Autosomal Recessive Hypohidrotic Ectodermal Dysplasia Research Articles

Different degree of loss-of-function among four missense mutations in the EDAR gene responsible for autosomal recessive hypohidrotic ectodermal dysplasia may be associated with the phenotypic severity.

Hypohidrotic ectodermal dysplasia is a rare condition characterized by hypohidrosis, hypodontia, and hypotrichosis. The disease can show X-linked recessive, autosomal dominant or autosomal recessive inheritance trait. Of these, the autosomal forms are caused by mutations in either EDAR or EDARADD. To date, the underlying pathomechanisms or genotype-phenotype correlations for autosomal forms have not completely been disclosed. In this study, we performed a series of in vitro studies for four missense mutations in the death domain of EDAR protein: p.R358Q, p.G382S, p.I388T, and p.T403M. The results revealed that p.R358Q- and p.T403M-mutant EDAR showed different expression patterns from wild-type EDAR in both western blots and immunostainings. NF-κB reporter assays demonstrated that all the mutant EDAR showed reduced activation of NF-κB, but the reduction by p.G382S- and p.I388T-mutant EDAR was moderate. Co-immunoprecipitation assays showed that p.R358Q- and p.T403M-mutant EDAR did not bind with EDARADD at all, whereas p.G382S- and p.I388T-mutant EDAR maintained the affinity to some extent. Furthermore, we demonstrated that all the mutant EDAR proteins analyzed aberrantly bound with TRAF6. Sum of the data suggest that the degree of loss-of-function is different among the mutant EDAR proteins, which may be associated with the severity of the disease.

Homozygous variants of EDAR underlying hypohidrotic ectodermal dysplasia in three consanguineous families.

Hypohidrotic ectodermal dysplasia (HED) is a congenital anomaly characterized by hypohydrosis, hypotrichosis and hypodontia. Mutations in at least four genes (EDAR, EDARADD, WNT10A, TRAF6) have been reported to cause both autosomal recessive and autosomal dominant forms of HED. Mutations in two other genes (EDA and IKBKG) have been reported to cause X-linked HED. To clinically characterize three consanguineous families (A-C) segregating with autosomal recessive HED and identify possible disease-causing variants of EDAR and EDARADD genes. The genes, EDAR and EDARADD, were sequenced in Family A and C, and exome sequencing was performed in Family B. Additionally, in Family A and C, the effect of the identified variants was examined by analysis of EDAR mRNA, extracted from hair follicles from both affected and unaffected members. Sequence analysis revealed three possible disease-causing EDAR variants including a novel splice acceptor site variant (IVS3-1G > A) in Family A and two previously reported mutations (p.[Ala26Val], p.[Arg25*]) in the two other families. Previously, the nonsense variant p.(Arg25*) was reported only in the heterozygous state. Analysis of the RNA, extracted from hair follicles, revealed skipping of a downstream exon in EDAR and complete degradation of EDAR mRNA in affected members in family A and C, respectively. Computational modelling validated the pathogenic effect of the two variants identified in Family B and C. The three variants reported here expand the spectrum of EDAR mutations associated with HED which may further facilitate genetic counselling of families segregating with similar disorders in the Pakistani population.

A recurrent missense mutation in the EDAR gene causes severe autosomal recessive hypohidrotic ectodermal dysplasia in two consanguineous Kashmiri families.

