Cell-cell interaction determines cell fate of mesoderm-derived cell in tongue development through Hh signaling.

Dysfunction of primary cilia leads to genetic disorder, ciliopathies, which shows various malformations in many vital organs such as brain. Multiple tongue deformities including cleft, hamartoma, and ankyloglossia are also seen in ciliopathies, which yield difficulties in fundamental functions such as mastication and vocalization. Here, we found these tongue anomalies in mice with mutation of ciliary protein. Abnormal cranial neural crest-derived cells (CNCC) failed to evoke Hh signal for differentiation of mesoderm-derived cells into myoblasts, which resulted in abnormal differentiation of mesoderm-derived cells into adipocytes. The ectopic adipose subsequently arrested tongue swelling formation. Ankyloglossia was caused by aberrant cell migration due to lack of non-canonical Wnt signaling. In addition to ciliopathies, these tongue anomalies are often observed as non-familial condition in human. We found that these tongue deformities could be reproduced in wild-type mice by simple mechanical manipulations to disturb cellular processes which were disrupted in mutant mice. Our results provide hints for possible future treatment in ciliopathies.

Homozygosity for a Rare Plec Variant Suggests a Contributory Role in Congenital Insensitivity to Pain.

Congenital insensitivity to pain is a rare human condition in which affected individuals do not experience pain throughout their lives. This study aimed to identify the molecular etiology of congenital insensitivity to pain in two Thai patients. Clinical, radiographic, histopathologic, immunohistochemical, and molecular studies were performed. Patients were found to have congenital insensitivity to pain, self-mutilation, acro-osteolysis, cornea scars, reduced temperature sensation, tooth agenesis, root maldevelopment, and underdeveloped maxilla and mandible. The skin biopsies revealed fewer axons, decreased vimentin expression, and absent neurofilament expression, indicating lack of dermal nerves. Whole exome and Sanger sequencing identified a rare homozygous variant c.4039C>T; p.Arg1347Cys in the plakin domain of Plec, a cytolinker protein. This p.Arg1347Cys variant is in the spectrin repeat 9 region of the plakin domain, a region not previously found to harbor pathogenic missense variants in other plectinopathies. The substitution with a cysteine is expected to decrease the stability of the spectrin repeat 9 unit of the plakin domain. Whole mount in situ hybridization and an immunohistochemical study suggested that Plec is important for the development of maxilla and mandible, cornea, and distal phalanges. Additionally, the presence of dental anomalies in these patients further supports the potential involvement of Plec in tooth development. This is the first report showing the association between the Plec variant and congenital insensitivity to pain in humans.

Genetic Variants in KCTD1 Are Associated with Isolated Dental Anomalies.

KCTD1 plays crucial roles in regulating both the SHH and WNT/ß-catenin signaling pathways, which are essential for tooth development. The objective of this study was to investigate if genetic variants in KCTD1 might also be associated with isolated dental anomalies. We clinically and radiographically investigated 362 patients affected with isolated dental anomalies. Whole exome sequencing identified two unrelated families with rare (p.Arg241Gln) or novel (p.Pro243Ser) variants in KCTD1. The variants segregated with the dental anomalies in all nine patients from the two families. Clinical findings of the patients included taurodontism, unseparated roots, long roots, tooth agenesis, a supernumerary tooth, torus palatinus, and torus mandibularis. The role of Kctd1 in root development is supported by our immunohistochemical study showing high expression of Kctd1 in Hertwig epithelial root sheath. The KCTD1 variants in our patients are the first variants found to be located in the C-terminal domain, which might disrupt protein-protein interactions and/or SUMOylation and subsequently result in aberrant WNT-SHH-BMP signaling and isolated dental anomalies. Functional studies on the p.Arg241Gln variant are consistent with an impact on ß-catenin levels and canonical WNT signaling. This is the first report of the association of KCTD1 variants and isolated dental anomalies.

Ift88 regulates enamel formation via involving Shh signaling.

