WNT10A Mutations Are a Frequent Cause of a Broad Spectrum of Ectodermal Dysplasias with Sex-Biased Manifestation Pattern in Heterozygotes

Odonto-onycho-dermal dysplasia (OODD), a rare autosomal-recessive inherited form of ectodermal dysplasia including severe oligodontia, nail dystrophy, palmoplantar hyperkeratosis, and hyperhidrosis, was recently shown to be caused by a homozygous nonsense WNT10A mutation in three consanguineous Lebanese families. Here, we report on 12 patients, from 11 unrelated families, with ectodermal dysplasia caused by five previously undescribed WNT10A mutations. In this study, we show that (1) WNT10A mutations cause not only OODD but also other forms of ectodermal dysplasia, reaching from apparently monosymptomatic severe oligodontia to Schöpf-Schulz-Passarge syndrome, which is so far considered a unique entity by the findings of numerous cysts along eyelid margins and the increased risk of benign and malignant skin tumors; (2) WNT10A mutations are a frequent cause of ectodermal dysplasia and were found in about 9% of an unselected patient cohort; (3) about half of the heterozygotes (53.8%) show a phenotype manifestation, including mainly tooth and nail anomalies, which was not reported before in OODD; and (4) heterozygotes show a sex-biased manifestation pattern, with a significantly higher proportion of tooth anomalies in males than in females, which may implicate gender-specific differences of WNT10A expression.     

Mutations in PVRL4, Encoding Cell Adhesion Molecule Nectin-4, Cause Ectodermal Dysplasia-Syndactyly Syndrome

Ectodermal dysplasias form a large disease family with more than 200 members. The combination of hair and tooth abnormalities, alopecia, and cutaneous syndactyly is characteristic of ectodermal dysplasia-syndactyly syndrome (EDSS). We used a homozygosity mapping approach to map the EDSS locus to 1q23 in a consanguineous Algerian family. By candidate gene analysis, we identified a homozygous mutation in the PVRL4 gene that not only evoked an amino acid change but also led to exon skipping. In an Italian family with two siblings affected by EDSS, we further detected a missense and a frameshift mutation. PVRL4 encodes for nectin-4, a cell adhesion molecule mainly implicated in the formation of cadherin-based adherens junctions. We demonstrated high nectin-4 expression in hair follicle structures, as well as in the separating digits of murine embryos, the tissues mainly affected by the EDSS phenotype. In patient keratinocytes, mutated nectin-4 lost its capability to bind nectin-1. Additionally, in discrete structures of the hair follicle, we found alterations of the membrane localization of nectin-afadin and cadherin-catenin complexes, which are essential for adherens junction formation, and we found reorganization of actin cytoskeleton. Together with cleft lip and/or palate ectodermal dysplasia (CLPED1, or Zlotogora-Ogur syndrome) due to an impaired function of nectin-1, EDSS is the second known “nectinopathy” caused by mutations in a nectin adhesion molecule.     

A novel c.1037C > G (p.Ala346Gly) mutation in TP63 as cause of the ectrodactyly-ectodermal dysplasia and cleft lip/palate (EEC) syndrome

Ectrodactyly – ectodermal dysplasia and cleft lip/palate (EEC) syndrome (OMIM 604292) is a rare disorder determined by mutations in the TP63 gene. Most cases of EEC syndrome are associated to mutations in the DNA binding domain (DBD) region of the p63 protein. Here we report on a three-generation Brazilian family with three individuals (mother, son and grandfather) affected by EEC syndrome, determined by a novel mutation c.1037C > G (p.Ala346Gly). The disorder in this family exhibits a broad spectrum of phenotypes: two individuals were personally examined, one presenting the complete constellation of EEC syndrome manifestations and the other presenting an intermediate phenotype; the third affected, a deceased individual not examined personally and referred to by his daughter, exhibited only the split-hand/foot malformation (SHFM). Our findings contribute to elucidate the complex phenotype-genotype correlations in EEC syndrome and other related TP63-mutation syndromes. The possibility of the mutation c.1037C > G being related both to acro-dermato-ungual-lacrimal-tooth (ADULT) syndrome and SHFM is also raised by the findings here reported.     

