Unsuspected effects of a lung‐specific cre deleter mouse line

Aubin, Josée; Bourque, Sylvie; Lemieux, Margot; Montaron, Séverine; St‐Pierre, Anne P.

doi:10.1002/dvg.20720

Cited by 35 publications

(26 citation statements)

References 23 publications

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“…In support of this observation, we observed increased apoptosis in WT osteoblast cultures on constitutive retrovirus-induced expression of Cre. To our knowledge, the effects of sustained Cre expression have not been described in osteoblastic cells, however, adverse effects of sustained systemic Cre expression on hematopoietic cells 45 and other tissues such as lung epithelium 46 have been reported. These findings reinforce the importance of considering Cre-expressing WT controls in addition to Cre Ϫ transgenic controls in experimental design and data analysis.…”

Section: Discussionmentioning

confidence: 96%

Rac signaling in osteoblastic cells is required for normal bone development but is dispensable for hematopoietic development

Lane

Vita

Alexander

et al. 2012

Blood

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IntroductionHematopoietic stem cells (HSCs) give rise to all lineages of mature blood cells and maintain hematopoiesis in vivo through a balance of self-renewal and differentiation. To maintain this balance, HSCs are supported within a complex milieu known as the hematopoietic microenvironment (HM) or HSC niche. 1,2 This HM includes cellular components (osteoblastic cells, 3,4 perivascular cells, 5 and sympathetic neurons 6 ), bone mineral matrix, 7 and ionic gradients. 8 Trabecular bone appears to be particularly important in HSC biology 3,9,10 ; however, there is ongoing controversy regarding the existence or identity of one predominant cell type that is necessary and sufficient for HSC survival in vivo. Apparently conflicting results have identified osteoblastic cells, 3,11-13 perivascular cells, 5 and a nestin-positive common precursor cell type with the ability to differentiate into either lineage as key cells within the HSC niche. Irrespective of this controversy, it has been firmly established that key ligand/receptor signaling interactions are responsible for HSC engraftment and mobilization from the HM. These include the interactions between CXCL12 (also known as SDF1) and CXCR4,14,15 between the cKit receptor and SCF, 16 and between fibronectin and ␤1-integrins. 17,18 The Rac family of Rho GTPases (encompassing Rac1, Rac2, and Rac3) integrates a critical downstream common pathway of the aforementioned signaling pathways. Through this, Rac proteins regulate the homing, engraftment, mobilization, and survival of HSCs in vivo (for a recent, comprehensive review, see Cancelas and Williams 19 ). Deletion of Rac1 in HSCs causes failed HSC engraftment and reduced HSC proliferation in vivo. 20 Deletion of Rac2 alone has modest but significant effects on HSC mobilization and engraftment 21 and leads to reduced HSC survival through impaired growth factor signaling and increased apoptosis. 20 Combined deletion of Rac1 and Rac2 causes a massive egress of HSCs from the HM and profoundly impaired engraftment. 20,22 Vav1, a hematopoietic-specific guanine exchange factor for Rac, differentially regulates endosteal/osteoblast and perivascular retention and subsequent engraftment. 23 Moreover, Rac1 and Rac2 were shown to be important for the survival of leukemia stem cells in a murine model of chronic myeloid leukemia. 24 These findings were reinforced by the development and preclinical testing of NSC23766, a small-molecule inhibitor of Rac signaling that has substantial in vivo effects including HSC mobilization 22 and antileukemic efficacy. 24 Whereas Rac3 is widely expressed with high levels of expression in the CNS 25 and Rac3-deficient mice show no obvious hematopoietic phenotype, we have previously shown functional redundancy of Rac3 in leukemic cells expressing p210-BCR-ABL. 24 Interestingly, despite the breadth of knowledge regarding the cell-intrinsic requirements for Rac signaling in HSC function, little is known about the function of Rac within HM components and therefore about cell-extrinsic Rac signaling...

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Section: Discussionmentioning

confidence: 96%

Rac signaling in osteoblastic cells is required for normal bone development but is dispensable for hematopoietic development

Lane

Vita

Alexander

et al. 2012

Blood

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“…The use of tissue-specific and ligandactivated promoters to regulate Cre expression is widespread, with a variety of Cre-expressing mice now available (34,35,103). However, the basal rates and stochastic nature of expression from many promoters have been associated with cell toxicity and lack of optimal regulation (104)(105)(106)(107)(108). An additional level of regulation has been achieved in recent years by requiring that two Cre fragments assemble to form an active enzyme.…”

