gms | German Medical Science

Dreiländertagung D-A-CH
24. Wissenschaftliche Jahrestagung der Deutschen Gesellschaft für Phoniatrie und Pädaudiologie e. V.

Deutsche Gesellschaft für Phoniatrie und Pädaudiologie e. V.

28. - 30.09.2007, Innsbruck, Österreich

A novel IRF6 missense mutation (Y67X) in a German family with Van der Woude syndrome

Eine neubeschriebene IRF6 Missense Mutation (Y67X) in einer deutschen Familie mit Van der Woude Syndrom

Poster

  • corresponding author presenting/speaker Sibylle Brosch - Sektion für Phoniatrie und Pädaudiologie, Univ.-HNO-Klinik, Ulm, Germany
  • author Rudolf Reiter - Sektion für Phoniatrie und Pädaudiologie, Univ.-HNO-Klinik, Ulm, Germany
  • Manuela Baur - Univ.-HNO-Klinik, Tuebingen, Germany
  • Siegmar Reinert - Univ.-Klinik für Zahn-, Mund-, Kieferheilkunde, Tuebingen, Germany
  • Markus Pfister - Univ.-HNO-Klinik, Tuebingen, Germany

Deutsche Gesellschaft für Phoniatrie und Pädaudiologie. Sektion Phoniatrie der Österreichischen Gesellschaft für HNO-Heilkunde, Kopf- und Halschirugie. Schweizerische Gesellschaft für Phoniatrie. Dreiländertagung D-A-CH, 24. Wissenschaftliche Jahrestagung der Deutschen Gesellschaft für Phoniatrie und Pädaudiologie e.V.. Innsbruck, Österreich, 28.-30.09.2007. Düsseldorf: German Medical Science GMS Publishing House; 2007. Doc07dgppP08

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Veröffentlicht: 28. August 2007

© 2007 Brosch et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielf&aauml;ltigt, verbreitet und &oauml;ffentlich zug&aauml;nglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Abstract

Van der Woude syndrome (VWS) is the most common type of syndromic orofacial cleft, which accounts for approximately 2% of all cleft lip and palate cases. It is characterised by variable association of lower lip pits, cleft lip and cleft palate, and hypodontia. VWS arises as the result of mutations in the gene encoding interferon regulatory factor 6 (IRF6). IRF6 is a member of a family of transcription factors which is characterized by a highly conserved helix-turn-helix DNA binding domain and a less conserved protein binding domain called SMIR (Smad-interferon regulatory factor binding domain). The VWS-disorder is transmitted in an autosomal dominant manner, with high penetrance and variable expressivity. Very recently, mutations of the (IRF6) gene on exons 2-9 have been found in VWS patients, suggesting that this gene plays an important role in the orofacial development. The VWS locus was mapped to a 1.6-cM region in 1q32-q41 between D1S491 and D1S205, and a 4.4-Mb counting of YAC clones of this region was constructed [1]. Up to now, there are 70 known pathogenic mutations in the IRF6 gen. Most of them are located in the exons 4 and 7 encoding the conserved DNA binding and SMIR domains [2], [3].

We report a novel mutation of the IRF6 gene in a German family. Five out of 12 persons affected could be investigated. The mutation produces a stop codon within exon 4 of the IRF6 gene. All 5 patients were heterozygous for a base substitution c.201C>A changing the Tyrosine codon at amino acid position 67 into a stop codon (p.Y67X) in exon 4. The premature stop codon is responsible for a truncated protein lacking parts of the DNA binding domain and the complete SMIR domain probably essential for interactions with the Smad transcription factors.

We can conclude that the present data confirm the association between IRF6 and VWS proving the pathogenetic role of IRF6 mutations in this syndrome and the important role of the IRF6 gene in the orofacial development. Furthermore, we could report on a novel nonsense mutation in the DNA binding domain. We suggest that molecular analysis of VWS and PPS patients should be performed on the complete coding region of the IRF6 gene by direct sequencing because mutations can be distributed all over the whole gene.


Text

Introduction

Van der Woude syndrome (VWS) is the most common type of syndromic orofacial cleft, which accounts for approximately 2% of all cleft lip and palate cases. It is characterised by variable association of lower lip pits, cleft lip and cleft palate, and hypodontia. VWS arises as the result of mutations in the gene encoding interferon regulatory factor 6 (IRF6). The disorder is transmitted in an autosomal dominant manner, with high penetrance and variable expressivity. Very recently, mutations of the (IRF6) gene on exons 2-9 have been found in VWS patients, suggesting that this gene plays an important role in the orofacial development [1], [4].

Methods

A German family with five first-degree relatives affected with CLP and one simplex case were investigated. After informed consent, a sample of buccal cells was obtained from all these five family members. DNA was extracted using the Puregene DNA Isolation Kit (Gentra Systems) according to the manufacturer's instructions. Exons 2-9, containing the coding region of IRF6, were amplified with primers already published before [5]. The sequences were compared with GenBank No. NT_021877 using the CEQ 8000 software (Beckman Coulter).

Results

A nine month old baby girl with unilateral cleft lip and palate and bilateral lower lip fistulas was referred for phoniatric assessment. Her mother also had VWS with similar fistulas, but with the clefts confined to the right side. Within the family, a sister of the mother had isolated lower lip pit, and a brother and a nephew bilateral lip and palate clefts with lower lip pits. The simplex case was a 2 year old boy with VWS (bilateral CLP and bilateral lower lip pits).

We sequenced exons 2-9 including all coding exons of the IRF6 gene as well as the flanking intronic regions in the simplex case and one member of the family. This approach led to the identification of one primarily non-described missense mutation, one nonsense mutation and two single nucleotide polymorphisms (SNP). In the sporadic case a heterozygous missense mutation in exon 4 could be identified. This mutation c.251G>A (p.R84H) has already been described [6]. Furthermore, this patient carried a c.459G>T transition at codon 153 in exon 5 not leading to an amino acid change. This sequence variant has also been reported before (refSNP ID: rs2013162). All 5 patients with the familial context were heterozygous for a base substitution c.201C>A changing the Tyrosine codon at amino acid position 67 into a stop codon (p.Y67X) in exon 4. One of our patients also carried the c.459G>T transition in a homozygous state and moreover, we found a homozygous change from C to G in intron 6 (refSNP ID: rs11811534). In all other affected members of the family we only analyzed exon 4. We found that all of them carried the p.Y67X disease causing mutation in a heterozygous state.

Discussion

We described a sporadic case and a new family with autosomal dominantly inherited VWS. The sporadic patient carried the p.R84H mutation in exon 4 of the IRF6 gene, leading to an amino acid change from Arginine to Histidine at amino acid position 84. This mutation was formerly described to cause popliteal pterygium syndrome (PPS) [7]. Due to the fact that this is the first case of VWS in the family, de novo mutation has to be assumed. We also found a novel mutation in the IRF6 gene. All of the available affected members of the family carried the p.Y67X mutation in exon 4. This mutation changes a Tyrosine codon into a stop codon at amino acid position 67. The premature stop codon is responsible for a truncated protein lacking parts of the well conserved DNA binding domain and the complete SMIR domain probably essential for interactions with the Smad transcription factors. The mutation produced different phenotypes within our family. This is a strong hint for at least one modifying gene [7].

We can conclude that the present data confirm the association between IRF6 and VWS proving the pathogenetic role of IRF6 mutations in this syndrome and the important role of the IRF6 gene in the orofacial development. We suggest that molecular analysis of VWS and PPS patients should be performed on the complete coding region of the IRF6 gene by direct sequencing because mutations can be distributed all over the whole gene.


References

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