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STUDY DESIGN: Mutation analysis of a candidate disease gene in a cohort of patients with moderate to severe Adolescent idiopathic scoliosis (AIS).OBJECTIVE: To investigate if damaging mutations in the planar cell polarity gene VANGL1 could be identified in AIS patients.SUMMARY OF BACKGROUND DATA: AIS is a spinal deformity which occurs in 1-3% of the population. The cause of AIS is often unknown, but genetic factors are important in the etiology. Rare variants in genes encoding regulators of WNT/planar cell polarity (PCP) signaling were recently identified in AIS patients.METHODS: We analyzed the coding region of the VANGL1 gene for mutations using Sanger sequencing in 157 unrelated patients with moderate to severe AIS. The frequency of mutations in the patient cohort was compared with their frequency in a large cohort of controls. Functional effect of mutations were predicted in silico and analyzed in vitro by transfection of normal and mutant recombinant VANGL1 protein in Madin-Darby Canine Kidney (MDCK) cells. Cellular localization of recombinant proteins was analyzed by immunofluorescence microscopy analysis.RESULTS: In the patient cohort we identified two rare missense mutations in VANGL1, encoding a receptor involved in WNT/PCP signalling. The mutations, p.I136N and p.F440 V are very rare in the normal population. Both mutations are predicted to be damaging, and to affect evolutionary conserved amino acid residues of VANGL1. Functional analysis in MDCK cells showed that the mutations abolished the normal translocation of VANGL1 to the cell membrane.CONCLUSION: Our data support that mutations in genes involved in WNT/PCP signalling may be associated with AIS, but replication in other patient cohorts and further analysis of the role of WNT/PCP signalling in AIS is needed.LEVEL OF EVIDENCE: 4.

Laurin-Sandrow syndrome (LSS) is a rare autosomal dominant disorder characterized by polysyndactyly of hands and/or feet, mirror image duplication of the feet, nasal defects, and loss of identity between fibula and tibia. The genetic basis of LSS is currently unknown. LSS shows phenotypic overlap with Haas type polysyndactyly (HTS) regarding the digital phenotype. Here we report on five unrelated families with overlapping microduplications encompassing the Sonic hedgehog (SHH) limb enhancer ZRS on chromosome 7q36. Clinically, the patients show polysyndactyly phenotypes and various types of lower limb malformations ranging from syndactyly to mirror image polydactyly with duplications of the fibulae. We show that larger duplications of the ZRS region (> 80 kb) are associated with HTS, whereas smaller duplications (< 80 kb) result in the LSS phenotype. Based on our data, the latter can be clearly distinguished from HTS by the presence of mirror image polysyndactyly of the feet with duplication of the fibula. Our results expand the clinical phenotype of the ZRS-associated syndromes and suggest that smaller duplications (<75 kb) are associated with a more severe phenotype. In addition, we show that these small microduplications within the ZRS region are the underlying genetic cause of Laurin-Sandrow syndrome.

Udgivelsesdato: 2010-Jun, A cis-regulatory sequence also known as zone of polarizing activity (ZPA) regulatory sequence (ZRS) located in intron 5 of LMBR1 is essential for expression of sonic hedgehog (SHH) in the developing posterior limb bud mesenchyme. Even though many point mutations causing preaxial duplication defects have been reported in ZRS, the underlying regulatory mechanism is still unknown. In this study, we analyzed the effect on transcription factor binding of a novel ZRS point mutation (463T>G) in a Pakistani family with preaxial polydactyly and triphalangeal thumb. Electrophoretical mobility shift assay demonstrated a marked difference between wild-type and the mutant probe, which uniquely bound one or several transcription factors extracted from Caco-2 cells. This finding supports a model in which ectopic anterior SHH expression in the developing limb results from abnormal binding of one or more transcription factors to the mutant sequence.

Udgivelsesdato: 2009-Jul

The ADULT syndrome (Acro-Dermato-Ungual-Lacrimal-Tooth, OMIM 103285) is a rare ectodermal dysplasia associated with limb malformations and caused by heterozygous mutations in p63. ADULT syndrome has clinical overlap with other p63 mutation syndromes, such as EEC (OMIM 604292), LMS (OMIM 603543), AEC (106260), RHS (129400) and SHFM4 (605289). ADULT syndrome characteristics are ectrodactyly, ectodermal dysplasia, mammary gland hypoplasia and normal lip and palate. The latter findings allow differentiation from EEC syndrome. LMS differs by milder ectodermal involvement. Here, we report three new unrelated ADULT syndrome families, all with mutations of arginine 298. On basis of 16 patients in five families with R298 mutation, we delineate the ADULT syndrome phenotype. In addition, we have documented a gain-of-function effect on the dNp63gamma isoform caused by this mutation. We discuss the possible relevance of oral squamous cell carcinoma in one patient, who carries this p63 germline mutation.

Udgivelsesdato: 2005-Aug-30, We report on a father and a son with nasal and limb defects characteristic of Laurin-Sandrow syndrome (LSS) excluding for the first time X-linked inheritance in this rare condition. Based on a search for genes expressed late during nose formation and early in limb formation we identified retinoic acid receptor B (RARB) and retinoic acid receptor G (RARG) as possible candidate genes and sequenced bidirectionally including all exons and intron-exon bounders. We identified a single nucleotide substitution in intron 2 of RARB, which is conserved in human, chimp, dog, mouse, rat, and chicken. However, it was located 83 bp from exon 2, suggesting it is a rare polymorphism which does not account for the phenotype. No other mutations were found. This suggests that another yet unknown gene is responsible for the condition.