Having implicated basal cells as a preferred cell of origin for ERG-positive PCa and demonstrated Tmprss2 expression in a subset of these basal cells (BasalLum), we next asked whether these tumors originate from BasalLum cells using the Nkx3-1-CreERT2 driver allele38,56,57. This evidence concerns the gene TMPRSS2 and posterior cortical atrophy.