These Nrn1 (or cpg15) knock-out mice may have applications in studies examining the roles played by synapse maturation and stabilization on learning ability.
Elly Nedivi, Massachusetts Institute of Technology
Cpg15-/- mice lack exons 2-3 of the neuritin 1 (Nrn1) gene, abolishing gene expression. CPG15 is a glycosyl-phosphoinositide (GPI) protein tethered to neural progenitors as well as postmitotic-differentiating neurons of the thalamus and forebrain, including hippocampus and cortex, as well as some brainstem sensory nuclei. CPG15 promotes neurite outgrowth and branching, synapse formation, and activity-dependent plasticity. These Cpg15-/- mice exhibit a delay in axonal and dendritic arborization and maturation of excitatory synapses. Neural progenitors seem unaffected. The development of excitatory synaptic contacts is delayed, leading to eventual dendritic spine loss. These mice also display poor learning with delayed acquisition of new memories. Heterozygous mice are viable and fertile. Homozygotes viable and fertile, 3% smaller, and weigh 20-30% less than wildtype littermates. Some post-natal lethality occurs.
A targeting vector was designed to insert a loxP site upstream of exon 2 and a floxed Frt-flanked neomycin resistance (neo) cassette downstream of exon 3 of the neuritin 1 (Nrn1) gene. The construct was electroporated into C57BL/6-derived embryonic stem (ES) cells and correctly targeted ES cells were injected into BALB/c blastocysts. The resulting Cpg15flox-neo/+ offspring were bred to C57BL/6 mice. To remove the neo cassette, fertilized eggs from Cpg15flox-neo/+ mice were transiently transfected with a pOG-Flpe6 expression plasmid resulting in Cpg15flox/+ offspring. These Cpg15flox/+ were then bred with B6.FVB-Tg(EIIa-cre)C5379Lmgd/J mice (Stock No. 003724) to removed exons 2-3. Cpg15+/- mice were bred together to create Cpg15-/- mice. Upon arrival, mice were bred to C57BL/6J inbred mice (Stock No. 000664) for at least one generation to establish the colony.
A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. Two of the 27 markers throughout the genome were segregating, and 2 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. It has been recently determined that the B6.FVB-Tg(EIIa-cre)C5379Lmgd/J mice (Stock No. 003724) used in strain development are on a mixed C57BL/6J ; C57BL/6N genetic background. This data also suggests that these mice were not completely backcrossed or contain a contaminating allele.
|Allele Name||targeted mutation 1.2, Elly Nedivi|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||Nrn1tm1.2Ndiv; targeted mutation 1.2, Elly Nedivi|
|Gene Symbol and Name||Nrn1, neuritin 1|
|Gene Synonym(s)||dJ380B8.2; cpg15; NRN; 0710008J23Rik; 0710008J23Rik; RIKEN cDNA 0710008J23 gene; Nrn|
|Strain of Origin||C57BL/6|
|Molecular Note||A loxP site was inserted upstream of exon 2 and a loxP and FRT flanked neo cassette was inserted downstream of exon 3 via homologous recombination. Recombinase mediated recombination removed the neo cassette and exons 2 and 3.|
|Mutations Made By|| |
Elly Nedivi, Massachusetts Institute of Technology
When maintaining a live colony, heterozygous mice may be bred together. Homozygous mice are viable and fertile, but the DI reports some post-natal lethality suggesting the Homs that survive have the mildest phenotype. They breed Het x Het to keep from attenuating the phenotype.
When using the Cpg15 KO mouse strain in a publication, please cite the originating article(s) and include JAX stock #018402 in your Materials and Methods section.
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