Figure 1.

Targeted disruption of the β3 locus. (a) A replacement vector was constructed to replace ≈2.8 kb of β3 genomic DNA including ≈1.8 kb of promoter and exons 1–3 with the selectable marker neomycin phosphotransferase (PGKNeo). (Note that restriction sites set in italics were destroyed during vector construction.) (b) Southern blot analyses of the parental cell line (R1), three correctly targeted ES cell clones, and mice demonstrating all genotypes. (c) Northern blot analysis of neonatal mouse brain poly(A)⁺ RNA that demonstrates the absence of β3 mRNA in brain of β3^−/− mice.