Section: Reconstitution Of Active Cre From Fragmentsmentioning

confidence: 99%

Cre Recombinase

Duyne

2015

Microbiol Spectr

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The use of Cre recombinase to carry out conditional mutagenesis of transgenes and insert DNA cassettes into eukaryotic chromosomes is widespread. In addition to the numerous in vivo and in vitro applications that have been reported since Cre was first shown to function in yeast and mammalian cells nearly 30 years ago, the Cre-loxP system has also played an important role in understanding the mechanism of recombination by the tyrosine recombinase family of site-specific recombinases. The simplicity of this system, requiring only a single recombinase enzyme and short recombination sequences for robust activity in a variety of contexts, has been an important factor in both cases. This review discusses advances in the Cre recombinase field that have occurred over the past 12 years since the publication of Mobile DNA II. The focus is on those recent contributions that have provided new mechanistic insights into the reaction. Also discussed are modifications of Cre and/or the loxP sequence that have led to improvements in genome engineering applications.

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“…Similarly, the TRE-Cre transgene is typically benign, although some effects were reported in the absence of a floxed allele (24). This effect may be attributable to the toxicity of Cre recombinase itself (25).…”

Section: B-catenin Stabilization Allelementioning

confidence: 99%

Roles for β-Catenin and Doxycycline in the Regulation of Respiratory Epithelial Cell Frequency and Function

Smith¹,

Hicks²,

Reynolds³

2012

Am J Respir Cell Mol Biol

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The expression of b-catenin-dependent genes can be increased through the Cre recombinase (Cre)-mediated elimination of the exon 3-encoded sequence. This mutant b-catenin is termed DE3, and promotes the expression of b-catenin-dependent genes. Our previous study used the DE3 model to demonstrate that persistent b-catenin activity inhibited bronchiolar Clara-to-ciliated cell differentiation. The present study was designed to evaluate the roles of b-catenin in regulating the tracheal progenitor cell hierarchy. However, initial experiments demonstrated that the tetracyclineresponsive element-Cre transgene (TRE-Cre) was active in the absence of a reverse tetracycline transactivator driver or inducer, doxycycline (Dox). This spurious TRE-Cre transgene activity was not detected using the ROSA26-floxed STOP-LacZ reporter. To determine if the phenotype was a consequence of genotype or treatment with Dox, tracheal and lung specimens were evaluated using quantitative histomorphometric techniques. Analyses of uninduced mice demonstrated a significant effect of genotype on tracheal epithelial cell mass, involving basal, Clara-like cell types. The bronchial and bronchiolar Clara cell mass was also decreased. Paradoxically, an effect on ciliated cell mass was not detected. Activation of the b-catenin reporter transgene TOPGal demonstrated that b-catenin-dependent gene expression led to the genotype-dependent tracheal and bronchiolar phenotype. Comparative analyses of wild-type or keratin 14-rtTA1/1 mice receiving standard or Dox chow demonstrated an effect of treatment with Dox on basal, Clara-like, and Clara cell masses. We discuss these results in terms of cautionary notes and with regard to alterations of progenitor cell hierarchies in response to low-level injury.Keywords: Clara cell; doxycycline; Cre recombinase; b-catenin; stereology LUNG EPITHELIAL CELL LINEAGESThe tracheobronchial, bronchiolar, and alveolar compartments of murine airway epithelia contain distinct cell lineages. Within the tracheobronchial compartment, basal cells act as progenitors of secretory and ciliated cells during lung development (1). However, Clara-like cells are the progenitors of ciliated cells in the adult steady-state trachea (2). After treatment with naphthalene (NA), the basal cell becomes the progenitor of nascent Clara-like and ciliated cells (3-7). We suggested that signaling from Clara-like cells to basal cells limits the fate of adult basal cells to self-renewal (3).The bronchiolar epithelium is maintained by Clara cells (8, 9), whereas the alveolar epithelium is maintained by Type II cells (10). Tracing the lineage of bronchiolar Clara cells demonstrated that the airway and alveolar epithelia comprise distinct lineages in the steady state (11). Although injury may lead to bronchiolarization of the alveolar duct or alveolarization of the terminal bronchiole (12-14), the roles for a dual-lineage cell, termed the bronchoalveolar stem cell, (13) have been challenged (9, 15). The molecular mechanisms that establish these lineages have re...

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Unsuspected effects of a lung‐specific cre deleter mouse line

Cited by 35 publications

References 23 publications

Rac signaling in osteoblastic cells is required for normal bone development but is dispensable for hematopoietic development

Rac signaling in osteoblastic cells is required for normal bone development but is dispensable for hematopoietic development

Cre Recombinase

Roles for β-Catenin and Doxycycline in the Regulation of Respiratory Epithelial Cell Frequency and Function

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