Development of the Goose Tongue Filiform Papillae: Could it be Tooth-Like Sense Organs? / Desarrollo de las Papilas Filiformes de la Lengua de Ganso: ¿Podrían ser Órganos Sensoriales Parecidos a los Dientes?

SUMMARY: The geese's tongue filiform papillae are particularly long, and exhibit the same morphology of a tooth, evoking the lingual teeth of several fishes. In adult animals, they contain numerous mechanical Herbst's corpuscles but no taste buds. In the embryo, they appear since stage 38 and acquire their definitive shape between stages 38 and 42. They express several proteins associated with mammalian tooth development (BMP4, β-catenin, SHH, PITX2, PAX9), also known to be linked to parrot's pseudoteeth and goose's denticulations development. Neurofilaments are early present in the papillae primordia, and appear particularly numerous in adult papillae. Our results suggest that these papillae constitute a mechanical organ with a « tooth shape » derived from ancestral odontodes, whose development is controlled by numerous genes involved in classical odontogenesis.

Las papilas filiformes de la lengua de los gansos son particularmente largas y exhiben la morfología de un diente, evocando los dientes linguales presentes en varios peces. En los animales adultos, contienen numerosos corpúsculos de Herbst mecánicos, aunque una ausencia de papilas gustativas. En el embrión, aparecen a partir del estadio 38 y adquieren su forma definitiva entre los estadios 38 y 42. Expresan varias proteínas asociadas al desarrollo dentario de los mamíferos (BMP4, β-catenina, SHH, PITX2, PAX9), también conocidas por estar asociadas al desarrollo de pseudodientes en el loro y denticulaciones en el ganso. Los neurofilamentos están presentes tempranamente en los primordios de las papilas y aparecen particularmente numerosos en las papilas adultas. Nuestros resultados sugieren que estas papilas constituyen un órgano mecánico con «forma de diente» derivado de odontoides ancestrales, cuyo desarrollo está controlado por numerosos genes implicados en la odontogénesis clásica.

IRF6, RYK, and PAX9 expression in facial tissue of children with cleft palate / Expresión de IRF6, RYK y PAX9 en el tejido facial de niños con paladar fisurado

Cleft lip and palate (CLP) is a congenital anomaly characterized by the inappropriate fusion of the upper lip, alveolus, and secondary palate. This study investigated whether expression of interferon regulatory fac tor 6 (IRF6), receptor-like tyrosine kinase (RYK), and paired-box 9 (PAX9), which are essential for the normal development and morphogenesis of craniofacial structures, is dysregulated in children with CLP. Oral mucosa tissue samples were obtained from patients with complete bilateral (CB) CLP (n= 19) during corrective plastic surgery and unaffected control subjects (n= 7). IRF6, RYK, and PAX9 expression was assessed by immunohistochemistry, and data were analyzed with the Mann-Whitney test. In patients, IRF6 immunoreactivity in the connective tissue was moderate to high, but the overall number of IRF6-positive oral epithelial cells was lower than that in controls (z= -3.41; P= 0.01). RYK expression was observed only sporadically in the oral epithelium of 4 patients, in contrast to the control group (z= -3.75; P< 0.001). PAX9-positive epithelial cells were present in low to moderate numbers in patients with CBCLP, while an abundance of these cells was observed in the basal layer of the oral epithelium in controls (z= -3.60; P<0.001). IRF6 is the main connective tissue regulatory factor in CBCLP, and its low level of expression in the oral epithelium suggests a reduced potential for epitheliocyte differentiation, while low PAX9 and RYK expression may explain the decreased cell migration and cleft remodeling in CBCLP.

