title: When Cre-mediated recombination in mice does not result in protein loss.
abstract: Cre/loxP recombination enables cellular specificity and, in the case of inducible systems, temporal control of genomic deletions. Here we used a SM22α tamoxifen-inducible Cre line to inactivate β1 integrin in adult smooth muscle. Interestingly, analysis of two distinct β1 loxP transgenic mice revealed vastly different outcomes after β1 integrin deletion. Lethality occurred 4 weeks postinduction in one Cre/loxP line, while no apparent phenotype was seen in the other line. Genetic analysis revealed appropriate DNA excision in both cases; however, differences were found in the degree of protein loss with absolutely no change in protein levels in the model that lacked a phenotype. Seeking to understand protein persistence despite appropriate recombination, we first validated the flox allele using a constitutive Cre line and demonstrated its ability to mediate effective protein inactivation. We then examined the possibility of heterozygous cell selection, protein turnover, and deletion efficiency with no success for explaining the phenotype. Finally, we documented the presence of the Cre-recombination episomal product, which persisted in tissue samples with no protein loss. The product was only noted in cells with low proliferative capacity. These findings highlight the potential for protein expression from the products of Cre-recombinase excised genes, particularly when deletion occurs in low turnover populations.
authors.affiliation: Molecular Biology Institute, University of California, Los Angeles, California 90095, USA.
authors.forename: Kirsten A
authors.initials: KA
authors.lastname: Turlo
authors.forename: Sean D
authors.initials: SD
authors.lastname: Gallaher
authors.forename: Roshni
authors.initials: R
authors.lastname: Vora
authors.forename: Frank A
authors.initials: FA
authors.lastname: Laski
authors.forename: M Luisa
authors.initials: ML
authors.lastname: Iruela-Arispe
mesh_terms: D000483:Alleles; D000818:Animals; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000378:metabolism; D017353:Gene Deletion; D006579:Heterozygote; D006720:Homozygote; D019426:Integrases / Q000378:metabolism*; D019012:Integrin beta1 / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011995:Recombination, Genetic
chemical_list: D019012:Integrin beta1; C045073:Cre recombinase; D019426:Integrases
references.citation: Neuron. 2001 Aug 16;31(3):367-79
references.pmid: 11516395
references.citation: Int J Biochem Cell Biol. 2009 Mar;41(3):482-6
references.pmid: 18378184
references.citation: EMBO J. 2005 Jun 1;24(11):1942-53
references.pmid: 15889143
references.citation: Dev Cell. 2010 Jan 19;18(1):39-51
references.pmid: 20152176
references.citation: J Virol. 2004 Jun;78(12):6556-66
references.pmid: 15163748
references.citation: Immunity. 2000 Jun;12(6):653-63
references.pmid: 10894165
references.citation: Curr Opin Biotechnol. 1999 Oct;10(5):470-6
references.pmid: 10508631
references.citation: Genesis. 2000 Sep;28(1):15-22
references.pmid: 11020712
references.citation: Dev Cell. 2004 Jan;6(1):7-28
references.pmid: 14723844
references.citation: Development. 1997 Aug;124(15):2923-34
references.pmid: 9247335
references.citation: Mol Cell Biol. 2008 Jan;28(2):794-802
references.pmid: 17984225
references.citation: Genes Dev. 1995 Aug 1;9(15):1883-95
references.pmid: 7544312
references.citation: J Cell Sci. 2004 Aug 15;117(Pt 18):4043-54
references.pmid: 15280429
references.citation: Circ Res. 2008 Mar 14;102(5):562-70
references.pmid: 18202311
references.citation: Genes Dev. 1995 Aug 1;9(15):1896-908
references.pmid: 7544313
references.citation: Plant Mol Biol. 2003 Jun;52(3):661-8
references.pmid: 12956534
references.citation: Mol Cell Biol. 2002 Nov;22(21):7372-84
references.pmid: 12370285
references.citation: J Cell Sci. 2002 Oct 1;115(Pt 19):3729-38
references.pmid: 12235283
references.citation: J Virol. 2009 Apr;83(7):3249-57
references.pmid: 19158239
references.citation: J Cell Biol. 2000 Sep 4;150(5):1149-60
references.pmid: 10974002
references.citation: Science. 1997 May 30;276(5317):1425-8
references.pmid: 9162012
references.citation: J Biol Chem. 2001 Jun 22;276(25):23018-27
references.pmid: 11304530
references.citation: Nat Genet. 1998 Feb;18(2):136-41
references.pmid: 9462741
references.citation: Science. 1993 May 21;260(5111):1124-7
references.pmid: 7684161
references.citation: Mol Cell Biol. 2000 Jan;20(2):648-55
references.pmid: 10611243
references.citation: Gene. 1985;40(2-3):325-9
references.pmid: 3007297
references.citation: J Cell Biol. 2006 Nov 6;175(3):505-14
references.pmid: 17088430
references.citation: Microcirculation. 2005 Jan-Feb;12(1):99-112
references.pmid: 15804978
references.citation: Nat Genet. 2006 Jun;38(6):626-35
references.pmid: 16645617
references.citation: Eur J Biochem. 1991 Jul 1;199(1):25-33
references.pmid: 1906002
references.citation: PLoS One. 2009;4(1):e4200
references.pmid: 19145242
references.citation: Cell. 2002 Sep 20;110(6):673-87
references.pmid: 12297042
references.citation: Proc Natl Acad Sci U S A. 2002 May 14;99(10):7142-7
references.pmid: 11997476
references.citation: Mol Cells. 2007 Apr 30;23(2):175-81
references.pmid: 17464194
references.citation: Am J Pathol. 2001 Mar;158(3):1079-90
references.pmid: 11238056
references.citation: Dev Dyn. 2006 Dec;235(12):3413-22
references.pmid: 17072878
references.citation: J Neurosci. 2006 Jul 19;26(29):7665-73
references.pmid: 16855094
references.citation: EMBO J. 2006 Nov 15;25(22):5270-83
references.pmid: 17082774
references.citation: Nat Genet. 1999 Jan;21(1):70-1
references.pmid: 9916792
references.citation: J Mol Biol. 1981 Aug 25;150(4):467-86
references.pmid: 6276557
references.citation: Proc Natl Acad Sci U S A. 1990 Jan;87(1):103-7
references.pmid: 2404272
references.citation: Development. 2004 Aug;131(16):3871-83
references.pmid: 15253938
references.citation: Development. 2008 Dec;135(24):3989-93
references.pmid: 18987025
references.citation: J Cell Biol. 1993 Nov;123(4):977-91
references.pmid: 8227153
references.citation: Plant Mol Biol. 2005 Jul;58(5):687-98
references.pmid: 16158243
references.citation: Differentiation. 1993 Dec;55(1):1-11
references.pmid: 8299876
references.citation: Liver Int. 2004 Jun;24(3):218-26
references.pmid: 15189273