Pax9 is required for filiform papilla development and suppresses skin-specific differentiation of the mammalian tongue epithelium

The epidermis is a derivative of the surface ectoderm. It forms a protective barrier and specific appendages including hair, nails, and different eccrine glands. The surface ectoderm also forms the epithelium of the oral cavity and tongue, which develop a slightly different barrier and form different appendages such as teeth, filiform papillae, taste papillae, and salivary glands. How this region-specific differentiation is genetically controlled is largely unknown. We show here that Pax9, which is expressed in the epithelium of the tongue but not in skin, regulates several aspects of tongue-specific epithelial differentiation. In Pax9-deficient mice filiform papillae lack the anterior–posterior polarity, a defect that is associated with temporal–spatial changes in Hoxc13 expression. Barrier formation is disturbed in the mutant tongue and genome-wide expression profiling revealed that the expression of specific keratins (Krt), keratin-associated proteins, and members of the epidermal differentiation complex is significantly down-regulated. In situ hybridization demonstrated that several ‘hard’ keratins, Krt1-5, Krt1-24, and Krt2-16, are not expressed in the absence of Pax9. Notably, specific ‘soft’ keratins, Krt2-1 and Krt2-17, normally weakly expressed in the tongue but present at high levels in skin and in orthokeratinized oral dysplasia are up-regulated in the mutant tongue epithelium. This result indicates a partial trans-differentiation to an epithelium with skin-specific characteristics. Together, our findings show that Pax9 regulates appendage formation in the mammalian tongue and identify Pax9 as an important factor for the region-specific differentiation of the surface ectoderm

Sox9 regulates cell proliferation and is required for Paneth cell differentiation in the intestinal epithelium

The HMG-box transcription factor Sox9 is expressed in the intestinal epithelium, specifically, in stem/progenitor cells and in Paneth cells. Sox9 expression requires an active β-catenin–Tcf complex, the transcriptional effector of the Wnt pathway. This pathway is critical for numerous aspects of the intestinal epithelium physiopathology, but processes that specify the cell response to such multipotential signals still remain to be identified. We inactivated the Sox9 gene in the intestinal epithelium to analyze its physiological function. Sox9 inactivation affected differentiation throughout the intestinal epithelium, with a disappearance of Paneth cells and a decrease of the goblet cell lineage. Additionally, the morphology of the colon epithelium was severely altered. We detected general hyperplasia and local crypt dysplasia in the intestine, and Wnt pathway target genes were up-regulated. These results highlight the central position of Sox9 as both a transcriptional target and a regulator of the Wnt pathway in the regulation of intestinal epithelium homeostasis

Metalloprotease-Dependent Attenuation of BMP Signaling Restricts Cardiac Neural Crest Cell Fate

心臓内での軟骨形成をおさえる仕組みを解明 --プロテアーゼが細胞の軟骨分化を防ぐ--. 京都大学プレスリリース. 2019-10-21.In higher vertebrates, cephalic neural crest cells (NCCs) form craniofacial skeleton by differentiating into chondrocytes and osteoblasts. A subpopulation of cephalic NCCs, cardiac NCCs (CNCCs), migrates to the heart. However, CNCCs mostly do not yield skeletogenic derivatives, and the molecular mechanisms of this fate restriction remain elusive. We identify a disintegrin and metalloprotease 19 (Adam19) as a position-specific fate regulator of NCCs. Adam19-depleted mice abnormally form NCC-derived cartilage in their hearts through the upregulation of Sox9 levels in CNCCs. Moreover, NCC-lineage-specific Sox9-overexpressing mice recapitulate CNCC chondrogenesis. In vitro experiments show that Adam19 mediates the cleavage of bone morphogenic protein (BMP) type I receptor Alk2 (Acvr1), whereas pharmacogenetic approaches reveal that Adam19 inhibits CNCC chondrogenesis by suppressing the BMP-Sox9 cascade, presumably through processing Alk2. These findings suggest a metalloprotease-dependent mechanism attenuating cellular responsiveness to BMP ligands, which is essential for both the positional restriction of NCC skeletogenesis and normal heart development

