Identification of a novel missense mutation of MSX1 gene in Chinese family with autosomal-dominant oligodontia

Identification of a novel missense mutation of MSX1 gene in Chinese family with autosomal-dominant oligodontia

archives of oral biology 53 (2008) 773–779 available at www.sciencedirect.com journal homepage: www.intl.elsevierhealth.com/journals/arob Identific...

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archives of oral biology 53 (2008) 773–779

available at www.sciencedirect.com

journal homepage: www.intl.elsevierhealth.com/journals/arob

Identification of a novel missense mutation of MSX1 gene in Chinese family with autosomal-dominant oligodontia Kun Xuan a, Fang Jin b, Yan-Li Liu c, Lin-Tian Yuan a, Ling-Ying Wen a, Fu-Sheng Yang a, Xiao-Jing Wang a, Guo-Hua Wang c, Yan Jin d,* a

Department of Pediatric Dentistry, School of Stomatology, Fourth Military Medical University, 145 West Changle Road, Xi’an 710032, PR China b Department of Orthodontics, School of Stomatology, Fourth Military Medical University, 145 West Changle Road, Xi’an 710032, PR China c Department of Biochemistry and Molecular Biology, Fourth Military Medical University, 17 West Changle Road, Xi’an 710032, PR China d Department of Oral Histology & Pathology, School of Stomatology, Fourth Military Medical University, 145 West Changle Road, Xi’an 710032, PR China

article info

abstract

Article history:

Objectives: Oligodontia is defined as the congenital absence of 6 or more permanent teeth

Accepted 16 February 2008

excluding the third molar. The occurrence of non-syndromic still remains poorly understood, but in recent years some cases have been reported where mutations or polymorph-

Keywords:

isms of PAX9 and MSX1 had been associated with non-syndromic oligodontia. The objective

Autosomal-dominant non-

of the present work was to study the phenotype and genotype of three generations of a Han

syndromic oligodontia

Chinese family affected by non-syndromic autosomal-dominant oligodontia.

MSX1

Design: We examined all individuals of the oligodontia family by clinical and radiographic

Missense mutation

examinations. Based on clinical manifestations, candidate genes MSX1 and PAX9 were picked up to analyse and screen mutations. Results: Dental evaluation showed that the most commonly missing teeth are the mandibular second premolars, followed by the maxillary second premolars and maxillary lateral incisors, and subsequently the maxillary first premolars. The probability of missing a particular type of tooth is not always bilaterally symmetrical, and differences exist between maxilla and mandible. PCR-SSCP analysis and DNA sequencing revealed a novel missense mutation c.662C>A in a highly conserved homeobox sequence of MSX1 and a known polymorphisms c.347C>G. Conclusion: Our finding suggests the missense transversion (c.662C>A) and the polymorphisms (c.347C>G) may be responsible for oligodontia phenotype in this Chinese family. # 2008 Elsevier Ltd. All rights reserved.

1.

Introduction

Congenital anomalies in number, size, shape, and structure of teeth are among the well-recognised morphologic anomalies

in humans. Congenital lack of one or more teeth is a common anomaly in man. The congenital lack of teeth has interested dentists for a long time. Arte and Pirinen have defined that the absence of one to six, more than six, and complete absence of

* Corresponding author. Tel.: +86 29 84776147; fax: +86 29 83218039. E-mail address: [email protected] (Y. Jin). 0003–9969/$ – see front matter # 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.archoralbio.2008.02.012

