Sam68 transcripts encoded by exons 1 to 5 were absent as evidenced by RT-PCR (Dataset S2), and Sam68−/− mice were devoid of Sam68 protein, as visualized by immunoblotting with anti-Sam68 AD1 and SC-333 antibodies or control normal rabbit serum or anti-Sam68 AD1 preabsorbed with peptide (Figure 2C).