OBJECTIVES: The ciliopathies are a wide spectrum of human diseases, which are caused by perturbations in the function of primary cilia. Tooth enamel anomalies are often seen in ciliopathy patients; however, the role of primary cilia in enamel formation remains unclear. MATERIALS AND METHODS: We examined mice with epithelial conditional deletion of the ciliary protein, Ift88, (Ift88fl / fl ;K14Cre). RESULTS: Ift88fl / fl ;K14Cre mice showed premature abrasion in molars. A pattern of enamel rods which is determined at secretory stage, was disorganized in Ift88 mutant molars. Many amelogenesis-related molecules expressing at the secretory stage, including amelogenin and ameloblastin, enamelin, showed significant downregulation in Ift88 mutant molar tooth germs. Shh signaling is essential for amelogenesis, which was found to be downregulated in Ift88 mutant molar at the secretory stage. Application of Shh signaling agonist at the secretory stage partially rescued enamel anomalies in Ift88 mutant mice. CONCLUSION: Findings in the present study indicate that the function of the primary cilia via Ift88 is critical for the secretory stage of amelogenesis through involving Shh signaling.

Perivascular Hedgehog responsive cells play a critical role in peripheral nerve regeneration via controlling angiogenesis.

Hh signaling has been shown to be activated in intact and injured peripheral nerve. However, the role of Hh signaling in peripheral nerve is not fully understood. In the present study, we observed that Hh signaling responsive cells [Gli1(+) cells] in both the perineurium and endoneurium. In the endoneurium, Gli1(+) cells were classified as blood vessel associated or non-associated. After injury, Gli1(+) cells around blood vessels mainly proliferated to then accumulate into the injury site along with endothelial cells. Hh signaling activity was retained in Gli1(+) cells during nerve regeneration. To understand the role of Hedgehog signaling in Gli1(+) cells during nerve regeneration, we examined mice with Gli1(+) cells-specific inactivation of Hh signaling (Smo cKO). After injury, Smo cKO mice showed significantly reduced numbers of accumulated Gli1(+) cells along with disorganized vascularization at an early stage of nerve regeneration, which subsequently led to an abnormal extension of the axon. Thus, Hh signaling in Gli1(+) cells appears to be involved in nerve regeneration through controlling new blood vessel formation at an early stage.

A novel P3H1 mutation is associated with osteogenesis imperfecta type VIII and dental anomalies.

OBJECTIVE: Our objective was to investigate the molecular etiology of osteogenesis imperfecta type VIII and dental anomalies in 4 siblings of a Karen tribe family. MATERIALS AND METHODS: Four patients and their unaffected parents were studied by clinical and radiographic examination. In situ hybridization of P3h1 during early murine tooth development, whole-exome sequencing, and Sanger direct sequencing were performed. RESULTS: A novel homozygous missense P3H1 mutation (NM_001243246.1; c.2141A>G; NP_001230175.1; p.Lys714Arg) was identified in all patients. Their unaffected parents were heterozygous for the mutation. The mutation is hypothesized to belong to isoform c of P3H1. Mutations in P3H1 are associated with autosomal recessive osteogenesis imperfecta type VIII. Hypodontia, a mesiodens, and single-rooted permanent second molars found in our patients have never been reported in patients with P3H1 mutations. Single-rooted second permanent molars or failure to form multiple roots implies effects of the P3H1 mutation on root development. CONCLUSIONS: We report a novel P3H1 mutation as the underlying cause of osteogenesis imperfecta type VIII with dental anomalies. Our study suggests that isoform c of P3H1 is also a functional isoform of P3H1. We report, for the first time, to our knowledge, the association of P3H1 mutation and osteogenesis imperfecta type VIII with dental anomalies.

Juberg-Hayward syndrome is a cohesinopathy, caused by mutation in ESCO2.

BACKGROUND: Juberg-Hayward syndrome (JHS; MIM 216100) is a rare autosomal recessive malformation syndrome, characterized by cleft lip/palate, microcephaly, ptosis, short stature, hypoplasia or aplasia of thumbs, and dislocation of radial head and fusion of humerus and radius leading to elbow restriction. OBJECTIVE: To report for the first time the molecular aetiology of JHS. PATIENT AND METHODS: Clinical and radiographic examination, whole exome sequencing, Sanger sequencing, mutant protein model construction, and in situ hybridization of Esco2 expression in mouse embryos were performed. RESULTS: Clinical findings of the patient consisted of repaired cleft lip/palate, microcephaly, ptosis, short stature, delayed bone age, hypoplastic fingers and thumbs, clinodactyly of the fifth fingers, and humeroradial synostosis leading to elbow restriction. Intelligence is normal. Whole exome sequencing of the whole family showed a novel homozygous base substitution c.1654C>T in ESCO2 of the proband. The sister was homozygous for the wildtype variant. Parents were heterozygous for the mutation. The mutation is predicted to cause premature stop codon p.Arg552Ter. Mutations in ESCO2, a gene involved in cohesin complex formation, are known to cause Roberts/SC phocomelia syndrome. Roberts/SC phocomelia syndrome and JHS share similar clinical findings, including autosomal recessive inheritance, short stature, cleft lip/palate, severe upper limb anomalies, and hypoplastic digits. Esco2 expression during the early development of lip, palate, eyelid, digits, upper limb, and lower limb and truncated protein model are consistent with the defect. CONCLUSIONS: Our study showed that Roberts/SC phocomelia syndrome and JHS are allelic and distinct entities. This is the first report demonstrating that mutation in ESCO2 causes JHS, a cohesinopathy.

