title: Incomplete cre-mediated excision leads to phenotypic differences between Stra8-iCre; Mov10l1(lox/lox) and Stra8-iCre; Mov10l1(lox/Δ) mice.
abstract: In the Cre-loxp system, expression level and activity of Cre recombinase in a Cre deleter line are critical because these determine not only the cell specificity of gene knockout (KO), but also the efficiency of Cre-mediated excision in a specific cell lineage. Although the spatiotemporal expression pattern of a Cre transgene is usually defined upon the generation of the mouse line, the Cre excision efficiency in a specific targeted cell lineage is rarely evaluated and often assumed to be 100%. Incomplete excision can lead to highly variable phenotypes owing to mosaicism (i.e., coexistence of cells with the flox or the recombined flox allele) and this problem has long been overlooked. Here, we report that Stra8-codon-improved Cre recombinase (iCre), a transgenic allele expressing iCre under the control of the male germ cell-specific Stra8 promoter, could efficiently delete one Mov10l1 flox allele in spermatogenic cells, whereas the excision was incomplete when two Mov10l1 flox alleles were present. The incomplete Cre-mediated excision led to a testicular phenotype that was much less severe than that in the true conditional KO (inactivation, 100%) mice. Our findings suggest that it is essential to determine the efficiency of Cre excision when Cre-loxp system is used for deleting genes in a specific cell lineage and the Cre; gene(lox) (/)(Δ) genotype should be used to evaluate phenotypes instead of Cre; gene(lox/lox) owing to the fact that the latter usually bears incomplete deletion of the flox allele(s).
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada Reno School of Medicine, Reno, NV, USA.
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Bao
authors.forename: Hsiu-Yen
authors.initials: HY
authors.lastname: Ma
authors.forename: Andrew
authors.initials: A
authors.lastname: Schuster
authors.forename: Yung-Ming
authors.initials: YM
authors.lastname: Lin
authors.forename: Wei
authors.initials: W
authors.lastname: Yan
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D000483:Alleles; D000818:Animals; D019070:Cell Lineage; D005260:Female; D017353:Gene Deletion; D005854:Germ Cells / Q000378:metabolism*; D019426:Integrases / Q000235:genetics* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009030:Mosaicism; D010641:Phenotype; D013091:Spermatogenesis; D013094:Spermatozoa / Q000502:physiology*; D013737:Testis / Q000502:physiology*; D019076:Transgenes
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C102019:Stra8 protein, mouse; C045073:Cre recombinase; D019426:Integrases
keywords: Cre; conditional gene knockout; germ line; loxp; mosaicism; phenotype; piRNA; testis
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