Mi2β preferentially regulates human β-globin locus gene expression in CID cells. CID cells were transiently transfected with siRNA for Mi2β, MBD2, or scramble control (siSCR) as indicated. (A) Transient knockdown of Mi2β by siRNA leads to a 3186.8-fold increase in the expression of γ-globin (hγ) gene expression in CID cells and a 31.3-fold increase in β-globin RNA (hβ) determined by qPCR. (B) Transient knockdown of MBD2 by siRNA leads to a 3.5-fold induction of γ-globin gene expression in CID cells and a 1.8-fold induction of β-globin RNA. (C) A 352.1-fold increase is seen in the expression of human ε-globin (hε) on knocking down Mi2β and a 31.3-fold increase in β-globin. (D) Combined knockdown of Mi2β and MBD2 leads to a 3210-fold increase in γ-globin gene expression and a 29.9-fold increase in β-globin RNA, similar to Mi2β knockdown alone. Data are expressed as human γ-, β-, or ε-globin RNA normalized to glycophorin A RNA. (E) qPCR analysis showing the expression of six murine genes (α-1-spectrin, aminolevulinate dehydratase [Alad], erythropoietin [Epo] receptor, GATA-1, glucose-6-phosphate dehydrogenase [G6PD], and uroporphynogen III synthase [Uros]) was not upregulated on Mi2β knockdown, whereas the mouse ferrochelatase and transferrin genes are slightly significantly down-regulated. (F) Western blot showing the degree of Mi2β and MBD2 protein knockdown in the CID cells used for the globin gene expression studies shown in Figures 1 and 2, respectively. Error bars represent the standard deviation of 3 independent experiments. *P < .05, and **P < .02, according to the Student t test.