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.

A Mutation in CACNA1S Is Associated with Multiple Supernumerary Cusps and Root Maldevelopment.

BACKGROUND: Enamel knots and Hertwig epithelial root sheath (HERS) regulate the growth and folding of the dental epithelium, which subsequently determines the final form of tooth crown and roots. We would like to investigate the genetic etiology of seven patients affected with unique clinical manifestations, including multiple supernumerary cusps, single prominent premolars, and single-rooted molars. METHODS: Oral and radiographic examination and whole-exome or Sanger sequencing were performed in seven patients. Immunohistochemical study during early tooth development in mice was performed. RESULTS: A heterozygous variant (c. 865A>G; p.Ile289Val) in CACNA1S was identified in all the patients, but not in an unaffected family member and control. Immunohistochemical study showed high expression of Cacna1s in the secondary enamel knot. CONCLUSIONS: This CACNA1S variant seemed to cause impaired dental epithelial folding; too much folding in the molars and less folding in the premolars; and delayed folding (invagination) of HERS, which resulted in single-rooted molars or taurodontism. Our observation suggests that the mutation in CACNA1S might disrupt calcium influx, resulting in impaired dental epithelium folding, and subsequent abnormal crown and root morphology.

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.

Expression of R-spondins/Lgrs in development of movable craniofacial organs.

Wnt signaling plays a critical role in the development of many organs, including the major movable craniofacial organs tongue, lip, and eyelid. Four members of the R-spondin family (Rspo1-4) bind to Lgr4/5/6 to regulate the activation of Wnt signaling. However, it is not fully understood how Rspos/Lgrs regulate Wnt signaling during the development of movable craniofacial organs. To address this question, we examined the expression of Rspos, Lgrs, and Axin2 (major mediator of canonical Wnt signaling) during tongue, lip, and eyelid development. The expression of Axin2, Rspos and Lgrs was observed in many similar regions, suggesting that Rspos likely activate canonical Wnt signaling through the Lgr-dependent pathway in these regions. Lgr expression was not detected in regions where Axin2 and Rspos were expressed, suggesting that Rspos might activate canonical Wnt signaling through the Lgr-independent pathway in these regions. In addition, the expression of Rspos and Lgrs were observed in some other regions where Axin2 was not expressed, suggesting the possibility that Rspos and/or Lgrs are involved in non-canonical Wnt signaling or the Wnt-independent pathway. Thus, we identified a dynamic spatiotemporal expression pattern of Rspos and Lgrs during the development of the eyelid, tongue, and lip.

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.

MicroRNAs regulate distal region of mandibular development through Hh signaling.

Mandibular anomalies are often seen in various congenital diseases, indicating that mandibular development is under strict molecular control. Therefore, it is crucial to understand the molecular mechanisms involved in mandibular development. MicroRNAs (miRNAs) are noncoding small single-stranded RNAs that play a critical role in regulating the level of gene expression. We found that the mesenchymal conditional deletion of miRNAs arising from a lack of Dicer (an essential molecule for miRNA processing, Dicerfl/fl ;Wnt1Cre), led to an abnormal groove formation at the distal end of developing mandibles. At E10.5, when the region forms, inhibitors of Hh signaling, Ptch1 and Hhip1 showed increased expression at the region in Dicer mutant mandibles, while Gli1 (a major mediator of Hh signaling) was significantly downregulated in mutant mandibles. These suggest that Hh signaling was downregulated at the distal end of Dicer mutant mandibles by increased inhibitors. To understand whether the abnormal groove formation inDicer mutant mandibles was caused by the downregulation of Hh signaling, mice with a mesenchymal deletion of Hh signaling activity arising from a lack of Smo (an essential molecule for Hh signaling activation, Smofl/fl ;Wnt1Cre) were examined. Smofl/fl ;Wnt1Cre mice showed a similar phenotype in the distal region of their mandibles to those in Dicerfl/fl ;Wnt1Cre mice. We also found that approximately 400 miRNAs were expressed in wild-type mandibular mesenchymes at E10.5, and six microRNAs were identified as miRNAs with binding potential against both Ptch1 and Hhip1. Their expressions at the distal end of the mandible were confirmed by in situ hybridization. This indicates that microRNAs regulate the distal part of mandibular formation at an early stage of development by involving Hh signaling activity through controlling its inhibitor expression level.