Expanding the clinical and mutational spectrum of Kaufman oculocerebrofacial syndrome with biallelic UBE3B mutations

Biallelic mutations of UBE3B have recently been shown to cause Kaufman oculocerebrofacial syndrome (also reported as blepharophimosis–ptosis–intellectual disability syndrome), an autosomal recessive condition characterized by hypotonia, developmental delay, intellectual disability, congenital anomalies, characteristic facial dysmorphic features, and low cholesterol levels. To date, six patients with either missense mutations affecting the UBE3B HECT domain or truncating mutations have been described. Here, we report on the identification of homozygous or compound heterozygous UBE3B mutations in six additional patients from five unrelated families using either targeted UBE3B sequencing in individuals with suggestive facial dysmorphic features, or exome sequencing. Our results expand the clinical and mutational spectrum of the UBE3B-related disorder in several ways. First, we have identified UBE3B mutations in individuals who previously received distinct clinical diagnoses: two sibs with Toriello–Carey syndrome as well as the patient reported to have a “new” syndrome by Buntinx and Majewski in 1990. Second, we describe the adult phenotype and clinical variability of the syndrome. Third, we report on the first instance of homozygous missense alterations outside the HECT domain of UBE3B, observed in a patient with mildly dysmorphic facial features. We conclude that UBE3B mutations cause a clinically recognizable and possibly underdiagnosed syndrome characterized by distinct craniofacial features, hypotonia, failure to thrive, eye abnormalities, other congenital malformations, low cholesterol levels, and severe intellectual disability. We review the UBE3B-associated phenotypes, including forms that can mimick Toriello–Carey syndrome, and suggest the single designation “Kaufman oculocerebrofacial syndrome”.     

Investigation into the possible cause of subjective decreased sensory perception in the nipple-areola complex of women with macromastia

Patients with macromastia often comment on a lack of sensation in their nipple-areola complex. A study was designed to investigate the cause of this decreased sensation. Two hypotheses were proposed. First, the decreased sensation could result from neuropraxia of the sensory nerve fibers secondary to traction caused by the heavy breast parenchyma. The second hypothesis proposed that tissue expansion of the nipple and areola by the voluminous breast parenchyma caused a decrease in nerve fibers per surface area and hence decreased sensory perception. Sixty-one patients were assessed in the study. All patients underwent surgery in which histological biopsy of either the areola alone (31 reduction mammaplasty patients) or the nipple and areola (30 mastectomy patients) was possible. Before surgery, each nipple-areola complex was tested with Weinstein Enhanced Sensory Test monofilaments as a quantitative test of tactile sensation. Breast cup size, ptosis, and weight of tissue excised were recorded to allow general assessment of the breast size. The nipple and areola biopsy specimens were assessed using immunohistochemistry (S-100 polyclonal antibody, Dako Z311) to measure nerve fiber count per unit area. Statistical analysis was undertaken to find any association among sensitivity, breast cup size, ptosis, weight of tissue resected, and nerve fiber density in the nipple and areola biopsy specimens. Sensitivity at the areola decreased with increasing breast cup size (r = 0.47, p < 0.001) and ptosis (r = 0.42, p = 0.002 for increasing distance between inframammary crease and nipple; r = 0.49, p < 0.001 for increasing manubrium to nipple distance). There was a weak correlation between nerve fiber density at the areola and breast cup size (r = -0.22, p = 0.1). Sensitivity at the nipple was higher than at the areola. Nerve fiber density count at the nipple was higher than at the areola, but there was no statistically significant correlation between nipple sensitivity and breast cup size, ptosis, or weight of tissue resected. The results suggest that the areola and nipple are different in their neuroanatomy. The areola is a thin, pliable structure that is predisposed to stretch as the breast enlarges and therefore experience a decrease in nerve fiber density. The nipple is a compact structure that is less likely to stretch with breast enlargement. In the nipple, neither sensory perception nor nerve fiber density varied with size or breast ptosis. The perceived lack of sensation in the nipple-areola complex is multifactorial. This study shows that neither traction injury to the sensory nerves nor decreased nerve density alone can explain the subjective numbness reported by patients with macromastia. Psychological factors, such as dissatisfaction with body form or interpretation of lack of sensation in the areola as also affecting the nipple, may influence the patient's assessment of the nipple-areola sensitivity.     

