Expression of an HIV Δgag/pol/nef transgene in mice induced FSGS and microcystic tubular dilation but not podocyte proliferation (Kajiyama et al., 2000); however, when this transgenic mice were back-crossed to a Nef-only transgenic mice, the severity of renal lesions increased (Dickie et al., 1993); these findings indicated the role of Nef and another gene in HIVAN pathogenesis. The gene discussed is S100B; the disease is HIV-associated nephropathy.