Frequent MSCV integrations at Sfpi1 and Mef2c in Sox4-induced leukemias. (A) MSCV integrations at Sfpi1 (top panel) or Mef2c (bottom panel). Exon-coding regions are highlighted in yellow and noncoding exons in gray. Arrows indicate translation start sites. The location and orientation of viral integrations are depicted by red triangles. (B) Southern blot analysis of spleen DNA of leukemic animals 5413 and 0841 and control C57BL/6 genomic DNA probed with neo or Sfpi1 probes. (C) Similar Southern blot analysis of spleen DNA from leukemic animals 0137 and 0249 probed with neo or Mef2c probe.