Overactivation of the NF-κB pathway impairs molar enamel formation.

OBJECTIVE: Hypohidrotic ectodermal dysplasia (HED) is a hereditary disorder characterized by abnormal structures and functions of the ectoderm-derived organs, including teeth. HED patients exhibit a variety of dental symptoms, such as hypodontia. Although disruption of the EDA/EDAR/EDARADD/NF-κB pathway is known to be responsible for HED, it remains unclear whether this pathway is involved in the process of enamel formation. EXPERIMENTAL SUBJECTS AND METHODS: To address this question, we examined the mice overexpressing Ikkß (an essential component required for the activation of NF-κB pathway) under the keratin 5 promoter (K5-Ikkß). RESULTS: Upregulation of the NF-κB pathway was confirmed in the ameloblasts of K5-Ikkß mice. Premature abrasion was observed in the molars of K5-Ikkß mice, which was accompanied by less mineralized enamel. However, no significant changes were observed in the enamel thickness and the pattern of enamel rods in K5-Ikkß mice. Klk4 expression was significantly upregulated in the ameloblasts of K5-Ikkß mice at the maturation stage, and the expression of its substrate, amelogenin, was remarkably reduced. This suggests that abnormal enamel observed in K5-Ikkß mice was likely due to the compromised degradation of enamel protein at the maturation stage. CONCLUSION: Therefore, we could conclude that the overactivation of the NF-κB pathway impairs the process of amelogenesis.

Gli3 is a Key Factor in the Schwann Cells from Both Intact and Injured Peripheral Nerves.

Hedgehog (Hh) signaling has been shown to be involved in regulating both intact and injured peripheral nerves. Therefore, it is critical to understand how Hh signaling is regulated in the peripheral nerve. One of the transcription factors of the Hh signaling pathway, Gli3, functions as both a repressor and an activator of Hh signaling activity. However, it remains unclear whether Gli3 is involved in controlling the intact and/or injured peripheral nerves. We found that Gli3 act as a repressor in the Schwann cells (SCs) of intact sciatic nerves. Although Dhh and Ptch1 expression were present, Hh signaling was not activated in these SCs. Moreover, heterozygous Gli3 mutation (Gli3-/+) induced ectopic Hh signaling activity in SCs. Hh signaling was thus suppressed by Gli3 in the SCs of intact sciatic nerves. Minor morphological changes were observed in the intact nerves from Gli3-/+ mice. Gli3 expression was significantly decreased following injury and ligand expression switched from Dhh to Shh, which activated Hh signaling in SCs from wild-type mice. Changes of these ligands was found to be important for nerve regeneration in which the downregulation of Gli3 was also involved. In fact, Gli3-/+ mice exhibited accelerated ligand switching and subsequent nerve regeneration. Both suppression of Hh signaling with Gli3 in the intact nerves and activation of Hh signaling without Gli3 in the injured nerve were observed in the SCs in an autocrine manner. Thus, Gli3 is a key factor in the control of intact peripheral nerve homeostasis and nerve regeneration.

R2TP/PAQosome as a promising chemotherapeutic target in cancer.

R2TP/PAQosome (particle for arrangement of quaternary structure) is a novel multisubunit chaperone specialized in the assembly/maturation of protein complexes that are involved in essential cellular processes such as PIKKs (phosphatidylinositol 3-kinase-like kinases) signaling, snoRNP (small nucleolar ribonucleoprotein) biogenesis, and RNAP II (RNA polymerase II) complex formation. In this review article, we describe the current understanding of R2TP/PAQosome functions and characteristics as well as how the chaperone complex is involved in oncogenesis, highlighting DNA damage response, mTOR (mammalian target of rapamycin) pathway as well as snoRNP biogenesis. Also, we discuss its possible involvement in HNSCC (head and neck squamous cell carcinoma) including OSCC (oral squamous cell carcinoma). Finally, we provide an overview of current anti-cancer drug development efforts targeting R2TP/PAQosome.

