SMAD independent BMP4 signaling leads to activation of MITF. (A) Quantitative RT-PCR for Mitf expression in different subpopulations of mouse BM (n = 3, P < .04). (B-D) KLS cells were cultured with SCF+TPO in addition to BMP4 alone or combined with dorsomorphin or SB203580, for 5 days (ST = SCF/TPO; STC = SCF/TPO/Chd; STB = SCF/TPO/BMP4; STBD = SCF/TPO/BMP4/Dorsomorphin; STBS = SCF/TPO/BMP4/SB203580), and analyzed by Western blot or immunostaining. (B) Immunostaining with an antibody against MITF and Hoechst33342. Representative example of 3 experiments. (C) Western blotting on nuclear extracts of KLS cell progeny with antibodies against MITF and Histone H3 as control. Representative example of 3 experiments. (D) Quantification of nuclear MITF protein levels in KLS cell progeny cultured for 5 days by densitometric analysis of MITF and histone H3 intensities (n = 3; *P < .04).