Among the genes associated with the inhibition of neuroregeneration via Rho signal transduction pathways (14, 15), the expression levels of RGMA were significantly elevated solely in HAM CD4+ T cells when compared with CD4+ T cells from HDs (non–HTLV-1–infected CD4+ T cells), HTLV-1–infected cells from asymptomatic carriers (ACs), and patients with smoldering/chronic-type adult T cell leukemia (ATL), as well as HTLV-1–infected cells from patients with acute ATL (P < 0.05) (Figure 1C). Here, RHO is linked to tropical spastic paraparesis.