Figure 1.

Replacement of the Cα gene membrane exon with a deletable neo cassette. (a) Top: structure of the targeted locus (not to scale), showing an unrearranged IgH locus and the extent of the deletion within the Cα gene. Middle: structure of the targeting vector in which Cα only includes the CH1, CH2, CH3 whereas the membrane α exon is replaced by a neo^r cassette flanked by two loxP sites. Bottom: the resulting locus is able to support the production of transcripts for the secreted form of the immunoglobulin α heavy chain but not for the membrane-anchored form, whereas the neo gene can be deleted by cre-mediated recombination. (b) Southern blot analysis of tail DNA from representative wild-type (wt), heterozygous, or homozygous mutant mice.