Lack of intrathyroidal tumor necrosis factorα in Graves' disease

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

PAX9 in Cancer Development

Paired box 9 (PAX9) is a transcription factor of the PAX family functioning as both a transcriptional activator and repressor. Its functional roles in the embryonic development of various tissues and organs have been well studied. However, its roles and molecular mechanisms in cancer development are largely unknown. Here, we review the current understanding of PAX9 expression, upstream regulation of PAX9, and PAX9 downstream events in cancer development. Promoter hypermethylation, promoter SNP, microRNA, and inhibition of upstream pathways (e.g., NOTCH) result in PAX9 silencing or downregulation, whereas gene amplification and an epigenetic axis upregulate PAX9 expression. PAX9 may contribute to carcinogenesis through dysregulation of its transcriptional targets and related molecular pathways. In summary, extensive studies on PAX9 in its cellular and tissue contexts are warranted in various cancers, in particular, HNSCC, ESCC, lung cancer, and cervical SCC

Gene expression changes associated with malignant transformation of oral potentially malignant disorders

Background A large number of oral squamous cell carcinomas (OSCCs) are believed to be preceded by oral potentially malignant disorders (OPMD) that have an increased likelihood of malignant transformation compared to clinically normal mucosa. This study was performed to identify differentially expressed genes between OPMDs that underwent malignant transformation (MT) and those that did not, termed ‘non‐transforming’ (NT) cases. Methods Total RNA was extracted from formalin‐fixed paraffin‐embedded tissue biopsies of 20 OPMD cases with known clinical outcomes (10 MT vs. 10 NT). Samples were assessed for quantity, quality and integrity of RNA prior to sequencing. Analysis for differential gene expression between MT and NT was performed using statistical packages in R. Genes were considered to be significantly differentially expressed if the False Discovery Rate corrected p‐value was 1.90). Analysis of RNA‐Sequencing outputs revealed 41 genes (34 protein‐coding; 7 non‐coding) that were significantly differentially expressed between MT and NT cases. The log2 fold change for the statistically significant differentially expressed genes ranged from ‐2.63 to 2.48, with 23 protein‐coding genes being downregulated and 11 protein‐coding genes being upregulated in MT cases compared to NT cases. Conclusion Several candidate genes that may play a role in malignant transformation of OPMD have been identified. Experiments to validate these candidates are underway. It is anticipated that this work will contribute to better understanding of the aetiopathogenesis of OPMD and development of novel biomarkers

Predicting the clinical outcome of oral potentially malignant disorders using transcriptomic-based molecular pathology

Background: This study was undertaken to develop and validate a gene expression signature that characterises oral potentially malignant disorders (OPMD) with a high risk of undergoing malignant transformation. Methods: Patients with oral epithelial dysplasia at one hospital were selected as the ‘training set’ (n = 56) whilst those at another hospital were selected for the ‘test set’ (n = 66). RNA was extracted from formalin-fixed paraffin-embedded (FFPE) diagnostic biopsies and analysed using the NanoString nCounter platform. A targeted panel of 42 genes selected on their association with oral carcinogenesis was used to develop a prognostic gene signature. Following data normalisation, uni- and multivariable analysis, as well as prognostic modelling, were employed to develop and validate the gene signature. Results: A prognostic classifier composed of 11 genes was developed using the training set. The multivariable prognostic model was used to predict patient risk scores in the test set. The prognostic gene signature was an independent predictor of malignant transformation when assessed in the test set, with the high-risk group showing worse prognosis [Hazard ratio = 12.65, p = 0.0003]. Conclusions: This study demonstrates proof of principle that RNA extracted from FFPE diagnostic biopsies of OPMD, when analysed on the NanoString nCounter platform, can be used to generate a molecular classifier that stratifies the risk of malignant transformation with promising clinical utility