La fisura labial y palatina (FLP) son anomalías congénitas caracterizadas por la fusión inadecuada del labio superior, alvéolo y paladar secundario. En este estudio se investigó si en niños con FLP hay una desregulación de la expresión del factor regulador de interferón 6 (IRF6), del receptor de la tirosina quinasa (RYK), y del factor de transcripción PAX9, que son esenciales para el desarrollo normal y la morfogénesis de las estructuras craneofaciales. Se obtuvieron muestras de la mucosa oral de pacientes con FLP completa bilateral (CB) (n= 19), tomadas durante la realización de cirugía plástica correctiva, y de sujetos de control no afectados (n= 7). Se evaluó la expresión de IRF6, RYK y PAX9 por inmunohistoquímica, y los datos se analizaron con la prueba de Mann-Whitney. En los pacientes, la inmunoreactividad de IRF6 en el tejido conectivo fue de moderada a alta, pero el número total de células epiteliales orales positivas para IRF6 fue menor que en los controles (z= -3,41; P= 0,01). La expresión de RYK se observó sólo esporádicamente en el epitelio oral de 4 pacientes, en contraste con el grupo control (z= -3,75; P<0.001). Células epiteliales positivas para PAX9 estaban presentes en números bajos a moderados en pacientes con FLP completa bilateral, mientras que se observó una abundante cantidad de estas células en la capa basal del epitelio oral en los controles (z= -3,60; P<0,001). IRF6 es el principal factor regulador del tejido conectivo con FLP completa bilateral, y su bajo nivel de expresión en el epitelio oral sugiere un potencial reducido para la diferenciación del epitelio, mientras que la expresión baja de PAX9 y RYK pueden explicar la disminución de la migración celular y la remodelación de la fisura con FLP completa bilateral.

PAX9 polymorphism and susceptibility to sporadic non-syndromic severe anodontia: a case-control study in southwest China

Our research aimed to look into the clinical traits and genetic mutations in sporadic non-syndromic anodontia and to gain insight into the role of mutations of PAX9, MSX1, AXIN2 and EDA in anodontia phenotypes, especially for the PAX9. Material and Methods The female proband and her family members from the ethnic Han families underwent complete oral examinations and received a retrospective review. Venous blood samples were obtained to screen variants in the PAX9, MSX1, AXIN2, and EDA genes. A case-control study was performed on 50 subjects with sporadic tooth agenesis (cases) and 100 healthy controls, which genotyped a PAX9 gene polymorphism (rs4904210). Results Intra-oral and panoramic radiographs revealed that the female proband had anodontia denoted by the complete absence of teeth in both the primary and secondary dentitions, while all her family members maintained normal dentitions. Detected in the female proband were variants of the PAX9 and AXIN2 including A240P (rs4904210) of the PAX9, c.148C>T (rs2240308), c.1365A>G (rs9915936) and c.1386C>T (rs1133683) of the AXIN2. The same variants were present in her unaffected younger brother. The PAX9 variations were in a different state in her parents. Mutations in the MSX1 and EDA genes were not identified. No significant diferences were found in the allele and genotype frequencies of the PAX9 polymorphism between the controls and the subjects with sporadic tooth agenesis. Conclusions These results suggest that the association of A240P with sporadic tooth agenesis still remains obscure, especially for different populations. The genotype/phenotype correlation in congenital anodontia should be verified. .

Bases moleculares de la agenesia dental no sindrómica: revisión de la información bibliográfica / Molecular bases of non-syndromic dental agenesis: a review of the literature

Este trabajo pretende actualizar los conocimientos acerca de las bases moleculares de la agenesia dental no sindrómica. Más de doscientos genes codifican múltiples proteínas con funciones necesarias para el desarrollo dental. Los factores de transcripción MSXC-1 y PAX-9 son fundamentales para activar la expresión proteica sinérgica de la cascada de señalización de las proteínas morfogénicas óseas, responsables de la progresión secuencial de la odontogénesis. En busca de las posibles causas de agenesias dentarias no sindrómicas, se han detectado dieciocho mutaciones de tipo missense de pares de dominio del gen humano PAX-9, mutaciones de haplo-insuficiencia funcional de los genes PAX-9 y MSX-1 y múltiples polimorfismos de localizaciones diversas. En todos los casos fue notable la disminución del nivel de expresión de las proteínas mutantes (a las que los genes antes mencionados codifican como transcriptores), la cual afectó la capacidad de unión al ADN de éstas. El impacto deletéreo de estas mutaciones para generar agenesias dentarias selectivas continúa siendo objeto de estudio.

