scholarly journals The Hippo effector TAZ cooperates with oncogenic β-catenin in experimental and human hepatoblastoma development

2019 ◽  
Author(s):  
Junyan Tao ◽  
Shu Zhang ◽  
Jie Zhang ◽  
Katja Evert ◽  
Xiaolei Li ◽  
...  
Keyword(s):  
Sleeping Beauty ◽  
Dominant Negative ◽  
Downstream Effector ◽  
Tail Vein Injection ◽  
Mesenchymal Differentiation ◽  
Dominant Negative Form ◽  
Transcription Factor 1 ◽  
Negative Form

Abstract Backgrounds: Hepatoblastoma (HB) is the most common pediatric liver tumor. Though Wnt/β-catenin and Hippo cascades are implicated in HB development, there is no study on the crosstalk of β-catenin and Hippo downstream effector TAZ in HB. Methods: The expression of TAZ and of β-catenin in human HB specimens was assessed by immunohistochemistry (IHC). The functional interplay between TAZ and β-catenin was tested through delivering either an activated form of TAZ (TAZS89A) alone or co-delivering TAZS89A and an activated form of β-catenin (∆N90-β-catenin) to mouse liver using sleeping beauty transposase via hydrodynamic tail vein injection (SBT-HTVI). In addition, the role of transcriptional enhanced associate domain (TEAD) factors, canonical Notch cascade, Yap, and the tumor modifier heat shock transcription factor 1 (HSF1) along TAZ/β-catenin-driven HB development was studied in vivo and vitro. Results: Activation of TAZ often co-occurred with that of β-catenin in clinical specimens. While overexpression of TAZS89A alone was unable to promote liver tumorigenesis, the concomitant overexpression of TAZ and ∆N90-β-catenin induced the development of HB lesions exhibiting both epithelial and mesenchymal features. Mechanistically, HB development driven by TAZ/β-catenin required TAZ interaction with TEAD factors. Furthermore, TAZ/β-catenin overexpression induced HB development in conditional Yes-associated protein knockout (Yap KO) mice, indicating that Yap activation is dispensable in this model. Activation of the Notch signaling was observed in TAZ/β-catenin mouse lesions, consistent with that reported in human HBs. Blocking of the canonical Notch cascade using the dominant negative form of RBP-J (dnRBP-J) did not inhibit TAZ/β-catenin dependent HB formation in mice, although suppressed the mesenchymal differentiation. Similarly, upregulation of HSF1 was detected in TAZ/β-catenin lesions, but its inactivation did not affect HB development. In human HB cell lines, silencing of TAZ resulted in decreased cell growth, which was reduced more substantially when TAZ knockdown was associated with suppression of either β-catenin or YAP gene. Conclusions: Overall, our study identifies TAZ as a critical oncogene in HB development and progression. Yap, Notch, and HSF1 are dispensable for TAZ/β-catenin induced HB development in mice.

scholarly journals Functional Myc-Max heterodimer is required for activation-induced apoptosis in T cell hybridomas.

1994 ◽  
Vol 180 (6) ◽  
pp. 2413-2418 ◽  
Author(s):  
R P Bissonnette ◽  
A McGahon ◽  
A Mahboubi ◽  
D R Green
Keyword(s):  
T Cell ◽  
Apoptotic Cell ◽  
Tolerance Induction ◽  
Dominant Negative ◽  
Binding Partner ◽  
Dominant Negative Form ◽  
Dominant Negative Activity ◽  
Induced Apoptosis ◽  
Negative Form

T cell hybridomas respond to activation signals by undergoing apoptotic cell death, and this is likely to represent comparable events related to tolerance induction in immature and mature T cells in vivo. Previous studies using antisense oligonucleotides implicated the c-Myc protein in the phenomenon of activation-induced apoptosis. This role for c-Myc in apoptosis is now confirmed in studies using a dominant negative form of its heterodimeric binding partner, Max, which we show here inhibits activation-induced apoptosis. Further, coexpression of a reciprocally mutant Myc protein capable of forming functional heterodimers with the mutant Max can compensate for the dominant negative activity and restore activation-induced apoptosis. These results imply that Myc promotes activation-induced apoptosis by obligatory heterodimerization with Max, and therefore, by regulating gene transcription.

