B6.129S7(Cg)-App^tm1.1Zhe/J

Stock number: 030770
Product name: APP^fl (APP floxed exon 3)
Research areas: Cancer Research, Cell Biology Research, Developmental Biology Research, Neurobiology Research, Research Tools

Description

The App^fl floxed allele has loxP sites flanking exon 3 of the amyloid precursor protein gene. Removal of the floxed sequence creates a null allele. These mice may be useful in neurobiological studies of APP, including neuronal differentiation/migration, synaptic regulation and Alzheimer's disease.

Detailed description

In the CNS, the amyloid precursor protein (encoded by App) has been implicated in many biological processes - including cell adhesion, gene transcription, neuronal differentiation, migration, neurite outgrowth and synapse formation. Disease-causing mutations in APP have been identified in early-onset Alzheimer's disease patients. The pathogenic mechanisms attribute the abnormal proteolytic processing of APP to aberrant production of amyloid-β (Aβ) peptides, which form toxic amyloid oligomers and fibrillar aggregates to elicit a cascade of neurotoxic events - ultimately resulting in synaptic and neuronal dysfunction and neurodegeneration.

The App^fl allele has loxP sites flanking App exon 3. Mice homozygous for this floxed allele are viable and fertile with no reported gross physical or behavioral abnormalities. When bred to mice that express Cre recombinase, the resulting offspring will have the floxed region deleted in cre-expressing tissues - this disrupts the App reading frame resulting in the null allele (App^ΔE3).

For example, when then APP knock-out allele is created after breeding to germline iCre-expressing mice (Stock No. 011062), the resulting APP global knock-out homozygotes (App^ΔE3/ΔE3) are overtly normal. However, further addition of a global APLP2 knock-out allele (Stock No. 004142) creates the APP::APLP2 double knock-out mice which exhibit postnatal lethality.

To address whether the function of APP in neuromuscular junction (NMJ) is mediated through a presynaptic or postsynaptic mechanism, specific deletion of APP in presynaptic motor neurons [neuronal conditional knock-out (N-CKO)] or in postsynaptic muscle [muscle conditional knock-out (M-CKO)] can be achieved by breeding App^fl to mice expressing Cre recombinase via the neuronal rat nestin promoter (Nestin-Cre ; Stock No. 003771) or the muscle creatine kinase promoter (Mck-Cre ; Stock No. 006475), respectively. Further addition of a global APLP2 knock-out allele (Stock No. 004142) creates the neuronal double conditional knock-out (N-dCKO) and muscle double conditional knock-out (M-dCKO) mice - allowing further investigation into NMJ defects.

When App^fl are bred to have the vGAT-Cre BAC transgene (Stock No. 017535), the resulting GABAergic deletion of APP allows testing of the functional role of GABAergic APP in adult neurogenesis.

If App^fl mice are bred to have the Nestin-CreERT2 transgene (Stock No. 016261), the resulting APP f/f;Nestin-CreER animals allow tamoxifen-inducible APP deletion in adult and developing mouse brain, including neural progenitor cells (NPCs) and glial cell precursors.

Development

The App^fl (floxed exon 3) allele was created by Dr. Hui Zheng (Baylor College of Medicine). First, a targeting vector was designed to insert a loxP-flanked PGK-neo cassette upstream of exon 3, and a third loxP site downstream of exon 3 of the amyloid beta (A4) precursor protein locus (App) on chromosome 16. The targeting vector was electroporated into 129S7/SvEvBrd-Hprt^b-m2-derived AB2.2 embryonic stem (ES) cells. Chimeric animals were bred to C57BL/6J mice for germline transmission. The mutant mice were then bred with CMV-Cre transgenic mice (on a C57BL/6 genetic background) for germline removal of the PGK-neo cassette. The resulting offspring that retained the loxP-flanked exon 3 (with the PGK-neo removed) were selected and called App^fl. The App^fl colony was backcrossed to C57BL/6J wildtype mice for at least ten generations (and the cre-expressing transgene was removed). In 2017, App^fl males with black coat color were sent to The Jackson Laboratory Repository. 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).
Of note, the donating investigator reports that, at least once during backcrossing, a App^fl female was bred to a C57BL/6J inbred male (thus the Y chromosome of the congenic strain is of C57BL/6J origin).

Allele

Symbol: App^tm1.1Zhe
Name: targeted mutation 1.1, Hui Zheng
MGI accession ID: MGI:4359011
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); No functional change
Marker symbol: App
Marker name: amyloid beta (A4) precursor protein
Marker synonyms: AAA; Abeta; ABPP; AD1; Adap; alpha-sAPP; APPI; appican; betaAPP; CTFgamma; Cvap; E030013M08Rik; PN2; PN-II; preA4; protease nexin II
Chromosome: 16
Strain of origin: 129S7/SvEvBrd-Hprt1^b-m2
Molecular note: Exon 3 was floxed. The floxed neo cassette inserted into intron 2 was removed by germ line, cre mediated recombination.