Expression of odontogenic genes in human bone marrow mesenchymal stem cells

Tooth loss is a common problem and since current tooth replacement methods cannot counter balance with biological tooth structures, regenerating natural tooth structures has become an ideal goal. A challenging problem in tooth regeneration is to find a proper clinically feasible cell to seed. This study was designed to investigate the odontogenic potential of human bone marrow mesenchymal stem cells [HBMSCs] for seeding in tooth regeneration. In this experimental study, three pregnant Sprague Dawley [SD] rats were used at the eleventh embryonic day and rat fetuses were removed surgically using semilunar flap under general anesthesia. The primary mandible was cut using a stereomicroscope. The epithelial and mesenchymal components were separated and the dissected oral epithelium was cultured for 3 days. We used flow cytometry analysis to confirm presence of mesenchymal stem cells and not hematopoietic cells and to demonstrate the presence of oral epithelium. Bone marrow mesenchymal stem cells [BMSCs] and cultured oral epithelium were then co-cultured for 14 days. BMSCs cultured alone were used as controls. Expression of two odontogenic genes Pax9 and DMP1 was assessed using quantitative reverse transcription- polymerase chain reaction [RT-PCR]. Expression of two odontogenic genes, Pax9 and DMP1, were detected in BMSCs co-cultured with oral epithelium but not in the control group. Expression of Pax9 and DMP1 by human BMSCs in the proximity of odontogenic epithelium indicates odontogenic potential of these cells

Identification of mutation in PAX9 gene in a Mongolian family with non-syndromic oligodontia / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the mutation in transcription factor paired box gene PAX9 in a mongolian family with non-syndromic oligodontia.</p><p><b>METHODS</b>Peripheral blood was collected from 17 core family members (9 unaffected, 8 affected) in this Mongolian family with non-syndromic oligodontia. Mutation in exons of PAX9 gene was identified by PCR amplification and DNA sequencing.</p><p><b>RESULTS</b>A point mutation c.87G > C at position 87 in exon 4 of PAX9 was identified from 8 affected members in the family, which were G/C heterozygous.While the 9 healthy members in the family were homozygous for C which was consistent with normal reference sequence in the GenBank(accession number: NC_000014).</p><p><b>CONCLUSIONS</b>The mutation of c.87G > C (p. Ala240Pro) in exon 4 of PAX9 was likely to cause the non-syndromic oligodontia in this Mongolian family.</p>

Hipodoncia y hueso navicular accesorio: una interesante asociación sindrómica / Hypodontia and accessory navicular bone: an interesting syndromic association

Los dientes se desarrollan a partir de múltiples interacciones recíprocas entre células del epitelio oral y el ectomesénquima. Una serie de genes participan en el desarrollo del diente, así como de otros órganos y miembros superiores e inferiores. PAX9, miembro de la familia de factores de transcripción, es uno de los principales responsables de este desarrollo, y juega un rol fundamental en la hipodoncia dental y malformaciones en los huesos del miembro inferior. El objetivo de este reporte es presentar un caso de asociación entre hipodoncia y el hueso navicular accesorio. Se trata de una paciente de 18 años de edad, que acude a la consulta dental por dolor agudo en la pieza dentaria 3.6 y dolor de 9 meses de evolución en la cara interna del pie izquierdo. Al examen radiográfico, se observó ausencia de las piezas dentarias 1.7, 2.7, 2.8, 3.8 y 4.8, además en el pie izquierdo se vio la presencia de un hueso navicular accesorio. Es interesante proponer esta rara asociación, de clara herencia autosómica dominante, dado que la agenesia dental y la presencia del hueso navicular accesorio, poseen una prevalencia semejante, lo que hace que pueda existir una nueva asociación sindrómica probablemente relacionada con la ausencia de PAX9(AU)

Teeth are developed from many interactions between oral epithelium and mesenchymal cells. A number of genes are involved in tooth development, as well as in other organs, and upper and lower limbs. PAX9, a member of the transcriptional factor family, is one of the main drivers of this development, playing a key role in dental hypodontia and malformations in the lower limb bones. The aim of this report was to present the association between hypodontia and the accessory navicular bone based on a case report. This is a 18 years old female patient, who attended a dental clinic because she had acute pain in the 3.6 tooth and also pain on the left foot's inner area. The radiographic examination showed loss of the teeth 1.7, 2.7, 2.8, 3.8 and 4.8; and the presence of an accessory navicular bone in the left foot. It is interesting to suggest that this rare association, with clear dominant autosomal inheritance, might exist; since the dental agenesis and the presence of accessory navicular bone have similar prevalence, which could point to a new syndromic association probably related to the lack of PAX9(AU)