Role of p21 Activated Kinase and Specific Guanine Exchange Factors of Rac Gtpases in Oncogenic KIT Induced Systemic Mastocytosis and Acute Myeloid Leukemia

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 810-810
Author(s):  
Holly Martin ◽  
Peilin Ma ◽  
Anindya Chatterjee ◽  
Baskar Ramdas ◽  
Emily Sims ◽  
...  
Keyword(s):  
Systemic Mastocytosis ◽  
Dominant Negative ◽  
Leukemic Cells ◽  
Rac Gtpases ◽  
Cell Counts ◽  
Dominant Negative Form ◽  
Kit Receptor ◽  
P21 Activated Kinase ◽  
Negative Form

Abstract Abstract 810 Gain-of-function mutations in the KIT receptor tyrosine kinase have been associated with highly malignant human neoplasms. In particular, an acquired somatic mutation at codon 816 in KIT involving an aspartic acid to valine substitution is found in ∼90% of patients with systemic mastocytosis (SM) and in ∼40% of core binding factor acute myeloid leukemia (AML). The presence of this mutation in SM and AML is associated with poor prognosis and overall survival. In mice, presence of this mutation is sufficient to recapitulate many cardinal features of human SM. This mutation changes the conformation of KIT receptor resulting in altered substrate recognition and constitutive tyrosine autophosphorylation leading to constitutive ligand independent growth, which is resistant to imatinib and shows little therapeutic efficacy in response to Dasatinib in most SM patients. As there are currently no efficacious therapeutic agents against this mutation, we sought to define novel therapeutic targets that contribute to aberrant signaling downstream from KITD816V that promote transformation of primary hematopoietic stem/progenitor cells (HSC/Ps) in diseases such as AML and SM. Previously, we and others have demonstrated that the regulatory subunit of PI3K, p85α, is required for KITD814V (murine homolog) induced transformation. Although difficult to target, we hypothesized that perhaps the downstream effectors of the PI3K signaling pathway, in particular p21 activated kinase (PAK1) and its upstream effectors including guanine exchange factors (GEF) such as Tiam1, Trio and Vav as well as the Rho family of GTPases (Rac) contribute to gain-of-function mutant-mediated transformation. We show that KITD814V (mouse) and KITD816V (human) bearing leukemic cells exhibit constitutive activation of PAK, Rac GTPases, and GEF Vav. Importantly, treatment of KITD814V bearing murine cells or mastocytosis patient derived cells bearing the KITD816V mutation with an allosteric inhibitor of PAK1 (i.e. IPA-3) results in significant inhibition in growth due to enhanced apoptosis. Consistently, expression of a dominant negative form of PAK1 (K299R) in KITD814V bearing cells profoundly inhibited their growth but not the growth of normal cells. Upstream of PAK, we show that suppression of Rac GTPases by expression of a dominant negative form of Rac (RacN17) abrogates activating KIT-induced hyperproliferation, and activity of downstream effector, PAK1. Although both Rac1 and Rac2 are activated due to the presence of KITD814V in primary HSC/Ps; loss of Rac1 only modestly corrects the growth of KITD814V bearing cells and loss of Rac2 contributes to only 50% correction. In contrast, loss of both Rac1 and Rac2 in HSC/Ps resulted in 75% correction in KITD814V induced ligand independent growth in vitro. In vivo, Rac repression significantly delayed the onset of KITD814V induced myeloproliferative neoplasms (MPN). Although, all KITD814V bearing mice died around 20 days of transplantation due to splenomegaly, increased white cell counts and massive lung infiltration by leukemic cells; KITD814V bearing mice in which Rac was repressed showed prolonged survival, significantly reducted spleen size, white cell counts and myeloid cell infiltration in the lungs. Prior studies have shown that Rac GTPases can be activated by GEFs such as Tiam1, Trio and Vav. To assess the specific role of these GEFs in KITD814V induced transformation, we utilized small molecule inhibitors that uniquely target different GEFs. We synthesized and utilized a novel inhibitor of Rac, EHop-016, which is based on the structure of an existing GEF inhibitor, NSC23766. While NSC23766 targets Tiam1 and Trio, EHop-016 targets Vav. The IC50 of EHop-016 is ∼50 fold lower than that of NSC23766. Using these two drugs, we demonstrate that EHop-016 is 50-fold more potent in inhibiting the growth of both murine and human patient derived leukemic cells compared to NSC23766. These observations were confirmed utilizing mice and bone marrow cells deficient in the expression of Vav1 engineered to express the KITD814V mutation. Taken together, a series of experiments using knockout mouse models, mouse models of MPN, dominant negative approaches, and a novel allosteric inhibitor of PAK1 and a novel small molecule inhibitor of GEF Vav provide a mechanism of KITD816V induced transformation and provide potential novel therapeutic targets for treating oncogenic KIT bearing neoplasms. Disclosures: No relevant conflicts of interest to declare.

