FIG. 3.

Phenotypes of E2F1 transgenic mice. (A) Gross physical appearance of 3-week-old Eμ-pp-E2F1 and Actin-Cre/R26E2F1/+ mice. Variability in the dwarf phenotype is demonstrated for the Actin-Cre/R26E2F1;+ mice. The bald spot on the smallest Actin-Cre/R26-E2F1;+ mouse was the result of excessive nurturing by the mother. (B) Northern blot analysis on poly(A)⁺ mRNA isolated from neck and trunk shows transgenic E2F1 gene expression in newborn Actin-Cre/R26E2F1;+ and Eμ-pp-E2F1 mice. RNA sample of CMV-Cre/R26E2F1;+ ES cells serves as a positive control for the 4.5-kb E2F1-IRES-PLAP transcript.