Fig. 3.

Survival of cortical neurons in the absence of Dnmt1 in vivo. A–D, X-gal staining of brain sections from a 3-week-old mouse carrying the CamK-cre transgene and a lacZ reporter gene under the control of the β-actin promoter (Akagi et al., 1997). The cells positive for β-gal enzymes (blue cells) represent those neurons having undergone cre-mediated gene recombination events. Scale bar, 675 μm.E, Southern blot analysis of cortex DNAs from conditional CamK-cre;Dnmt^2lox/+(2lox/+) heterozygous andCamK-cre;Dnmt1^2lox/C mutant animals (2lox/C). Note that the wild-type (WT) and null C-alleles were detected at the same size in this blot. The genotypes of wild-type and C-alleles were ascertained by the absence and presence of the neomycin gene in the Dnmt1 locus. F, Methylation analysis in cortex DNAs. IAP, Intra-cisternal A particle retrovirus; MMLV, Moloney murine leukemia virus.