FGF suppresses apoptosis and induces differentiation of fibre cells in the mouse lens

Development ◽  
1995 ◽  
Vol 121 (12) ◽  
pp. 4383-4393 ◽  
Author(s):  
R.L. Chow ◽  
G.D. Roux ◽  
M. Roghani ◽  
M.A. Palmer ◽  
D.B. Rifkin ◽  
...  
Keyword(s):  
Growth Factor ◽  
Transgenic Mice ◽  
Dominant Negative ◽  
Fgf Receptor ◽  
Fibre Cell ◽  
Dominant Negative Form ◽  
Lens Fibre ◽  
Mouse Lens ◽  
Negative Form

To determine whether fibroblast growth factor (FGF) has a role in lens development, we have generated transgenic mice expressing a dominant-negative form of the murine FGF receptor-1 (FGFRDN) in the lens. Using the fibre cell-specific alpha A-crystallin promoter to express the FGFRDN, we have asked whether FGF is required for fibre cell differentiation. The transgenic mice display diminished differentiation of fibre cells as indicated by their reduced elongation. In addition, transgenic lenses have an unusual refractile anomaly that morphological and biochemical data show results from the apoptosis of fibre cells in the central region of the lens. These results show that lens fibre cells are dependent on FGF for their survival and differentiation, and demonstrate that growth factor deprivation in vivo can lead to apoptosis.

scholarly journals Attenuating endogenous Fgfr2b ligands during bleomycin-induced lung fibrosis does not compromise murine lung repair

2015 ◽  
Vol 308 (10) ◽  
pp. L1014-L1024 ◽  
Author(s):  
BreAnne MacKenzie ◽  
Ingrid Henneke ◽  
Stefanie Hezel ◽  
Denise Al Alam ◽  
Elie El Agha ◽  
...  
Keyword(s):  
Lung Injury ◽  
Lung Fibrosis ◽  
Dominant Negative ◽  
Wild Type ◽  
Dominant Negative Form ◽  
Lung Epithelial ◽  
Organ Repair ◽  
The Impact ◽  
Negative Form

Fibroblast growth factors (Fgfs) mediate organ repair. Lung epithelial cell overexpression of Fgf10 postbleomycin injury is both protective and therapeutic, characterized by increased survival and attenuated fibrosis. Exogenous administration of FGF7 (palifermin) also showed prophylactic survival benefits in mice. The role of endogenous Fgfr2b ligands on bleomycin-induced lung fibrosis is still elusive. This study reports the expression of endogenous Fgfr2b ligands, receptors, and signaling targets in wild-type mice following bleomycin lung injury. In addition, the impact of attenuating endogenous Fgfr2b-ligands following bleomycin-induced fibrosis was tested by using a doxycycline (dox)-based inducible, soluble, dominant-negative form of the Fgfr2b receptor. Double-transgenic (DTG) Rosa26rtTA/+;tet(O)solFgfr2b mice were validated for the expression and activity of soluble Fgfr2b (failure to regenerate maxillary incisors, attenuated recombinant FGF7 signal in the lung). As previously reported, no defects in lung morphometry were detected in DTG (+dox) mice exposed from postnatal days (PN) 1 through PN105. Female single-transgenic (STG) and DTG mice were subjected to various levels of bleomycin injury (1.0, 2.0, and 3.0 U/kg). Fgfr2b ligands were attenuated either throughout injury ( days 0– 11; days 0– 28) or during later stages ( days 6– 28 and 14– 28). No significant changes in survival, weight, lung function, confluent areas of fibrosis, or hydroxyproline deposition were detected in DTG mice. These results indicate that endogenous Fgfr2b ligands do not significantly protect against bleomycin injury, nor do they expedite the resolution of bleomycin-induced lung injury in mice.

scholarly journals Pax6 Regulates the Proglucagon Processing Enzyme PC2 and Its Chaperone 7B2

