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Two-amino acid molecular switch in an epithelial morphogen that regulates binding to two distinct receptors.

Ectodysplasin, a member of the tumor necrosis factor family, is encoded by the anhidrotic ectodermal dysplasia (EDA) gene. Mutations in EDA give rise to a clinical syndrome characterized by loss of hair, sweat glands, and teeth. EDA-A1 and EDA-A2 are two isoforms of ectodysplasin that differ only by an insertion of two amino acids. This insertion functions to determine receptor binding specificity, such that EDA-A1 binds only the receptor EDAR, whereas EDA-A2 binds only the related, but distinct, X-linked ectodysplasin-A2 receptor (XEDAR). In situ binding and organ culture studies indicate that EDA-A1 and EDA-A2 are differentially expressed and play a role in epidermal morphogenesis.

Amino Acid Sequence↗

Postnatal lower jaw dentition in different phenotypes of tabby mice.

The tabby (Ta) syndrome in mouse is homologous to human anhidrotic ectodermal dysplasia, including defective development of hair, teeth, and glands. To complete the available data on the functional dentition in the Ta mice, we analyzed the mandibular cheek teeth in 261 postnatal specimens arranged in several phenotype/genotype groups: 51 Ta-hemizygous males, 56 Ta-homo/hemizygous females, 64 Ta-heterozygous females, and 40 and 50 wild-type control males and females, respectively. We evaluated tooth number, size, shape and eruption and compared these parameters in the different groups. In any individual group of Ta mice, there was variability mainly in the size and shape of the most mesial tooth and in the tooth patterns. The incidence of a reduction in tooth number in homozygous and hemizygous mice was dependent on the breeding scheme.

Animals↗

Detection of human papillomavirus type 10 DNA in eccrine syringofibroadenomatosis occurring in Clouston's syndrome.

Syringofibroadenomatosis is often associated with an underlying condition such as diabetes mellitus or hidrotic ectodermal dysplasia. By reason of these associations, a reactive or hamartomatous cause is suspected. We report a case of a 71-year-old woman with Clouston's syndrome in whom progressive multiple palmoplantar syringofibroadenomas developed over a 10-year period. The syringofibroadenomas formed flat-topped papules simulating verruca plana; the widespread distribution and chronic progressive course resembled epidermodysplasia verruciformis. Contiguous with the syringofibroadenoma's characteristic epithelial-stromal proliferation were epidermal changes of verruca plana. Evidence of human papillomavirus (HPV) infection was verified by immunolabeling with antibodies to bovine papillomavirus type 1 and detection of HPV 10 viral DNA by means of polymerase chain reaction. Rather than a hamartomatous process, these findings suggest that syringofibroadenomas occurring in the setting of Clouston's syndrome could represent an HPV-induced epithelial proliferation.

Aged↗

Identification of sporadic mutations in the helix initiation motif of keratin 6 in two pachyonychia congenita patients: further evidence for a mutational hot spot.

Pachyonychia congenita (PC) is a rare, autosomal dominant, ectodermal dysplasia characterized most distinctly by the presence of symmetric nail hypertrophy. In the Jadassohn-Lewandowsky form, or PC-1, additional cutaneous manifestations may include palmoplantar hyperkeratosis, hyperhidrosis, follicular keratoses, and oral leukokeratosis. Mutations have previously been identified in the 1A helix initiation motif of either keratin 6 or keratin 16 in patients with PC-1. In the current study, we have identified 2 sporadic, heterozygous mutations in the 1A helix region of the K6 isoform (K6a). The first mutation identified was a 3 base pair deletion (K6adelta N171). The second mutation was a C-to-A transversion resulting in an amino acid substitution (K6a N171K). These data, in combination with previous reports, provide further evidence that this location is a mutational hot spot.

Amino Acid Sequence↗

Hereditary hypodontia and onychorrhexis of the fingernails and toenail koilonychia: Witkop's tooth-and nail syndrome.

