Southern blot analysis. Genomic DNAs extracted from 6 PMBLs (no. 12, 6, 7, 11, 10, and 5) and 3 peripheral DLBLs (no. 15, 19, and 14) were subjected to EcoRI digestion, agarose gel electrophoresis, Nylon N+ membrane transfer, and hybridization with 2 MAL probes. (A) The physical map of the MAL gene and localization of the 2 probes are represented at the top of the figure. The boxes represent the exons, which are not drawn to scale for the clarity of the figure. (B) A 1.5-kb EcoRI-HindIII fragment (probe a) exploring the 5′ part of the MAL gene showed the same 17-kb DNA fragment in all samples. (C) A PCR-generated fragment of MAL cDNA (probe b) spanning exons 2, 3, and 4 showed 2 DNA fragments of 5 and 2.6 kb. The faint bands observed for case no. 5 in (B) and (C) are due to the lower amount of DNA loaded on the gel. However, longer autoradiographic expositions demonstrated the same DNA fragments in this sample.