B6.129(Cg)-Gsk3b^tm2Jrw/J

Stock number: 029592
Product name: GSK-3β^FL (floxed exon 2)
Research areas: Cancer Research, Cell Biology Research, Diabetes and Obesity Research, Immunology, Inflammation and Autoimmunity Research, Neurobiology Research, Research Tools

Description

The GSK-3β-floxed exon 2 allele (GSK-3β^FL) has loxP sites flanking exon 2 of the glycogen synthase kinase 3 beta gene. Removal of the floxed sequence creates a null allele. These mice may be useful in studying developmental signaling pathways (e.g., Wnt/β-catenin, Hedgehog, Notch), tumorigenesis/cancer and metabolism/diabetes.

Detailed description

Glycogen synthase kinase 3 (GSK-3) is a serine-threonine kinase with two isoforms (α and β). The GSK-3β protein functions in energy metabolism, cell development (division, proliferation, motility, survival) and body pattern formation. GSK-3β mutations are implicated in Parkinson's disease risk modifiers, Alzheimer's disease pathogenesis and signaling pathway abnormalities/tumorigenesis.

The GSK-3β-floxed allele (GSK-3β^FL) has loxP sites flanking exon 2 of the Gsk3b gene. Mice homozygous for this floxed allele are viable and fertile, with GSK-3β levels equivalent to wildtype and no reported abnormalities. When bred to mice that express Cre recombinase, the resulting offspring will have the floxed region deleted in cre-expressing tissues; creating a knock-out allele.

Mice with global GSK-3β-deficiency are reported to die in late embryogenesis (liver apoptosis) or neonatally (also with cleft palate and sternum).

When GSK-3β-floxed mice are bred to Albumin-Cre transgenic mice (Stock No. 003574), the resulting liver-specific GSK-3β knockout homozygotes (LβKO) are viable with no gross metabolic defects (glucose/insulin tolerant and normal insulin signaling). In contrast, when bred to mice with myosin light chain 1f (MLC1f) promoter-driven Cre expression (Stock No. 027413), the resulting skeletal muscle-specific GSK-3β KO homozygoes (Mβ KO) are viable with improved glucose tolerance that is coupled with enhanced insulin-stimulated glycogen synthase regulation and glycogen deposition.

When GSK-3β-floxed mice are bred to have the RIP-Cre transgene (similar to Stock No. 003573) and also the insulin receptor 2 knock-out allele (Stock No. 004421), the resulting animals (C57BL/6;129) show that pancreatic β-cell-specific knock-out of GSK-3β prevents the diabetic phenotype of global IRS-2 knock-out.

For studying breast cancer on an FVB genetic background, the GSK-3β-floxed mice can be bred to harbor the Wap-Cre transgene (see Stock No. 008735) and the global GSK-3α knockout allele (Gsk3a^tm1.1Jrw). The mammary-specific knock-out of both GSK-3 isoforms (called WAP-double knock-out or WAP-DKO) results in activation of Wnt/β-catenin signaling and induces mammary intraepithelial neoplasia that progresses to squamous transdifferentiation and development of adenosquamous carcinomas at ~six months of age. When further bred to also have the β-catenin floxed exons 2-6 allele (see Stock No. 004152), the resulting animals with mammary-specific knock-out of both GSK-3 isoforms as well as β-catenin (called WAP-triple knock-out or WAP-TKO) exhibit attenuated squamous transdifferentiation and longer tumor latency.

Development

The GSK-3β-floxed exon 2 allele (GSK-3β^FL) was created by the laboratory of Dr. James R. Woodgett (Mount Sinai Hospital, Toronto). First, a targeting vector was designed to insert a loxP site upstream of exon 2 and a frt::loxP::neo::frt::loxP cassette downstream of exon 2 of the glycogen synthase kinase 3 beta gene (Gsk3b) on the chromosome 16. The targeting vector was electroporated into (129X1/SvJ x 129S1/Sv)F1-Kitl⁺-derived R1 embryonic stem cells. Chimeric mice were bred with C57BL/6J wildtype for germline transmission. Next, germline removal of the neo cassette was achieved by breeding to FLPe-expressing mice (on a C57BL/6 genetic background) - resulting in mice with the GSK-3β-floxed exon 2 allele (GSK-3β^FL). The GSK-3β^FL colony was backcrossed to C57BL/6J wildtype mice for six generations (and the FLPe-expressing transgene was removed) prior to sending male mice (black coat color) to The Jackson Laboratory Repository in 2017. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).
Of note, it is not known if the Y chromosome has been fixed to the C57BL/6J background during backcrossing.

Allele

Symbol: Gsk3b^tm2Jrw
Name: targeted mutation 2, James R Woodgett
MGI accession ID: MGI:3794785
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); No functional change
Synonyms: FLbeta; Gsk-3^F; Gsk3b^loxP; GSK-3beta Fl; Gsk3beta^F; GSK3beta^fl; GSK-3beta^FL; GSK3beta-floxed
Marker symbol: Gsk3b
Marker name: glycogen synthase kinase 3 beta
Marker synonyms: 7330414F15Rik; 8430431H08Rik; GSK3; GSK-3; GSK-3beta
Chromosome: 16
Strain of origin: (129X1/SvJ x 129S1/Sv)F1-Kitl⁺
Molecular note: Exon 2 was flanked by loxP sites and an FRT site flanked neomycin resistance gene cassette was inserted. Flp-mediated recombination in ES cells removed the neo cassette.