1,720,965 research outputs found
Pax8 modulates the expression of Wnt4 that is necessary for the maintenance of the epithelial phenotype of thyroid cells
No full textBackground: The transcription factor Pax8 is expressed during thyroid development and is involved in the morphogenesis of the thyroid gland and maintenance of the differentiated phenotype. In particular, Pax8 has been shown to regulate genes that are considered markers of thyroid differentiation. Recently, the analysis of the gene expression profile of FRTL-5 differentiated thyroid cells after the silencing of Pax8 identified Wnt4 as a novel target. Like the other members of the Wnt family, Wnt4 has been implicated in several developmental processes including regulation of cell fate and patterning during embryogenesis. To date, the only evidence on Wnt4 in thyroid concerns its down-regulation necessary for the progression of thyroid epithelial tumors. Results: Here we demonstrate that Pax8 is involved in the transcriptional modulation of Wnt4 gene expression directly binding to its 5'-flanking region, and that Wnt4 expression in FRTL-5 cells is TSH-dependent. Interestingly, we also show that in thyroid cells a reduced expression of Wnt4 correlates with the alteration of the epithelial phenotype and that the overexpression of Wnt4 in thyroid cancer cells is able to inhibit cellular migration. Conclusions: We have identified and characterized a functional Pax8 binding site in the 5'-flanking region of the Wnt4 gene and we show that Pax8 modulates the expression of Wnt4 in thyroid cells. Taken together, our results suggest that in thyroid cells Wnt4 expression correlates with the integrity of the epithelial phenotype and is reduced when this integrity is perturbed. In the end, we would like to suggest that the overexpression of Wnt4 in thyroid cancer cells is able to revert the mesenchymal phenotype
Neuropilin-2 Is a Newly Identified Target of PAX8 in Thyroid Cells.
No full textPAX8 is a transcription factor essential for thyroid gland development, as well as for the maintenance of the thyroid differentiated state in the adult. In particular, PAX8 has been comprehensively shown to regulate genes that are considered markers of thyroid differentiation. However, a better knowledge of genes transcriptionally regulated by PAX8 is desirable to clarify its role in endocrine syndromes and cancer susceptibility. In order to further investigate PAX8 downstream targets, we recently performed a genome-wide expression analysis following PAX8 knockdown in FRTL-5 thyroid cells and Neuropilin-2 was identified as a potential transcriptional target of PAX8. In this study, we determined the role of the transcription factor PAX8 in the regulation of Neuropilin-2 expression. Indeed, in thyroid cells PAX8 directly binds the Neuropilin-2 promoter leading to its transcriptional repression. Interestingly, we observed an inverse correlation between the expression of PAX8 and Neuropilin-2 in thyroid carcinoma tissues and cell lines compared to non-tumor counterparts, suggesting a critical role of PAX8 in regulating Neuropilin-2 expression in vivo. Notably, ectopic overexpression of PAX8 in FB-2 thyroid cancer cells promotes Neuropilin-2 downregulation producing a significant reduction in cell proliferation, migration ability, and invasion activity and reverting the cell phenotype from mesenchymal to a more epithelial one. These findings uncover the novel interplay between PAX8 and Neuropilin-2, which is likely to be important in the pathogenesis of thyroid diseases
Pax8 has a critical role in epithelial cell survival and proliferation
No full textThe transcription factor Pax8, a member of the Paired-box gene family, is a critical regulator required for proper development and
differentiation of thyroid follicular cells. Despite being Pax8 well characterized with respect to its role in regulating genes
responsible for thyroid differentiation, its involvement in cell survival and proliferation has been hypothesized but remains
unclear. Here, we show that Pax8 overexpression significantly increases proliferation and colony-forming efficiency of Fischer
rat thyroid line 5 epithelial cells, although it is not sufficient to overcome their hormone dependence. More interestingly, we show
that Pax8-specific silencing induces apoptosis through a p53-dependent pathway that involves caspase-3 activation and
cleavage of poly(ADP)ribose polymerase. Our data indicate that tumor protein 53 induced nuclear protein 1 (tp53inp1), a positive
regulator of p53-dependent cell cycle arrest and apoptosis, is a transcriptional target of Pax8 and is upregulated by Pax8