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teeth have been termed hypodontia, oligodontia and anodontia, respectively.1,2 Moreover, teeth agenesis is classified as isolated/non-syndromic and syndromic missing teeth. In the majority of cases tooth agenesis has a genetic basis, though tooth agenesis is also occasionally caused by environmental factors (trauma, chemotherapy and radiation therapy, use of thalidomide during pregnancy).2,3 In recent years, our knowledge of the genes involved in tooth agenesis has increased. The isolated/non-syndromic tooth agenesis has been associated with mutations or polymorphisms of MSX1, PAX9, and AXIN2.4–7 But the genetic etiology for syndromic tooth agenesis is poorly understood. More than 150 syndromes with tooth agenesis are included in British dysmorphology database. Some best known of these syndromes, cleft lip/palate,8 Van der Woude syndrome,9 ectodermal dysplasias,10 Axenfeld–Rieger syndrome,11 He– Zhao deficiency,12 Down syndrome13 and Wolf–Hirschhorn syndrome14, have been shown to be due to the mutations of MSX1,8 IRF6,9 EDA,10 PITX2,11 KROX-26/ZNF22,12 and deletions of a critical portion of chromosome 21(21q22.3)13 and chromosome 4(4p16.3),14 respectively. Isolated oligodontia has a prevalence of 0.08–0.16% in some studies.15 The type of inheritance in the majority of families seems to be autosomal-dominant with incomplete penetrance and variable expressivity. Variability in expression includes the number and region of missing teeth, and various other dental features associated with the trait.16 The obscure mechanisms underlying congenital lack of teeth and the differing results of genetic studies have drawn attention to the phenotypic and genotypic variation in this phenomenon. Prior to this report, It has been reported that some different MSX1 defects could cause multiple congenitally missing teeth or oligodontia, such as p.R196P,5 p.M61K,17 p.A194V,18 p.A219T19 and the frameshift mutations of G22RfsX168.20 Patients with MSX1-associated oligodontia were more preferentially to be missing maxillary and mandibular second bicuspids and maxillary first bicuspids. More recently, PAX9 mutations responsible for oligodontia were identified, including missense mutation p.M1V21 and p.R26W,22 nonsense mutation p.K114X4 and p.Q145X,23 frameshift mutations I37fsX4124 and I207fsX211.6 Patients with PAX9 defects were more likely to be missing maxillary first molars, maxillary second molars, and mandibular second molars. Asians, in particular Chinese, have a higher prevalence of oligodontia. However, reported mutations underlying non-syndromic oligodontia in Chinese patients are limited. Thus, the objective of the present study was to identify the mutation responsible for the familial tooth agenesis in our kindred and to identify genotype/phenotype correlations that could improve our understanding of better prioritise candidate genes based upon the pattern of partial tooth agenesis.

2.

Materials and methods

2.1.

Patient and controls

The present study was reviewed and approved by Institutional Review Board and the Ethics Committee at Fourth Military Medical University and was conducted under the written

consent of all participants. The male proband was a patient of Department of Pediatric Dentistry, School of Stomatology, Fourth Military Medical University in PR China. A pedigree of his family was made by clinical examinations and interviews with all available family members and the diagnosis of oligodontia was verified by panoramic dental radiographs. Furthermore, 50 unrelated individuals, who were not affected with tooth agenesis (excluding third molars), were used as controls.

2.2.

DNA extraction and PCR of candidate genes

Blood samples were collected from all members of the family and controls. Genomic DNA was extracted from these samples by means of QIAamp DNA Blood Mini Kit (Qiagen, USA). Two exons of MSX1 were PCR amplified with the use of primer pairs, as previously published.20 The PCR primers for exon 1, MSX1x1F (50 -CTGGCCTCGCCTTATTAGC-30 ) and MSX1x1R (50 GCCTGGGTTCTGGCTACTC-30 ), used an annealing temperature of 58 8C and generated a 766-bp amplification product. The primers for exon 2, MSX1x2F (50 -ACTTGGC GGCACTCAATATC-30 ) and MSX1x2R (50 -CAGGGAGCAAAGAGGTGAAA-30 ), had an annealing temp of 57 8C and generated a 698-bp product. PCR amplifications used the Platinum1 Taq DNA polymerase (Invitrogen, USA), and 10% DMSO was added for exon 1 amplification. Moreover, the 4 exons of PAX9 were also amplified with the use of 6 sets of designed primers (sequence of primers and conditions available on request), as previously reported.21

2.3.

