TMPRSS6 expression is controlled by ID1 in response to BMP6. Hep3B cells transfected with 10nM of siRNA control, siRNA SMAD7 (A-B), or siRNA ID1 (C-D), and treated in the absence or presence of 25 ng/mL of BMP6 for 24 hours were analyzed for TMPRSS6 (B,D) SMAD7 (A), and ID1 (C) mRNA expression relative to RPL19 mRNA by quantitative real-time RT-PCR. Results are reported as the mean ± SEM for the fold change from mock, and significant changes represent the comparisons with mock (siRNA control alone). Significant changes are as follows: *P < .05.