Validation of a Novel Fgf10Cre–ERT2 Knock-in Mouse Line Targeting FGF10Pos Cells Postnatally

Abstract

Fgf10 is a key gene during development, homeostasis and repair after injury. We previously reported a knock-in Fgf10Cre–ERT2 line (with the Cre-ERT2 cassette inserted in frame with the start codon of exon 1), called thereafter Fgf10Ki–v1, to target FGF10Pos cells. While this line allowed fairly efficient and specific labeling of FGF10Pos cells during the embryonic stage, it failed to target these cells after birth, particularly in the postnatal lung, which has been the focus of our research. We report here the generation and validation of a new knock-in Fgf10Cre–ERT2 line (called thereafter Fgf10Ki–v2) with the insertion of the expression cassette in frame with the stop codon of exon 3. Fgf10Ki−v2/+ heterozygous mice exhibited comparable Fgf10 expression levels to wild type animals. However, a mismatch between Fgf10 and Cre expression levels was observed in Fgf10Ki–v2/+ lungs. In addition, lung and limb agenesis were observed in homozygous embryos suggesting a loss of Fgf10 functional allele in Fgf10Ki–v2 mice. Bioinformatic analysis shows that the 3′UTR, where the Cre-ERT2 cassette is inserted, contains numerous putative transcription factor binding sites. By crossing this line with tdTomato reporter line, we demonstrated that tdTomato expression faithfully recapitulated Fgf10 expression during development. Importantly, Fgf10Ki–v2 mouse is capable of significantly targeting FGF10Pos cells in the adult lung. Therefore, despite the aforementioned limitations, this new Fgf10Ki–v2 line opens the way for future mechanistic experiments involving the postnatal lung.

GLI1+ cells are a source of repair-supportive mesenchymal cells (RSMCs) during airway epithelial regeneration

“…Using our novel Fgf10 Cre−ERT2 mice recently reported [ 28 ], we also examined the localization of FGF10+ cells in non-injured lungs. In addition to being located in the alveolar region [ 28 ], FGF10+ cells were also observed around the bronchi and distinct from ASMCs (Fig. 5 E), similarly to what was observed for GLI1+ cells (Fig.…”

FGF10 Triggers De Novo Alveologenesis in a Bronchopulmonary Dysplasia Model: Impact on Resident Mesenchymal Niche Cells

“…In that respect, the Fgf10 CreERT2 line that we recently generated and validated will be instrumental in targeting the rMC Sca1 Pos Fgf10 Pos cells. 41 In addition, other Dre lines, with genes expressed specifically in clusters 2 or 6 will have to be generated and validated.…”

FGF10 triggers de novo alveologenesis in a BPD model: impact on the resident mesenchymal niche cells

“…In addition, a genetic model using dual Dre/Cre recombinase strategies will have to be established to specifically lineage-trace and characterize these 2 subpopulations. In that respect, the Fgf10 CreERT2 line that we recently generated and validated will be instrumental in targeting the rMC Sca1 Pos Fgf10 Pos cells [38]. In addition, other Dre lines, with genes expressed specifically in clusters 2 or 6 will have to be generated and validated.…”