The tooth-and-nail syndrome (Witkop's syndrome) is a rare autosomal dominant ectodermal dysplasia manifest by defects of the nail plates of the fingers and toes and hypodontia with normal hair and sweat gland function. We report a thirteen year-old girl who presented with marked longitudinal ridging of the nail plates of all ten fingers. The toenails were mildly ridged with koilonychia. Her mother's fingers were similarly affected to a lesser degree while her toenails appeared normal. Examination of the child's dentition revealed a hyperplastic frenulum and the absence of one of the usual four mandibular incisors. History provided by the mother described the maternal grandmother and maternal great aunt as having identical nail findings and the presence of only three lower incisors. Hair examination was normal in the mother and child, and no history or findings of sweat gland dysfunction was present. This report describes familial hypodontia, fingernail onychorrhexis, and toenail koilonychia consistent with Witkop's syndrome.

Adolescent↗

Twenty-four cases of the EEC syndrome: clinical presentation and management.

Twenty-four cases of EEC syndrome were identified as part of a nationwide study. Ectodermal dysplasia, by study definition, was present in all cases and hair and teeth were universally affected. Nail dysplasia was present in 19 subjects (79%) and the skin was affected in 21 (87%). The presence of hypohidrosis was not noted as a predominant feature in the syndrome and its occurrence appeared to depend on the presence of all other features. Distal limb defects from simple syndactyly to tetramelic cleft hand and foot were identified, including preaxial anomalies. Orofacial clefting was identified in 14 cases (58%) and lacrimal duct anomaly in 21 (87%). Significant clinical problems encountered were chiefly cosmetic or ophthalmological, but conductive deafness and genitourinary problems in some cases required surgical intervention. Altered self-image was also noted in some cases. Multidisciplinary management is necessary with the early involvement of the clinical geneticist. Developmentally, the EEC syndrome and related disorders represent disorders of ectodermal/mesodermal interaction. Candidate regions include 7q21.3, the "ectrodactyly" locus; other candidates include developmental genes implicated in the ectodermal/mesodermal interactive process.

Abnormalities, Multiple↗

NEMO mutations in 2 unrelated boys with severe infections and conical teeth.

X-linked recessive anhidrotic ectodermal dysplasia with immunodeficiency is a developmental and immunologic disorder caused by mutations in nuclear factor-kappaB essential modulator (NEMO), which is essential for nuclear factor-kappaB activation. Early in life, affected boys present a typical appearance, with hypotrichosis or atrichosis, hypohidrosis or anhidrosis, and hypodontia or anodontia with conical incisors. They are also susceptible to various microorganisms, mostly pyogenic bacteria and mycobacteria. Here we report 2 unrelated boys, aged 6 and 11 years, who have novel mutations in NEMO and present conical incisors and hypodontia as their sole and long-unrecognized developmental anomaly. One child had isolated recurrent pneumococcal disease, whereas the other had multiple infections. Our observations indicate that conical incisors should prompt the search for NEMO mutations in boys with unusual infectious diseases.

Anodontia↗

The gene for Naegeli-Franceschetti-Jadassohn syndrome maps to 17q21.

Naegeli-Franceschetti-Jadassohn syndrome is a rare autosomal dominant form of ectodermal dysplasia affecting sweat glands, nails, teeth, and skin. We have studied a multigeneration family of Anglo-Saxon British descent using microsatellite markers to screen candidate loci, including the epidermal differentiation complex on 1q, the keratin gene clusters on chromosomes 12q and 17q and the desmosomal cadherin gene cluster on chromosome 18q. Significant genetic linkage to chromosome 17q was observed using marker D17S 1787, with a maximum two-point LOD score of 4.166 at a recombination fraction of theta = 0. Recombination events in the family place the gene in a 26.97 cM interval between markers D17S798 and D17S957, a region known to contain the type I keratin gene cluster and other genes expressed in epithelia. Keratins K15, K19, and K20, plakoglobin, and MEOX1 were excluded as candidates by direct sequencing of genomic polymerase chain reaction products.

Chromosome Mapping↗

Refined mapping of Naegeli-Franceschetti- Jadassohn syndrome to a 6 cM interval on chromosome 17q11.2-q21 and investigation of candidate genes.

