Figure 1. Partial recombination of the Nle1^flox allele by Meox2^Cre and detection of Nle1-deficient cells.

A. At gastrulation, Meox2^Cre-mediated recombination was detected by staining for β-galactosidase activity using Rosa26^STOP-LacZ reporter allele in Rosa26^STOP-LacZ/+; Nle1^flox/+; Meox2^Cre/+ control embryo (left, n = 3) and in Rosa26^STOP-LacZ/+; Nle1^flox/Δ; Meox2^Cre/+ mutant embryo (right, n = 3). B. PCR amplification of genomic DNA from Nle1^flox/+; Meox2^Cre/+ control embryos showing partial recombination of the Nle1^flox allele at E7.5 (n = 4), E8.5 (n = 12). The recombined (Nle1 ^Δ) allele is detected as soon as E7.5. Note that PCR analysis underestimates the recombination efficiency at this stage. Indeed, PCR analysis was performed on whole embryo containing extraembryonic tissues (visceral endoderm, extraembryonic ectoderm) that do not express the Cre recombinase. Presence of Nle1-deficient cells was evaluated by PCR amplification of genomic DNA performed on Nle1^mcKO mutant embryos at E7.5 (n = 9) and E8.5 (n = 6). Representative results of PCR are shown. C. PCR amplification of genomic DNA from Nle1^flox/+; Meox2^Cre/+ control embryos showing partial recombination of the Nle1^flox allele in several tissues at E10.5 (n = 3) and E15.5 (n = 3). Efficiency of recombination was estimated through comparison with a reference DNA sample (*) derived from a Nle1^{flox/ Δ} adult mouse. Nested PCR were performed for the E7.5 and E8.5 stages. sp. cord: spinal cord, ag: adrenal glands.