2009 ◽  
Vol 29 (8) ◽  
pp. 2322-2334 ◽  
Author(s):  
Liora S. Katz ◽  
Yvan Gosmain ◽  
Eric Marthinet ◽  
Jacques Philippe
Keyword(s):  
Target Genes ◽  
Dominant Negative ◽  
Prohormone Convertase ◽  
Endocrine Differentiation ◽  
Processing Enzyme ◽  
Dominant Negative Form ◽  
Prohormone Convertase 2 ◽  
Interfering Rna ◽  
Negative Form

ABSTRACT Pax6 is important in the development of the pancreas and was previously shown to regulate pancreatic endocrine differentiation, as well as the insulin, glucagon, and somatostatin genes. Prohormone convertase 2 (PC2) is the main processing enzyme in pancreatic α cells, where it processes proglucagon to produce glucagon under the spatial and temporal control of 7B2, which functions as a molecular chaperone. To investigate the role of Pax6 in glucagon biosynthesis, we studied potential target genes in InR1G9 α cells transfected with Pax6 small interfering RNA and in InR1G9 clones expressing a dominant-negative form of Pax6. We now report that Pax6 controls the expression of the PC2 and 7B2 genes. By binding and transactivation studies, we found that Pax6 indirectly regulates PC2 gene transcription through cMaf and Beta2/NeuroD1 while it activates the 7B2 gene both directly and indirectly through the same transcription factors, cMaf and Beta2/NeuroD1. We conclude that Pax6 is critical for glucagon biosynthesis and processing by directly and indirectly activating the glucagon gene through cMaf and Beta2/NeuroD1, as well as the PC2 and 7B2 genes.

scholarly journals Myocardial Expression of a Dominant-Negative Form of Daxx Decreases Infarct Size and Attenuates Apoptosis in an In Vivo Mouse Model of Ischemia/Reperfusion Injury

Circulation ◽  
2007 ◽  
Vol 116 (23) ◽  
pp. 2709-2717 ◽  
Author(s):  
François Roubille ◽  
Stéphane Combes ◽  
Juani Leal-Sanchez ◽  
Christian Barrère; ◽  
Frédéric Cransac ◽  
...  
Keyword(s):  
Mouse Model ◽  
Infarct Size ◽  
Reperfusion Injury ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Dominant Negative ◽  
Dominant Negative Form ◽  
Negative Form

Requirement ofFoxD3-class signaling for neural crest determination inXenopus

Development ◽  
2001 ◽  
Vol 128 (13) ◽  
pp. 2525-2536 ◽  
Author(s):  
Noriaki Sasai ◽  
Kenji Mizuseki ◽  
Yoshiki Sasai
Keyword(s):  
Neural Crest ◽  
Dominant Negative ◽  
Related Factor ◽  
Embryonic Patterning ◽  
Loss Of Function ◽  
Upstream Regulator ◽  
Dominant Negative Form ◽  
Neural Crest Differentiation ◽  
Negative Form

Fox factors (winged-helix transcription factors) play important roles in early embryonic patterning. We show here that FoxD3 (Forkhead 6) regulates neural crest determination in Xenopus embryos. Expression of FoxD3 in the presumptive neural crest region starts at the late gastrula stage in a manner similar to that of Slug, and overlaps with that of Zic-r1. When overexpressed in the embryo and in ectodermal explants, FoxD3 induces expression of neural crest markers. Attenuation of FoxD3-related signaling by a dominant-negative FoxD3 construct (FoxD3delN) inhibits neural crest differentiation in vivo without suppressing the CNS marker Sox2. Interestingly, these loss-of-function phenotypes are reversed by coinjecting Slug. In animal cap explants, neural crest differentiation induced by Slug and Wnt3a is also inhibited by FoxD3delN but not by a dominant-negative form of XBF2. Loss-of-function studies using dominant-negative forms of FoxD3 and Slug indicate that Slug induction by Zic factors requires FoxD3-related signaling, and that FoxD3 and Slug have different requirements in inducing downstream neural crest markers. These data demonstrate that FoxD3 (or its closely related factor) is an essential upstream regulator of neural crest determination.

scholarly journals Functional Verification of Novel ELMO1 Variants By Live Imaging in Zebrafish