FREM1 Mutations Cause Bifid Nose, Renal Agenesis, and Anorectal Malformations Syndrome

An autosomal-recessive syndrome of bifid nose and anorectal and renal anomalies (BNAR) was previously reported in a consanguineous Egyptian sibship. Here, we report the results of linkage analysis, on this family and on two other families with a similar phenotype, which identified a shared region of homozygosity on chromosome 9p22.2-p23. Candidate-gene analysis revealed homozygous frameshift and missense mutations in FREM1, which encodes an extracellular matrix component of basement membranes. In situ hybridization experiments demonstrated gene expression of Frem1 in the midline of E11.5 mouse embryos, in agreement with the observed cleft nose phenotype of our patients. FREM1 is part of a ternary complex that includes FRAS1 and FREM2, and mutations of the latter two genes have been reported to cause Fraser syndrome in mice and humans. The phenotypic variability previously reported for different Frem1 mouse mutants suggests that the apparently distinct phenotype of BNAR in humans may represent a previously unrecognized variant of Fraser syndrome.     

Mutations in the SPARC-related modular calcium-binding protein 1 gene, SMOC1, cause waardenburg anophthalmia syndrome

Waardenburg anophthalmia syndrome, also known as microphthalmia with limb anomalies, ophthalmoacromelic syndrome, and anophthalmia-syndactyly, is a rare autosomal-recessive developmental disorder that has been mapped to 10p11.23. Here we show that this disease is heterogeneous by reporting on a consanguineous family, not linked to the 10p11.23 locus, whose two affected children have a homozygous mutation in SMOC1. Knockdown experiments of the zebrafish smoc1 revealed that smoc1 is important in eye development and that it is expressed in many organs, including brain and somites.     

Limb mammary syndrome: a new genetic disorder with mammary hypoplasia, ectrodactyly, and other Hand/Foot anomalies maps to human chromosome 3q27.

We report on a large Dutch family with a syndrome characterized by severe hand and/or foot anomalies, and hypoplasia/aplasia of the mammary gland and nipple. Less frequent findings include lacrimal-duct atresia, nail dysplasia, hypohydrosis, hypodontia, and cleft palate with or without bifid uvula. This combination of symptoms has not been reported previously, although there is overlap with the ulnar mammary syndrome (UMS) and with ectrodactyly, ectodermal dysplasia, and clefting syndrome. Allelism with UMS and other related syndromes was excluded by linkage studies with markers from the relevant chromosomal regions. A genomewide screening with polymorphic markers allowed the localization of the genetic defect to the subtelomeric region of chromosome 3q. Haplotype analysis reduced the critical region to a 3-cM interval of chromosome 3q27. This chromosomal segment has not been implicated previously in disorders with defective development of limbs and/or mammary tissue. Therefore, we propose to call this apparently new disorder "limb mammary syndrome" (LMS). The SOX2 gene at 3q27 might be considered an excellent candidate gene for LMS because the corresponding protein stimulates expression of FGF4, an important signaling molecule during limb outgrowth and development. However, no mutations were found in the SOX2 open reading frame, thus excluding its involvement in LMS.     

Assessment of long-term nipple projection: a comparison of three techniques

Nipple-areola reconstruction represents the final stage of breast reconstruction, whereby a reconstructed breast mound is transformed into a breast facsimile that more closely resembles the original breast. Although numerous nipple reconstruction techniques are available, all have been plagued by eventual loss of long-term projection. In this report, the authors present a comparative assessment of nipple and areola projection after reconstruction using either a bell flap, a modified star flap, or a skate flap and full-thickness skin graft for areola reconstruction. The specific technique for nipple-areola reconstruction following breast reconstruction was selected on the basis of the projection of the contralateral nipple and whether or not the opposite areola showed projection. Patients with 5 mm or less of opposite nipple projection were treated with either the bell flap or the modified star flap. In patients where the areola complex exhibited significant projection, a bell flap was chosen over the modified star flap. In those patients with greater than 5-mm nipple projection, reconstruction with a skate flap and full-thickness skin graft was performed. Maintenance of nipple projection in each of these groups was then carefully assessed over a 1-year period of follow-up using caliper measurements of nipple and areola projection obtained at 3-month intervals. The best long-term nipple projection was obtained and maintained by the skate and star techniques. The major decrease in projection of the reconstructed nipple occurred during the first 3 months. After 6 months, the projection was stable. The loss of both nipple and areola projection when using the bell flap was so remarkable that the authors would discourage the use of this procedure in virtually all patients.     