Screening for mutations and sequencing

In order to screen for mutations, amplified fragments were subjected to single-stranded conformational polymorphism (SSCP) analysis. The PCR samples, mixed with formamide dye (95% formamide with 0.05% bromophenol blue and xylenecyanol), were heated to 100 8C for 10 min, quenched on ice for 10 min, and then loaded onto a 12.5% non-denaturant polyacrylamide gel (including 5% glycerol). Electrophoresis was performed with the conditions of 150 V, at 15 8C for 6 h. After electrophoresis, the gel was silver-stained to detect abnormal band shift. The amplified fragments of MSX1 and PAX9 in all affected individuals were gel-purified by means of E.Z.N.A. Gel Extraction Kit (Omega, USA) according to the manufacture’s protocol. Sequencing analyses were performed by ABI BigDyeTM terminator cycle sequencing ready reaction kit with AmpliTaq DNA polymerase on the ABI PRISMTM 377XL DNA sequencer (Applied Biosystems, USA).

3.

Results

3.1.

Clinical examination

The proband was a 8-year-old boy, who first visited the pediatric dental clinic for suffering from late eruption of permanent teeth. He was diagnosed for congenital oligodontia because of missing 17 permanent teeth. The pedigree reflected an autosomal-domain pattern of transmission and variable expression (Fig. 1). Clinical and radiographic

archives of oral biology 53 (2008) 773–779

775

Fig. 1 – (A) Pedigree of the family. (B) Panoramic radiograph shows that proband’s grandfather (I:1) was missing 9 teeth at the age of 52 years. (C) Panoramic radiograph shows that proband’s mother (II:1) was missing 13 teeth at the age of 31 years. (D) Panoramic radiograph show that proband’s uncle (II:4) was missing 9 teeth at the age of 18 years. (E) Panoramic radiograph show that proband (III:1) was missing 17 teeth at the age of 8 years.

examinations revealed that other members of his family (I:1, II:1, II:4) lacked 9, 13, 9 permanent teeth, respectively (Table 1). The proband (III:1) lacked all incisors, most of canines, all third molars, and lower second premolars (Fig. 1E). His grandfather (I:1) lacked all second premolars and left upper first premolar, and all third molars. The peg-shaped upper lateral incisors and impacted upper canine were observed (Fig. 1B). His mother (II:1) lacked both upper lateral incisors and canines, all second premolars except left upper second premolars, all upper second molars, and all third molars (Fig. 1C). His uncle (II:4) was missing all second premolars except left lower second premolars, right upper 1st premolars, lateral incisor and all third molars (Fig. 1D). In this kindred, the probability of missing a particular type of tooth is not always bilaterally symmetrical, and differences exist between maxilla and mandible. But the most commonly missing teeth are the mandibular second premolars, followed by the maxillary second premolars and maxillary lateral incisors and subsequently the maxillary first premolars. The findings are in agreement with previous reports on frequency of tooth loss with MSX1 mutations.17,20 In this family, all individuals have presented normal physical development and normal intelligence, and clinical examination for other ectodermal abnormalities of nails, hair, skin and sweat glands as well as for craniofacial and ocular malformations, including orofacial clefts and glaucoma, did not reveal any

defects in all family members. So we suggested that the family might show non-syndromic oligodontia.

3.2.

Mutation analysis

In the family with non-syndromic oligodontia, the abnormal mobility of single-stranded fragments of DNA was demonstrated upon SSCP analysis of the amplified fragment of exon 2 of MSX1 (Fig. 2A). An abnormal pattern is detected in the affected individuals (I:1, II:1, II:4, and III:1) but not in the unaffected family members (I:2, II:2, II:3) and unrelated control individuals. But we did not find the abnormal mobility of four exons of PAX9. More specifically, sequencing analysis of proband and his mother revealed a novel mutation c.662C>A localised in a conserved homeobox sequence, which results in alanine to glutamic acid substitution at 221st amino acid (Fig. 2B and C). In addition, DNA sequencing showed that the novel mutation was present in heterozygous state, not only in proband but also in the other affected family members. These results further confirmed SSCP analysis of MSX1 gene among the family. In the healthy members of the analysed family, as well as in 50 unrelated control individuals, this mutation was not detected (Fig. 2D). Furthermore, we screened 4 exons of PAX9 and found no mutations in coding regions. Moreover, we found a known polymorphism of MSX1 (c.347C>G) in some family members (Fig. 2E). No other mutations in coding regions

