FIGURE 1.

ARRB1 controls cell proliferation and apoptosis in granule cell progenitors (GCPs) via E2F1 acetylation. (A) Murine cerebellum Western blot. Representative images of endogenous GLI1 and ARRB1 in murine cerebella at different days (2, 5, 7, 15) of cerebellar development. GAPDH: loading control. (B–G) GCPs experiments. Shh was added to cultures of murine cerebellar GCPs that had or had not undergone siRNA-mediated silencing of ARRB1 (siArrb1). After 48 h of Shh stimulation, GCPs were assayed for: (B) Gli1 mRNA and protein levels (as a read-out of Shh signaling activity), and ARRB1 protein level; ACTIN as loading control; (C) proliferation reflected by bromodeoxyuridine (BrdU) uptake; (D) left: p27 mRNA levels ((D) right and Supplementary Figure S4B: Overexpression data are consistent); (E) differentiation reflected by β III tubulin mRNA levels; (F) apoptosis evaluated by TUNEL assay, and (G) ARRB1, E2F1, E2F1-ac, cleaved CASPASE-3 protein expression levels. ACTIN and HISTONE H3: loading controls. For Western blot, densitometry values are shown below the blots and densitometric graphs are presented in Supplementary Figure S2. Data represent means ± S.D., from at least three independent experiments; *p < 0.05; **p < 0.01; ***p < 0.001.