Acrofacial Dysostosis,Cincinnati Type,a Mandibulofacial Dysostosis Syndrome with Limb Anomalies,Is Caused by POLR1A Dysfunction

We report three individuals with a cranioskeletal malformation syndrome that we define as acrofacial dysostosis, Cincinnati type. Each individual has a heterozygous mutation in POLR1A, which encodes a core component of RNA polymerase 1. All three individuals exhibit varying degrees of mandibulofacial dysostosis, and two additionally have limb anomalies. Consistent with this observation, we discovered that polr1a mutant zebrafish exhibited cranioskeletal anomalies mimicking the human phenotype. polr1a loss of function led to perturbed ribosome biogenesis and p53-dependent cell death, resulting in a deficiency of neural-crest-derived skeletal precursor cells and consequently craniofacial anomalies. Our findings expand the genotypic and phenotypic heterogeneity of congenital acrofacial disorders caused by disruption of ribosome biogenesis.     

Mutations in PIK3R1 Cause SHORT Syndrome

SHORT syndrome is a rare, multisystem disease characterized by short stature, anterior-chamber eye anomalies, characteristic facial features, lipodystrophy, hernias, hyperextensibility, and delayed dentition. As part of the FORGE (Finding of Rare Disease Genes) Canada Consortium, we studied individuals with clinical features of SHORT syndrome to identify the genetic etiology of this rare disease. Whole-exome sequencing in a family trio of an affected child and unaffected parents identified a de novo frameshift insertion, c.1906_1907insC (p.Asn636Thrfs^∗18), in exon 14 of PIK3R1. Heterozygous mutations in exon 14 of PIK3R1 were subsequently identified by Sanger sequencing in three additional affected individuals and two affected family members. One of these mutations, c.1945C>T (p.Arg649Trp), was confirmed to be a de novo mutation in one affected individual and was also identified and shown to segregate with the phenotype in an unrelated family. The other mutation, a de novo truncating mutation (c.1971T>G [p.Tyr657^∗]), was identified in another affected individual. PIK3R1 is involved in the phosphatidylinositol 3 kinase (PI3K) signaling cascade and, as such, plays an important role in cell growth, proliferation, and survival. Functional studies on lymphoblastoid cells with the PIK3R1 c.1906_1907insC mutation showed decreased phosphorylation of the downstream S6 target of the PI3K-AKT-mTOR pathway. Our findings show that PIK3R1 mutations are the major cause of SHORT syndrome and suggest that the molecular mechanism of disease might involve downregulation of the PI3K-AKT-mTOR pathway.     

Mutations in DDX58, which Encodes RIG-I,Cause Atypical Singleton-Merten Syndrome

Singleton-Merten syndrome (SMS) is an autosomal-dominant multi-system disorder characterized by dental dysplasia, aortic calcification, skeletal abnormalities, glaucoma, psoriasis, and other conditions. Despite an apparent autosomal-dominant pattern of inheritance, the genetic background of SMS and information about its phenotypic heterogeneity remain unknown. Recently, we found a family affected by glaucoma, aortic calcification, and skeletal abnormalities. Unlike subjects with classic SMS, affected individuals showed normal dentition, suggesting atypical SMS. To identify genetic causes of the disease, we performed exome sequencing in this family and identified a variant (c.1118A>C [p.Glu373Ala]) of DDX58, whose protein product is also known as RIG-I. Further analysis of DDX58 in 100 individuals with congenital glaucoma identified another variant (c.803G>T [p.Cys268Phe]) in a family who harbored neither dental anomalies nor aortic calcification but who suffered from glaucoma and skeletal abnormalities. Cys268 and Glu373 residues of DDX58 belong to ATP-binding motifs I and II, respectively, and these residues are predicted to be located closer to the ADP and RNA molecules than other nonpathogenic missense variants by protein structure analysis. Functional assays revealed that DDX58 alterations confer constitutive activation and thus lead to increased interferon (IFN) activity and IFN-stimulated gene expression. In addition, when we transduced primary human trabecular meshwork cells with c.803G>T (p.Cys268Phe) and c.1118A>C (p.Glu373Ala) mutants, cytopathic effects and a significant decrease in cell number were observed. Taken together, our results demonstrate that DDX58 mutations cause atypical SMS manifesting with variable expression of glaucoma, aortic calcification, and skeletal abnormalities without dental anomalies.     

