The skin tumor promotion susceptibility locus, Psl1, was previously mapped to a 59.1-Mb region of mouse chr 9 (Angel et al. 1997, 2001, 2010; Angel and Digiovanni 1999) and the glutathione S-transferase gene, Gsta4, was shown to underlie at least some of the effect of this locus on skin tumor promotion susceptibility in mice (Abel et al. 2010). The gene discussed is HPGDS; the disease is skin neoplasm.