Naegeli-Franceschetti-Jadassohn syndrome and dermatopathia pigmentosa reticularis are autosomal dominant ectodermal dysplasias characterized by the absence of dermatoglyphics, reticulate hyper pigmentation of the skin, hypohidrosis, and heat intolerance. Palmoplantar keratoderma, nail dystrophy, and enamel defects are common in Naegeli-Franceschetti-Jadassohn syndrome, whereas diffuse alopecia is only seen in dermatopathia pigmentosa reticularis. We studied a large Swiss family with Naegeli-Franceschetti-Jadassohn syndrome originally described by Naegeli in 1927 and assessed linkage to chromosome 17q, which was proposed to harbor the Naegeli-Franceschetti-Jadassohn syndrome gene. Our results considerably narrow the Naegeli-Franceschetti-Jadassohn syndrome gene region from 27 cM to 6 cM flanked by D17S933 and D17S934 with a maximum multipoint LOD score of 2.7 at marker locus D17S800. In addition, we studied a small family with dermatopathia pigmentosa reticularis, and our linkage data suggest that dermatopathia pigmentosa reticularis may map to the same chromosomal region. The Naegeli-Franceschetti-Jadassohn syndrome critical interval spans approximately 5.4 Mb and contains a minimum of 45 distinct genes. We scrutinized 13 new prime candidates in addition to five genes previously examined, established the genomic organization of 10 of these genes, and excluded all of them by mutation analysis. Moreover, we identified a cDNA (KRT24) encoding a new keratin protein that bears high similarity to the type I keratins and displays a unique expression profile. No pathogenic mutations were identified in this novel gene either, however. In summary, our results substantially refine the Naegeli-Franceschetti-Jadassohn syndrome region and will aid in identifying a gene that is critical for ontogenesis of multiple ectodermal tissues.

Amino Acid Sequence↗

Transient hemophagocytosis with deficient cellular cytotoxicity, monoclonal immunoglobulin M gammopathy, increased T-cell numbers, and hypomorphic NEMO mutation.

X-linked osteopetrosis, anhydrotic ectodermal dysplasia, and immunodeficiency (XL-O-EDA-ID) is a disorder that is caused by hypomorphic mutations in the nuclear factor kappaB essential modulator (NEMO). These mutations lead to an impaired NF-kappaB activation. In vitro analyses and studies in animal models show that inhibition of NF-kappaB leads to a decrease of cytokine production and T-cell proliferation. Patients classically display poor or delayed inflammatory response to infections. We describe a boy with XL-O-EDA-ID, 1167-1168insC NEMO mutation, and recurrent infections. In early infancy, he experienced hemophagocytosis with transient deficiency of natural killer activity. Increased immunoglobulin M levels in blood resulted from a monoclonal immunoglobulin M gammopathy. Blood T-cell numbers were constantly increased, most probably resulting from a peripheral T-cell expansion. Our observations suggest that patients with hypomorphic NEMO mutations and repeated infections may experience inflammatory dysregulation.

Bacterial Infections↗

Cephalometric analysis of Rapp-Hodgkin syndrome.

Rapp-Hodgkin syndrome (RHS) is a rare form of ectodermal dysplasia with variable involvement of the hair, eyes, sweat glands, nails, and teeth. Oral findings may include hypodontia, hypoplastic enamel, cleft lip/palate, and a pronounced midfacial hypoplasia. The objective of this study was to determine if the pronounced midfacial hypoplasia is the result of a true tissue hypoplasia or displacement of midfacial tissues. We have identified a family in which three members, a mother and two daughters, display clinical features characteristic of RHS. Clinical and intraoral examination of these affected persons showed manifestations characteristic of RHS, and several new findings were observed, including subcutaneous abscesses, palmoplantar keratosis, and keratotic lesions located on the chest and trunk. To assess the midfacial hypoplasia, lateral cephalometric analysis was performed on lateral headplates. Results of the cephalometric analysis suggest that the midfacial hypoplasia results from both a deficiency and a displacement of the maxilla. These findings are significant because successful dental treatment of RHS relies upon accurate assessment of current and projected orofacial development, particularly for the skeletal relations of the maxilla and mandible.

Adolescent↗

Heterozygous germline mutations in the p53 homolog p63 are the cause of EEC syndrome.

