Screening of EDA1 Gene in X-Linked Anhidrotic Ectodermal Dysplasia Using DHPLC: Identification of 14 Novel Mutations in Italian Patients

Rare X-Linked Hypohidrotic Ectodermal Dysplasia in Females Associated with Ectodysplasin-A Variants and the X-Chromosome Inactivation Pattern

The goal of this study was to identify the pathogenic gene variants in female patients with severe X-linked hypohidrotic ectodermal dysplasia (XLHED). Whole-exome sequencing (WES) and Sanger sequencing were used to screen for the pathogenic gene variants. The harmfulness of these variations was predicted by bioinformatics. Then, skewed X-chromosome inactivation (XCI) was measured by PCR analysis of the CAG repeat region in the human androgen receptor (AR) gene in peripheral blood cells. Two novel Ectodysplasin-A (EDA) heterozygous variants (c.588_606del19bp and c.837G>A) and one heterozygous variant (c.1045G>A, rs132630317) were identified in the three female XLHED patients. The bioinformatics analysis showed that these variants might be pathogenic. The tertiary structure analysis showed that these variants could cause structural damage to EDA proteins. Analysis of the skewed X-chromosome inactivation revealed that extreme skewed X-chromosome inactivation was found in patient #35 (98:2), whereas it was comparatively moderate in patients #347 and #204 (21:79 and 30:70). Our results broaden the variation spectrum of EDA and the phenotype spectrum of XLHED, which could help with clinical diagnosis, treatment, and genetic counseling.

Conservation analysis and pathogenicity prediction of mutant genes of ectodysplasin a

Background

Hypohidrotic ectodermal dysplasia (HED) is a common recessive X-linked hereditary disease that affects the development of ectoderm. Gene mutations of ectodysplasin A (EDA) play key roles in process of this disease. In our preliminary study, three unknown mutation sites (c.878 T > G, c.663-697del and c.587-615del) were detected from the pedigrees of HED.

Methods

Conservation analysis of the related homologous proteins in 3 unknown EDA gene mutation sites was conducted using the University of California Santa Cruz (UCSC) Genome Browser database. SIFT and PolyPhen-2, the online gene function prediction software, were utilized to predict the pathogenicity of point mutation of c.878 T > G.

Results

All three unknown mutation sites were located in the highly-conserved region of EDA and possessed strong amino acid conservation among different species. In addition, the results of the pathogenicity prediction of point mutation of c.878 T > G by SIFT (P = 0.00) and PolyPhen-2 (S = 0.997) demonstrated that the mutation site had considerable pathogenicity theoretically.

Conclusions

The EDA mutations of c.878 T > G, c.663-697del and c.587-615del may be responsible for the pathogenesis of HED in their pedigrees.

Eight Mutations of Three Genes (EDA, EDAR, and WNT10A) Identified in Seven Hypohidrotic Ectodermal Dysplasia Patients

Hypohidrotic ectodermal dysplasia (HED) is characterized by abnormal development of the teeth, hair, and sweat glands. Ectodysplasin A (EDA), Ectodysplasin A receptor (EDAR), and EDAR-associated death domain (EDARADD) are candidate genes for HED, but the relationship between WNT10A and HED has not yet been validated. In this study, we included patients who presented at least two of the three ectodermal dysplasia features. The four genes were analyzed in seven HED patients by PCR and Sanger sequencing. Five EDA and one EDAR heterozygous mutations were identified in families 1–6. Two WNT10A heterozygous mutations were identified in family 7 as a compound heterozygote. c.662G>A (p.Gly221Asp) in EDA and c.354T>G (p.Tyr118*) in WNT10A are novel mutations. Bioinformatics analyses results confirmed the pathogenicity of the two novel mutations. In family 7, we also identified two single-nucleotide polymorphisms (SNPs) that were predicted to affect the splicing of EDAR. Analysis of the patient’s total RNA revealed normal splicing of EDAR. This ascertained that the compound heterozygous WNT10A mutations are the genetic defects that led to the onset of HED. Our data revealed the genetic basis of seven HED patients and expended the mutational spectrum. Interestingly, we confirmed WNT10A as a candidate gene of HED and we propose WNT10A to be tested in EDA-negative HED patients.

Correlation between the phenotypes and genotypes of X-linked hypohidrotic ectodermal dysplasia and non-syndromic hypodontia caused by ectodysplasin-A mutations

Mutations in the ectodysplasin-A (EDA) gene can cause both X-linked hypohidrotic ectodermal dysplasia (XLHED) and non-syndromic hypodontia (NSH). The correlation between the phenotypes and genotypes of these two conditions has yet to be described. In the present study, 27 non-consanguineous Chinese XLHED subjects were screened and 17 EDA mutations were identified. In order to investigate the correlation between genotype and phenotype, we also reviewed related studies on NSH subjects with confirmed EDA mutations and compared the differences in the clinical manifestations and EDA mutations of the two conditions. Tooth agenesis was observed in addition to abnormalities of other ectodermal organs. Tooth agenesis was more severe in XLHED subjects than in NSH subjects, and there were statistically significant differences in 10 tooth positions in the XLHED and NSH subjects, including canines, premolars, and molars. With the exception of one splicing mutation, all mutations in the NSH subjects were missense mutations, and these were most likely to be located in the tumor necrosis factor (TNF) domain. Further, more than half of the mutations in the XLHED subjects were speculated to be loss of function mutations, such as nonsense, insertion, and deletion mutations, and these mutations were distributed across all EDA domains. Our results show that there exists a correlation between the phenotypes and genotypes of XLHED and NSH subjects harboring EDA mutations. Further, our findings suggest that NSH is probably a variable expression of XLHED. This finding might be useful for clinical diagnosis and genetic counseling in clinical practice, and provides some insight into the different manifestations of EDA mutations in different ectodermal organs.

A miniaturized spatial temperature gradient capillary electrophoresis system with radiative heating and automated sample introduction for DNA mutation detection

A miniaturized spatial temperature gradient CE system with automated sample introduction for DNA mutation detection was established. Continuous electrokinetic sample injection was achieved by combining an automated slotted-vial array sample introduction device to the spatial temperature gradient CE system. The temperature gradient was produced by a radiative heating system with a single graphite block heater, and the stability of the temperature gradient was investigated. The temperature variation of each measure point was 0.12-0.21% RSD (n=7) within 6 h. A 14-cm Teflon AF-coated silica capillary was used both as the separation channel and as the liquid-core waveguide tube of fluorescence signal. Under a temperature gradient from 54.8 to 59.5°C, a low range control mutation standard (209 bp) was separated within 4 min with only 5.6 nL sample consumption. Automated continuous sample introducing and changing were realized with a carryover of 3.3%. Utility of the system was further demonstrated by detecting K-ras gene mutations in paraffin tissue sections from two colorectal cancer patients.