Detection Of EDA Gene Mutations And Phenotypic Analysis In Patients With Hypohidrotic Ectodermal Dysplasia

Objective:To detect the ectodysplasin A（EDA）gene mutation in patients with hypohidrotic ectodermal dysplasia（HED）,and to analyze the manifestation and the distribution pattern of missing permanent tooth of HED patients with EDA gene mutation.Methods:1.Twelve HED families were enrolled from clinic for genetic,systemic 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（NM₀01399.5）.2.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 guideline of the American College of Medical Genetics and Genomics（ACMG）.3.According to the results of clinical and X-ray examinations,the missing permanent teeth of HED male patients with EDA gene mutations were recorded and statistically analyzed.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:1.Eight out of twelve HED families including nine male patients were identified to carry eight EDA gene mutations,the detection rate was 66.67%,including:c.164T>C,p.Leu55Pro;c.457C>T,p.Arg153Cys;c.466C>T,p.Arg156Cys;c.584G>A,p.Gly195Glu;c.619de1G,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.2.Polyphen-2,Mutation Taster and PROVEAN were used to predict the functional impact of the eight mutant proteins.According to the ACMG pathogenicity classification guidelines,it was found that these mutations showed varying degrees of pathogenicity.3.The HED male patients with EDA gene mutations found in this study had the typical symptoms of hypotrichosis,hypohidrosis,hypodontia.HED male patients had varying degrees of tooth loss,and the remaining front teeth were mostly tapered teeth.Female carriers of HED had diverse phenotypes,with varying severity of symptoms,but overall symptoms were milder than those of male patients.4.The average number of missing permanent teeth in HED male patients with EDA gene mutations 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）.Specifically,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 five new pathogenic mutations and three known pathogenic mutations of EDA gene in twelve HED families,expanded the EDA gene mutation spectrum,and summarized the selective tooth loss rules of HED patients related to EDA gene mutations,which not only had provided new evidence for genetic diagnosis and prenatal consultation,but also had instructive suggestion for clinicians to initially judge suspected disease-causing gene mutatins.