Aspectos clínicos e moleculares da agenesia dentária congênita / Molecular and clinical aspects of congenital dental agenesis

A agenesia dentária consiste em uma anomalia comum de desenvolvimento, que resulta na alteração do número de dentes preentes na cavidade bucal e afeta aproximadamente 20% da população. Sua etiologia está associada a fatores ambientais, como infecções, traumas, quimioterapia, radioterapia e causas genéticas. Atualmente a etiologia mais aceita para explicar a ocorrência das anomalias dentárias é a alteração na expressão de genes específicos. Com base no conhecimento dos genes e fatores de transcrição envolvidos na odontogênese, presume-se que diferentes formas fenotípicas de agenesia dentária são causadas por mutações em diferentes genes. Os genes envolvidos na agenesia dentária em humanos incluem os fatores de transcrição (MSX1 e PAX9) que desempenham um papel crítico durante o desenvolvimento craniofacial e o gene que codifica uma proteína envolvida na via de sinalização canônica Wnt (AXIN2). Dessa maneira, a proposta do presente estudo é discorrer sobre os principais genes que têm sido relatados como reguladores da formação dental e a ocorrência de mutações nestes genes que poderiam resultar em agenesias dentárias

Dental agenesis is a common developmental anomaly which affects approximately 20% of the population and results in a reduction of number of teeth present in the oral cavity. The etiology is associated with environmental factors, such as infections, trauma, chemotherapy, radiotherapy, and genetic causes. Currently the widely accepted theory to explain the occurrence of dental agenesis is the change in the expression of specific genes. Different phenotypic patterns of dental agenesis are caused by mutations in genes and transcription factors involved in odontogenesis. In humans those genes include transcription factors (MSX1 and PAX9) that play a critical role during development and the gene coding for a protein involved in the canonical Wnt signaling (AXIN2). Therefore, the purpose of this study is to discuss about dental agenesis and the key genes that have been reported as regulators of dental formation and how the occurrence of mutations in these genes could result in dental agenesis

Transcriptional analysis of the human PAX9 promoter

OBJECTIVES: PAX9 belongs to the Pax family of transcriptional factor genes. This gene is expressed in embryonic tissues such as somites, pharyngeal pouch endoderm, distal limb buds and neural crest-derived mesenchyme. Polymorphisms in the upstream promoter region of the human PAX9 have been associated with human non-syndromic tooth agenesis. In the present study, we verified the in vitro mRNA expression of this gene and the luciferase activity of two constructs containing promoter sequences of the PAX9 gene. MATERIAL AND METHODS: Embryonic tissues were obtained from digits, face, and midbrain/hindbrain regions. Fragments containing PAX9 promoter sequences were cloned into reporter plasmids and were transfected into the different cell cultures. mRNA were extracted from primary cell cultures. RESULTS: The semi-quantitative RT-PCR results showed that in vitro E13.5 limb bud and CNS cells express PAX9, but cells derived from the facial region do not. Moreover, the luciferase assay showed that protein activity of the constructed vector was weaker than pgl3 -basic alone. CONCLUSIONS: The present results suggest that the promoter sequences analyzed are not sufficient to drive PAX9 gene transcription.

Correlation between the phenotype and genotype of tooth agenesis patients by tooth agenesis code / 中国医学科学院学报

<p><b>OBJECTIVE</b>To analyze the correlation between the phenotype and genotype of tooth agenesis using the tooth agenesis code (TAC) and the traditional descriptor for missing teeth.</p><p><b>METHODS</b>Patients with isolated hypodontia caused by PAX9 or MSX1 mutation reported before May 2007 were enrolled. The teeth missing rate and TAC code were recorded. The missing teeth patterns caused by the two mutations were compared.</p><p><b>RESULTS</b>The teeth missing rates in each teeth positions were significantly different between maxillary and mandibular except maxillary central incisor, lateral incisor and mandibular canine, first molar (P<0.05, P<0.001). MSX1 gene mutation often led to the loss of maxillary first premolar, maxillary second premolar, and mandibular second premolar, while PAX9 gene mutation often led to the loss of the first, second, and third molars. The results were similar when analyzed either by TAC code analysis or by traditional descriptor.</p><p><b>CONCLUSIONS</b>PAX9 and MSX1 gene mutation can cause different phenotypes of tooth agenesis. The TAC code can be used in the analysis of the correlation between phenotype and genotype of the missing teeth patients.</p>

