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.     

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.     

Mutations in EDAR account for one-quarter of non-ED1-related hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia (HED) is characterized by abnormal development of the eccrine sweat glands, hair, and teeth. The X-linked form of the disease, caused by mutations in the ED1 gene, represents the majority of HED cases. Autosomal-dominant and -recessive forms occur occasionally and result from mutations in at least two genes: EDAR and EDARADD. These different forms are phenotypically indistinguishable. To better assess the implication of the EDAR gene in HED, we screened for mutations in 37 unrelated HED families or sporadic cases with no detected mutations in the ED1 gene. We identified 11 different mutations, nine of which are novel variants, in two familial and seven sporadic cases. Seven of the 11 are recessive mutations (c.140G>A (p.Cys47Tyr), c.266G>A (p.Arg89His), c.329A>C (p.Asp110Ala), c.442T>C (p.Cys148Arg), c.1208C>T (p.Thr403Met), c.1302G>T (p.Trp434Cys) and c.528+1G>A), and the other four are probably dominant (c.1129C>T (p.Leu377Phe), c.1237A>C (p.Thr413Pro), c.1253T>C (p.Ile418Thr), and c.1259G>A (p.Arg420Gln)). Our study demonstrates that EDAR is implicated in about 25% of non-ED1 HED, and may account for both autosomal-dominant and -recessive forms. The correlation between the nature and location of EDAR mutations and their mode of inheritance is discussed. A genotype-phenotype relationship was evaluated, since such data could be helpful for genetic counseling.     

Scarcity of mutations detected in families with X linked hypohidrotic ectodermal dysplasia: diagnostic implications.

Indirect molecular diagnosis of X linked hypohidrotic ectodermal dysplasia (XLHED), a congenital disorder of hair, teeth, and eccrine sweat glands, has been possible by linkage analysis. Direct mutation detection would enable carrier detection in female relatives of sporadic cases, as well as help distinguish XLHED from the rarer, clinically indistinguishable, autosomal recessive disorder ARHED. Recently, a candidate gene for XLHED has been identified. Genomic DNA from 162 affected males and 21 females, who were either obligate carriers or had manifestations of the disorder, were screened by SSCP analysis. A subset of the patients had been previously screened for large genomic deletions and had limited screening of a single exon by SSCP analysis. The two known exons were amplified using flanking primers. Approximately 7% of patients, all males, had putative mutations identified within exon 1, but no variants were found within exon 2. Ten different putative mutations and four probable polymorphisms were identified. Both of the known exons were sequenced in 10 patients who had no detectable SSCP changes, but no additional mutations were found. No correlation between phenotype and genotype was evident between either affected subjects or subjects with or without detectable mutations. The results of the study indicate that only a small minority of affected males can be diagnosed by direct mutation analysis, and that the remainder of the patients are likely to have mutations in as yet unidentified exons of the EDA gene. Linkage analysis, in informative situations, therefore remains the only practical diagnostic option available.     

Only four genes (EDA1, EDAR, EDARADD, and WNT10A) account for 90% of hypohidrotic/anhidrotic ectodermal dysplasia cases

Hypohidrotic and anhidrotic ectodermal dysplasia (HED/EDA) is a rare genodermatosis characterized by abnormal development of sweat glands, teeth, and hair. Three disease-causing genes have been hitherto identified, namely, (1) EDA1 accounting for X-linked forms, (2) EDAR, and (3) EDARADD, causing both autosomal dominant and recessive forms. Recently, WNT10A gene was identified as responsible for various autosomal recessive forms of ectodermal dysplasias, including onycho-odonto-dermal dysplasia (OODD) and Sch?pf-Schulz-Passarge syndrome. We systematically studied EDA1, EDAR, EDARADD, and WNT10A genes in a large cohort of 65 unrelated patients, of which 61 presented with HED/EDA. A total of 50 mutations (including 32 novel mutations) accounted for 60/65 cases in our series. These four genes accounted for 92% (56/61 patients) of HED/EDA cases: (1) the EDA1 gene was the most common disease-causing gene (58% of cases), (2)WNT10A and EDAR were each responsible for 16% of cases. Moreover, a novel disease locus for dominant HED/EDA mapped to chromosome 14q12-q13.1. Although no clinical differences between patients carrying EDA1, EDAR, or EDARADD mutations could be identified, patients harboring WNT10A mutations displayed distinctive clinical features (marked dental phenotype, no facial dysmorphism), helping to decide which gene should be first investigated in HED/EDA.     

X连锁隐性遗传性少汗性外胚层发育不全一家系EDA基因突变分析

目的 对1个X连锁隐性遗传性少汗性外胚层发育不全(X-linked hypohidrotic ectodermal dysplasia,XLHED)家系进行EDA基因检测,分析基因突变类型,探讨其遗传学因素及发病原因.方法 对该XLHED家系进行家系调查,收集家系患者及部分成员和50名无亲缘关系的正常个体的外周血标本并提取基因组DNA,应用聚合酶链反应扩增EDA基因8个外显子,DNA直接测序进行突变检测.结果 该家系中患者检出EDA基因第3外显子存在c.467G＞A突变,导致R156H错义突变.先证者的母亲及姨妈携带c.467G＞A杂合突变,家系中正常个体和正常对照个体均未检测到该突变.结论 EDA基因的R156H突变可能是引起该XLHED家系先证者少汗性外胚层发育不全的致病原因.     

