B6.129S6(FVB)-Gt(ROSA)26Sor^{tm1(Pik3ca*H1047R)Egan}/BoseJ

Stock number: 041202
Product name: R26-Pik3ca^H1047R
Research areas: Cancer Research, Cell Biology Research, Research Tools

Description

R26-Pik3ca^H1047R mice express a Cre-inducible Pik3ca gene with a H1047R mutation inserted into the Gt(ROSA)26Sor locus. Cre-mediated recombination results in the excision of a floxed STOP cassette, enabling the tissue and time-dependent expression of Pik3ca^H1047R. This strain is useful when studying the role of PI3K mutations on the development of mammary tumors as well as lymphoid and skin malignancies.

Detailed description

Pik3ca (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha; also called PI3K) encodes the p110alpha catalytic subunit of phosphatidylinositol 3-kinase. It is one of the most frequently mutated genes in human cancer. H1047R mutations in the kinase domain account for approximately 40% of breast cancer PIK3CA mutant alleles. In this R26-Pik3ca^H1047R strain, an H1047R mutant form of Pik3ca was targeted to the Gt(ROSA)26Sor locus downstream of a floxed STOP cassette.

When crossed with an MMTV-Cre strain (see Stock No. 003551 and Stock No. 003553) to excise the floxed stop cassette, Pik3ca^H1047R is expressed in mammary epithelium. Starting at 5 months of age, females develop mammary tumors as well as lymphoid and skin malignancies. The percentage of animals affected by tumors varied based on the particular MMTV-Cre strain used. Mammary tumors were observed in both virgin and multiparous mice. Males were not studied.

R26-Pik3ca^H1047R mice were also bred to HER2^V777L mice, with a Cre-inducible ERBB2 human gene with the activating mutation, V777L, found in breast and colorectal cancer patients. Adenovirus Cre injection into the mammary glands of HER2^V777L; PIK3CA^H1047R double mutant (HP) mice results in breast cancers with accelerated tumor formation in vivo and increased invasion and migration in in vitro assays. HP breast cancers have resistance to the pan-HER tyrosine kinase inhibitor, neratinib.

Of note, this R26-Pik3ca^H1047R allele is also available on an FVB congenic background as Stock No. 016977.

A small percentage of R26-Pik3ca^H1047R mutant mice show reduced survival on the original FVB congenic background due to development of blood vessel lesions. This has not been detected in this C57BL/6J congenic strain by the donating investigator.

Development

R26-Pik3ca^H1047R mice have a floxed stop cassette containing a neomycin resistance (neo) cassette upstream of a mutant murine phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (Pik3ca) gene cDNA. The Pik3ca gene was designed to encode a histidine to arginine activating at amino acid position 1047 (H1047R). This targeting vector also included 5' and 3' homology arms for site-directed recombination into the Gt(ROSA)26Sor locus. The construct was electroporated into 129S6/SvEvTac-derived W4 embryonic stem (ES) cells and correctly targeted ES cells were injected into blastocysts. The resulting chimeric mice were bred to FVB mice for at least 12 generations and FVB congenic R26-Pik3ca^H1047R mice were sent to The Jackson Laboratory as Stock No. 016977. Dr. Ron Bose (Washington University School of Medicine) purchased some of these mice and performed speed congenic backcrosses to C57BL/6J inbred mice (Stock No. 000664) for more than 5 generations before sending some C57BL/6J congenic R26-Pik3ca^H1047R mice back to The Jackson Laboratory. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes.

Allele

Symbol: Gt(ROSA)26Sor^{tm1(Pik3ca*H1047R)Egan}
Name: targeted mutation 1, Sean E Egan
MGI accession ID: MGI:5000472
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); Inserted expressed sequence
Synonyms: R26-Pik3ca^H1047R
Marker symbol: Gt(ROSA)26Sor
Marker name: gene trap ROSA 26, Philippe Soriano
Marker synonyms: beta geo; Gtrgeo26; Gtrosa26; R26; ROSA26; SETD5-AS1; Thumpd3as1
Chromosome: 6
Strain of origin: 129S6/SvEvTac
Expressed genes: Pik3ca,phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha,mouse, laboratory
Molecular note: The following sequences were inserted into intron 1: splice acceptor site, a STOP cassette (loxP site flanked neomycin resistance gene cassette), Pik3ca cDNA sequence where histidine codon 1047 (CAT) was changed to arginine (p.H1047R), and bovine GH poly(A) signal sequences.