For sub-populations, cells were dissociated as above and sorted based on positive or negative Cit fluorescence. Total RNA was harvested from populations of 10,000 cells collected and stored in RLT Lysis Buffer (Qiagen) and 2-Mercaptoethanol (Sigma Aldrich). RNA was extracted (Qiagen RNeasy Micro Kit) and validated with a RNA Pico Chip on a Bioanalyzer 2100 (Agilent). cDNA was amplified using SmartSeq2 on total RNA, and libraries constructed by tagmentation with as with single cell libraries. To characterize sub-populations of fixed and stained primary human cortical cells, FRISCR was carried out on 100-cell sample just as with single cells, however three fewer PCR cycles were used.