EEC syndrome is an autosomal dominant disorder characterized by ectrodactyly, ectodermal dysplasia, and facial clefts. We have mapped the genetic defect in several EEC syndrome families to a region of chromosome 3q27 previously implicated in the EEC-like disorder, limb mammary syndrome (LMS). Analysis of the p63 gene, a homolog of p53 located in the critical LMS/EEC interval, revealed heterozygous mutations in nine unrelated EEC families. Eight mutations result in amino acid substitutions that are predicted to abolish the DNA binding capacity of p63. The ninth is a frameshift mutation that affects the p63alpha, but not p63beta and p63gamma isotypes. Transactivation studies with these mutant p63 isotypes provide a molecular explanation for the dominant character of p63 mutations in EEC syndrome.

Abnormalities, Multiple↗

TAB2, TRAF6 and TAK1 are involved in NF-kappaB activation induced by the TNF-receptor, Edar and its adaptator Edaradd.

Activation of the NF-kappaB pathway by the TNF-receptor Edar (Ectodysplasin receptor) and its downstream adaptator Edaradd (Edar-associated death domain) is essential for the development of hair follicles, teeth, exocrine glands and other ectodermal derivatives. Dysfunction of Edar signalling causes hypohidrotic/anhidrotic ectodermal dysplasia (ED), a disorder characterized by sparse hair, lack of sweat glands and malformation of teeth. The Edar signalling pathway stimulates NF-kappaB transcription factors via an activation of the IkappaB kinase (IKK) complex. To gain further insight into the mechanism of IKK activation by Edar and Edaradd, we performed a yeast two-hybrid screen and isolated TAB2 (TAK1-binding protein 2) as a binding partner of Edaradd. TAB2 is an adaptator protein that brigdes TRAF6 (TNF-receptor-associated factor 6) to TAK1 (TGFbeta-activated kinase 1), allowing TAK1 activation and subsequent IKK activation. Here, we show that endogenous and overexpressed TAB2, TRAF6 and TAK1 co-immunoprecipitated with Edaradd in 293 cells. Moreover, we show that dominant negative forms of TAB2, TRAF6 and TAK1 blocked the NF-kappaB activation induced by Edaradd. These results support the involvement of the TAB2/TRAF6/TAK1 signalling complex in the Edar signal transduction pathway and have important implications for our understanding of NF-kappaB activation and EDs in human.

Adaptor Proteins, Signal Transducing↗

Absence of active cutaneous vasodilation associated with congenital absence of sweat glands in humans.

In the rare syndrome, hereditary anhidrotic ectodermal dysplasia (AED), sweat glands are congenitally absent. Assuming normal vasculature and normal central mechanisms, presence or absence of active cutaneous vasodilation (AVD) in hyperthermic subjects with AED critically tests the hypothesis that AVD is a consequence of sudomotor activity. Three men with full expression of the syndrome and a woman who is mosaic were heated in water-perfused suits until oral temperature was 1.4-1.7 degrees C above control. The men showed no sweat gland imprints on iodine-treated paper nor significant elevation in forearm blood flow (FBF, determined plethysmographically). In the woman, we observed sweat gland activity, approximately 9 and 22 glands/cm2, on the right and left side, respectively, and vasodilation, slight on the right and more on the left. Cutaneous vasoconstriction in response to negative pressure applied to the lower body was observed (3 subjects) and local FBF increased in response to local heating (2 subjects). Therefore, in AED, with apparently normal cutaneous vasculature and sympathetic innervation, AVD is absent as well as sweat glands.

Adolescent↗

NMR structure of the p63 SAM domain and dynamical properties of G534V and T537P pathological mutants, identified in the AEC syndrome.

The p63 protein is crucial for epidermal development, and its mutations cause the extrodactyly ectodermal dysplasia and cleft lip/palate syndrome. The three-dimensional solution structure of the p63 sterile alpha-motif (SAM) domain (residues 505-579), a region crucial to explaining the human genetic disease ankyloblepharonectodermal dysplasia-clefting syndrome (AEC), has been determined by nuclear magnetic resonance spectroscopy. The structure indicates that the domain is a monomer with the characteristic five-helix bundle topology observed in other SAM domains. It includes five tightly packed helices with an extended hydrophobic core to form a globular and compact structure. The dynamics of the backbone and the global correlation time of the molecule have also been investigated and compared with the dynamical properties obtained through molecular dynamics simulation. Attempts to purify the pathological G534V and T537P mutants, originally identified in AEC, were not successful because of the occurrence of unspecific proteolytic degradation of the mutated SAM domains. Analysis of the structural dynamic properties of the G534V and T537P mutants through molecular dynamics simulation and comparison with the wild type permits detection of differences in the degree of freedom of individual residues and discussion of the possible causes for the pathology.

