C57BL/6-Tg(JAK2*V617F)FF1Rsko/J

Stock number: 037558
Product name: JAK2-FF1
Research areas: Cancer Research, Cardiovascular Research, Cell Biology Research, Hematological Research, Immunology, Inflammation and Autoimmunity Research, Research Tools

Description

JAK2-V617F transgenic mice conditionally express the human JAK2 (Janus kinase 2) gene carrying the pathological V617F substitution. Breeding JAK2-V617F mice to a strain carrying Cre recombinase flips the orientation of the JAK2 cDNA and allows expression of the mutant transgene in offspring. This strain may be useful for studying myeloproliferative disorders, as well as the myeloproliferative neoplasm (MPN) polycythemia vera (PV).

Of note, mice carrying the JAK2 exon 12 (N542-E543del) mutation are available as Stock No. 037560).

Detailed description

JAK2 is a protein tyrosine kinase involved in a specific subset of cytokine receptor signaling pathways and is misregulated or mutated in some myeloproliferative diseases and cancers. The V617F mutation results in constitutive activation of JAK2 kinase signaling. When activated, JAK2 phosphorylates STAT transcription factors and initiates the JAK-STAT signaling pathway. V617F has been identified in 95% of patients with polycythemia vera, and 50% of patients with primary myelofibrosis and essential thrombocythemia.

JAK2-V617F transgenic mice conditionally express the human JAK2 (Janus kinase 2) gene carrying the pathological valine to phenylalanine mutation (V617F). JAK2 sequence is placed in reverse orientation and is surrounded by lox71 and lox66 sites, allowing for cre-mediated inversion of the JAK2 cDNA, which restores the transgene to a functionally active configuration. Recombination is unidirectional and irreversible leaving one loxP site and a double lox66/71 site with a reduced affinity for cre.  Mice homozygous for the unrecombined transgene are viable, but do not breed well.

When JAK2-V617F transgenic mice are combined with mice carrying the hematopoiesis-specific Tg(Vav1-icre)A2Kio (Stock No. 008610) allele, offspring develop an essential thrombocythemia (ET)-like phenotype characterized by elevated platelet counts, moderate neutrophilia, splenomegaly, and in later stages, myelofibrosis. When combined with mice carrying the interferon inducible Tg(Mx1-cre)1Cgn (Stock No. 003556) allele, pIpC induced offspring develop a polycythemia vera (PV)-like phenotype characterized by increased hemoglobin, thrombocytosis, neutrophilia, splenomegaly, and in later stages, myelofibrosis. Alternatively, other cre-expressing strains can be used to activate the transgene.

Of note, mice carrying the JAK2 exon 12 (N542-E543del) mutation are available as Stock No. 037560.

Development

The JAK2-V617F transgenic construct contains exons 1-12 and a part of intron 12 from the human JAK2 gene (190 kb bacterial artificial chromosome clone, CTD2025A15), an antiparallel lox66 site inserted into the remaining part of intron 12, a partial cDNA encoding JAK2 exons 13-25 (with a V617F substitution in exon 14), a polyA signal, a lox71 site, and an FRT-flanked Ampicillin resistance gene (removed following induction of flp recombinase). The segment between the lox sites was inverted by restriction enzyme digest, creating an inducible Flip-Flop transgene. In the flipped configuration, the full length JAK2 protein cannot be made. The donating investigator indicates that BAC clone does not include any other known genes. Following genotyping verification, the modified BAC was microinjected into the pronuclei of fertilized C57BL/6 oocytes. Founder line FF1 was bred to C57BL/6N mice and maintained on the C57BL/6N background. Further analysis determined that the FF1 founder line integrated on chromosome 8 and has 9 copies of the transgene inserted in head to tail orientation. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6NJ oocytes (Stock No. 005304).

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 males sent to The Jackson Laboratory Repository. One of the 5 markers that determine C57BL/6J from C57BL/6N was found to be segregating on Chromosome 6. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6N;C57BL/6J genetic background.

Allele

Symbol: Tg(JAK2*V617F)FF1Rsko
Name: transgene insertion FF1, Radek C Skoda
MGI accession ID: MGI:5553468
Generation method: Transgenic
Attributes: Inserted expressed sequence; Humanized sequence
Marker symbol: Tg(JAK2*V617F)FF1Rsko
Marker name: transgene insertion FF1, Radek C Skoda
Chromosome: 8
Strain of origin: C57BL/6
Molecular note: The human BAC, CTD2025A15, containing JAK2 exons 1-12 was combined with a partial cDNA encoding JAK2 exons 13-25 containing the V617F mutation and a polyadenylation signal. To create an inducible Flip-Flop transgene, this construct was modified by inserting a lox66 site into intron 12 and a lox71 site after the polyadenylation signal and the segment between the loxP sites was inverted. Cre-recombination of antiparallel loxP sites flips the orientation of the cDNA and places the intron 12 splice acceptor into the correct position to allow proper splicing of the transgenic pre-mRNA. Recombination generates one wild-type loxP and one double mutant lox66/77 site, which is no longer a substrate for the cre recombinase. This line carries 9 copies of the transgene that integrated in a single chromosomal locus on chromosome 8, band A1.