Figure 5.

Transgenic expression of the K18 mlacZ construct in mouse lungs. (a) F₀ transgenic embryos were harvested at 15.5 days postconception and the lungs were dissected, fixed, washed, and stained with X-gal for 3 hr. (b) The same lung shown in a was cleared by methyl salicylate after dehydration in methanol (2 changes, 30 min each). The LacZ expression pattern is restricted in the major airways. (c) The lung was subsequently sectioned in paraffin and counterstained with neutral red. Microscopic examination confirmed that the X-gal staining is only present in the epithelium lining the airways. (d) A control lung from a 15.5 day nontransgenic embryo was stained with X-gal for 16 hr.