Fig. 5.

Liver-specific expression of a Zhx2 transgene restores H19 repression in an Afr1^b/b background. Three founder mice containing the TTR-Afr1 transgene were backcrossed to BALB/cJ; liver RNA from F₂ offspring was harvested 4 weeks after birth. Data are shown from F₂ littermates from line 1 (high-copy transgene, lanes 1–3) and line 2 (low-copy transgene, lanes 4–7); similar results were seen with the third line. The presence or absence of the TTR-Afr1 transgene (+ or -, respectively) and the endogenous Afr1 genotype (a/b or b/b) were determined by PCR analysis of tail-biopsied DNA from each mouse. RT-PCR (using the same oligonucleotides as those shown in Fig. 1d) confirmed the expression of the endogenous Zhx2 gene in mouse 6. Northern analysis (using an exon 3 probe) confirmed the presence of Zhx2 mRNA from the endogenous locus (4.4-kb band) in mouse 6 and the TTR-Afr1 transgene (Afr1 TG) (3.2-kb band) in mice 1, 3, 6, and 7. H19 levels were determined by Northern analysis and shown to be reduced in the presence of the TTR-Afr1 transgene relative to nontransgenic littermates. GAPDH was used as a control for RNA loading.