Analysis of clinical features and mutation associated with oligodontia / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the mutation characteristics of paired box homeotic gene 9 (PAX9) and muscle segment homeobox gene 1 (MSX1) of patients with congenital oligodontia.</p><p><b>METHODS</b>Clinical manifestations were recorded by taking complete oral examinations in patients with congenital nonsyndromic oligodontia and some of his normal family members. Pedigree information was confirmed by extended interviews and a pedigree was constructed. Inheritance mode and clinical features were analyzed. Assessment of crown width compared to normal value of crown width in Chinese people was based on the registrations and measurements of study cast. Comparison of craniofacial form, malocclusion types and characteristics were conducted via cephalometric analysis by taking lateral cephalometric radiographics. Venous blood samples were collected and DNA was extracted from leukocytes. DNA sequencing and mutation analysis were analyzed in exon 1, 2, 3, 4 of PAX9 and exon 1, 2 of MSX1 coding region by polymerase chain reaction (PCR).</p><p><b>RESULTS</b>The teeth shape abnormality of the patient was noticed by a measured smaller crown width compared to normal values of crown width in Chinese people. The result of cephalometric analysis indicated no obvious inherited tendency in the proband in terms of facial osseo type and jaw bone pattern. One mutation was found in the proband and his mother in exon 3 of PAX9, the missense mutation G718C causing a conservative change A240P was present. Mutation was not found in MSX1.</p><p><b>CONCLUSION</b>These findings suggest that the missense mutation G718C in exon 3 of PAX9 is likely the cause of oligodontia.</p>

Novel mutations of PAX9 gene in Chinese patients with oligodontia / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the mutational characteristics of PAX9 gene in Chinese patients with congenital oligodontia and thus to provide a molecular basis for studying the pathogenesis of oligodontia.</p><p><b>METHODS</b>Thirteen individuals with oligodontia and 9 healthy individuals, from 4 unrelated autosomal dominant families, and 16 sporadic patients with hypodontia in China, as well as 196 healthy control individuals (without oligodontia or hypodontia) were screened. Congenital absence of teeth was confirmed by panoramic X-ray analysis. Mutations of PAX9 gene were detected using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. After the finding of abnormal SSCP bands, analysis was carried out with DNA sequencing.</p><p><b>RESULTS</b>PCR-SSCP detected SSCP bands alteration in exon2 of PAX9 gene in two unrelated families. Sequencing of PAX9 gene revealed a novel frameshift mutation (109InsG) and a novel missense mutation (C139T). All the affected members of each family were heterozygous for the mutations. In sporadic patients and the other two families, no similar sequence changes in PAX9 gene were found.</p><p><b>CONCLUSIONS</b>The results extend the spectrum of mutations in PAX9 gene associated with oligodontia. The novel mutations will play an important role in gene diagnosis of oligodontia.</p>

Functional analysis of novel mutations in PAX9 associated with familial oligodontia / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To gain new insights into the molecular pathogenesis of the 109(InsG) and 139(C--> T) mutations and their roles in familial oligodontia.</p><p><b>METHODS</b>The region of PAX9 paired domain (PAX9PD) was amplified and the expression plasmids were constructed in pGEXlambda -1T by PCR-based cloning. PAX9PD proteins were prepared on the basis of GST instruction. The binding of wild type and two novely mutant PAX9 paired domain to double-stranded DNA targets were analyzed by gel mobility shift assay.</p><p><b>RESULTS</b>Wild type PAX9PD protein bind to the high affinity paired domain recognition sequences, CD19-2(A-ins) and Pax6CON, the 109(InsG) and 139(C--> T) mutant PAX9PD protein were unable to bind to these cognate DNA-binding sites.</p><p><b>CONCLUSION</b>The functional defects in DNA binding of mutant 109(InsG) PAX9 and 139(C--> T) PAX9, as well as loss-of-function of PAX9 most likely result in its haploinsufficiency during the patterning of dentition and the subsequent loss of posterior teeth.</p>