The Formation of Endoderm-Derived Taste Sensory Organs Requires a <i>Pax9</i>-Dependent Expansion of Embryonic Taste Bud Progenitor Cells

<div><p>In mammals, taste buds develop in different regions of the oral cavity. Small epithelial protrusions form fungiform papillae on the ectoderm-derived dorsum of the tongue and contain one or few taste buds, while taste buds in the soft palate develop without distinct papilla structures. In contrast, the endoderm-derived circumvallate and foliate papillae located at the back of the tongue contain a large number of taste buds. These taste buds cluster in deep epithelial trenches, which are generated by intercalating a period of epithelial growth between initial placode formation and conversion of epithelial cells into sensory cells. How epithelial trench formation is genetically regulated during development is largely unknown. Here we show that <i>Pax9</i> acts upstream of <i>Pax1</i> and <i>Sox9</i> in the expanding taste progenitor field of the mouse circumvallate papilla. While a reduced number of taste buds develop in a growth-retarded circumvallate papilla of <i>Pax1</i> mutant mice, its development arrests completely in <i>Pax9</i>-deficient mice. In addition, the <i>Pax9</i> mutant circumvallate papilla trenches lack expression of K8 and <i>Prox1</i> in the taste bud progenitor cells, and gradually differentiate into an epidermal-like epithelium. We also demonstrate that taste placodes of the soft palate develop through a <i>Pax9</i>-dependent induction. Unexpectedly, <i>Pax9</i> is dispensable for patterning, morphogenesis and maintenance of taste buds that develop in ectoderm-derived fungiform papillae. Collectively, our data reveal an endoderm-specific developmental program for the formation of taste buds and their associated papilla structures. In this pathway, <i>Pax9</i> is essential to generate a pool of taste bud progenitors and to maintain their competence towards prosensory cell fate induction.</p></div

Msx1 haploinsufficiency modifies the Pax9-deficient cardiovascular phenotype

International audienceBackground: Successful embryogenesis relies on the coordinated interaction between genes and tissues. The transcription factors Pax9 and Msx1 genetically interact during mouse craniofacial morphogenesis, and mice deficient for either gene display abnormal tooth and palate development. Pax9 is expressed specifically in the pharyngeal endoderm at mid-embryogenesis, and mice deficient for Pax9 on a C57Bl/6 genetic background also have cardiovascular defects affecting the outflow tract and aortic arch arteries giving double-outlet right ventricle, absent common carotid arteries and interruption of the aortic arch. Results: In this study we have investigated both the effect of a different genetic background and Msx1 haploinsufficiency on the presentation of the Pax9-deficient cardiovascular phenotype. Compared to mice on a C57Bl/6 background, congenic CD1-Pax9-/mice displayed a significantly reduced incidence of outflow tract defects but aortic arch defects were unchanged. Pax9-/mice with Msx1 haploinsufficiency, however, have a reduced incidence of interrupted aortic arch, but more cases with cervical origins of the right subclavian artery and aortic arch, than seen in Pax9-/mice. This alteration in arch artery defects was accompanied by a rescue in third pharyngeal arch neural crest cell migration and smooth muscle cell coverage of the third pharyngeal arch arteries. Although this change in phenotype could theoretically be compatible with post-natal survival, using tissue-specific inactivation of Pax9 to maintain correct palate development whilst inducing the cardiovascular defects was unable to prevent postnatal death in the mutant mice. Hyoid bone and thyroid cartilage formation were abnormal in Pax9-/mice. Conclusions: Msx1 haploinsufficiency mitigates the arch artery defects in Pax9-/mice, potentially by maintaining the survival of the 3rd arch artery through unimpaired migration of neural crest cells to the third pharyngeal arches. With the neural crest cell derived hyoid bone and thyroid cartilage also being defective in Pax9-/mice, we speculate that the pharyngeal endoderm is a key signalling centre that impacts on neural crest cell behaviour highlighting the ability of cells in different tissues to act synergistically or antagonistically during embryo development