Detection of de novo mutations and analysis of their origin in families with X linked hypohidrotic ectodermal dysplasia.

Hypohidrotic ectodermal dysplasia (EDA) has been localised to the q12-q13.1 region of the X chromosome by both physical and genetic mapping methods. Although linkage analysis using closely linked flanking markers can clarify the carrier status for many females at risk for the disorder, knowledge of the origin of the mutation in instances of possible de novo mutation is critical for accurate genetic counselling of families. Two methods have been used to confirm de novo mutation in families with EDA and to trace their origin. Direct detection of three de novo molecular deletions, one arising during oogenesis and the other two during spermatogenesis, was achieved by Southern analyses using cosmids isolated from the EDA region as probes. Seven de novo mutations arising during spermatogenesis, and two possible de novo mutations during oogenesis, were identified by an analysis of the cosegregation of the disorder with polymorphic markers closely linked to and flanking the EDA locus. The confirmation and analysis of the origin of the 10 de novo mutations greatly assisted genetic counselling in these families. The apparent 3.5:1 excess of male to female origin of mutation in families studied with unidentified types of mutation is similar to other studies of X linked disorders, and suggests that the majority of these mutations may involve single base pair substitutions.     

六个少汗性外胚层发育不全家系ED1基因的突变分析

目的 对6个少汗性外胚层发育不全(hypohidrotic ectodermal dysplasia,HED)家系进行ED1基因突变分析,为其提供遗传咨询和产前诊断.方法 采用聚合酶链反应和DNA直接测序对6个家系的先证者及其成员ED1基因的8个外显子进行序列分析.结果 6个家系患者中均检出了ED1基因突变,分别为R153C、A349T、G299S、A349T、X392Q和第9外显子缺失突变,其中R153C、X392Q和第9外显子缺失突变在中国人群中首次报告.上述位点的杂合突变在部分女性亲属中检出.结论 错义突变R153C、A349T、G299S和X392Q和第9外显子缺失是导致6个少汗性外胚层发育不全家系患者临床表型的主要原因,通过对家系个体ED1基因分析可进行携带者筛查和产前诊断.     

X-连锁无汗性外胚层发育不良一家系EDA新发突变

目的检测一X连锁无汗性外胚层发育不良家系EDA基因突变。方法提取先证者、其姐和父母外周血基因组DNA,PCR扩增EDA基因编码区的8个外显子,PCR产物测序,明确突变位点。结果先证者EDA基因6号外显子第781位胞嘧啶C突变成胸腺嘌呤T,使其编码的蛋白第261位谷氨酰胺密码子CAA变成终止密码子UAA,蛋白表达提前终止;患者的姐姐和母亲在该位点均为C/T杂合子,患者父亲在该位点为C纯合子。结论本家系中c.781C>T突变为国内外首报,是导致X连锁无汗性外胚层发育不良临床表型的原因。     

EDAR mutation in autosomal dominant hypohidrotic ectodermal dysplasia in two Swedish families

Background  

Hypohidrotic ectodermal dysplasia (HED) is a genetic disorder characterized by defective development of teeth, hair, nails and eccrine sweat glands. Both autosomal dominant and autosomal recessive forms of HED have previously been linked to mutations in the ectodysplasin 1 anhidrotic receptor (EDAR) protein that plays an important role during embryogenesis.     

A novel de novo frame-shift mutation of the EDA gene in a Chinese Han family with hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia (HED) is characterized by severe hypohidrosis, hypotrichosis, and hypodontia. It can be inherited in autosomal dominant, autosomal recessive, or X-linked patterns. Mutations in the EDA gene, which encodes ectodysplasin-A, are responsible for X-linked HED (XLHED). In the present study, we identified a Chinese Han family with XLHED. Direct DNA sequence analysis of the entire coding region and exon–intron boundaries of EDA identified a novel de novo mutation, c.573_574insT, in two affected males and one carrier female. Restriction fragment length polymorphism (RFLP) analysis showed that the mutation was not present in 200 controls. The 1-bp insertion mutation resulted in a frameshift, which causes premature termination of EDA polypeptide and truncation of the EDA protein. These results suggest that the c.573_574insT mutation of the EDA gene is a cause for XLHED in the family. To the best of our knowledge, this is the first de novo insertion mutation of EDA described for XLHED.Changzheng Huang and Qinbo Yang contribute equally to this work.     

A new form of hypohidrotic ectodermal dysplasia

We report on a 17-yr-old young woman with an apparently new tricho-onycho-hypohidrotic ectodermal dysplasia. The manifestations include primary interdigital webbing, contractures of fingers and toes, conjunctivitis from narrowing of nasolacrimal ducts, and a small cortical opacity in the lens of the left eye. Psychosocial problems due to the cosmetic appearance are severe. Cause is uncertain.     

