X-linked anhidrotic (hypohidrotic) ectodermal dysplasia caused by a novel mutation in EDA1 gene: 406T > G (Leu55Arg)

Ectodysplasin pathogenic variants affecting the furin-cleavage site and unusual clinical features define X-linked hypohidrotic ectodermal dysplasia in India

Hypohidrotic ectodermal dysplasia (HED) is a rare genetic disorder caused by mutational inactivation of a developmental pathway responsible for generation of tissues of ectodermal origin. The X-linked form accounts for the majority of HED cases and is caused by Ectodysplasin (EDA) pathogenic variants. We performed a combined analysis of 29 X-linked hypohidrotic ectodermal dysplasia (XLHED) families (including 12 from our previous studies). In addition to the classical triad of symptoms including loss (or reduction) of ectodermal structures, such as hair, teeth, and sweat glands, we detected additional HED-related clinical features including facial dysmorphism and hyperpigmentation in several patients. Interestingly, global developmental delay was identified as an unusual clinical symptom in many patients. More importantly, we identified 22 causal pathogenic variants that included 15 missense, four small in-dels, and one nonsense, splice site, and large deletion each. Interestingly, we detected 12 unique (India-specific) pathogenic variants. Of the 29 XLHED families analyzed, 11 (38%) harbored pathogenic variant localized to the furin cleavage site. A comparison with HGMD revealed significant differences in the frequency of missense pathogenic variants; involvement of specific exons and/or protein domains and transition/transversion ratios. A significantly higher proportion of missense pathogenic variants (33%) localized to the EDA furin cleavage when compared to HGMD (7%), of which p.R155C, p.R156C, and p.R156H were detected in three families each. Therefore, the first comprehensive analysis of XLHED from India has revealed several unique features including unusual clinical symptoms and high frequency of furin cleavage site pathogenic variants.

Defective NaCl Reabsorption in Salivary Glands of Eda-Null X-LHED Mice

Mutations in the ectodysplasin A gene ( EDA) cause X-LHED (X-linked hypohidrotic ectodermal dysplasia), the most common human form of ectodermal dysplasia. Defective EDA signaling is linked to hypoplastic development of epithelial tissues, resulting in hypotrichosis, hypodontia, hypohidrosis, and xerostomia. The primary objective of the present study was to better understand the salivary gland dysfunction associated with ectodermal dysplasia using the analogous murine disorder. The salivary flow rate and ion composition of the 3 major salivary glands were determined in adult Eda-deficient Tabby hemizygous male (Ta/Y) and heterozygous female (Ta/X) mice. Submandibular and sublingual glands of Eda-mutant mice were smaller than wild-type littermates, while parotid gland weight was not significantly altered. Fluid secretion by the 3 major salivary glands was essentially unchanged, but the decrease in submandibular gland size was associated with a dramatic loss of ducts in Ta/Y and Ta/X mice. Reabsorption of Na+ and Cl-, previously linked in salivary glands to Scnn1 Na+ channels and Cftr Cl- channels, respectively, was markedly reduced at high flow rates in the ex vivo submandibular glands of Ta/Y mice (~60%) and, to a lesser extent, Ta/X mice (Na+ by 14%). Consistent with decreased Na+ reabsorption in Ta/Y mice, quantitative polymerase chain reaction analysis detected decreased mRNA expression for Scnn1b and Scnn1g, genes encoding the β and γ subunits, respectively. Moreover, the Na+ channel blocker amiloride significantly inhibited Na+ and Cl- reabsorption by wild-type male submandibular glands to levels comparable to those observed in Ta/Y mice. In summary, fluid secretion was intact in the salivary glands of Eda-deficient mice but displayed marked Na+ and Cl- reabsorption defects that correlated with the loss of duct cells and decreased Scnn1 Na+ channel expression. These results provide a likely mechanism for the elevated NaCl concentration observed in the saliva of affected male and female patients with X-LHED.

