TMPRSS2-ERG gene fusions lead to overexpression of the usually lowly expressed ERG master transcription factor driven by the androgen-regulated promoter of TMPRSS2. This is considered an early event in PCa development and phenotypically results in increased PCa cell migration, invasion and incomplete differentiation compared to benign prostate epithelial cells due to an altered transcriptional profile (Tomlins et al. 2008, Mounir et al. 2015, Kron et al. 2017). The gene discussed is TMPRSS2; the disease is posterior cortical atrophy.