B6.Cg-Sf3b1^tm1.1Mdf Atm^tm2.1Fwa/CjwuJ

Stock number: 035513
Product name: Sf3b1^K700E Atm^c
Research areas: Cancer Research, Research Tools

Description

These Sf3b1^K700E Atm^c mice contain a cre-conditional K700E mutation in the Sf3b1 gene, and loxP site flanking exons 57 and 58 of the Atm gene. These mutant mice are useful when studying chronic lymphocytic leukemia (CLL).

Detailed description

These Sf3b1^K700E Atm^c mice contain conditional alleles present in Stock No. 029766 and Stock No. 021444.

The targeted Sf3b1 gene encodes splicing factor 3b protein complex subunit 1 that is involved with spliceosome assembly and pre-mRNA splicing. Mutations in this gene are frequently associated with several myeloid malignancies, predominantly myelodysplastic syndromes (MDS), as well as other hematologic malignancies, including chronic lymphocytic leukemia (CLL). CLL is the most common B cell leukemia in adults, involving the peripheral blood and lymphoid organs such as lymph nodes and bone marrow. These Sf3b1^K700E conditional knock-in mice carry an allele with a knock-in sequence of loxP sites, in opposite orientation, flanking inverted copies of exon 15, with the K700E mutation, and exon 16 downstream of endogenous exon 16. Cre recombinase activity results in deletion of the endogenous wildtype exon 15 and 16, and an inversion of the mutant exon 15 and 16, allowing expression of the mutant allele. Homozygous Sf3b1^K700E knock-in mice are not viable. The non-recombined conditional allele is hypomorphic. Heterozygotes are viable and fertile.

This strain also contains a conditional Atm gene, with exons 57 and 58 floxed. Atm (Ataxia-telangiectasia mutated) encodes a phosphoinositide 3-kinase related protein kinase (PIKK) family member that is activated by DNA double-strand breaks and regulates the DNA double-strand break response and repair. Human SF3B1 mutations commonly co-occur in CLL with focal deletion in chromosome 11 [del(11q)], a region that contains this essential DNA damage response gene, Atm.

When the Sf3b1^K700E conditional knock-in mice are bred CD19-cre mice (Stock No. 006785), the total number of splenocytes is significantly reduced in these mice with B cell-restricted expression of Sf3b1-K700E versus WT mice at 12-months of age as a result of significant reduction in B cells. Spleen weight is also decreased, while body weight and the number of total bone marrow mononuclear cells (BMCs) are unaffected. The percentage and absolute number of marginal zone (MZ) B cells were increased and percentages of splenic transitional B cells were decreased. At 24-months of age, the percentages of T, B, and macrophage subpopulations in peripheral blood remained similar between WT and Sf3b1^K700E mice, with no evidence of lymph node enlargement. With additional deletion of Atm in this mouse model, the metabolic profile is restored, B cell cellular senescence is overcome, and animals develop chronic lymphocytic leukemia with ~10% penetrance and a 18-20 month onset.

Development

These Sf3b1^K700E Atm^c mice contain alleles present in Stock No. 029766 and Stock No. 021444. Mutant mice also contained the Cd19cre allele present in Stock No. 006785. Triple allelic mice were backcrossed to C57BL/6J mice for at least 10 generations and the Cd19cre allele was bred out before mice arrived at The Jackson Laboratory. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J (Stock No. 000664) oocytes.

Allele

Symbol: Sf3b1^tm1.1Mdf
Name: targeted mutation 1.1, Mark D Fleming
MGI accession ID: MGI:5818977
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); Hypomorph; Humanized sequence
Synonyms: Sf3b1^K700E
Marker symbol: Sf3b1
Marker name: splicing factor 3b, subunit 1
Marker synonyms: 2810001M05Rik; Hsh155; MDS; Prp10; PRPF10; Sap155; SF3b155; Targ4
Chromosome: 1
Strain of origin: (C57BL/6 x 129S4/SvJae)F1
Molecular note: A mutant loxP site was inserted into intron 14, and an FRT site flanked neomycin resistance gene/lacZ cassette, a loxP site, and, in reverse orientation, a copy of exon 16, a modified copy of exon 15, a second mutant loxP site and a second loxP site were inserted into intron 16. Flp-mediated recombination removed the neo cassette. The modification in exon 15 entails changing lysine codon 700 (AAA) to glutamic acid (GAA) (p.K700E). This is the equivalent of the same human mutation associated with myelodysplastic syndromes. This allele expresses the wild-type protein and only after Cre-mediated inversion of the inserted exon copies and deletion of the equivalent endogenous exons will it express the mutant protein. Nevertheless, this allele is hypomorphic.

Allele

Symbol: Atm^tm2.1Fwa
Name: targeted mutation 2.1, Frederick W Alt
MGI accession ID: MGI:3851145
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); No functional change
Synonyms: Atm^c
Marker symbol: Atm
Marker name: ataxia telangiectasia mutated
Marker synonyms: AT1; ATA; ATC; ATD; ATDC; ATE; C030026E19Rik; TEL1; TELO1
Chromosome: 9
Strain of origin: 129S6/SvEvTac
Molecular note: Sequence encoding the core PIKK kinase domain of the protein protein product were floxed by placing a loxP site upstream of exon 57 and floxed neomycin cassette downstream of exon 58. The neomycin cassette was subsequently removed by transient infection of cre recombinase.