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Table 1 – Summary of congenitally missing teeth in family ID number

Right 8

a

7

6

5

I-1 Maxillary Mandibular

* *

II-1 Maxillary Mandibular

* *

II-4 Maxillary Mandibular

* *

* *

III-1 Maxillary Mandibular

* *

*

Left 4

3

2

1

1

2

3

* *

*

* *

*

*

*

4

5

*

* *

*

*

* *

* *

*

* *

* *

* *

*

7

*

8 * *

* *

*

6

* *

* *

* *

a

1, Central incisor; 2, lateral incisor; 3, canine; 4 and 5, first and second premolars, respectively; 6, 7, and 8, first, second, and third molars, respectively.

of MSX1 were identified. This sequence variant should be associated with oligodontia in the investigated family, since it was presented in the affected but not in the unaffected individuals.

4.

Discussion

We collected a family in which oligodontia was segregating in an autosomal-dominant manner in order to define clinical features of oligodontia and to localise the gene locus behind this anomaly. Our clinical examinations and interviews of the kindred revealed all affected members were missing more than 6 teeth and had not the other systemic abnormality. They were diagnosed for non-syndromic oligodontia. As causative genes, MSX1 and PAX9 have been confirmed by the observation that mutations of these genes cause familial and sporadic forms of selective tooth agenesis.25–27 PAX9 defect was shown to be responsible for ‘‘molar oligodontia’’.28 In contrast, the developmental absence of maxillary and mandibular second bicuspids and maxillary first bicuspids, whilst most mandibular first bicuspids are retained, appears to be the pattern of tooth agenesis that best indicates the presence of an MSX1 mutation.20 In the family, our findings are in agreement with previous reports on frequency of tooth loss with MSX1 mutations. Furthermore, we have identified a MSX1 missense mutation (c.662C>A) localised in exon 2 of MSX1 gene from all affected members. The novel heterozygous transition found in MSX1 might be responsible for selective tooth agenesis, including premolars and third molar of all affected individuals, lateral incisors and canines of proband (III:1) and his mother (II:1), occasionally second molars of II:1 and central incisors of III:1. Moreover, our finding further supported these criteria as being able to distinguished accurately between MSX1 and PAX9 mutations, based upon the dental phenotype. In our MSX1 kindred, missing third molars were observed in affected and unaffected individuals and were considered to be part of the genetic background. This finding confirms the views that haploinsufficiency of MSX1 protein preferentially affects the development of third molars and second pre-

molars.4 Whilst the reason for these particular teeth to be affected is unknown, it is probably related to the developmental sequence of tooth formation. It is suggested that those teeth that develop latest are less stable and do not reach a critical threshold at an early stage of development. Moreover, our finding shows that the probability of missing a particular type of tooth is not always bilaterally symmetrical, and differences exist between maxilla and mandible. We suggest that they are different expression of a dominant autosomal gene. The presence of impacted upper canine and peg-shaped upper lateral incisor were observed in the family member (I:1) affected by congenital missing teeth. It is considered to represent a different phenotypical expression from congenital teeth agenesis caused by the same dominant autosomal gene with reduced penetrance. Mutations of MSX1 have been associated not only with the isolated teeth agenesis (hypodontia and oligodontia), but also with the syndromic teeth loss combining with cleft lip, cleft palate, or Witkop syndrome.29,30 Moreover, the chromosomal abnormality could cause agenesis of many permanent teeth. Wolf–Hirschhorn syndrome is a malformation syndrome caused by deletions of the distal short arm of chromosome 4 (4p16.3), which is characterised by severe growth and psychomotor retardation, microcephaly, cleft lip or palate, coloboma of the eye, cardiac septal defects, and teeth agenesis. The deletions are found to be a gene-dense region, and the MSX1 gene is located nearby.31 Some reports indicated that mutation position or polymorphisms of MSX1 might constitute risk factors for variable phenotype of isolated or syndromic teeth agenesis.32 To date, some MSX1 defects, including missense mutations in the homeobox domain and a frameshift mutation, were reported to be responsible for isolated oligodontia (Fig. 3). The homeodomain consisting of 60 amino acids (166–225) is subdivided into the N-terminal arm (NT arm) and helices I, II and III. Those missense mutations could affect protein stability, DNA binding specificity, protein expression and interactions. In this family, a novel point mutation c.662C>A also localised in the conserved homeobox sequence. This mutation resulting in Ala221Glu substitution is localised at the third helix of the highly conserved