Hypohidrotic ectodermal dysplasia associated with glucose-6-phosphate dehydrogenase deficiency

Hypohidrotic ectodermal dysplasia (HED) is a syndrome characterized by hypodontia, hypotrichosis, and partial or total ecrine sweat gland deficiency. The most prevalent form of HED is inherited as an X linked pattern. Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is an X-linked recessive disease, which leads to hemolytic anemia and jaundice. It is expressed in males, while heterozygous females are usually clinically normal. A 12-year-old boy with the complaints of hair and eyebrow disturbances, teeth disfigurement, decreased sweating, and xerosis presented to the outpatient clinic. Dermatological examination revealed sparse hair and eyebrows, conical-shaped teeth, xerosis, syndactylia, transverse grooves, and discoloration of nails. Laboratory findings indicated anemia. His 3-year-old sister also had sparse hair and eyebrows, xerosis, and syndactylia. We learned that the patient had a previous history of neonatal jaundice and a diagnosis of G-6-PD deficiency. Although it has been shown that loci of ectodermal dysplasia and G-6-PD deficiency genes are near to one another, we did not find any case study reporting on occurrence of these two genetic diseases together. With the aspect of this rare and interesting case, the relationship between HED and G-6-PD deficiency was defined.

Two novel mutations in the ED1 gene in Japanese families with X-linked hypohidrotic ectodermal dysplasia

X-linked hypohidrotic ectodermal dysplasia (XLHED), which is characterized by hypodontia, hypotrichosis, and hypohidrosis, is caused by mutations in ED1, the gene encoding ectodysplasin-A (EDA). This protein belongs to the tumor necrosis factor ligand superfamily. We analyzed ED1 in two Japanese patients with XLHED. In patient 1, we identified a 4-nucleotide insertion, c.119-120insTGTG, in exon 1, which led to a frameshift mutation starting from that point (p.L40fsX100). The patient's mother was heterozygous for this mutation. In patient 2, we identified a novel missense mutation, c.1141G>C, in exon 9, which led to a substitution of glycine with arginine in the TNFL domain of EDA (p.G381R). This patient's mother and siblings showed neither symptoms nor ED1 mutations, so this mutation was believed to be a de novo mutation in maternal germline cells. According to molecular simulation analysis of protein structure and electrostatic surface, p.G381R increases the distance between K375 in monomer A and K327 in monomer B, which suggests an alteration of overall structure of EDA. Thus, we identified two novel mutations, p.L40fsX100 and p.G381R, in ED1 of two XLHED patients. Simulation analysis suggested that the p.G381R mutation hampers binding of EDA to its receptor via alteration of overall EDA structure.

A point mutation of the ED1 gene in a Japanese family with X-linked hypohidrotic ectodermal dysplasia

X-linked hypohidrotic ectodermal dysplasia (EDA) is characterized by the hypoplasia or absence of hair, teeth and sweat glands. In this study, the authors investigated the ED1 gene in a Japanese family with X-linked hypohidrotic ectodermal dysplasia. The only affected male fulfils the diagnostic criteria for this disorder. His parents were not consanguineous and both of them were healthy. After informed consent, genomic DNA was isolated from the peripheral blood lymphocytes or oral buccal epithelial cells of all members of the family. A polymerase chain reaction fragment containing exon 9 of the ED1 gene was amplified using primers. The patient's amplified fragment, as well as those from his father, mother and sister, were directly sequenced. The sequence from the patient revealed a point mutation (G1149A) in exon 8 of the ED1 gene, which changes codon 291 from glycine to arginine. Heterozygosity was demonstrated in his mother and sister. This mutation has not been reported previously. The amino acid substitution is predicted to disrupt the transmembrane domain, which strongly implies that this is the disease-causing mutation in the family.

Clinical and genetic aspects of X-linked ectodermal dysplasia in the dog -- a review including three new spontaneous cases

This review presents the clinical, dermato-histopathological and genetic features of canine X-linked ectodermal dysplasia in previously reported cases and in three new spontaneous cases. The condition is compared with anhidrotic ectodermal dysplasia in humans and, based on current genetic concepts, we suggest that the two conditions are caused by the same gene and, consequently, represent a single pathological entity that affects both humans and dogs.

A frameshift mutation of the ED1 gene in sibling cases with X-linked hypohidrotic ectodermal dysplasia

X-linked hypohidrotic ectodermal dysplasia (XLHED; MIM 305100) is characterized by the absence or hypoplasia of hair, teeth, and sweat glands. The ED1 gene was identified as a responsive gene for XLHED. The patients were 2 Japanese brothers. Both had the same mutation in exon 1 of the ED1 gene, i.e. C deletion at nucleotide 49, which induced a frameshift starting from amino acid 17 and made a stop codon at amino acid 56, encoding the transmembrane site. The mutation caused the extracellular domain of ectodysplasin A to be completely absent. Their mother had a heterozygous allele; she congenitally lacked 1 tooth, and incisors appeared conical in form.

