These Grp78f/f mice possess loxP sites flanking exons 5-7 of the heat shock protein 5 (Hspa5) (commonly referred to as Grp78) targeted gene. This strain is useful for studying the role of GRP78 and endoplasmic reticulum (ER) stress in embryonic development, organ homeostasis during the animal life span, as well as suppressor of tumorigenesis and therapeutic resistance.
Amy Lee, University of Southern California
These Grp78f/f mice possess loxP sites flanking exons 5-7 of the heat shock protein 5 (Hspa5) (commonly referred to as Grp78) targeted gene. GRP78, also known as BiP, is a central regulator of endoplasmic reticulum (ER) homeostasis due to its multiple functional roles in protein folding, ER calcium binding, and controlling of the activation of transmembrane ER stress sensors. Upon stress, GRP78 can also relocalize to other cellular compartments including the cell surface and mitochondria. GRP78 has been shown to be important in both health and diseases, including cancer development, progression, drug resistance as well as metabolic and neurodegenerative diseases. GRP78 has also been implicated in viral infectivity. Mice that are homozygous for this allele are viable and fertile. When these mutant mice are bred to mice that express Cre recombinase, resulting offspring will have exons 5-7, and the neo cassette, deleted in cre-expressing tissues.
Pdx1-Cre;KrasG12D/+;p53f/+;Grp78f/+ (PKC78f/+) mice express 50% of GRP78, one activated KrasG12D allele, and have deletion of one p53 allele in pancreatic cells (see Stock No. 014647, Stock No. 008179, and Stock No. 002101). These mice maintain normal sizes during the early months of age, with reduced proliferation and suppression of Kras-driven tumorigenic proteins such as AKT, S6, ERK, and STAT3 activation. This is in comparison to PKC mice, with wild-type Grp78 expression, which show pancreatic ductal adenocarcinoma (PDAC) as early as 3 months of age and rapid subsequent tumor growth, suggesting that GRP78 could exert a protective effect on acinar cells under stress and suppress Kras-driven pancreatic tumorigenesis.
The Grp78f targeting vector was designed to insert a loxP-flanked neomycin resistance (neo) cassette, in reverse orientation, upstream of exon 5, and a single loxP site downstream of exon 7 of the heat shock protein 5 (Hspa5) gene. The construct was electroporated into 129/Sv-derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6J blastocysts and resulting chimeric males were bred with C57BL/6 females. Resulting offspring were bred to E2a-cre mice (Stock No. 003724) to remove the neo cassette and mice were crossed to remove the cre expressing transgene. This colony of Grp78f/f mice were maintained on a mixed genetic background. Upon arrival at The Jackson Laboratory, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).
|Allele Name||targeted mutation 1.1, Amy S Lee|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Hspa5, heat shock protein 5|
|Strain of Origin||129|
|Molecular Note||A vector was designed to insert a floxed neo into intron 4 and a third loxP site into intron 7. Cre expression in the germline resulted in the excision of exons 5-7.|
When maintaining a live colony, mice homozygous for the floxed allele may be bred together.
When using the Grp78f mouse strain in a publication, please cite the originating article(s) and include JAX stock #035444 in your Materials and Methods section.