Updated 28 January 2005
Transgene: Used Cre/loxP recombination system to develop a PS1 conditional
knockout (cKO) mouse.
1. Generated a floxed PS1 mouse, (PS1 exons 2 and 3 are flanked
by two loxP sites). Using homologous recombination in J1 (129/Sv) ES cells,
we generated a modified PS1 allele, in which a loxP site and a
floxed drug selection cassette were introduced into PS1 introns 1 and 3,
respectively. The floxed PS1 allele (fPS1) was then generated
by transient transfection of a cDNA encoding Cre recombinase, which mediates
site-specific recombination between two loxP sites flanking the drug selection
cassette, thus excise the selection cassette. ES cells carrying the fPS1
allele were injected into mouse blastocysts to generate chimeric mice, which were
then used to generate heterozygous and homozygous fPS1 mice.
2. Generated a Cre transgenic mouse (CaM-Cre), in which Cre
recombinase is expressed selectively in pyramidal neurons of the postnatal forebrain
under the control of the α-calcium-calmodulin-dependent kinase II (αCaMKII)
promoter. The αCaMKII-Cre (CaM-Cre) transgene was injected into the
pronucleus of C57BL/6J and CBA hybrid embryos.
The PS1 conditional knockout (cKO) mouse was then generated by crossing the fPS1
mouse to the CaM-Cre transgenic mouse
Mutation: (αCaMKII) promoter for CaM-Cre tg mice.
Mouse Strain: The CaM-Cre tg mice were generated in C57BL/6J x CBA hybrid, and then
backcrossed several generations to C57BL/6J. The floxed PS1 mouse was generated
in C57BL/6J and 129/Sv hybrid.
Expression of PS1 is selectively eliminated in most neurons of the cerebral
cortex beginning at postnatal day 18. Substantial reduction of both mouse and human
Aβ40 and Aβ42 in the adult cortex while the carboxy-terminal fragments
of the amyloid precursor protein differentially accumulate in the cerebral cortex
of cKO mice. Expression of Notch downstream effector genes, Hes1, Hes5, and Dll1,
is unaffected in the cKO cortex. Although basal synaptic transmission, long-term
potentiation, and long-term depression at hippocampal area CA1 synapses are normal,
the PS1 cKO mice exhibit subtle but significant deficits in long-term spatial memory.
The PS1 cKO mouse is viable and exhibits no obvious phenotypic or gross abnormalities.
Center for Neurologic Diseases
Brigham and Woman's Hospital
Boston, MA 02115 USA and Program in Neuroscience
Harvard Medical School
Boston, MA 02115 USA
Phone: (617) 525-5561
Fax: (617) 525-5522
Yu H, Saura CA, Choi SY, Sun LD, Yang X, Handler M, Kawarabayashi T, Younkin L,
Fedeles B, Wilson MA, Younkin S, Kandel ER, Kirkwood A, Shen J. APP processing and
synaptic plasticity in presenilin-1 conditional knockout mice. Neuron. 2001 Sep
13 ; 31(5):713-26. Abstract
Yu H, Kessler J, Shen J. Heterogeneous populations of ES cells in the generation
of a floxed Presenilin-1 allele. Genesis. 2000 Jan 1 ; 26(1):5-8.