RNA-Seq was performed as previously described19 (link). Briefly, RNA was isolated from 50,000 FACS-sorted cells using miRNeasy Mini Kit (QIAGEN). NEBNext Ultra RNA Library Prep Kit for Illumina was used to generate RNA-Seq libraries, following mRNA selection with Poly(A) mRNA Magnetic Isolation Module (New England Biolabs). 12 cycles of index PCR was performed for multiplexing with NEBNext Multiplex Oligos for Illumina. The libraries were sequenced on a HiSeq 3000 in a 50-bp single read run.