B6(129S4)-Csf2^tm1.1Lky/J

Stock number: 040331
Product name: Csf2^{flox-tdTomato} , Csf2^fl
Research areas: Internal/Organ Research, Research Tools

Description

Csf2^{flox-tdTomato} (Csf2^fl) mice mark CSF2 (GM-CSF) expression via a fluorescent tdTomato reporter and enable the generation of a Csf2 gene conditional knock-out through Cre recombinase-mediated excision of floxed exons 3 and 4. These mice have been useful in profiling CSF2 expression in both immune cells, including group 2 innate lymphoid cells and γδ T cells, as well as alveolar epithelial type 2 cells (AT2s).

Detailed description

Alveolar epithelial type 2 cell (AT2)-derived CSF2 (colony stimulating factor 2 (granulocyte-macrophage); also called GM-CSF) is the necessary signal to initiate and promote pre- and post-natal alveolar macrophage (AM) differentiation and their subsequent maintenance throughout adulthood.

In the absence of Cre recombinase, transcription of this Csf2^{flox-tdTomato} (Csf2^fl) allele results in the production of a bicistronic mRNA encoding CSF2 and a tdTomato reporter. This marks CSF2-producing cells with fluorescent tdTomato signal while maintaining normal CSF2 expression. Crosses with mice expressing Cre recombinase excise floxed exons 3 and 4 to create a knock-out allele. Knock-out of CSF2 in the hematopoietic compartment, achieved through crosses with Vav1^iCre mice (Stock No. 008610), demonstrates that this source of CSF2 is dispensable for the development of alveolar macrophages in the neonatal lung. Widespread excision of floxed region (created through crosses with SPC^Cre mice) results in the absence of alveolar macrophages from the adult lung.

These mice have been useful in profiling CSF2 expression in both immune cells, including group 2 innate lymphoid cells and γδ T cells, as well as alveolar epithelial type 2 cells (AT2s).

Development

A loxP site was introduced to intron 2 and a loxP-IRES-tdTomato-FRT-neomycin-FRT cassette was placed downstream of the protein-coding sequences (CDS) in exon 4 of the mouse Csf2 gene (ENSMUST00000019060.6 Csf2-201) via homologous recombination in C57BL/6J-derived PRXB6T embryonic stem (ES) cells. Resultant mice were bred with mice expressing FLPe/FLP1 recombinase (Stock No. 009086) to excise the FRT-flanked neomycin cassette, and crossed with C57BL/6J mice by the donating laboratory to remove the FLPe/FLP1 allele. Upon arrival, sperm was cryopreserved. To establish a live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

Allele

Symbol: Csf2^tm1.1Lky
Name: targeted mutation 1.1, Richard M. Locksley
MGI accession ID: MGI:7482635
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); Reporter; No functional change
Synonyms: Csf2^fl; Csf2^RFP
Marker symbol: Csf2
Marker name: colony stimulating factor 2 (granulocyte-macrophage)
Marker synonyms: CSF; Csfgm; GMCSF; Gm-csf; MGI-IGM
Chromosome: 11
Strain of origin: C57BL/6J
Molecular note: The targeting construct inserted a loxP site upstream of exon 3 and loxP site, IRES, tdTomato reporter gene, and FRT-flanked neomycin resistance cassette downstream of exon 4. Flp-mediated recombination removed the selection cassette. tdTomato is expressed both in the presence and absence of recombination of the loxP sites flanking exons 3 and 4.