STOCK Gt(ROSA)26Sor^{tm1(CAG-APOBEC3B)Rshar}/J

Stock number: 038176
Product name: Rosa26::CAG-LSL-A3Bi
Research areas: Cancer Research, Research Tools

Description

Rosa26::CAG-LSL‐A3Bi knock-in mice express tumor-like levels of human APOBEC3B (apolipoprotein B mRNA editing enzyme catalytic subunit 3B; also called A3B) after Cre recombinase-mediated excision of a loxP-flanked Stop cassette. This strain enables studies of tumor evolution, as well as preclinical studies.

A control line is available having Cre-inducible expression of a catalytically inactive APOBEC3B mutant (Stock No. 038177).

Detailed description

Antiviral APOBEC3B (apolipoprotein B mRNA editing enzyme catalytic subunit 3B; also called A3B) has been implicated as a source of mutation in many different cancers because it deaminates DNA cytosines to uracils, which can haphazardly accumulate as mutations in the genome. It has recently been confirmed to be an oncogene.

Rosa26::CAG-LSL‐A3Bi knock-in mice represent a new murine model for inducible expression of human A3B. In these animals, a human A3B minigene is integrated into the mouse Gt(ROSA)26Sor (Rosa26) locus downstream of the Rosa26 promoter, a stronger heterologous CAG promoter, and a strong transcription stop cassette flanked by loxP sites. Cre-mediated removal of the transcription stop cassette results in strong A3B expression. Upon induction, mice develop tumors at an accelerated rate due to increased mutations associated with A3B.

Widespread expression of human A3B, initiated through crosses with CMV-Cre mice (Stock No. 006054), recapitulates protein levels reported in many human cancers. Young animals show no overt phenotypes except males never become fertile. In comparison to naturally aged wildtype animals, compound mutant mice (CAG-A3B) of both sexes develop tumors, predominantly blood and liver cancers, at an average of 5.2 months earlier. A subset of animals also show clear evidence for metastasis. Both primary and metastatic tumors manifest a clear APOBEC mutation signature (SBS2), which interestingly also associates with an elevated occurrence of structural variations, including small insertion and deletion mutations (indels) and larger-scale events.

Attempts to induce A3B expression in mammary epithelial cells (through crosses with MMTV-Cre mice, Stock No. 003553) also trigger the formation of lymphomas due to the leaky expression of Cre recombinase in hematopoietic cells.

A control line is available having Cre-inducible expression of a catalytically inactive APOBEC3B mutant (Stock No. 038177).

Development

Using pAi38 (Addgene 34883) as a backbone for the targeting construct, a CAG promoter followed by a loxP‐Stop(neomycin)‐loxP cassette and the human DNA mutating enzyme APOBEC3B were introduced to intron 1 of the mouse Gt(ROSA)26Sor locus via homologous recombination in B6(Cg)-Tyr^c-2J/J-derived embryonic stem cells. Resultant mice were backcrossed to C57BL/6J for at least 10 generations by the donating laboratory (see SNP note below).

Upon arrival at The Jackson Laboratory in September 2023, the strain was rederived with C57BL/6J (Stock No. 000664). Cryopreservation was performed in May 2024.

In 2024, 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 rederived living colony at The Jackson Laboratory Repository. Six of the 43 markers throughout the genome were segregating with an unknown source. Also, 2 of the 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed genetic background.

Allele

Symbol: Gt(ROSA)26Sor^{tm1(CAG-APOBEC3B)Rshar}
Name: targeted mutation 1, Reuben S Harris
MGI accession ID: MGI:7461466
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); Inserted expressed sequence; Humanized sequence
Synonyms: Rosa26::CAG-LSL-A3Bi; Rosa26::LSL-CAG-A3B
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: B6(Cg)-Tyr^c-2J/J
Molecular note: A CAG promoter followed by a loxP‐Stop (neomycin)‐loxP cassette and the human DNA mutating enzyme APOBEC3B were introduced to intron 1.