Fig. 4.

BrdU induces mitotic recombination between homologous chromosomes in ESCs. Southern blot analysis for methylation imprint at Snrpn promoter, as described in Liu et al. (2002). TaqαI and SacII digest of genomic DNA generates a ~5-kb band corresponding to the maternal (m) allele and a ~3-kb band corresponding to the paternal (p) epi-allele. Effects of 1.25- and 10-μM BrdU exposure for 7 h were tested on wt JM8.N4 ESCs. In the 10-μM sample, three cases of homozygosis to the di-maternal allele configuration were detected on this blot (arrows). In total, we found 4 of 60 homozygosis cases in the 10-μM BrdU group, and none in the 1.25-μM BrdU or control groups (additional blots not shown)