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3121-3121
Author(s):  
Rongtao Xue ◽  
Ying Wang ◽  
Tienan Wang ◽  
Mei Lyu ◽  
Guiling Mo ◽  
...  
Keyword(s):  
Cell Motility ◽  
Conflicts Of Interest ◽  
Live Imaging ◽  
Dominant Negative ◽  
Functional Verification ◽  
Transient Expression Assay ◽  
Dominant Negative Form ◽  
Reduced Mobility ◽  
Negative Form

Abstract ELMO1 (Engulfment and Cell Motility1) is a gene involved in regulating cell motility through the ELMO1-DOCK2-RAC complex. Contrary to DOCK2 (Dedicator of Cytokinesis 2) deficiency, which has been reported to be associated with immunodeficiency diseases, variants of ELMO1 have been associated with autoimmune diseases, such as diabetes and rheumatoid arthritis (RA). To explore the function of ELMO1 in immune cells and to verify the functions of novel ELMO1 variants in vivo, we established a zebrafish elmo1 mutant model. Live imaging revealed that similar to mammals, the motility of neutrophils and T-cells was largely attenuated in zebrafish mutants. Consequently, the response of neutrophils to injury or bacterial infection was significantly reduced in the mutants. Furthermore, the reduced mobility of neutrophils could be rescued by the expression of constitutively activated Rac proteins, suggesting that zebrafish elmo1 mutant functions via a conserved mechanism. With this mutant, three novel human ELMO1 variants were transiently and specifically expressed in zebrafish neutrophils. Two variants, p.E90K (c.268G>A) and p.D194G (c.581A>G) could efficiently recover the motility defect of neutrophils in the elmo1 mutant; however, the p.R354X (c.1060C>T) variant failed to rescue the mutant. Acts as a dominant-negative form, p.R354X (c.1060C>T) which failed to rescue the elmo1 mutant and inhibited neutrophil movement in siblings. Based on those results, we identified that zebrafish elmo1 played conserved roles in cell motility, similar to higher vertebrates. Using the transient-expression assay, zebrafish elmo1 mutants could serve as an effective model for human variant verification in vivo. Disclosures No relevant conflicts of interest to declare.

Role of Rab Proteins In Endocytosis and Trafficking of Factor VIIa and Endothelial Cell Protein C Receptor In Endothelial Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1145-1145
Author(s):  
Ramesh C Nayak ◽  
Shiva Keshava ◽  
Usha Pendurthi ◽  
L. Vijaya Mohan Rao
Keyword(s):  
Endothelial Cells ◽  
Protein C ◽  
Dominant Negative ◽  
Rab Proteins ◽  
Rab Gtpases ◽  
Wild Type ◽  
Dominant Negative Form ◽  
Negative Form ◽  
Constitutively Active

