Genomic DNA and total RNA were extracted from CD19+ MCL cells and purified. RNA was reverse-transcribed and DNA samples were PCR-amplified before sequencing with Exon4 D1F and Intron4 D1R primers. Only the cyclin D1b mRNA form can be amplified with this couple of primers. Nucleotides at position 9630 (AP001888, GenBank) of genomic DNA and at position 870 of cDNA (M64349, GenBank) are indicated. * R, the relative ratio of cyclin D1a mRNA vs. cyclin D1b mRNA was calculated with the formula R = 2-(ΔCta-ΔCtb). nd, not determined.