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Fig. 2 – (A) SSCP analysis of exon 1 of the MSX1 gene from the family individuals and a normal control. An abnormal pattern is detected in the affected individuals (I:1, II:1, II:4, and III:1) but not in the unaffected family members (I:2, II:2, II:3) and unrelated control individual. (B and C) Sequencing chromatograph of genomic DNA from proband and his mother (III:1, II:1) are showed. Arrow indicated the position of the heterozygous mutation (c.662C>A, p.221A>E). Mut, mutation; Wt, wildtype. (D) This mutation was not observed in the wild-type (Wt) MSX1gene in the unaffected members of the pedigree. (E) A known polymorphisms of MSX1 (c.347C>G) was found in some family members (I:1, II:1, II:4, and III:1). Arrow indicated the position of the single nucleotide polymorphism (SNP).

homeodomain (amino acids 207–225). The helix III of the MSX1 homeodomain is important for DNA binding and DLX interaction. The Ala221Glu mutation may alter normal MSX1 function by a variety of mechanisms. Msx and Dlx proteins could form heterodimeric complexes to involve in epithelial–mesenchymal signaling cascades of odontogenesis via functional antagonism.33 Many genes have been identified to be expressed in the mammalian developing tooth, which include growth factors, transcription factors, receptors, signaling molecules, plasma membrane molecules and so on. The spatial and temporal expression pattern of these molecules forms a signaling network that regulates odontogenesis. The homeobox-containing genes, including MSXs, Paxs, Dlxs, Barxs, Lhxs, are the specific regulators in teeth patterning. Functional analysis, using gene targeting and transgenic technique, have hitherto revealed the critical role of these genes in the development. Defect of LIM homeodomain protein Islet1 (Isl1) may result in inhibition of incisor development, and knockout of Barx1 can lead to arrested molar development. Msx1 can maintain Isl1 and Barx1 function by Bmp4 pathway.34,35 Pax9 is able to directly regulate Msx1 expression and interact with Msx1 at the protein level to enhance its ability to transactivate Msx1 and Bmp4 pathway during tooth development.36,37 Dlxs can interact with Msx1 to control early morphogenesis of teeth. If this certain network consisting of these genes is disturbed,

selective tooth agenesis will occur. But it needs further study on the etiology and pathogenesis of ‘‘premolar oligodontia’’ resulted by MSX1 defects and ‘‘molar oligodontia’’ associated with PAX9 defect. Recently, it has been suggested that not only mutations in PAX9 and MSX1 but also that of other unidentified genes are involved in human tooth agenesis.38 Moreover, we found a known polymorphism (c.347C>G) in some affected and healthy members of the investigated family. Some reports showed polymorphism for MSX1 produced an increased risk for organ anomalies by a gene– environment interaction.39 Our study suggest that the missense transversion (c.662C>A) and the polymorphisms

Fig. 3 – Genomic structure, functional domains and mutations in the MSX1 gene associated with oligodontia. The arrowheads point to the approximate positions of identified mutations in previous studies (581C>T, 587G>C, 620T>A, 655G>A, 62dupG) and our study (662C>A).

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(c.347C>G) should be responsible for oligodontia phenotype in this Chinese family.

