B6(Cg)-Grn^tm1.1Aidi/J

Stock number: 013175
Product name: PGRN KO
Research areas: Developmental Biology Research, Immunology, Inflammation and Autoimmunity Research, Neurobiology Research, Research Tools

Description

Grn knock-out has exons 1-4 deleted from the granulin locus (Grn). Homozygous null mice exhibit progressive frontotemporal dementia, a dysregulated inflammatory response and a high rate of pre-wean female mortality. Some incidence of eye abnormalities has also been observed.

Detailed description

In these Grn^-/- mice exons 1-4 are deleted from the targeted granulin (Grn) locus. Homozygous null mice show progressive development of frontotemporal dementia-like behavior and neuropathology. This includes enhanced activation of microglia and astrocytes, and ubiquitination and cytoplasmic accumulation of phosphorylated transactivation response element DNA binding protein-43 (TDP-43) in hippocampal and thalamic neurons. By eighteen months they demonstrate impaired spatial learning and memory. Macrophages from these mice release less interleukin-10 and more inflammatory cytokines in response to microbial agents. Contrary to the increased inflammation, these mice exhibit a delay in clearing infections due to a dysregulated inflammatory response, allowing bacteria to proliferate in vivo. Activated PGRN-deficient macrophages and microglia are cytotoxic to hippocampal cells, and PGRN-deficient hippocampal slices are hypersusceptible to deprivation of oxygen and glucose.

Although homozygotes are reported to be viable and fertile, significant pre-wean loss of females is observed in The Jackson Laboratory homozygous breeding colony. Of 285 pups born over 8 months, the percentage of males weaned was as expected (50%), but only 36% of females were successfully weaned (October 2017).

In 2020, The Jackson Laboratory colony reported some incidence of homozygotes showing cataracts, small eyes and missing eyes. In autumn 2021, our live colony was refreshed using the original 2010 cryopreserved bankstock. The resulting live colony still observes some incidence (~25%) of homozygotes showing these eye issues.

Development

A targeting vector was designed to insert a single loxP site upstream of the promoter region of the granulin (Grn) gene. A second loxP site 3' to a FRT-flanked neomycin/kanamycin (neo/kan) resistance cassette was placed downstream of exon 4 . The construct was electroporated into C57BL/6-derived C2J embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6 blastocysts and chimeric mice were bred with mice expressing Cre-recombinase driven by chicken actin gene promoter (CAG-cre; predominately on a C57BL/6 background) to remove the neo/kan selection cassette. Mice lacking both the intact Grn gene and the CAG-cre transgene were backcrossed to C57BL/6 for at least five generations to establish a colony of (Grn^-/-). In 2010, homozygous males (black coat color) were sent to The Jackson Laboratory. 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).

Allele

Symbol: Grn^tm1.1Aidi
Name: targeted mutation 1.1, Aihao Ding
MGI accession ID: MGI:4421705
Generation method: Targeted
Attributes: Null/Knockout
Marker symbol: Grn
Marker name: granulin
Chromosome: 11
Strain of origin: B6(Cg)-Tyr^c-2J/J
Molecular note: Cre mediated recombination removed exons 1 through 4. The absence of protein expression was confirmed by western blot analysis on bone marrow-derived macrophages.