This B6/Mir-146a-/- knock-out mouse strain develops loss of peripheral T cell tolerance and may be useful in studies of autoimmune diseases, lymphoproliferative and myeloproliferative disease, the FOXP3-miR-146-NF-ΚB axis and cancer.
Dr. David Baltimore, California Institute of Technology
Mice that are homozygous for this targeted mutation develop splenomegaly (due to both myeloproliferation and expanded hematopoiesis), lymphadenopathy, multi-organ inflammation with lymphocytic and monocytic infiltrates, tissue damage, and reduced lifespan. At 6-8 weeks of age, homozygotes do not display a visible autoimmune or inflammatory phenotype. By 6-8 months of age, homozygotes start to develop lymphoproliferative and myeloproliferative disease, and a 60-fold higher titer for auto-antibodies against double-stranded DNA compared to wildtype controls. As mice age, they develop anemia, thrombocytopenia, lymphopenia, extramedullary erythropoiesis, as well as tumors in secondary lymphoid organs (mostly in the spleen). By 1 year of age, the mice exhibit a severe phenotype. Homozygotes on the 129.B6 background have a survival rate of less than 20%, while approximately 40% of knock out mice on the C57BL/6 background survive past 500 days, as compared to the more than 80% survival rate of wildtype controls.
Homozygotes exhibit an enhanced inflammatory response to endotoxin-challenge, due to macrophage hyperresponsiveness, and are more susceptible to lethal LPS dose than wildtype controls. The increased numbers of regulatory T (Treg) cells found in the periphery, but not in the thymus, of mice homozygous for this targeted mutation is not alleviated by IFNgamma blocker treatment. Prostate hyperplasia is detected in homozygotes as early as 9 months, early prostatic intraepithelial neoplasia (PIN) lesions at 12 months, with 60% of homozygotes developing PIN by 15 months of age. Northern Blot analysis of splenocytes isolated from homozygotes and qRT-PCR analysis of bone marrow, spleen and thymus from homozygotes do not detect gene product (mRNA). Mice that are homozygous for the targeted mutation are fertile and normal in size.
Due to the presence of FVB in this strain, albino coat color has occurred in the colony here at The Jackson Laboratory.
A targeting vector containing a floxed NEO cassette was used to disrupt 295 bp of genomic sequence encoding all of the precursor sequence. The construct was electroporated into B6.Cg-Thy1 derived Bruce4 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6-Tyr blastocysts. The resulting chimeric animals were crossed to B6.FVB-Tg(EIIa-cre)C5379Lmgd/J (JR3724) to remove floxed NEO cassette. Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6J (Stock No. 000664) at least once to establish the colony.
|Allele Name||targeted mutation 1.1, David Baltimore|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Mir146, microRNA 146|
|Strain of Origin||B6.Cg-Thy1a|
|Molecular Note||The 295 bp of the pre-microRNA was replaced with a floxed neo cassette. Cre-mediated recombination removed the neo cassette. The absence of transcript expression was confirmed by qRT-PCR on bone marrow, spleen, and thymus extracts.|
|Mutations Made By|| |
Jimmy Zhao, California Institute of Technology
When maintaining a live colony, these mice can be bred as homozygotes. Due to the presence of FVB in this strain, albino coat color has occurred in the colony here at The Jackson Laboratory.
When using the Mir-146a- mouse strain in a publication, please cite the originating article(s) and include JAX stock #016239 in your Materials and Methods section.