Modification: Bace1: Conditional Knock-out
Disease Relevance: Alzheimer's Disease
Strain Name: N/A
Genetic Background: C57BL/6J
Availability: Bace1fl/fl not yet available. UBC-Cre-ERT2 available from The Jackson Laboratory, Stock# 007001.
These transgenic mice were designed to mimic BACE1 inhibition, while avoiding the developmental effects of Bace1 deficiency that are seen in germline knock-outs. They were generated by crossing mice with a floxed Bace1 gene (Bace1fl/fl) to mice carrying a transgene encoding Cre recombinase fused to a modified human estrogen receptor, driven by the ubiquitin C promoter (UBC-Cre-ERT2)—and were expected to express Cre only in the presence of tamoxifen. However, expression of the Cre transgene turned out to be quite leaky, and Cre expression was found to occur in the absence of tamoxifen.
Hereafter, the Bace1fl/fl X UBC-Cre-ERT2 mice are referred to as “BACE1-deficient” mice.
In BACE1-deficient mice in the absence of tamoxifen, BACE1 levels progressively declined, beginning between 20 and 30 days of age: BACE1 levels in the brain were reduced by approximately 40 percent at 30 days, 50 percent at 60 days, and 80 percent at 120 days, compared with BACE1 levels in the brains of Bace1fl/fl mice.
Hypomyelination and astrogliosis, seen in germline Bace1 knock-out mice, were not observed in BACE1-deficient mice.
Long-term potentiation at Schaffer collateral–CA1 synapses was impaired in slices obtained from 10- to 12-month-old BACE1-deficient mice.
BACE1-deficient mice and Bace1fl/fl mice performed similarly in tests of contextual and cued fear conditioning at 8 to 10 months of age.
These mice were generated by crossing (Bace1fl/fl) mice (Hu et al., 2018) with UBC-Cre-ERT2 mice (The Jackson Laboratory, Stock# 007001). In the former line, exon 2 of the mouse Bace1 gene is flanked by loxP sites. The latter line carries a transgene encoding Cre recombinase fused to a modified human estrogen receptor, driven by the ubiquitin C promoter; this transgene integrated into chromosome 2, causing a 5 bp deletion in the NADPH-dependent diflavin oxidoreductase 1 (Ndor1) locus (Goodwin et al., 2017).
When visualized, these models will distributed over a 18 month timeline demarcated at the following intervals: 1mo, 3mo, 6mo, 9mo, 12mo, 15mo, 18mo+.
- Neuronal Loss
- Cognitive Impairment
- Synaptic Loss
No astrogliosis at 1-2 months.
Changes in LTP/LTD
Long-term potentiation at Schaffer collateral–CA1 synapses impaired in slices obtained from 10- to 12-month-old mice.
Contextual and cued fear conditioning normal at 8-10 months.
Last Updated: 18 Jan 2019
- Hu X, Das B, Hou H, He W, Yan R. BACE1 deletion in the adult mouse reverses preformed amyloid deposition and improves cognitive functions. J Exp Med. 2018 Mar 5;215(3):927-940. Epub 2018 Feb 14 PubMed.
- Goodwin LO, Splinter E, Davis TL, Urban R, He H, Braun RE, Chesler EJ, Kumar V, van Min M, Ndukum J, Philip VM, Reinholdt LG, Svenson K, White JK, Sasner M, Lutz C, Murray SA. Large-scale discovery of mouse transgenic integration sites reveals frequent structural variation and insertional mutagenesis. bioRχiv preprint first posted online Dec. 18, 2017