Abnormalities, Multiple↗

The range of defects associated with nuclear factor kappaB essential modulator.

PURPOSE OF REVIEW: Impaired ability to signal and activate specific gene transcription through nuclear factor kappaB (NFkappaB) has been directly linked to immunodeficiency. Hypomorphic mutations in the gene encoding NFkappaB essential modulator (NEMO), located on the X chromosome, impair NFkappaB function and lead to ectodermal dysplasia with immunodeficiency (ED-ID) with increased susceptibility to pyogenic bacteria, viruses and nonpathogenic mycobacterial infections. This is due to impaired, but not abolished, response to a variety of stimuli including Toll-like receptor agonists. Alternatively, loss-of-function (amorphic) mutations in the same gene lead to incontinentia pigmenti. The purpose of this review is to explore the range of immunologic defects associated with mutations in NEMO, a key regulatory molecule in the NFkappaB pathway. RECENT FINDINGS: In addition to the discovery of X-linked recessive hypomorphic mutations in NEMO as the cause of anhidrotic ED-ID, autosomal-dominant hypermorphic mutations in inhibitor of NFkappaB (IkappaB) alpha have been described recently. In addition, a better understanding of genotype-phenotype correlation in ED-ID patients is evolving. SUMMARY: ED-ID is a combined, variable but profound immunodeficiency characterized by susceptibility to pyogenic bacteria and mycobacterial infection. Understanding the features of particular NEMO mutations will provide insight into the role of this gene and will help define the crucial role of the function and regulation of NFkappaB in the immune response.

Animals↗

Traf6 is essential for murine tooth cusp morphogenesis.

Ectodermal appendages such as skin, hair, teeth, and sweat glands are affected in patients with hypohidrotic (anhydrotic) ectodermal dysplasia (HED). It has been established that mutations in the tumor necrosis factor (TNF) superfamily of molecules, i.e., ectodysplasin (EDA), EDA receptor (EDAR), and EDAR-associated death domain (EDARADD; the intracellular adaptor for EDAR), are responsible for several forms of HED in humans and mice. We show here by in situ hybridisation that another TNF family (orphan) receptor, TROY (also known TAJ, TAJ-alpha, TRADE, and TNFRSF19), is strongly coexpressed with Edar in the epithelial enamel knot signalling centres that are believe to regulate cuspal morphogenesis during murine tooth development. Traf6 is known to function as an intracellular adaptor protein for Troy and examination of Traf6 mutant mice revealed abnormalities in molar teeth that are similar but more severe than those produced by mutations in Eda signalling molecules. This finding suggests that, in additional to ectodysplasin, another TNF pathway involving Troy/Traf6 is involved in molar tooth cusp formation and identifies an essential role for a Traf in tooth development. Developmental Dynamics 229:131-135, 2004.

Animals↗

Specific NEMO mutations impair CD40-mediated c-Rel activation and B cell terminal differentiation.

Hypomorphic mutations in the zinc finger domain of NF-kappaB essential modulator (NEMO) cause X-linked hyper-IgM syndrome with ectodermal dysplasia (XHM-ED). Here we report that patient B cells are characterized by an absence of Ig somatic hypermutation (SHM) and defective class switch recombination (CSR) despite normal induction of activation-induced cytidine deaminase (AID) and Iepsilon-Cepsilon transcripts. This indicates that AID expression alone is insufficient to support neutralizing antibody responses. Furthermore, we show that patient B cells stimulated with CD40 ligand are impaired in both p65 and c-Rel activation, and whereas addition of IL-4 can enhance p65 activity, c-Rel activity remains deficient. This suggests that these NF-kappaB components have different activation requirements and that IL-4 can augment some but not all NEMO-dependent NF-kappaB signaling. Finally, using microarray analysis of patient B cells we identified downstream effects of impaired NF-kappaB activation and candidate factors that may be necessary for CSR and SHM in B cells.

Adolescent↗