Acknowledgements We are grateful to the patients and their family members for their kind cooperation and participation, and to the members of Department of Oral Histology and Pathology in Fourth Military Medical University for their excellent technical assistance. The study is supported by National Natural Science Foundation of China (No. 30600709).

references

1. Arte S, Nieminen P, Apajalahti S, Haavikko K, Thesleff I, Pirinen S. Characteristics of incisor-premolar hypodontia in families. J Dent Res 2001;80:1445–50. 2. Arte S, Pirinen S. Hypodontia. Orphanet encyclopedia (http://www.orpha.net/data/patho/GB/uk-hypodontia.pdf). 3. Na¨sman M, Forsberg C-M, Dahllo¨f G. Long-term dental development in children after treatment for malignant disease. Eur J Orthod 1997;19:151–9. 4. Nieminen P, Arte S, Tanner D, Paulin L, Alaluusua S, Thesleff I. Identification of a nonsense mutation in the PAX9 gene in molar oligodontia. Eur J Hum Genet 2001;9: 743–7. 5. Vastardis H, Karimbux N, Guthua SW, Seidman JG, Seidman CE. A human MSX1 homeodomain missense mutation causes selective tooth agenesis. Nat Genet 1996;13: 417–21. 6. Mostowska A, Biedziak B, Trzeciak WH. A novel mutation in PAX9 causes familial form of molar oligodontia. Eur J Hum Genet 2006;14:173–9. 7. Lammi L, Arte S, Somer M, Jarvinen H, Lahermo P, Thesleff I, et al. Mutations in AXIN2 cause familial tooth agenesis and predispose to colorectal cancer. Am J Hum Genet 2004;74:1043–50. 8. Van den Boogaard MJ, Dorland M, Beemer FA, van Amstel HK. MSX1 mutation is associated with orofacial clefting and tooth agenesis. Nat Genet 2000;24:342–3. 9. Ye XQ, Jin HX, Shi LS, Fan MW, Song GT, Fan HL, et al. Identification of novel mutations of IRF6 gene in Chinese families with Van der Woude syndrome. Int J Mol Med 2005;16:851–6. 10. Tao R, Jin B, Guo SZ, Qing W, Feng GY, Brooks DG, et al. A novel missense mutation of the EDA gene in a Mongolian family with congenital hypodontia. J Hum Genet 2006;51: 498–502. 11. Martinez-Glez V, Lorda-Sanchez I, Ramirez JM, Ruiz-Barnes P, Rodriguez de Alba M, Diego-Alvarez D, et al. Clinical presentation of a variant of Axenfeld–Rieger syndrome associated with subtelomeric 6p deletion. Eur J Med Genet 2007;50:120–7. 12. Gao Y, Kobayashi H, Ganss B. The human KROX-26/ZNF22 gene is expressed at sites of tooth formation and maps to the locus for permanent tooth agenesis (He-Zhao deficiency). J Dent Res 2003;82:1002–7. 13. Shapira J, Chaushu S, Becker A. Prevalence of tooth transposition, third molar agenesis, and maxillary canine impaction in individuals with Down syndrome. Angle Orhod 2000;70:290–6. 14. Johnston NJ, Franklin DL. Dental findings of a child with Wolf–Hirschhorn syndrome. Int J Paediatr Dent 2006;16: 139–42.

