STOCK Cdkn2a^tm1.1Gsu/J

Stock number: 036933
Product name: p16^f
Research areas: Cancer Research, Research Tools

Description

P16^flox conditional mutant mice possess loxP sites flanking exon 1A (E1A) of the Cdkn2a (cyclin dependent kinase inhibitor 2A) gene.  The targeting construct is designed to allow conditional expression of the Cdkn1a splice variant p16(INK4a) while leaving the alternative splice variant p19(ARF) intact. This strain may be useful in generating conditional mutations to study pancreatic tumorigenesis.

Detailed description

The Cdkn2a (cyclin dependent kinase inhibitor 2A) gene generates at least three splice variants, which differ in their first exons. The p16(INK4A) protein (this strain) contains sequences beginning with exon 1A and functions as a tumor suppressor. Specifically, p16(INK4A) is involved in the control of cell cycle, senescence, and tumorigenic growth through inhibition of Cdk4 activity. Mutations in p16(INK4A) are associated with multiple cancer types, including but not limited to melanomas, gliomas, pancreatic and bladder cancers, and leukemias. The alternative reading frame (ARF)p19 protein is initiated by using sequence from the first exon (exon 1B), which is located upstream of exon1A and continues through exon 2 (skipping exon 1A).

P16^flox conditional mutant mice possess loxP sites flanking exon 1A (E1A). Mice homozygous for the mutation are viable and fertile. When bred to mice that express tissue-specific Cre recombinase, resulting offspring will have exon 1A deleted in cre-expressing tissues. Deletion of exon 1A abolishes p16 expression, but not p19 expression, in a tissue-specific manner.

For example, when bred to a strain expressing Cre recombinase in pancreas (for example, B6.FVB-Tg(Pdx1-cre)6Tuv/J, Stock No. 014647) and LSL-Kras^G12D mice (for example, B6.129S4-Kras^tm4Tyj/J, Stock No. 008179), triple mutant progeny develop pancreatic cancer and metastasis at 100% penetrance. Median survival is 25.5 +/- 8.9 weeks of age. By 6 weeks of age mice begin to develop weight loss, jaundice, ascites and increased abdominal girth.

Of note, a floxed p19(ARF) strain with loxP sites flanking exon 1B is available as B6.129S1-Cdkn2a^tm4Cjs/J, Stock No. 023323.

Development

The targeting construct contains from 5' to 3': a loxP site upstream of exon 1A (E1A) and an FRT-flanked neomycin cassette followed by a second loxP site downstream of exon 1A of the Cdkn1a gene on chromosome 4. Exon 1A of the splice variant p16 is not shared with the p19 variant, thus, the construct is designed to leave p19 expression intact, while making p16 expression conditional. The construct was electroporated into 129-derived unspecified embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts. Chimeric males were crossed to C57BL/6J females. Offspring were bred with CMV-Flp transgenic mice on an unknown background to delete the neo cassette. The resulting progeny were crossed to remove the Flp-expressing transgene. The strain was backcrossed to C57BL/6J for 5 generations. Upon arrival, mice were bred to C57BL/6J (Stock No. 000664) for at least one generation to establish the colony.

In 2022, a 48 SNP (single nucleotide polymorphism) panel analysis, with 43 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the mice sent to The Jackson Laboratory Repository. Markers on chromosomes 12 and 15 were segregating with 129, and a marker on chromosome 14 was of unknown genetic background. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed genetic background.

Allele

Symbol: Cdkn2a^tm1.1Gsu
Name: targeted mutation 1.1, Gloria H Su
MGI accession ID: MGI:5502377
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); No functional change
Synonyms: p16^f
Marker symbol: Cdkn2a
Marker name: cyclin dependent kinase inhibitor 2A
Marker synonyms: Arf; ARF-INK4a; CAI2; CDK4I; CDKN2; CMM2; INK4; INK4A; Ink4a/Arf; INK4a-ARF; MLM; MTS1; MTS-1; P14; P14ARF; P16; p16Cdkn2a; P16INK4; P16INK4A; P19; p19^ARF; P19ARF; Pctr1; TP16
Chromosome: 4
Strain of origin: 129
Molecular note: An FRT-flanked neomycin resistance (neo) cassette with a loxP site was inserted upstream of exon E1A. An additional loxP site was inserted downstream of exon E1A. Flp-mediated recombination removed the neo cassette and left exon E1A floxed.