Fig. 3
From: Considerations for the use of Cre recombinase for conditional gene deletion in the mouse lens
Comparison of Le-Cre and P0-3.9GFPCre embryos using both real-time transgene expression and lineage tracing. GFP (top two rows) co-expressed with the CRE transgene in both Le-Cre and P0-3.9GFPCre mice made it possible to compare real-time transgene expression of both transgenes in whole mount embryos. X-Gal staining (bottom two rows) in embryos carrying both the ROSA26 CRE reporter (Gt(ROSA)26Sortm1Sor) and either the Le-Cre or P0–3.9GFPCre transgene provided an alternate way to compare the CRE transgenic lines based on lineage tracing of CRE expressing cells. Le-Cre (first row) and P0-3.9GFPCre (second row) transgenic embryos exhibit largely identical GFP expression patterns from E9.5 through E15.5 with the exception of expression in the apical ectodermal ridge (AER) of the forelimb observed specifically in the P0-3.9GFPCre transgenic embryos at E10.5. In contrast to the largely identical pattern of GFP expression, X-Gal staining revealed marked differences in expression between the Le-Cre (third row) and P0-3.9GFPCre (fourth row) transgenic embryos. Although P0-3.9GFPCre exhibited extensive embryo-to-embryo variability, all embryos from this strain exhibited extensive non-ocular X-Gal staining patterns at every stage examined. Externally visible X-Gal staining in the Le-Cre embryos remained restricted to the eye and surface ectoderm surrounding the eye proceeding in a streak of ectoderm toward the developing snout and the pancreas. Some X-Gal staining in the forebrain showed through the surface ectoderm at E9.5 and E10.5 in Le-Cre embryos (asterisks)