Abstract Abstract 1145 Recent studies from our laboratory and others showed that endothelial cell protein C receptor (EPCR), the cellular receptor for protein C and activated protein C (APC), also serves as a receptor for factor VII (FVII) and activated factor VII (FVIIa). At present, the physiological importance of FVII/FVIIa binding to EPCR is largely unknown, but this interaction may play a role in the clearance or transport of FVII/FVIIa from circulation to tissues. Our recent studies showed that FVIIa (or APC) binding to EPCR promoted the endocytosis of EPCR via dynamin and caveolar-dependent pathways, and the endocytosed receptor-ligand complexes were accumulated in the recycling compartment (REC) before being targeted back to the cell surface (Blood 2009;114:1974-1986). Rab GTPases (Rab 4, Rab 5, Rab 7 and Rab 11 etc.), which localize to specific endosomal structures, have been shown to play crucial roles in the endocytic and exocytic pathways of receptor or receptor/ligand complexes. The role of these Ras-like small GTPases is unknown in endocytosis and trafficking of EPCR and EPCR/FVIIa complexes. The present study was undertaken in order to investigate the role of different Rab GTPases (Rab 4A, Rab 5 and Rab11) in the intracellular trafficking of EPCR and internalized FVIIa in endothelial cells. For this, we examined the effect of expressing wild-type (wt) or mutant Rab proteins on the intracellular distribution of FVIIa in human umbilical vein endothelial cells (HUVEC). The wild-type, constitutively active and dominant negative mutants of Rab 4A, Rab 5 and Rab 11 were cloned in adenoviral shuttle vector pacAd5 K-N pA CMV and the recombinant adenoviruses expressing these Rab GTPase variants were generated in human embryonic kidney (HEK) cells. HUVEC were infected with recombinant adenoviruses encoding for the wild-type, active or dominant negative mutant of Rab 4A, Rab 5 and Rab 11 (25 moi/cell). After culturing the cells for 24 h, they were incubated with recombinant FVIIa conjugated with Alexa fluor 488 fluorescent dye (AF488-FVIIa) for 1 h at 37°C. The intracellular distribution of FVIIa was analyzed by monitoring the fluorescence of AF488-FVIIa by confocal microscopy. The intracellular distribution of EPCR and Rab proteins was evaluated by confocal microscopy after immunofluorescence staining. Expression of Rab 4A wt or constitutively active Rab 4A (Q67L) forms led to accumulation of AF488-FVIIa within the Rab 4A positive early/sorting endosomes, whereas FVIIa accumulation in the REC was inhibited. In cells expressing Rab 4A dominant negative form (S22N), FVIIa was trafficked normally and accumulated in the REC. Rab 4A is known to regulate fusion of early and sorting endosomes, as well as recycling of the internalized receptor or receptor/ligand complexes from early/sorting endosomes back to the cell surface. Increased accumulation of FVIIa in early/sorting endosomes but a decrease in REC in HUVEC transduced to express wt and constitutively active Rab 4A, suggests that Rab 4A plays a role in the transport of internalized FVIIa and FVIIa-EPCR complexes from sorting endosomes back to the cell surface. HUVEC expressing Rab 5 wt or active mutant (Q79L) showed larger endosomal structures beneath the plasma membrane where EPCR and FVIIa were accumulated; very little FVIIa entered the REC. The trafficking of internalized FVIIa remained unaffected in HUVEC expressing Rab 5A dominant negative form (S34N). As Rab 5 is known to induce receptor internalization and fusion between early endosomes, the large endosomal structures containing AF488-FVIIa found in HUVEC expressing wt or constitutively active form but not in cells expressing the dominant negative form suggests that Rab 5 facilitates internalization of FVIIa-EPCR complexes. In contrast to the data obtained in HUVEC expressing Rab 4A and Rab 5, the intracellular trafficking of AF488-FVIIa remained unaffected in HUVEC expressing either wt or constitutively active Rab 11 mutant. Rab 11 dominant negative mutant (S34N) prevented the entry of AF488-FVIIa into REC. The observation that the dominant negative form of Rab 11 inhibits the entry of internalized FVIIa to the REC indicates that the activation of Rab 11 by GTP is required for the transport of FVIIa from sorting endosomes toward the recycling compartment. Overall our present data show that Rab GTPases regulate the internalization and intracellular trafficking of EPCR and internalized FVIIa in endothelial cells. Disclosures: No relevant conflicts of interest to declare.

scholarly journals FOXA1 plays a role in regulating secretoglobin 1a1 expression in the absence of CCAAT/enhancer binding protein activities in lung in vivo

2011 ◽  
Vol 300 (3) ◽  
pp. L441-L452 ◽  
Author(s):  
Taketomo Kido ◽  
Takeshi Tomita ◽  
Minoru Okamoto ◽  
Yan Cai ◽  
Yoshimi Matsumoto ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Regulation Of Gene Expression ◽  
Dominant Negative ◽  
Clara Cell ◽  
Small Molecular Weight ◽  
Dominant Negative Form

Secretoglobin (SCGB) 1A1, also called Clara cell secretor protein (CCSP) or Clara cell-specific 10-kDa protein (CC10), is a small molecular weight secreted protein mainly expressed in lung, with anti-inflammatory/immunomodulatory properties. Previous in vitro studies demonstrated that CCAAT/enhancer-binding proteins (C/EBPs) are the major transcription factors for the regulation of Scbg1a1 gene expression, whereas FOXA1 had a minimum effect on the transcription. To determine the in vivo role of C/EBPs in the regulation of SCGB1A1 expression, experiments were performed in which A-C/EBP, a dominant-negative form of C/EBP that interferes with DNA binding activities of all C/EBPs, was specifically expressed in lung. Surprisingly, despite the in vitro findings, expression of SCGB1A1 mRNA was not decreased in vivo in the absence of C/EBPs. This may be due to a compensatory role assumed by FOXA1 in the regulation of Scgb1a1 gene expression in lung in the absence of active C/EBPs. This disconnect between in vitro and in vivo results underscores the importance of studies using animal models to determine the role of specific transcription factors in the regulation of gene expression in intact multicellular complex organs such as lung.

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