knockdown. Remarkably, tp53inp1 silencing significantly abolishes Pax8-induced apoptosis thus suggesting that tp53inp1 may
be the mediator of the observed effects. In conclusion, our data highlight that Pax8 is required for the survival of differentiated
epithelial cells and its expression levels are able to modulate the proliferation rate of such cells
AMOTL2 interaction with TAZ causes the inhibition of surfactant proteins expression in lung cells
No full textBackground: TAZ (Transcriptional co-Activator with PDZ-binding motif), is a biologically potent transcriptional coactivator and functions by binding to the PPXY motif present in several transcription factors. Notably, TAZ behaves as a transducer linking cytoplasmic signaling events to transcriptional regulation in the nucleus. Several different factors regulate TAZ expression and/or function. In particular, a major regulation of TAZ activity occurs through the Hippo pathway by a phosphorylation-mediated mechanism that causes its cytoplasmic sequestration or degradation. Results: Here we demonstrate that AMOTL2 robustly co-immunoprecipitates with TAZ, and their interaction is dependent on the WW domain of TAZ and the PPXY motif in the N-terminus of AMOTL2. Furthermore, we show that AMOTL2 colocalizes with TAZ in the cytoplasm of H441 human lung cells and regulates TAZ cytoplasm-to-nucleus translocation through direct protein-protein interaction. Interestingly, the overexpression of AMOTL2 inhibits the functional cooperation between the transcription factor TTF-1 and TAZ on the Surfactant C gene promoter, as well as the expression of other known target genes of these regulatory factors. Conclusions: Taken together, our results suggest an inhibitory role of AMOTL2 on TAZ ability to co-activate transcription and describe a different mechanism, Hippo pathway-independent, that modulates the activity of TAZ in lung cells through the interaction with Angiomotin-like 2 (AMOTL2)
Candidate genes and pathways downstream of PAX8 involved in ovarian high-grade serous carcinoma
No full textUnderstanding the biology and molecular pathogenesis of ovarian epithelial cancer (EOC) is key to developing improved diagnostic and prognostic indicators and effective therapies. Although research has traditionally focused on the hypothesis that high-grade serous carcinoma (HGSC) arises from the ovarian surface epithelium (OSE), recent studies suggest that additional sites of origin exist and a substantial proportion of cases may arise from precursor lesions located in the Fallopian tubal epithelium (FTE). In FTE cells, the transcription factor PAX8 is a marker of the secretory cell lineage and its expression is retained in 96% of EOC. We have recently reported that PAX8 is involved in the tumorigenic phenotype of ovarian cancer cells. In this study, to uncover genes and pathways downstream of PAX8 involved in ovarian carcinoma we have determined the molecular profiles of ovarian cancer cells and in parallel of Fallopian tube epithelial cells by means of a silencing approach followed by an RNA-seq analysis. Interestingly, we highlighted the involvement of pathways like WNT signaling, epithelial-mesenchymal transition, p53 and apoptosis. We believe that our analysis has led to the identification of candidate genes and pathways regulated by PAX8 that could be additional targets for the therapy of ovarian carcinom
Characterization of a novel loss-of-function mutation of PAX8 associated with congenital hypothyroidism.
No full textBackground Congenital hypothyroidism (CH) is a common endocrine disease that occurs in about 1:3000 newborns. In 80–85% of the cases, CH is presumably secondary to thyroid dysgenesis (TD), a defect in the organogenesis of the gland leading to an ectopic (30–45%), absent (agenesis, 35–40%) or hypoplastic (5%) thyroid gland. The pathogenesis of TD is still largely unknown. Most cases of TD are sporadic, although familial occurrences have occasionally been described. Recently, mutations in the PAX8 transcription factor have been identified in patients with TD.
Objective Our aim was to identify and functionally characterize novel PAX8 mutations with autosomal dominant transmission responsible for TD.
Design The PAX8 gene was sequenced in a mother and child both suffering from congenital hypothyroidism (CH) because of thyroid hypoplasia. Subsequently, expression vectors encoding the mutated PAX8 were generated, and the effects of the mutation on both the DNA-binding capability and the transcriptional activity were evaluated.
