Illumina sequencing data were aligned to a composite genome consisting of GRCm38.81 and transgenes as previously described (Macosko et al., 2015). Full details are available online (http://mccarrolllab.com/wp-content/uploads/2016/03/Drop-seqAlignmentCookbookv1.2Jan2016.pdf). Digital gene expression (DGE) matrices from each sequencing pool were compiled before ICA-based analysis.