Hypohidrotic ectodermal dysplasia (HED) is a rare congenital disorder arising from the abnormal development of ectoderm derived structures, including skin, hair, nails, teeth and glands. These patients have sparse hair on the whole body, including the scalp, as well as hypoplastic teeth. They have no resistance to heat as a result of abnormal sweat glands. In total, four genes, namely ectodysplasin A (EDA), ectodysplasin A receptor (EDAR), EDAR-associated death domain protein (EDARADD) and Wnt family member 10A (WNT10A), are known to be involved in the etiology of HED. In the present study, we investigated two consanguineous Kashmiri families (A &B) with an autosomal recessive form of HED. Using whole exome sequencing and different bioinformatics tools, we detected a recurrent mutation causing severe HED. We identified an already known rare homozygous missense (NM_022336 c.1300T>C; p.W434R; minor allele frequency 0.00007) variant in exon 12 of the EDAR gene. This variant segregated with a homozygous form in all patients and their obligate carriers were heterozygous. A panel of >100 unrelated ethnically matched controls was screened, and the mutation was not identified outside the families. Furthermore, the candidate variant is predicted to be damaging by in silico software giving a CADD (Combined Annotation Dependent Depletion) score of 25.5, which indicates that the variant is among the top 1% of the deleterious variants in the human genome. The identification of the same homozygous mutation segregating with disease in two different families supports the important role of the gene in the development of the disorder and this may contribute to novel approaches, prenatal diagnosis and genetic counseling of families with EDAR related disorders.

Autosomal Recessive Hypohidrotic Ectodermal Dysplasia Caused by a Novel Mutation in EDAR Gene

Backgrounds: Hypohidrotic ectodermal dysplasia (HED) is a rare genetic disorder, distinguished by hypotrichosis, hypohidrosis, and hypodontia. HDE can be inherited in X-linked recessive manner as a result of mutations in the ectodysplasin A (EDA) gene as well as autosomal dominant and autosomal recessive manners both of them caused by mutations in EDA receptor (EDAR) and EDAR-associated death domain (EDARADD) genes.Findings: In this report, we investigated a consanguineous Iranian family with autosomal recessive form of HED. A homozygous missense mutation was detected in exon 1 of EDAR gene in the proband (c.278C>G) resulting in p.C93S that alters the sequence of the EDAR protein. Conclusions: We facilitated the effective genetic counseling and prenatal diagnosis in this family through detection of the disease causing mutation.

Whole-exome sequencing identifies a novel missense mutation in EDAR causing autosomal recessive hypohidrotic ectodermal dysplasia with bilateral amastia and palmoplantar hyperkeratosis

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Two novel mutations in the gene EDAR causing autosomal recessive hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia (HED) is a human heritable disorder characterized by sparse hair, reduced ability to sweat and hypodontia. The HED exhibits X-linked, autosomal recessive and autosomal dominant mode of inheritance. Mutations in four genes including EDA, EDAR, EDARADD, and WNT10A are known to cause hypohidrotic and anhidrotic ectodermal dysplasia. Genotyping of both affected and normal individuals of two consanguineous Pakistani families (A, B), showing autosomal recessive HED, was carried out using microsatellite markers linked to EDAR gene on chromosome 2q11-q13. To screen for mutations in the gene EDAR, all of its exons and splice junction were amplified and sequenced directly, using an automated DNA sequencer. Genotyping using microsatellite markers analysis showed linkage of the two families to gene EDAR on chromosome 2q11-2q13. Subsequently, screening of all the 12 exons and splice junctions of gene EDAR revealed a novel missense mutation (c.1163T>C; p.Ile388Thr) in family A and a novel insertion mutation (c.1014insA; p.V339SfsX6) in family B. Our findings extend the body of evidence supporting the role of EDAR signaling pathway as a powerful regulator of development of ectodermal appendages.

Molecular genetic analysis of consanguineous Pakistani families with autosomal recessive hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia is an inherited disorder characterized by defective development of teeth, hairs and sweat glands. X-linked hypohidrotic ectodermal dysplasia is caused by mutations in the EDA gene, and autosomal forms of hypohidrotic ectodermal dysplasia are caused by mutations in either the EDAR or the EDARADD genes. To study the molecular genetic cause of autosomal recessive hypohidrotic ectodermal dysplasia in three consanguineous Pakistani families (A, B and C), genotyping of 13 individuals was carried out by using polymorphic microsatellite markers that are closely linked to the EDAR gene on chromosome 2q11-q13 and the EDARADD gene on chromosome 1q42.2-q43. The results revealed linkage in the three families to the EDAR locus. Sequence analysis of the coding exons and splice junctions of the EDAR gene revealed two mutations: a novel non-sense mutation (p.E124X) in the probands of families A and B and a missense mutation (p.G382S) in the proband of family C. In addition, two synonymous single-nucleotide polymorphisms were also identified. The finding of mutations in Pakistani families extends the body of evidence that supports the importance of EDAR for the development of hypohidrotic ectodermal dysplasia.

