Gene expression is first normalized to account for total expression within each cell, then a log transform is applied. To select genes for downstream unsupervised analyses (e.g. PCA, t-SNE), the expression values are corrected for heteroscedasticity using the variance stabilizing transformation (VST). We also apply a method to regress out the per-cell measures of total UMI counts, total genes detected, and percentage of reads mapping to mitochondria.