Interaction between Foxc1 and Fgf8 during Mammalian Jaw Patterning and in the Pathogenesis of Syngnathia

Syngnathia (bony fusion of the upper and lower jaw) is a rare human congenital condition, with fewer than sixty cases reported in the literature. Syngnathia typically presents as part of a complex syndrome comprising widespread oral and maxillofacial anomalies, but it can also occur in isolation. Most cartilage, bone, and connective tissue of the head and face is derived from neural crest cells. Hence, congenital craniofacial anomalies are often attributed to defects in neural crest cell formation, survival, migration, or differentiation. The etiology and pathogenesis of syngnathia however remains unknown. Here, we report that Foxc1 null embryos display bony syngnathia together with defects in maxillary and mandibular structures, and agenesis of the temporomandibular joint (TMJ). In the absence of Foxc1, neural crest cell derived osteogenic patterning is affected, as osteoblasts develop ectopically in the maxillary prominence and fuse with the dentary bone. Furthermore, we observed that the craniofacial musculature is also perturbed in Foxc1 null mice, which highlights the complex tissue interactions required for proper jaw development. We present evidence that Foxc1 and Fgf8 genetically interact and that Fgf8 dosage is associated with variation in the syngnathic phenotype. Together our data demonstrates that Foxc1 – Fgf8 signaling regulates mammalian jaw patterning and provides a mechanistic basis for the pathogenesis of syngnathia. Furthermore, our work provides a framework for understanding jaw patterning and the etiology of other congenital craniofacial anomalies, including temporomandibular joint agenesis.     

Mutation p.Leu354Pro in EDA causes severe hypohidrotic ectodermal dysplasia in a Chinese family

X-linked recessive hypohidrotic ectodermal dysplasia (XLHED) is characterized by the defective morphogenesis of teeth, hair, and eccrine sweat glands. It is associated with mutations in the EDA gene. Up to now, more than 100 mutations in the EDA gene have been reported to cause XLHED. The product of EDA gene is a trimeric type II transmembrane protein that belongs to the tumor necrosis factor (TNF) family of ligands. In this study, we identified a Chinese family with XLHED. Direct DNA sequencing of the whole coding region of EDA revealed a novel missense mutation, p.Leu354Pro in a patient affected with XLHED. This mutation was not found in either unaffected male individuals of the family or 168 normal controls. The substitution of Leu354 with Pro was found to be located in the TNF-like domain of EDA and may influence the epithelial signaling pathway required for the normal ectodermal development through altering the topology of EDA. Our finding broadens the spectrum of EDA mutations and may help to understand the molecular basis of XLHED and aid genetic counseling.     

Ectodermal dysplasia-cutaneous syndactyly syndrome maps to chromosome 7p21.1-p14.3

Ectodermal dysplasia syndromes are genetically heterogeneous group of disorders involving one or more of the classical ectodermal appendages (hair, nail, teeth, sweat glands) in association with anomalies of other organs or systems. In the present study a novel form of ectodermal dysplasia syndrome, ectodermal dysplasia cutaneous syndactyly (EDCS), segregating in an autosomal recessive pattern in a Pakistani family was investigated. The clinical features of the affected individuals included large prominent ear pinnae, tooth enamel hypoplasia, hypoplastic nails, bilateral partial cutaneous syndactyly, hypotrichosis, palmoplantar keratoderma and hyperhidrosis. Through genetic linkage study, EDCS syndrome was mapped on human chromosome 7p21.1-p14.3 flanked by markers D7S488 and D7S817. A maximum two-point LOD score of 2.94 (θ = 0.00) was obtained at marker D7S2496 while a maximum multipoint LOD score of 3.07 was obtained with several markers along the disease-interval. This interval spans 19.80-cM, which corresponds to 13.74-Mbp according to the sequence-based physical map (Build 36.1). Sequence analysis of 27 candidate genes, located in the candidate interval, did not reveal any functional sequence variant.