X‐linked and autosomal recessive Hypohidrotic Ectodermal Dysplasia: genotypic‐dental phenotypic findings

Hypohidrotic ectodermal dysplasia (HED) is characterized by abnormal development of ectodermal structures and its molecular etiology corresponds to mutations of EDA-EDAR genes. The aim of this study was first to investigate the genotype and dental phenotype associated with HED and second, to explore possible correlations between dental features and molecular defects. A total of 27 patients from 24 unrelated families exhibiting clinical signs of HED (22 XLHED males, 5 autosomal recessive forms) were retrospectively included. In the sample, 25 different mutations on EDA and EDAR genes were detected; 10 were not previously described. EDA and EDAR mutations corresponded respectively to 80.0% and 20.0% of the mutations. The dental phenotype analysis revealed a mean number of primary and permanent missing teeth ranging respectively from 14.5 (4-20) to 22.5 (10-28); the majority of the patients exhibited dysmorphic teeth. Overall, no differential expression in the degree of oligodontia according to either the mutated gene, the mutated functional sub-domains, or the mutation type, could be observed. Nevertheless, the furin group exhibited severe phenotypes unobserved in the TNF group. Significant differences in the number of some primary missing teeth (incisor and canine) related to EDA-EDAR genes defects were detected for the first time between XLHED and autosomal recessive HED, suggesting differential local effects of EDA-EDAR genes during odontogenesis. The present genotypic-phenotypic findings may add to the knowledge of the consequences of the molecular dysfunction of EDA-NF-kB in odontogenesis, and could be helpful in genetic counseling to distinguish autosomal forms from other HED syndromes.

A compound heterozygous mutation in the EDAR gene in a Spanish family with autosomal recessive hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia (HED) is a genetic disorder characterised by sparse hair, lack of sweat glands and malformation of teeth. The X-linked form of the disease, caused by mutations in the EDA gene, represents the majority of HED cases. Autosomal forms result from mutations in either the EDAR or the EDARADD gene. The X-linked and autosomal forms are phenotypically indistinguishable. For the purpose of genetic counselling, it is, therefore, important to know which gene is involved. In this study, we ascertained a Spanish family demonstrating the autosomal recessive form of HED. Affected individuals in the family showed the characteristic features of HED, including fine and sparse scalp hair, sparse eyebrows and eyelashes, periorbital hyperpigmentation, prominent lips, hypodontia and conical teeth, reduced sweating, and dry and thin skin. Sequence analysis of the EDAR gene revealed a novel compound heterozygous mutation [c.52-2A>G; c.212G>A (p.Cys71Tyr)]. Our finding extends the body of evidence that supports the significance of the EDAR signalling pathway in the ectodermal morphogenesis.

Recurrent mutations in functionally-related EDA and EDAR genes underlie X-linked isolated hypodontia and autosomal recessive hypohidrotic ectodermal dysplasia

Mutations in three functionally related genes EDA, EDAR and EDARDD have been reported to cause hypohidrotic ectodermal dysplasia (HED), which is characterized by sparse hair, reduced ability to sweat, and hypodontia. In few cases mutations in the EDA gene have been found to result in X-linked recessive isolated hypodontia. In the study, presented here, we have ascertained two large Pakistani families (A and B) with autosomal recessive form of hypohidrotic ectodermal dysplasia and X-linked recessive isolated hypodontia. Genetic mapping showed linkage of family A to EDAR gene on chromosome 2q11-q13 and family B to EDA gene on chromosome Xq12-q13.1. Subsequently, DNA sequencing of the coding regions of EDAR and EDA genes revealed previously described mutations. Sequence analysis identified a four base-pair splice-junction deletion mutation (c.718_721delAAAG) in EDAR gene in family A and a missense mutation (c.T1091C; p.M364T) in EDA gene in family B. Recurrence of mutations in EDAR and EDA genes in unrelated families is evocative of the dispersion of ancestral chromosome in different locality groups through common ancestors.

