Abstract
X-linked hypohidrotic ectodermal dysplasia (XLHED) is a genetic disorder due to a mutation of the EDA gene and is mainly characterized by an impaired formation of hair, teeth and sweat glands, and craniofacial dysmorphologies. Although tooth abnormalities in Tabby (Ta) mutant mice – the murine model of XLHED – have been extensively studied, characterization of the craniofacial complex, and more specifically the mandibular morphology has received less attention. From 3D micro-CT reconstructions of the left mandible, the mandibular outline observed in lateral view, was quantified using 2D elliptical Fourier analysis. Comparisons between Ta specimens and their wild-type controls were carried out showing significant shape differences between mouse strains enabling a clear distinction between hemizygous Ta specimens and the other mouse groups (WT and heterozygous EdaTa/+ specimens). Morphological differences associated with HED correspond not only to global mandibular features (restrained development of that bone along dorsoventral axis), but also to subtle aspects such as the marked backward projection of the coronoid process or the narrowing of the mandibular condylar neck. These modifications provide for the first time, evidence of a predominant effect of the Ta mutation on the mandibular morphology. These findings parallel the well described abnormalities of jugal tooth row and skeletal defects in Ta mice, and underline the role played by EDA-A in the reciprocal epithelial–mesenchymal interactions that are of critical importance in normal dental and craniofacial development.
Highlights
Hypohidrotic ectodermal dysplasias (HED) are a large and heterogenous group of heritable genodermatoses, encompassing more than 200 distinct syndromes and characterized by structural abnormalities of ectodermal appendages (DiGiovanna et al, 2009; Itin, 2009)
Elliptical Fourier analysis treats the shape of the mandible as a whole (Kuhl and Giardana, 1982; Schmittbuhl et al, 2003) contrary to other morphometric approaches based on anatomical landmarks and their associated measurements (Richtsmeier et al, 2002)
To our knowledge no quantitative analysis of the mandibular phenotype has been undertaken the skull and facial bones are dysmorphic in the tooth abnormalities inTabby (Ta) mutant and in human embryos with X-linked hypohidrotic ectodermal dysplasia (XLHED) (Montonen et al, 1998)
Summary
Hypohidrotic ectodermal dysplasias (HED) are a large and heterogenous group of heritable genodermatoses, encompassing more than 200 distinct syndromes and characterized by structural abnormalities of ectodermal appendages (DiGiovanna et al, 2009; Itin, 2009). The most prevalent HED is X-linked hypohidrotic ectodermal dysplasia (XLHED) and is due to a mutation in EDA gene (Vincent et al, 2001). Craniofacial and anthropometric changes are described in XLHED and consist in reduced and retrognathic maxilla, frontal prominence, cranial base modifications, reduced facial convexity and facial height with deficiencies in sagittal and transverse skeletal growth (Johnson et al, 2002; Arslan et al, 2007; Clauss et al, 2008). Heterozygous female carriers of XLHED exhibit moderate phenotypic manifestations consisting in hypodontia, mild dental morphological defects, distribution of abnormal skin along Blaschko lines, and some craniofacial changes as midface hypoplasia and abnormal cranial base length (Cambiaghi et al, 2000)
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