15. Rolling S, Poulsen S. Oligodontia in Danish school children. Acta Odontol Scand 2001;59:111–2. 16. Hu G, Vastardis H, Bendall AJ, Wang Z, Logan M, Zhang H, et al. Haploinsufficiency of MSX1: a mechanism for selective tooth agenesis. Mol Cell Biol 1998;18:6044–51. 17. Lidral AC, Reising BC. The role of MSX1 in human tooth agenesis. J Dent Res 2002;81:274–8. 18. Mostowska A, Biedziak B, Trzeciak WH. A novel c.581C>T transition localized in a highly conserved homeobox sequence of MSX1: is it responsible for oligodontia? J Appl Genet 2006;47:159–64. 19. Chishti MS, Muhammad D, Haider M, Ahmad W. A novel missense mutation in MSX1 underlies autosomal recessive oligodontia with associated dental anomalies in Pakistani families. J Hum Genet 2006;51:872–8. 20. Kim JW, Simmer JP, Lin BP, Hu JC. Novel MSX1 frameshift causes autosomal-dominant oligodontia. J Dent Res 2006;85:267–71. 21. Klein ML, Nieminen P, Lammi L, Niebuhr E, Kreiborg S. Novel mutation of the initiation codon of PAX9 causes oligodontia. J Dent Res 2005;84:43–7. 22. Lammi L, Halonen K, Pirinen S, Thesleff I, Arte S, Nieminen P. A missense mutation in PAX9 in a family with distinct phenotype of oligodontia. Eur J Hum Genet 2003;11:866–71. 23. Hansen L, Kreiborg S, Jarlov H, Niebuhr E, Eiberg H. A novel nonsense mutation in PAX9 is associated with marked variability in number of missing teeth. Eur J Oral Sci 2007;115:330–3. 24. Zhao JL, Chen YX, Bao L, Xia QJ, Wu TJ, Zhou L. Novel mutations of PAX9 gene in Chinese patients with oligodontia. Zhonghua Kou Qiang Yi Xue Za Zhi 2005;40:266– 70. 25. Jumlongras D, Lin JY, Chapra A, Seidman CE, Seidman JG, Maas RL. A novel missense mutation in the paired domain of PAX9 causes non-syndromic oligodontia. Hum Genet 2004;114:242–9. 26. De Muynck S, Schollen E, Matthijs G, Verdonck A, Devriendt K, Carels C. A novel MSX1 mutation in hypodontia. Am J Med Genet 2004;128:401–3. 27. Mostowska A, Kobielak A, Trzeciak WH. Molecular basis of non-syndromic tooth agenesis: mutations of MSX1 and PAX9 reflect their role in patterning human dentition. Eur J Oral Sci 2003;111:365–70. 28. Tallo´n-Walton V, Manzanares-Ce´spedes MC, Arte S, Carvalho-Lobato P, Valdivia-Gandur I, Garcia-Susperregui A, et al. Identification of a novel mutation in the PAX9 gene in a family affected by oligodontia and other dental anomalies. Eur J Oral Sci 2007;115:427–32. 29. Jumlongras D, Bei M, Stimson JM, Wang WF, DePalma SR, Seidman CE. A nonsensemutation in MSX1 causes Witkop syndrome. Am J Hum Genet 2001;69:67–74. 30. Jezewski PA, Vieira AR, Nishimura C, Ludwig B, Johnson M, O’Brien SE. Complete sequencing shows a role for MSX1 in non-syndromic cleft lip and palate. J Med Genet 2003;40:399– 407. 31. Wright TJ, Ricke DO, Denison K, Abmayr S, Cotter PD, Hirschorn K, et al. A transcript map of the newly defined 165 kb Wolf–Hirschhorn syndrome critical region. Hum Mol Genet 1997;6:317–24. 32. Fallin MD, Hetmanski JB, Park J, Scott AF, Ingersoll R, Fuernkranz HA, et al. Family-based analysis of MSX1 haplotypes for association with oral clefts. Genet Epidemiol 2003;25:168–75. 33. Zhang H, Hu G, Wang H, Sciavolino P, Iler N, Shen MM, et al. Heterodimerization of Msx and Dlx homeoproteins results in functional antagonism. Mol Cell Biol 1997;17:2920–32. 34. Mitsiadis TA, Angeli I, James C, Lendahl U, Sharpe PT. Role of Islet1 in the patterning of murine dentition. Development 2003;130:4451–60.

archives of oral biology 53 (2008) 773–779

35. Song Y, Zhang Z, Yu X, Yan M, Zhang X, Gu S, et al. Application of lentivirus-mediated RNAi in studying gene function in mammalian tooth development. Dev Dynam 2006;235:1334–44. 36. Ogawa T, Kapadia H, Feng JQ, Raghow R, Peters H, D’Souza RN. Functional consequences of interactions between Pax9 and Msx1 genes in normal and abnormal tooth development. J Biol Chem 2006;281:18363–9.

779

37. Ogawa T, Kapadia H, Wang B, D’Souza RN. Studies on Pax9–Msx1 protein interactions. Arch Oral Biol 2005;50: 141–5. 38. Kapadia H, Mues G, D’Souza R. Genes affecting tooth morphogenesis. Orthod Craniofac Res 2007;10:105–13. 39. Carmichael SL, Shaw GM, Yang W, Lammer EJ, Zhu H, Finnell RH. Limb deficiency defects, MSX1, and exposure to tobacco smoke. Am J Med Genet A 2004;125:285–9.