Fig. 2.

. Zeb2-NAT expression is upregulated in old fibroblasts and correlates with retention of Zeb2 intron 1. a Schematics of the murine Zeb2 and Zeb2-NAT locus. An internal ribosome entry site (IRES) is located in the first intron of the Zeb2 transcript. Double arrows indicate the position of primers used to detect Zeb2-NAT RNA. b qRT-PCR analysis of Zeb2-NAT RNA in MEFs and fibroblasts from adult and old mice. Transcript levels were normalized to GAPDH mRNA and depicted as fold change relative to MEFs. c qRT-PCR analysis of Zeb2-NAT RNA in MEFs and in a iPS cell line derived from i4F fibroblasts. d qRT-PCR analysis of spliced and unspliced Zeb2 RNA in MEFs and old fibroblasts. Double arrows indicate the position of primers. For all graphics depicted, Student’s t test (two-tailed) statistics, *p < 0.05, **p < 0.01; error bars represent standard deviation; n=experiments with independent cell cultures