(676.4) F1A-CreERT2 Mice: Targeting and Tracing Cardiomyocytes with Fgf1 Expression in Adult Mouse

Poster Board Number: A428

Ing-Ming Chiu (National Health Research Institutes, National Health Research Institutes), Yu-Fen Chung (National Health Research Institutes), Mei-Shu Chen (National Health Research Institutes), Chi-Kuang Wang (National Applied Research Laboratories), Si-Tse Jiang (National Applied Research Laboratories), Yi-Chao Hsu (Mackay Medical College)

Fibroblast growth factor 1 (FGF1) regulates many biological and homeostatic processes, including obesity and metabolic syndrome. In mice, Fgf1 gene contains at least three upstream promoters and their respective adjacent untranslated exons that spliced to the first protein coding exon mutually exclusively, giving rise to different Fgf1 mRNA variants. Among them, the Fgf1A transcript is predominantly expressed in the heart. FGF1 can induce cardiomyocyte regeneration and cardiogenesis in vitro and in vivo. Here, we generated a novel mouse line Fgf1A promoter (F1A)-driven inducible Cre recombinase (CreERT2). We firstly demonstrated that the highest mRNA expression of CreERT2 were detected in the heart specifically of F1A-CreERT2 mice, similar to that of Fgf1A mRNA. The F1A-CreERT2 mice were crossed with ROSA26 mice, and the F1 mice were analyzed. The LacZ-positive signals were detected exclusively in the heart after tamoxifen administration. The CreERT2-mediated recombination in the tissues is monitored through LacZ-positive signals, indicating the in situ localization of F1A-positive cells. Consistently, these F1A-positive cells with RFP-positive signals or LacZ-positive blue signals were co-localized with cardiomyocytes expressing cardiac troponin T, suggesting cardiomyocyte-specific activation of Fgf1A promoter. Our data suggested that the F1A-CreERT2 mouse line could be used for time-dependent and lineage tracing of Fgf1A-expressing cells in vivo.  F1A-CreERT2 line is a valuable tool for in vivo lineage tracing of Fgf1A-expressing cells during heart development and will facilitate the elucidation of the physiological and pathological role of Fgf1A in heart failure and metabolic syndrome.

Support or Funding Information

National Health Research Institutes, Ministry of Science and Technology, and Ministry of Health and Welfare, Taiwan.





Figure 1. Breeding of F1A-CreERT2 x ROSA26 F1 mice. The F1A-CreERT2 transgenic mice were crossed to LacZ reporter mouse line, ROSA26. After tamoxifen treatment, the CreERT2 fusion protein will bind to tamoxifen and translocate into the nucleus to recombine its loxP-flanked DNA targets, removing the transcriptional termination polyA cassette and producing β-galactosidase. The β-galactosidase activity could be detected by staining tissues with X-Gal and showing punctate blue signals.; Figure 2. Expression profile of F1A-driven expression of LacZ gene in F1A-CreERT2 x ROSA26 F1 mice. (A) LacZ-positive signals showed tissue-specific and dose-dependent manner after tamoxifen treatment. LacZ-positive blue signals of LacZ staining were detected only in heart tissues of F1A-CreERT2 x ROSA26 F1 transgenic mice after 1-mg or 2-mg tamoxifen treatment but not in brain and kidney. Scale bar, 2 mm (a-c); 50 µm (d-i).