Primary cilia in murine palatal rugae development.

Periodic patterning of iterative structures is a fundamental process during embryonic development, since these structures are diverse across the animal kingdom. Therefore, elucidating the molecular mechanisms in the formation of these structures promotes understanding of the process of organogenesis. Periodically patterned ridges, palatal rugae (situated on the hard palate of mammals), are an excellent experimental model to clarify the molecular mechanisms involved in the formation of periodic patterning of iterative structures. Primary cilia are involved in many biological events, including the regulation of signaling pathways such as Shh and non-canonical Wnt signaling. However, the role of primary cilia in the development of palatal rugae remains unclear. We found that primary cilia were localized to the oral cavity side of the interplacode epithelium of the palatal rugae, whereas restricted localization of primary cilia could not be detected in other regions. Next, we generated mice with a placodal conditional deletion of the primary cilia protein Ift88, using ShhCre mice (Ift88 fl/fl;ShhCre). Highly disorganized palatal rugae were observed in Ift88 fl/fl;ShhCre mice. Furthermore, by comparative in situ hybridization analysis, many Shh and non-canonical Wnt signaling-related molecules showed spatiotemporal expression patterns during palatal rugae development, including restricted expression in the epithelium (placodes and interplacodes) and mesenchyme. Some of these expression were found to be altered in Ift88 fl/fl;ShhCre mice. Primary cilia is thus involved in development of palatal rugae.

Ift88 limits bone formation in maxillary process through suppressing apoptosis.

OBJECTIVE: The development of the maxillary bone is under strict molecular control because of its complicated structure. Primary cilia play a critical role in craniofacial development, since defects in primary cilia are known to cause congenital craniofacial dysmorphologies as a wide spectrum of human diseases: the ciliopathies. The primary cilia also are known to regulate bone formation. However, the role of the primary cilia in maxillary bone development is not fully understood. DESIGN: To address this question, we generated mice with a mesenchymal conditional deletion ofIft88 using the Wnt1Cre mice (Ift88fl/fl;Wnt1Cre). The gene Ift88 encodes a protein that is required for the function and formation of primary cilia. RESULTS: It has been shown thatIft88fl/fl;Wnt1Cre mice exhibit cleft palate. Here, we additionally observed excess bone formation in the Ift88 mutant maxillary process. We also found ectopic apoptosis in the Ift88 mutant maxillary process at an early stage of development. To investigate whether the ectopic apoptosis is related to the Ift88 mouse maxillary phenotypes, we generated Ift88fl/fl;Wnt1Cre;p53-/- mutants to reduce apoptosis. The Ift88fl/fl;Wnt1Cre;p53-/- mice showed no excess bone formation, suggesting that the cells evading apoptosis by the presence of Ift88 in wild-type mice limit bone formation in maxillary development. On the other hand, the palatal cleft was retained in the Ift88fl/fl;Wnt1Cre;p53-/- mice, indicating that the excess bone formation or abnormal apoptosis was independent of the cleft palate phenotype in Ift88 mutant mice. CONCLUSIONS: Ift88 limits bone formation in the maxillary process by suppressing apoptosis.

Semaphorin 3A Inhibits Nerve Regeneration During Early Stage after Inferior Alveolar Nerve Transection.

Neuroma formation at sites of injury can impair peripheral nerve regeneration. Although the involvement of semaphorin 3A has been suggested in neuroma formation, this detailed process after injury is not fully understood. This study was therefore undertaken to examine the effects of semaphorin 3A on peripheral nerve regeneration during the early stage after injury. Immunohistochemistry for semaphorin 3A and PGP9.5, a general neuronal marker, was carried out for clarify chronological changes in their expressions after transection of the mouse inferior alveolar nerve thorough postoperative days 1 to 7. At postoperative day 1, the proximal stump of the damaged IAN exhibited semaphorin 3A, while the distal stump lacked any immunoreactivity. From this day on, its expression lessened, ultimately disappearing completely in all regions of the transected inferior alveolar nerve. A local administration of an antibody to semaphorin 3A into the nerve transection site at postoperative day 3 inhibited axon sprouting at the injury site. This antibody injection increased the number of trigeminal ganglion neurons labeled with DiI (paired t-test, p < 0.05). Immunoreactivity of the semaphorin 3A receptor, neuropilin-1, was also detected at the proximal stump at postoperative day 1. These results suggest that nerve injury initiates semaphorin 3A production in ganglion neurons, which is then delivered through the nerve fibers to the proximal end, thereby contributes to the inhibition of axonal sprouting from the proximal region of injured nerves in the distal direction. To our knowledge, this is the first report to reveal the involvement of Sema3A in the nerve regeneration process at its early stage.

