Protein kinase R (PKR) is an interferon (IFN)-inducible, double-stranded RNA-activated kinase that initiates apoptosis in response to cellular stress and inhibits DNA damage response signaling. Increased PKR activity is reported in myeloid progenitor cell populations from patients with myelodysplastic syndrome (MDS) and is associated with poor survival for many cancers.

These vav-PKR transgenic mice (TgPKR) have the mouse HS21/45-vav regulatory elements directing expression of wildtype (catalytically-active) human PKR to hematopoietic cells/tissues. High PKR expression is reported in thymus, spleen and bone marrow (BM) compared with non-hematopoietic tissues (small intestine, liver or kidney) as demonstrated by real-time quantitative PCR and western blotting. This PKR overexpression results in significantly defective hematopoiesis, BM failure and increased sensitivity to apoptosis-inducing cell stress. 

 Specifically, TgPKR mice have increased PKR expression/activation that leads to features of defective hematopoiesis and BM failure, as demonstrated by mild pancytopenia of all peripheral blood elements (significantly lower total white blood cell, neutrophil, lymphocyte, platelet, and hemoglobin counts compared with non-transgenic mice). Hematopoiesis defects are even more pronounced in older mice (16-18 months old). In addition, the BM contains dysplasic-appearing cells, reduced hematopoietic stem/progenitor cell populations (HSPCs), reduced mature myeloid cell populations, reduced hematopoietic colony-forming capacity, and increased sensitivity to apoptosis-inducing cell stress (including inflammatory cytokines, growth factor starvation and irradiation) when compared with cells from non-transgenic mice. TgPKR mice display a mutator phenotype characterized by an increased frequency of radiation-induced or age-associated mutations in peripheral blood cells.

Furthermore, an increased percentage of HSPCs isolated from TgPKR mice are quiescent (G0) compared with non-transgenic mice.

Hemizygous TgPKR mice are viable and fertile. To date (July 2015), it has not been attempted to make this strain homozygous. 

The phenotype of hemizygous TgPKR mice is in contrast to hemizygous mice expressing a catalytically-null/dominant-negative variant of human PKR from the same HS21/45-vav regulatory elements (TgDNPKR; Stock No. <a href="https://www.jax.org/strain/027461">027461</a>). Those TgDNPKR mice exhibit loss of PKR activity in BM cells and increased HSPCs, as well as BM cell-resistance to apoptosis-inducing cell stress.

TgPKR mice express wildtype (catalytically-active) human PKR exclusively in hematopoietic cells/tissues under control of the mouse HS21/45-vav regulatory elements. This PKR overexpression results in significantly defective hematopoiesis, bone marrow failure and increased sensitivity to apoptosis-inducing cell stress. These TgPKR mice may be useful in studying increased PKR activity in diseases such as myelodysplastic syndrome (MDS).

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