SPP1 and ocular melanoma: As shown in Figure 1, Tβ4 siRNA successfully knocked down Tβ4 mRNA and protein expression in HPDCs (Figure 1B) and blocked OM-induced alkaline phosphatase (ALP) activity and mRNA expression of the odontogenic differentiation genes (ALP, OPN, OCN, DMP1, and DSPP), whereas transfection of cells with an equivalent amount of nonspecific siRNA had no effect (Figure 1B–E).