Generation of chimeras, floxed mice, and mutant mice.
Targeted Atrx flox ES cell clones were injected into C57BL/6 blastocysts and transferred into 2.5 dpc pseudopregnant recipients by standard techniques. Resulting chimeras were mated with C57BL/6 to establish germline transmission. Offspring with the Atrx flox allele were identified by Southern blotting of SacI-digested tail DNA using the intron 17 probe as shown in Figure 2A and 2C. For Cre-recombination, Atrx flox mice were crossed with GATA1-Cre transgenic mice as described in the text. Recombinant alleles were detected by Southern blotting as described above or by PCR as described in Protocol S1.