Mutation screening of the Ectodysplasin-A receptor gene EDAR in hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia (HED) can be caused by mutations in the X-linked ectodysplasin A (ED1) gene or the autosomal ectodysplasin A-receptor (EDAR) and EDAR-associated death domain (EDARADD) genes. X-linked and autosomal forms are sometimes clinically indistinguishable. For genetic counseling in families, it is therefore important to know the gene involved. In 24 of 42 unrelated patients with features of HED, we found a mutation in ED1. ED1-negative patients were screened for mutations in EDAR and EDARADD. We found mutations in EDAR in 5 of these 18 patients. One mutation, p.Glu354X, is novel. In EDARADD, a novel variant p.Ser93Phe, probably a neutral polymorphism, was also found. Clinically, there was a difference between autosomal dominant and autosomal recessive HED patients. The phenotype in patients with mutations in both EDAR alleles was comparable to males with X-linked HED. Patients with autosomal dominant HED had features comparable to those of female carriers of X-linked HED. The teeth of these patients were quite severely affected. Hypohidrosis and sparse hair were also evident, but less severe. This study confirms Chassaing et al's earlier finding that mutations in EDAR account for approximately 25% of non-ED1-related HED. Mutations leading to a premature stop codon have a recessive effect except when the stop codon is in the last exon. Heterozygous missense mutations in the functional domains of the gene may have a dominant-negative effect with much variation in expression. Patients with homozygous or compound heterozygous mutations in the EDAR gene have a more severe phenotype than those with a heterozygous missense, nonsense or frame-shift mutation.

A novel deletion mutation in the EDAR gene in a Pakistani family with autosomal recessive hypohidrotic ectodermal dysplasia

A novel deletion mutation in the EDAR gene in a Pakistani family with autosomal recessive hypohidrotic ectodermal dysplasia

Novel mutations in the EDAR gene in two Pakistani consanguineous families with autosomal recessive hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia (HED) is a human heritable disorder characterized by sparse hair, a lack of sweat glands and malformation of teeth. There are X-linked, autosomal recessive and autosomal dominant forms of this disorder. Mutations in the EDA gene cause X-linked HED and mutations in either the EDAR or the EDARADD genes cause autosomal forms of HED. To identify pathogenic mutations in two consanguineous Pakistani families (A and B) with 11 affected individuals demonstrating the autosomal recessive form of HED. Genotyping of 17 members of the two families, including eight affected and nine unaffected individuals, was carried out by using polymorphic markers D2S293, D2S1893 and D2S1891, which are closely linked to the EDAR gene on chromosome 2q11-q13. To screen for mutations in the EDAR gene, all of its exons and splice junctions were polymerase chain reaction amplified from genomic DNA and sequenced directly in an ABI Prism 310 automated sequencer. Genotyping results showed linkage in both the Pakistani families to the EDAR locus. Sequence analysis of the EDAR gene identified two novel mutations in the families: a missense mutation (G382S) in family A and a 4-bp deletion (718delAAAG) in family B. We describe novel mutations in the EDAR gene in two Pakistani families affected with the autosomal recessive form of HED. Our findings extend the body of evidence that supports the importance of the ectodysplasin A1 isoform receptor, a member of the tumour necrosis factor receptor family, in the development of ectodermal appendages.

Clinical findings in mosaic carriers of hypohidrotic ectodermal dysplasia.

