen gas (95% O2 and 5% CO2). For samples collected after 12/16/2016, the ACSF formulation also included trehalose (13.2 mM). Mice were anesthetized with isoflurane and perfused with cold carbogen-bubbled ACSF. The brain was dissected, submerged in ACSF, embedded in 2% agarose, and sliced into 250-µm coronal sections on a compresstome (Precisionary). Enzymatic digestion, trituration into single cell suspension, and fluorescence-activated cell sorting (FACS) of single cells were carried out as previously described (Tasic et al., 2016). Cells were sorted into 8-well strips containing lysis buffer from SMART-Seq v4 kit with RNase inhibitor (0.17 U/µl), immediately frozen on dry ice, and stored at -80°C. For nuclei isolation, dissected regions of interest were transferred to microcentrifuge tubes, snap frozen in a slurry of dry ice and ethanol, and stored at -80°C until the time of use. To isolate nuclei, frozen tissues were placed into a homogenization buffer that consisted of 10mM Tris pH 8.0, 250mM sucrose, 25mM KCl, 5mM MgCl2, 0.1% Triton-X 100, 0.5% RNasin Plus RNase inhibitor (Promega), 1X protease inhibitor (Promega), and 0.1mM DTT. Tissues were placed into a 1ml dounce homogenizer (Wheaton) and homogenized using 10 strokes of the loose dounce pestle followed by 10 strokes of the tight pestle to liberate nuclei. Homogenate was strained through a 30μm cell strainer (Miltenyi Biotech) and centrifuged at 900xg for 10 minutes to pellet nuclei. Nuclei were then resuspended in staining buffer containing 1X PBS supplemented with 0.8% nuclease-free BSA and 0.5% RNasin Plus RNase inhibitor. We used the SMART-Seq v4 Ultra Low Input RNA Kit for Sequencing (Takara Cat#634894) to reverse transcribe poly(A) RNA and amplify cDNA according to the manufacturer's instructions. We performed reverse transcription and cDNA amplification for 18 PCR cycles in 8-well strips, in sets of 12-24 strips at a time. At least 1 control strip was used per amplification set, which contained 4 wells without cells and 4 wells with 10 pg control RNA. Control RNA was either Mouse Whole Brain Total RNA (Zyagen, MR-201) or control RNA provided in the SMART-Seq v4 kit. All samples proceeded through NexteraXT DNA Library Preparation (Illumina FC-131-1096) using NexteraXT Index Kit V2 Set A (FC-131-2001). NexteraXT DNA Library prep was performed according to manufactorer's instructions except that the volumes of all reagents including cDNA input were decreased to 0.4× or 0.5× by volume. Details are available in Documentation on the Allen Institute data portal at: http://celltypes.brain-map.org/.