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.

Molecular mechanisms in palatal rugae development.

BACKGROUND: Periodic patterning of iterative structures is diverse across the animal kingdom. Clarifying the molecular mechanisms involved in the formation of these structures helps to elucidate the genetic commonality of developmental processes, as organs with these structures are believed to share the same molecular mechanisms and fundamental processes. Palatal rugae are periodic corrugated structures on the hard palate and are conserved in all mammals. Although the numbers and patterns of the palatal rugae are species specific, they are consistent in each mammalian species, except humans. HIGHLIGHT: Palatal rugae development is thus under strict genetic control in most mammals and is an excellent model to investigate the genetic commonality of developmental processes to form periodic patterning. CONCLUSION: This review highlights the current understanding of the molecular mechanisms of palatal rugae development.

Ift88 is involved in mandibular development.

The mandible is a crucial organ in both clinical and biological fields due to the high frequency of congenital anomalies and the significant morphological changes during evolution. Primary cilia play a critical role in many biological processes, including the determination of left/right axis patterning, the regulation of signaling pathways, and the formation of bone and cartilage. Perturbations in the function of primary cilia are known to cause a wide spectrum of human diseases: the ciliopathies. Craniofacial dysmorphologies, including mandibular deformity, are often seen in patients with ciliopathies. Mandibular development is characterized by chondrogenesis and osteogenesis; however, the role of primary cilia in mandibular development is not fully understood. To address this question, we generated mice with mesenchymal deletions of the ciliary protein, Ift88 (Ift88fl/fl ;Wnt1Cre). Ift88fl/fl ;Wnt1Cre mice showed ectopic mandibular bone formation, whereas Ift88 mutant mandible was slightly shortened. Meckel's cartilage was modestly expanded in Ift88fl/fl ;Wnt1Cre mice. The downregulation of Hh signaling was found in most of the mesenchyme of Ift88 mutant mandible. However, mice with a mesenchymal deletion of an essential molecule for Hh signaling activity, Smo (Smofl/fl ;Wnt1Cre), showed only ectopic mandibular formation, whereas Smo mutant mandible was significantly shortened. Ift88 is thus involved in chondrogenesis and osteogenesis during mandibular development, partially through regulating Sonic hedgehog (Shh) signaling.

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.

Bmp signaling in molar cusp formation.

Tooth cusp is a crucial structure, since the shape of the molar tooth is determined by number, shape, and size of the cusp. Bone morphogenetic protein (Bmp) signaling is known to play a critical role in tooth development, including in initiation. However, it remains unclear whether Bmp signaling is also involved in cusp formation. To address this question, we examined cusp in two different transgenic mouse lines: mice with overexpression of Bmp4 (K14-Bmp4), and those with Bmp inhibitor, Noggin, (K14-Noggin) under keratin14 (K14) promoter. K14-Noggin mice demonstrated extra cusps, whereas reduced number of cusps was observed in K14-Bmp4 mice. To further understand how Bmps are expressed during cusp formation, we performed whole-mount in situ hybridisation analysis of three major Bmps (Bmp2, Bmp4, and Bmp7) in murine maxillary and mandibular molars from E14.5 to P3. The linear expressions of Bmp2 and Bmp4 were observed in both maxillary and mandibular molars at E14.5. The expression patterns of Bmp2 and Bmp4 became significantly different between the maxillary and mandibular molars at E16.5. At P3, all Bmps were expressed in all the cusp regions of the maxillary molar; however, the patterns differed. All Bmps thus exhibited dynamic temporo-spatial expression during the cusp formation. It could therefore be inferred that Bmp signaling is involved in regulating cusp formation.

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.

MicroRNAs control eyelid development through regulating Wnt signaling.