X-linked hypohidrotic ectodermal dysplasia mutations in Brazilian families

X-linked hypohidrotic ectodermal dysplasia (XLHED) is characterized by severe hypohidrosis, hypotrichosis, and hypodontia. The gene responsible for this pleiotropic syndrome (ED1) consists of 12 exons, 8 of them coding for a transmembrane protein (ectodysplasin-A; EDA-A) involved in the developmental process of epithelial-mesenchymal interaction. ED1 mutations that cause alterations in this protein lead to the XLHED phenotype. The major objective of the present study was to detect ED1 mutations in four Brazilian families with the XLHED phenotype and to compare them to the more than 60 different mutations already reported. DNA of the EDA-A coding exons was amplified by PCR, and single strand conformation analysis (SSCA) of the electrophoretic bands was carried out in polyacrylamide gel stained with silver nitrate. Two of these four families showed altered DNA band patterns. Subsequent DNA sequencing of the two mutated exons showed: (1) a 36 nucleotide deletion at exon 5 responsible for the loss of four Gly-X-Y repeats of the collagen subdomain of EDA-A; (2) a guanine deletion at exon 6 (966 or 967 sites) that alters EDA-A after amino acid 241 and leads to a premature ending at amino acid 279. This mutation at exon 6 seems not to have been reported previously and determines a truncated EDA-A without a part of its extracellular domain that contains the whole TNF homologue subdomain. These two DNA mutations are compatible with the XLHED phenotype. In the other two families the PCR-SSCA methodology was unable to detect any mutation responsible for the XLHED phenotype.

Mutations in the ED1 gene in Japanese families with X-linked hypohidrotic ectodermal dysplasia

X-linked hypohidrotic ectodermal dysplasia (XLHED; OMIM 305100) is characterized by sparse hair, abnormal teeth and decreased sweating as a result of abnormal development of the sweat glands. Mutations in the ED1 gene, which encodes ectodysplasin-A (EDA), are responsible for XLHED. Ectodysplasin-A, a ligand for the EDA receptor, plays an important role in epidermal morphogenesis. We identified ED1 mutations including three novel mutations by sequencing genomic DNAs from eight unrelated Japanese XLHED families. Data from all reported mutations revealed that codon 156 in the furin subdomain is the most frequent site of change in EDA.

Ectodysplasin signaling in development

Ectodysplasin (Eda), a signaling molecule belonging to the tumor necrosis factor family, is required for normal development of several ectodermally derived organs in humans and mice. Two closely related isoforms of ectodysplasin, Eda-A1 and Eda-A2, have been described which bind to and activate two different receptors, Edar and X-linked Eda-A2 receptor (Xedar), respectively. Mutations in Eda, Edar or other molecules of this signaling pathway cause ectodermal dysplasias characterized by defective development of teeth, hairs, and several exocrine glands such as sweat glands presumably due to impaired NF-kappaB response. Studies with mice either lacking the functional proteins of Edar pathway or overexpressing the ligand or receptor suggest that Eda-A1-Edar signaling has multiple roles in ectodermal organ development regulating their initiation, morphogenesis, and differentiation.

Mutations leading to X-linked hypohidrotic ectodermal dysplasia affect three major functional domains in the tumor necrosis factor family member ectodysplasin-A

Mutations in the epithelial morphogen ectodysplasin-A (EDA), a member of the tumor necrosis factor (TNF) family, are responsible for the human disorder X-linked hypohidrotic ectodermal dysplasia (XLHED) characterized by impaired development of hair, eccrine sweat glands, and teeth. EDA-A1 and EDA-A2 are two splice variants of EDA, which bind distinct EDA-A1 and X-linked EDA-A2 receptors. We identified a series of novel EDA mutations in families with XLHED, allowing the identification of the following three functionally important regions in EDA: a C-terminal TNF homology domain, a collagen domain, and a furin protease recognition sequence. Mutations in the TNF homology domain impair binding of both splice variants to their receptors. Mutations in the collagen domain can inhibit multimerization of the TNF homology region, whereas those in the consensus furin recognition sequence prevent proteolytic cleavage of EDA. Finally, a mutation affecting an intron splice donor site is predicted to eliminate specifically the EDA-A1 but not the EDA-A2 splice variant. Thus a proteolytically processed, oligomeric form of EDA-A1 is required in vivo for proper morphogenesis.