These mice carry a floxed allele of the Arf tumor supressor encoded by a Cdkn2a alternative reading frame.
Charles J. Sherr, St. Jude Children's Research Hospital
The alternate reading frame of the Cdkn2a (cyclin-dependent kinase inhibitor-2A) locus encoding the Arf tumor suppressor, is expressed transiently during mouse male germ cell and eye development. Its inactivation compromises spermatogenesis as mice age and leads to aberrant postnatal proliferation of cells in the vitreous of the eye, resulting in blindness. The gene is frequently deleted or epigenetically silenced in a wide variety of tumors. Mice lacking Arf spontaneously develop tumors later in life.
The first coding exon (exon-1β) of the mouse Arf gene is flanked by loxP sites in this conditional mutant strain. Floxed homozygotes are viable and fertile, appear phenotypically normal, and are not prone to cancer development. Cre-mediated excision of the floxed segment results in directed knockouts of the Arf gene but leave the linked Ink4a (Cdkn2a) gene intact. Infection of cultured embryonic fibroblast cells or pre-B cells with cre-expressing retroviruses can produce immortalized Arf-null cell lines.
A loxP-flanked neomycin resistance cassette was placed upstream of first coding exon (exon 1β) and a third loxP site was placed in the intron just downstream of the exon. The targeting vector was introduced to 129S1/Sv-Oca2+Tyr+Kitl+-derived W9.5 embryonic stem (ES) cells. Recombined and karyotypically normal ES cells were electroporated with a cre-expressing vector to remove the loxP-flanked neomycin selection cassette. Colonies retaining floxed exon 1β were injected into C57BL/6 blastocysts. Resultant male chimeric mice were bred to C57BL/6 females. This strain was backcrossed to C57BL/6J for six generations by the donating laboratory. The genetic background was tested at each generation with MaxBax until results demonstrated a 100% C57BL/6J result.
|Allele Name||targeted mutation 4, Charles J Sherr|
|Allele Type||Targeted (Conditional ready (e.g. floxed), No functional change)|
|Allele Synonym(s)||ArfFL; ArfLoxP; Cdkn2aflx|
|Gene Symbol and Name||Cdkn2a, cyclin dependent kinase inhibitor 2A|
|Strain of Origin||129S1/Sv-Oca2+ Tyr+ Kitl+|
|Molecular Note||The first coding exon (1Beta) is flanked by loxP sites. A loxP-neoTK-loxP cassette was inserted downstream of the floxed exon and was excised in the targeted ES cells. Cell clones with the selection cassette removed were used to generated mouse lines with a conditional Cdkn2a allele.|
Homozygous and heterozygous floxed mice are viable and fertile.
When using the ArfFL/+ mouse strain in a publication, please cite the originating article(s) and include JAX stock #023323 in your Materials and Methods section.