Results PAX8 gene sequencing revealed a heterozygous mutation that consists of the substitution of a histidine residue with a glutamine at position 55 of the PAX8 protein (H55Q). When tested in cotransfection experiments with a thyroglobulin promoter reporter construct, the mutant protein turned out to be still able to bind DNA in Electrophoretic Mobility Shift Assay assays but transcriptionally inactive.
Conclusions Our findings confirm the important role of PAX8 in normal thyroid development and support the evidence that in humans haploinsufficiency of PAX8 is associated with TD
Functional inactivation of the transcription factor Pax8 through oligomerization chain reaction.
No full textAmong the approaches used to provide a functional inactivation of a target protein, we have chosen the recently described oligomerization chain reaction (OCR) strategy to functionally inactivate the transcription factor Pax8, a member of the Pax gene family expressed in thyroid cells. The OCR strategy is based on the fusion of the self-associating coiled-coil (CC) domain of the nuclear factor promyelocytic leukemia (PML) to target proteins that are able to self-associate naturally or that form heterocomplexes. In the thyroid tissue, the transcription factor Pax8 is involved in the morphogenesis of the gland and in the transcriptional regulation of thyroid-expressed genes. We have recently demonstrated that in thyroid cells Pax8 interacts biochemically and functionally with the transcription factor TTF-1 (thyroid transcription factor 1), and that such interaction leads to the synergistic activation of thyroglobulin (Tg) gene expression. Fusion of the CC domain to Pax8 leads to the formation of aberrant, nonfunctional high-molecular mass complexes to which TTF-1 is also recruited. The CC-Pax8 chimera inhibits the transcriptional activity of Pax8 and of TTF-1 on both synthetic and physiological promoters and prevents the synergistic activation of the Tg promoter mediated by these two transcription factors. Furthermore, the expression of the CC-Pax8 chimera in differentiated thyroid cells leads to the down-regulation of the endogenous expression of several differentiation markers such as Tg, sodium/iodide symporter, Foxe1, TTF-1, and thyroid oxidase 2. These results demonstrate that the OCR is a useful tool to functionally inactivate a transcription factor. Moreover, by this approach, we identified Foxe1, TTF-1, and thyroid oxidase 2 as new direct targets of Pax8 or TTF-1
A role for PAX8 in the tumorigenic phenotype of ovarian cancer cells
Full text linkBackground: PAX8 is a member of the paired box (Pax) multigene family of transcription factors, which are involved in the developmental and tissue-specific control of the expression of several genes in both vertebrates and invertebrates. Previously, several studies reported that PAX8 is expressed at high levels in specific types of tumors. In particular, PAX8 has been recently reported to be conspicuously expressed in human ovarian cancer, but the functional role of PAX8 in the carcinogenesis of this type of tumor has not been addressed. In this study, we investigated the contribution of PAX8 in ovarian cancer progression. Methods: Stable PAX8 depleted ovarian cancer cells were generated using short hairpin RNA (shRNA) constructs. PAX8 mRNA and protein were detected by RT-PCR, immunoblot and immunofluorescence. Cell proliferation, motility and invasion potential of PAX8 silenced cells were analyzed by means of growth curves, wound healing and Matrigel assays. In addition, PAX8 knockdown and control cells were injected into nude mice for xenograft tumorigenicity assays. Finally, qPCR was used to detect the expression levels of EMT markers in PAX8-overexpressing and control cells. Results: Here, we show that PAX8 plays a critical role in the migration, invasion and tumorigenic ability of ovarian cancer cells. Our results show that RNA interference-mediated knockdown of PAX8 expression in SKOV-3 ovarian cancer cells produces a significant reduction of cell proliferation, migration ability and invasion activity compared with control parental SKOV-3 cells. Moreover, PAX8 silencing strongly suppresses anchorage-independent growth in vitro. Notably, tumorigenesis in vivo in a nude mouse xenograft model is also significantly inhibited. Conclusions: Overall, our results indicate that PAX8 plays an important role in the tumorigenic phenotype of ovarian cancer cells and identifies PAX8 as a potential new target for the treatment of ovarian cancer
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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