Figure 7. Decrease in connective tissue gene expression in perinatal lung with Klf4 deficiency.

(A) Cells from the Klf4 null lung were immortalized with SV40Tag as described in Methods. These Klf4 null fibroblasts (Fib-Klf4) express vimentin, the alpha 1 chain of Type 1 collagen (Col a1) and smooth muscle actin (SMA) in common with the mouse lung fibroblasts (MLg), but neither SP-C nor cytokeratin 8 which are found in mouse lung epithelial cells (MLE). The ribosomal marker 28S is shown as a loading control. (B) Klf4 cDNA was constitutively expressed in Fib-Klf4 cells to generate Fib+Klf4 cells as described in Methods. Compared to the empty vector control cells (C), these Klf4 expressing fibroblasts (Fib+Klf4) exhibit up-regulated expression of messenger RNA for p21^cip1/Waf1 (2 fold), SMA (3.5 fold), the alpha 1 chain of Type 1 collagen, tenascin C and fibronectin (2–2.5 fold each) but not fibronectin receptor beta (Itgb1). The ribosomal marker 18S is shown as a loading control. These data represent two independent Northern blot experiments. (C) Comparative levels of expression for these Klf4 target genes in Klf4 null lung (null) relative to normal lung (Nor) at fetal day 19 of gestation and 6 h after birth in room air (n = 3 for each sample, asterisk denotes difference in level of expression in Klf4 null lung versus normal lung at p<0.05).