Analysis of craniofacial development in children with hypohidrotic ectodermal dysplasia

Ectodermal dysplasias (ED) are a heterogeneous group of inheritable disorders characterized by abnormal development of embryologic ectoderm derivatives. The purposes of this study were to: 1) create baseline cephalometric norms for male children with ED; 2) assess craniofacial growth and development in hypohidrotic ED male children with severe hypodontia, compared with non-ED children with class I dental relationships; 3) compare the craniofacial morphology of titanium dental implant-treated ED males with non-implant-treated ED males; and 4) correlate the severity of hypodontia to craniofacial dysmorphology. Cephalometric radiographs of class I individuals and implant-treated and nontreated ED groups were used to evaluate craniofacial morphology. Traditional cephalometric landmarks and measurements were used to compare groups using the generalized estimate equation analysis. Age, gender, and the number of permanent maxillary teeth present had a significant (P =.01) explanatory relationship with the craniofacial measures when comparing untreated ED children to norms. Mean craniofacial differences between ED and non-ED children still existed when the explanatory effects of these variables were controlled, indicating dysmorphology in several craniofacial structures (e.g., cranial base, mandibular length). The number of missing maxillary permanent teeth was significantly related with craniofacial dysmorphology in the ED population. Craniofacial morphology did not differ significantly between implant-treated and nontreated ED children, suggesting that treatment with intraosseous dental implants, as applied in this population, did not rescue normal craniofacial growth and development.     

两个X连锁少汗性外胚层发育不良家系的基因突变分析

目的 对两个X连锁隐性遗传少汗性外胚层发育不良(X-linked hypohidrotic ectodermal dysplasia,XLHED)家系进行ED1基因突变分析,为罹患家庭提供遗传咨询及产前诊断.方法 综合应用序列分析及多重连接依赖性探针扩增方法,对两个家系的先证者进行ED1基因突变分析,并针对检测到的突变位点对女性成员进行检测.采集家系1胎儿的羊水细胞进行产前诊断,包括致病突变位点的分析、ED1基因内4个短串联重复序列(short tandem repeat,STR)位点的单倍型连锁分析、性别鉴定及核型分析.结果 家系1先证者缺失ED1基因第1外显子及下游2个STR位点DXS8269,DXS1422区域,其余外显子序列分析未见异常,其女儿为该缺失突变的携带者;结合连锁分析、性别鉴定及核型分析结果,家系1胎儿为男性非ED1基因缺失突变携带者,胎儿足月分娩后随访,为健康个体.家系2先证者经序列分析检测到ED1基因第3外显子c.463C＞T(R155C)错义突变,母亲为c.463C＞T(R155C)杂合突变携带者.结论 ED1基因第1外显子区域缺失和错义突变R155C是导致2个少汗性外胚层发育不全家系患者临床表型的主要原因,ED1基因的突变检测结合单倍型分析,能准确地对该类家系提供产前诊断.     

Subtotal amelia in a child with autosomal recessive hypohidrotic ectodermal dysplasia

We report an inbred Tunisian family, in which the proband manifested signs of hypohidrotic ectodermal dysplasia, subtotal amelia, scoliosis and left renal agenesis. Two other family members had the full clinical criteria of hypohidrotic ectodermal dysplasia, characterized by deficient sweat glands, hypodontia, hypoplasia of the mucous glands, and fine hair. Nine family subjects had variable clinical expression of the disorder.     

X-linked hypohidrotic ectodermal dysplasia. Genetic and dental findings in 67 Danish patients from 19 families

This study aimed to investigate genotype and phenotype in males affected with X-linked hypohidrotic ectodermal dysplasia (HED) and in female carriers, to analyse a possible genotype–phenotype correlation, and to analyse a possible relation between severity of the symptoms and the X-chromosome inactivation pattern in female carriers. The study group comprised 67 patients from 19 families (24 affected males and 43 female carriers). All participants had clinical signs of ectodermal dysplasia and a disease-causing EDA mutation. The EDA gene was screened for mutations by single-stranded conformational polymorphism and direct sequencing. Multiplex ligation-dependent probe amplification (MLPA) analysis was used to detect deletions/duplications in female probands. Sixteen different EDA mutations were detected in the 19 families, nine not described previously. The MLPA analysis detected a deletion of exon 1 in one female proband. No genotype–phenotype correlations were observed, and female carriers did not exhibit a skewed X-chromosome inactivation pattern. However, in two female carriers with pronounced clinical symptoms, in whom the parental origin of each allele was known, we observed that mainly the normal allele was inactivated.     

X-连锁无汗性外胚层发育不良一家系产前诊断

目的基因诊断方法及连锁分析对一X连锁无汗性外胚层发育不良（XLHED）家系进行产前诊断。方法提取患儿、患儿母亲外周血以及胎儿脐血中的基因组DNA,PCR扩增该疾病相关基因EDA的五个外显子,并直接测序;选择与该基因连锁的STR位点,位于基因上游的一个（CA）n进行家系内的连锁分析。结果患儿的基因突变未发现,连锁分析提示胎儿为男性未携带风险X染色体,出生后证实胎儿正常。结论基因检测及多态性连锁分析在XLHED家系中进行产前诊断是一种较好的方法。