Figure 1.

Recombination of a floxed laminin γ1 allele by a CaMKIIα promoter-Cre transgene leads to reduced expression of laminin γ1 in the sciatic nerve. (A) Details of the laminin γ1 gene targeting construct. The two loxP sites (open triangles) were inserted into the laminin γ1 gene to flank exon 2 (E2). The neomycin resistance gene pGKneo (long open rectangle) used for ES cell selection was flanked by two frt sites (closed triangles). The P1 and P2 primer sites were used in B to monitor recombination by PCR. Restriction endonuclease sites are indicated (A, AvrII; H, HindIII; T, Tth111I; X, XcmI). (B) PCR analysis of tail DNA from wild-type and homozygous fLAMγ1 mice (f/f), and of DNA from various tissues from CaMKII/Cre:fLAMγ1 mice (f/f, CaMKII-Cre/+). The primers used allow amplification of the wild-type allele and the unrecombined and recombined fLAMγ1 allele. In tissues where recombination takes place, both unrecombined and recombined alleles are detected because there are some cells (e.g., vascular tissue) in which recombination does not occur. Recombination is prominent in the hippocampus (Hip) as expected, and also in the spinal cord (SC) and sciatic nerve (SN); but it is minimal in the skeletal muscle from the leg. (C) Transverse sections of sciatic nerve from control and mutant mice at P1 were double stained for laminin γ1 (a and c) and S-100 (b and d). (a) The nerve from a control animal shows strong laminin γ1 staining; (c) nerve from a mutant mouse shows greatly reduced expression of laminin γ1 (arrowheads) but there was still some expression (closed arrows). Laminin expression in the epineurium is not affected (open arrows). Even though laminin γ1 expression is dramatically decreased in mutant sciatic nerve, the S-100 staining was similar to control (b and d). Con, control; Mt, mutant.