Vascularization via activation of VEGF-VEGFR signaling is essential for peripheral nerve regeneration.

Peripheral nerve injury has been suggested to up-regulate mRNA for the vascular endothelial growth factor (VEGF) which enhances nerve regeneration. VEGF is known to regulate angiogenesis by binding with a specific receptor, the vascular endothelial growth factor receptor (VEGFR). However, little is known about the involvement of VEGF-VEGFR signaling in the nerve regeneration at early stages though previous studies contained a lengthy observation. The present study examined that relationship between angiogenesis and peripheral nerve regeneration at the early stage after nerve transection by focusing on the chronological changes in the expression patterns of VEGF-VEGFR signaling. This study used our previously reported experimental model for nerve regeneration following the transection of the inferior alveolar nerve (IAN) in mice. In a double staining of PGP9.5 and CD31, respective markers for the nerve fibers and endothelial cells, CD31 immunoreactions first appeared in the injury site on postoperative (PO) day 2 when the transected nerve fibers had not been re-connected. The most intense immunoreaction for CD31 was found around the regenerating nerve fibers extending from the proximal stump on PO day 3, but it gradually lessened to disappear by PO day 7. The expression patterns of VEGFR1 and VEGFR2 showed similar chronological changes through the observation periods, with most intense immunoreaction found on PO day 3. Western blotting of total protein extracted from the injury site demonstrated the clear bands for VEGF-A and VEGF-B on PO day 2, indicating a time lag for the expression of ligands and receptors. A local administration of antibody to VEGF-A inhibited the elongation of the nerve fibers from the proximal stump. Furthermore, this administration of VEGF-A antibody inhibited the expression of CD31 in the gap between proximal and distal stumps. These results indicated that a nerve injury initiates productions in VEGF-A and VEFG-B, followed with the expression of VEGFR1 and VEGFR2 at early stages after the nerve injury. Taken these findings together, it is reasonable to postulate that immediate response of VEGF-VEGFR signaling to nerve injury plays a crucial role in local angiogenesis, resulting in a trigger for the regeneration of the nerve fibers in mouse IAN.

Expanding the Oro-Dental and Mutational Spectra of Kabuki Syndrome and Expression of KMT2D and KDM6A in Human Tooth Germs.

Kabuki syndrome is a rare genetic disorder characterized by distinct dysmorphic facial features, intellectual disability, and multiple developmental abnormalities. Despite more than 350 documented cases, the oro-dental spectrum associated with kabuki syndrome and expression of KMT2D (histone-lysine N-methyltransferase 2D) or KDM6A (lysine-specific demethylase 6A) genes in tooth development have not been well defined. Here, we report seven unrelated Thai patients with Kabuki syndrome having congenital absence of teeth, malocclusion, high-arched palate, micrognathia, and deviated tooth shape and size. Exome sequencing successfully identified that six patients were heterozygous for mutations in KMT2D, and one in KDM6A. Six were novel mutations, of which five were in KMT2D and one in KDM6A. They were truncating mutations including four frameshift deletions and two nonsense mutations. The predicted non-functional KMT2D and KDM6A proteins are expected to cause disease by haploinsufficiency. Our study expands oro-dental, medical, and mutational spectra associated with Kabuki syndrome. We also demonstrate for the first time that KMT2D and KDM6A are expressed in the dental epithelium of human tooth germs.

The Sonic Hedgehog signaling pathway regulates inferior alveolar nerve regeneration.

Activation of Shh signaling is known to be observed following injury of the peripheral nerves such as the sciatic nerve. However, the precise role of Shh signaling during peripheral nerve regeneration is not fully understood. The inferior alveolar nerve (IAN) is most commonly injured during oral surgery. Unlike the sciatic nerve, the IAN is isolated from other craniofacial tissues, as it resides in a long bony canal within the mandible. The IAN is thus an excellent experimental model for investigating peripheral nerve regeneration. In this study, the role of Shh signaling in peripheral nerve regeneration was investigated using the mouse IAN transection model. During regeneration, Shh signaling was activated within the entire distal region of the IAN and proximal stumps. Inhibition of Shh signaling by cyclopamine application at the transection site led to abnormal axon growth in random directions, a reduced number of macrophages, and an increase in myelin debris within the distal region. Shh signaling is thus involved in peripheral nerve regeneration via the regulation of myelin degradation.

