[Detection of EDA gene mutation and phenotypic analysis in patients with hypohidrotic ectodermal dysplasia]

OBJECTIVE

To detect the ectodysplasin A (EDA) gene mutation in patients with hypohidro-tic ectodermal dysplasia (HED), and to analyze the distribution pattern of missing permanent teeth and the systemic manifestation of HED patients with EDA gene mutation.

METHODS

Twelve HED families were enrolled from clinic for genetic history collection, systemic physical examination and oral examination. Peripheral blood or saliva samples were collected from the probands and the family members to extract genomic DNA. PCR amplification and Sanger sequencing were utilized to detect the EDA gene variations, which were compared with the normal sequence (NM_001399.5). The functional impact of EDA gene variants was then evaluated by functional prediction of mutation, conservation analysis and protein structure prediction. The pathogenicity of each EDA gene variation was assessed according to the stan-dards and guidelines of the American College of Medical Genetics and Genomics (ACMG). The systemic phenotype and missing permanent tooth sites of HED patients with EDA gene mutations were summarized, and the missing rate of each tooth position was analyzed and compared.

RESULTS

Eight out of twelve HED families were identified to carry EDA gene mutations, including: c.164T>C(p.Leu55Pro); c.457C>T (p.Arg153Cys); c.466C>T(p.Arg156Cys); c. 584G>A(p.Gly195Glu); c.619delG(p.Gly207Profs*73); c.673C>T(p.Pro225Ser); c.676C>T(p.Gln226*) and c.905T>G(p.Phe302Cys). Among them, c.164T>C(p.Leu55Pro); c.619delG(p.Gly207Profs*73); c.673C>T(p.Pro225Ser); c.676C>T(p.Gln226*) and c.905T>G(p.Phe302Cys) were novel mutations. The HED patients with EDA gene mutations in this study were all male. Our results showed that the average number of missing permanent teeth was 13.86±4.49, the average number of missing permanent teeth in the upper jaw was 13.14±5.76, the missing rate was 73.02%. And in the lower jaw, the average number of missing permanent teeth was 14.57±3.05, the missing rate was 80.95%. There was no significant difference in the number of missing teeth between the left and right sides of the permanent dentition (P>0.05). Specifi-cally, the maxillary lateral incisors, the maxillary second premolars and the mandibular lateral incisors were more likely to be missing, while the maxillary central incisors, the maxillary and mandibular first molars had higher possibility of persistence.

CONCLUSION

This study detected novel EDA gene pathogenic variants and summarized the distribution pattern of missing permanent teeth of HED patients, thus enriched the variation and phenotype spectrum of EDA gene, and provided new clinical evidence for genetic diagnosis and prenatal consultation.

Mutation Screening of the EDA Gene in Seven Chinese Families with X-Linked Hypohidrotic Ectodermal Dysplasia

BACKGROUND

As the most common form of ectodermal dysplasia (ED), X-linked hypohidrotic ED (XLHED) is characterized by the triad of hypohidrosis, hypotrichosis, and anodontia in male patients. The gene responsible for XLHED is EDA. To date, more than 300 mutations have been identified in this gene, including point mutations, deletions, and insertions. Most of the mutations result in XLHED, while the rest cause X-linked dominant incisor hypodontia.

OBJECTIVE

Mutation screening was performed in seven Chinese families with XLHED.

RESULTS

Mutations were identified in all seven families, including four previously reported missense mutations (p.M1T, p.R156C, p.G299S, and p.A349T) and three novel mutations; missense mutation (p.Q358 L), indel (P228Tfs*52), as well as a large deletion.

CONCLUSION

Our results extend the mutational spectrum of EDA and can be helpful with genetic counseling and prenatal diagnosis for these families.

De novo EDA mutations: Variable expression in two Egyptian families

OBJECTIVE

Mutations in the EDA gene, encoding the epithelial morphogen ectodysplasin-A, can result in different but overlapping phenotypes. Therefore the aim of the study was to search for etiological variations of EDA and other candidate genes in two unrelated Egyptian male children with sporadic non-syndromic tooth agenesis (NTA) and hypohidrotic ectodermal dysplasia (HED).

DESIGN

Direct sequencing of the coding regions including exon-intron boundaries of EDA, MSX1, PAX9, WNT10A and EDAR was performed in probands and their available family members.

RESULTS

Two etiological mutations were found in the EDA coding region. The patient with NTA in both deciduous and permanent dentition was a carrier of a novel in-frame deletion situated in the short collagenous domain (c.663-680delTCCTCCTGGTCCTCAAGG, p.222-227delPPGPQG). The second mutation, located outside the minimal furin consensus motif (c.463C>T, p.Arg155Cys, rs132630312), was identified in the patient exhibiting all typical features of HED. The identified EDA mutations were not detected in probands' family members as well as in 188 unrelated control individuals. No pathogenic variants were found in the MSX1, PAX9, WNT10A and EDAR genes.

CONCLUSION

Our results increase the knowledge of the spectrum of EDA mutations and confirm that this gene is an important candidate gene for two developmental diseases sharing the common feature of the congenital lack of teeth. In addition, these results can support the hypothesis that X-linked HED and EDA-related NTA are the same disease with different degrees of severity.

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.

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.