BACKGROUND: The timing, location, and level of gene expression are crucial for normal organ development, because morphogenesis requires strict genetic control. MicroRNAs (miRNAs) are noncoding small single-stranded RNAs that play a critical role in regulating gene expression level. Although miRNAs are known to be involved in many biological events, the role of miRNAs in organogenesis is not fully understood. Mammalian eyelids fuse and separate during development and growth. In mice, failure of this process results in the eye-open at birth (EOB) phenotype. RESULTS: It has been shown that conditional deletion of mesenchymal Dicer (an essential protein for miRNA processing; Dicer fl/fl ;Wnt1Cre) leads to the EOB phenotype with full penetrance. Here, we identified that the up-regulation of Wnt signaling resulted in the EOB phenotype in Dicer mutants. Down-regulation of Fgf signaling observed in Dicer mutants was caused by an inverse relationship between Fgf and Wnt signaling. Shh and Bmp signaling were down-regulated as the secondary effects in Dicer fl/fl ;Wnt1Cre mice. Wnt, Shh, and Fgf signaling were also found to mediate the epithelial-mesenchymal interactions in eyelid development. CONCLUSIONS: miRNAs control eyelid development through Wnt. Developmental Dynamics 248:201-210, 2019. © 2019 Wiley Periodicals, Inc.

Sox Genes Show Spatiotemporal Expression during Murine Tongue and Eyelid Development.

The tongue is a critical organ, involved in functions such as speaking, swallowing, mastication, and degustation. Although Sox genes are known to play critical roles in many biological processes, including organogenesis, the expression of the Sox family members during tongue development remains unclear. We therefore performed a comparative in situ hybridization analysis of 17 Sox genes (Sox1-14, 17, 18, and 21) during murine tongue development. Sox2, 4, 6, 8, 9, 10, 11, 12, and 21 were found to be expressed in the tongue epithelium, whereas Sox2, 4-6, 8-11, 13, and 21 showed expression in the mesenchyme of the developing tongue. Expression of Sox1, 4, 6, 8-12, and 21 were observed in the developing tongue muscle. Sox5 and 13 showed expression only at E12, while Sox1 expression was observed only on E18. Sox6, 8, 9, and 12 showed expression at several stages. Although the expression of Sox2, 4, 10, 11, and 21 was detected during all the four stages of tongue development, their expression patterns differed among the stages. We thus identified a dynamic spatiotemporal expression pattern of the Sox genes during murine tongue development. To understand whether Sox genes are involved in the development of other craniofacial organs through similar roles to those in tongue development, we also examined the expression of Sox genes in eyelid primordia, which also contain epithelium, mesenchyme, and muscle. However, expression patterns and timing of Sox genes differed between tongue and eyelid development. Sox genes are thus related to organogenesis through different functions in each craniofacial organ.

Lrp4/Wise regulates palatal rugae development through Turing-type reaction-diffusion mechanisms.

Periodic patterning of iterative structures is diverse across the animal kingdom. Clarifying the molecular mechanisms involved in the formation of these structure helps to elucidate the process of organogenesis. Turing-type reaction-diffusion mechanisms have been shown to play a critical role in regulating periodic patterning in organogenesis. Palatal rugae are periodically patterned ridges situated on the hard palate of mammals. We have previously shown that the palatal rugae develop by a Turing-type reaction-diffusion mechanism, which is reliant upon Shh (as an inhibitor) and Fgf (as an activator) signaling for appropriate organization of these structures. The disturbance of Shh and Fgf signaling lead to disorganized palatal rugae. However, the mechanism itself is not fully understood. Here we found that Lrp4 (transmembrane protein) was expressed in a complementary pattern to Wise (a secreted BMP antagonist and Wnt modulator) expression in palatal rugae development, representing Lrp4 expression in developing rugae and Wise in the inter-rugal epithelium. Highly disorganized palatal rugae was observed in both Wise and Lrp4 mutant mice, and these mutants also showed the downregulation of Shh signaling, which was accompanied with upregulation of Fgf signaling. Wise and Lrp4 are thus likely to control palatal rugae development by regulating reaction-diffusion mechanisms through Shh and Fgf signaling. We also found that Bmp and Wnt signaling were partially involved in this mechanism.

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.

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.

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.