Establishing F1A-CreERT2 Mice to Trace Fgf1 Expression in Adult Mouse Cardiomyocytes.

Yi-Chao Hsu,Chi-Kuang Wang,Si-Tse Jiang,Mei-Shu Chen,Yu-Fen Chung,Ing-Ming Chiu

doi:10.3390/cells11010121

Abstract

Fibroblast growth factor 1 (FGF1) regulates many biological and physiological processes. In mice, Fgf1 gene contains at least three upstream promoters and are alternatively spliced to the first protein coding exon, giving rise to different Fgf1 mRNA variants (1A, 1B and 1G). 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 using the Fgf1A promoter (F1A) driving the expression of the 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.

Highlights

The Cre/loxP site-specific recombination system has been widely used for the studies of promoter activation for genes of interest and conditional knockout mice [1]
Tamoxifen-Activated Cre-loxP Recombination of Genomic DNA Is Tissue-Specific and. We further explored this unique Fgf1A and CreERT2 heart-specific gene expression patterns and performed lineage tracing in Fgf1A promoter (F1A)-CreERT2 × ROSA26 mice
Using heart tissue sections of ROSA26/F1A-CreERT2 mice for the staining of X-Gal, we further demonstrated that LacZ-positive signals were detected in the right atrium (RA), right ventricle (RV), atrium and ventricle (AV) groove, IVS, left atrium (LA), left ventricle (LV) of the heart (Figure 5C2)

Summary

Introduction

The Cre/loxP site-specific recombination system has been widely used for the studies of promoter activation for genes of interest and conditional knockout mice [1]. To target and trace the lineage-specific cells in the cardiovascular system, Kimura et al reported a ubiquitous CAG promoter or the cardiomyocyte-specific αMHC promoter driven HIF-1α-ODD-CreERT2 transgene line. Cuervo et al reported that PDGFRβ-P2A-CreERT2 mouse line can be used to target and trace NG2+ , desmin+ , PDGFRβ+ perivascular cells in the brain and retina when crossing with a fluorescent reporter mouse line. They demonstrated the feasibility to delete Notch

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Conclusion