SMARCA4 and retinoblastoma: Next, to determine if Brg1 inactivation promotes retinoblastoma tumorigenesis, we generated Chx10-Cre;RbLox/Lox;p107+/−;Brg1Lox/Lox mice and compared tumor formation in these animals with that in Chx10-Cre;RbLox/Lox;p107+/− and Chx10-Cre;RbLox/Lox;p107−/− mice.