Al-Awadi-Raas-Rothschild syndrome with dental anomalies and a novel WNT7A mutation.

Al-Awadi-Raas-Rothschild syndrome (AARRS; OMIM 276820) is a very rare autosomal recessive limb malformation syndrome caused by WNT7A mutations. AARRS is characterized by various degrees of limb aplasia and hypoplasia. Normal intelligence and malformations of urogenital system are frequent findings. Complete loss of WNT7A function has been shown to cause AARRS, however, its partial loss leads to the milder malformation, Fuhrmann syndrome. An Indian boy affected with AARRS is reported. A novel homozygous base substitution mutation c.550A > C (p.Asn184Asp) is identified in the patient. Parents were heterozygous for the mutation. In addition to the typical features of AARRS, the patient had agenesis of the mandibular left deciduous lateral incisor. The heterozygous parents had microdontia of the maxillary left permanent third molar and taurodontism (enlarged dental pulp chamber at the expense of root) in a number of their permanent molars. Whole exome sequencing of the patient and his parents ruled out mutations in 11 known hypodontia-associated genes including WNT10A, MSX1, EDA, EDAR, EDARADD, PAX9, AXIN2, GREM2, NEMO, KRT17, and TFAP2B. In situ hybridization during tooth development showed Wnt7a expression in wild-type tooth epithelium at E14.5. All lines of evidence suggest that WNT7A has important role in tooth development and its mutation may lead to tooth agenesis, microdontia, and taurodontism. Oral examination of patients with AARRS and Fuhrmann syndromes is highly recommended.

The effect of bone mass and architecture on mandibular condyle after mandibular distraction.

OBJECTIVE: Mandibular distraction surgery is a critical treatment for jaw deformity. However, abnormal mandibular condylar bone resorption is often seen as complication after surgery. Our previous study using a rat mandibular distraction model suggested that overloading leads to mandibular condylar resorption. Host factors are also believed to influence the resorption. To understand the relationship between host factors and resorption, we investigated the effect of changing bone mass and architecture on the mandibular condyle using FK506. STUDY DESIGN: FK506, an immunosuppressant, was used to compromise bone mass and architecture in this study. Animals were divided into 4 groups: distraction surgery (Dist), FK506 administration (FK), distraction surgery with FK506 administration (FK + Dist), and no surgery or FK506 administration (Cont). RESULTS: The FK group showed reduced bone mass and impaired bone architecture. The Dist group exhibited abnormal bone resorption on the surface of the condyles, which was slightly exacerbated in the FK + Dist group. Bone defect length decreased over time as a result of bone apposition in the Dist group. However, in the FK + Dist group, the bone defect length remained the same. CONCLUSIONS: These results suggest that bone mass and architecture strongly affect the tolerance to the overloading and adaptation with bone apposition in condylar resorption site.

TFAP2B mutation and dental anomalies.

Mutations inTFAP2B has been reported in patients with isolated patent ductus arteriosus (PDA) and Char syndrome. We performed mutation analysis of TFAP2B in 43 patients with isolated PDA, 7 patients with PDA with other congenital heart defects and 286 patients with isolated tooth agenesis with or without other dental anomalies. The heterozygous c.1006G>A mutation was identified in 20 individuals. Those mutation carriers consisted of 1 patient with term PDA (1/43), 16 patients with isolated tooth agenesis with or without other dental anomalies (16/286; 5.6%), 1 patient with PDA and severe valvular aortic stenosis and tooth agenesis (1/4) and 2 normal controls (2/100; 1%). The mutation is predicted to cause an amino-acid substitution p.Val336Ile in the TFAP2B protein. Tfap2b expression during early mouse tooth development supports the association of TFAP2B mutation and dental anomalies. It is hypothesized that this incidence might have been the result of founder effect. Here we report for the first time that TFAP2B mutation is associated with tooth agenesis, microdontia, supernumerary tooth and root maldevelopment. In addition, we also found that TFAP2B mutations, the common causes of PDA in Caucasian, are not the common cause of PDA in Thai population.