Leucine codon 430 (CTG) in exon 7 was changed to glutamine (CAG) (p.L430Q) and a loxP site flanked neomycin resistance gene cassette was inserted into intron 6. The neo cassette was removed through subsequent Cre-mediated recombination. The mutation, in the highly conserved Rb-binding domain of the encoded peptide, blocks retinoblastoma-family-protein-binding. (J:277585)