Hypohidrotic ectodermal dysplasia (HED) is a severe developmental disorder in which nonallelic genetic heterogeneity has been demonstrated. Even though X-linked and autosomal recessive forms are phenotypically similar, identification of the way of transmission is mandatory to give reliable genetic counseling to the family and to address molecular studies. Complete examination of relatives of patients with HED and identification of carriers of partial forms of the disorder in their families is the key to clarifying intrafamilial genetic transmission. Seven patients diagnosed as having HED and their first-degree relatives were carefully examined and tested with starch-iodine. Useful signs for identifying possible carriers of and postzygotic mosaics for X-linked HED and for finding distinctive features between the X-linked and the autosomal recessive forms of the disorder were recorded. Of these, the most striking finding was the clinical evidence of the distribution of normal and abnormal skin along Blaschko lines in heterozygous and postzygotic mutation carriers of X-linked HED. Six heterozygous female carriers of X-linked HED, 2 males with postzygotic mutations for X-linked HED, and 1 female with autosomal recessive HED were clinically identified. At the end, 6 families had a diagnosis of X-linked HED, while 1 had a diagnosis ofautosomal recessive HED. Clinical data, family history, and starch-iodine test results were never in conflict in the 7 families. Careful clinical examination is the best way to detect heterozygous carriers and postzygotic mutation of X-linked HED. Heterozygous parents of patients with autosomal recessive HED show no features of the disorder. The starch-iodine test is not superior to a clinical examination in heterozygous carrier detection but may play a confirmative role and be of help in differentiating X-linked and autosomal recessive HED in isolated patients.

COMPLETE EXPRESSION AND NORMAL FERTILITY IN A WOMAN WITH X-LINKED HYPOHIDROTIC ECTODERMAL DYSPLASIA ASSOCIATED WITH t(X;19). •473

We report on a woman with normal fertility and characteristic features of X-linked hypohidrotic ectodermal dysplasia (HED) associated with an X;19 translocation. She was reported on previously (Gorlin, et al., Z Kinderheilk, 1970) as an example of autosomal recessive inheritance of HED. The purpose of this report is to provide follow up to the paper of Gorlin, et al. and to document vertical transmission from an affected female, which to our knowledge is the first such report. The proband presented at age 30 years for preconception counseling of inheritance of HED. On physical examination, she was edentulous, with very sparse scalp hair, eyebrows and eyelashes, hyperkeratosis of the face, fingers and soles, and absence of sweat glands by visual inspection. Karyotype was 46,XX,t(X;19)(q11;q13.4). She subsequently became pregnant, and chorionic villus sampling showed the fetus to have a 46,XY,t(X;19)(q11;q13.4) karyotype. Based on these findings, autosomal recessive inheritance of HED is unlikely. Although some cases of autosomal recessive inheritance of HED are believed to occur, it is likely that many fully-manifesting females reported previously actually have an X-autosome translocation, similar to our patient and 3 others reported recently. X-autosome translocations are usually associated with gonadal dysgenesis and infertility, especially when it involves breakpoints between Xq13 and Xq26. The findings in this patient support the assignment of the ovarian dysgenesis locus telomeric to Xq11. However, in regard to the HED locus, the q11 breakpoint is centromeric to the HED region identified in previous reports. The findings in this patient suggest that (1) many cases of autosomal recessive HED may be the result of X-autosome translocations; (2) fertility in some fully-manifesting females may be normal; and (3) study of cases such as the one herein presented may provide important clues to the location of both the HED and ovarian dysgenesis loci.

Hypohidrotic ectodermal dysplasia: argument against an autosomal recessive form clinically indistinguishable from X-linked hypohidrotic ectodermal dysplasia (Christ-Siemens-Touraine syndrome)

Hypohidrotic ectodermal dysplasia (HED) is a well-described, X-linked recessive disorder characterized by hypohidrosis, hypodontia, and hypotrichosis in males. Reports of similarly affected females have suggested autosomal recessive inheritance in some families. The evidence for two clinically identical but genetically distinct disorders is not convincing, however. In two families with X-linked recessive inheritance of HED, the condition was severe in females. A critical review of previously reported cases of presumed autosomal recessive HED suggests that an autosomal recessive form of the condition identical to the X-linked HED may not exist. All sporadic instances of females with classic HED should be considered to be X-linked recessive, and counseling for X-linked recessive inheritance as well as autosomal recessive inheritance should be given.

Sweat pore counts in ectodermal dysplasias

In three families with X-linked anhidrotic ectodermal dysplasia and in one family with autosomal recessive hypohidrotic ectodermal dysplasia, sweat pore counts of fingertips were used in genetic counselling.