A caveat in mouse genetic engineering: ectopic gene targeting in ES cells by bidirectional extension of the homology arms of a gene replacement vector carrying human PARP-1.
Here we report an approach to generate a knock-in mouse model using an 'ends-out' gene replacement vector to substitute the murine Parp-1 (mParp-1) coding sequence (32 kb) with its human orthologous sequence (46 kb). Unexpectedly, examination of mutant ES cell clones and mice revealed that site-specific homologous recombination was mimicked in three independently generated ES cell clones by bidirectional extension of the vector homology arms using the endogenous mParp-1-flanking sequences as templates. This was followed by adjacent integration of the targeting vector, thus leaving the endogenous mParp-1 locus functional. A related phenomenon termed 'ectopic gene targeting' has so far only been described for 'ends-in' integration-type vectors in non-ES cell gene targeting. We provide reliable techniques to detect such ectopic gene targeting which represents an unexpected caveat in mouse genetic engineering that should be considered in the design and validation strategy of future gene knock-in approaches.
Mangerich
Aswin
A
Molecular Toxicology Group, Department of Biology, University of Konstanz, Box X911, 78457, Constance, Germany.
Scherthan
Harry
H
Diefenbach
Jörg
J
Kloz
Ulrich
U
van der Hoeven
Franciscus
F
Beneke
Sascha
S
Bürkle
Alexander
A
D000818:Animals; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D053595:Embryonic Stem Cells / Q000378:metabolism*; D055879:Gene Knock-In Techniques; D018390:Gene Targeting; D005818:Genetic Engineering / Q000379:methods*; D005822:Genetic Vectors; D006579:Heterozygote; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D051379:Mice; D008957:Models, Genetic; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics*; D011995:Recombination, Genetic
C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases