Identification Of Pathogenic Gene In A Family With Hypohidrotic Ectodermal Dysplasia

Objective1.Clinical examination and pedigree investigation were carried out in detail for the pedigree with hypohidrotic ectodermal dysplasia(HED)collected by the proband.2.Using target region sequencing technology to screen the pathogenic genes of the collected HED families,analyze possible potential mutations and enrich the HED-related gene mutation spectrum in Chinese patients.And provide a basis for the pathogenesis and molecular genetic research of the disease,at the same time,provide genetic counseling and prenatal diagnosis for patients and carriers in the family to reduce birth defects.Methods1.Through the oral and physical examination of a child with congenital majority teeth loss,our research group found that the child has typical clinical manifestations including abnormal development of the hair,skin,sweat glands,and teeth.These were consistent with the typical clinical manifestations of HED(OMIM),and the clinical diagnosis was HED.We collected the clinical data of the HED family members through the proband,inquired the basic information of the family members,and carried out detailed oral examination.According to the clinical data of the pedigree,we drew the pedigree map and analyzed the genetic pattern and phenotypic characteristics of the pedigree.Blood samples were obtained from 4 members of this family including the proband(?3),his siblings(?4)and parents(?3,?4).Genomic DNA was extracted from peripheral blood by phenol-chloroform method.2.For the known pathogenic genes of HED,the genomic DNA of the proband was sequenced by the target region sequencing technology to screen out candidate pathogenic gene in this patient.3.Using Sanger sequencing,the proband(III3),other members of the family(III4,II3,II4)and the normal populations outside the family were tested for candidate pathogenic genes to determine the pathogenic genes.Results1.The research family has 11 members in 3 generations,including 2 patients and 2 carriers.The clinical examination results of patients(III3,III4)showed the clinical feature of sparse hair,absence of eyelashes and eyebrows,absence of sweating,intolerance to heat,periorbital hyperpigmentation and wrinkling,a saddle-shaped nose,protuberant lips,perioral pigmentation.The results of oral examination showed that the congenitally missing teeth and conical teeth,the alveolar alveolar ridge was low and flatthe in the edentulous area,but the number and location of the missing teeth were slightly different.The proband(III3),male,7 years old,was in the mixed dentition stage,with 9 erupted deciduous teeth at the position of 51,53,55,63,65,73,75,83,85,and 4 erupted permanent teeth at the position of 16,26,36,46.And the crown of 51,53,63,73,83 were conical.The X-ray showed that there were permanent tooth germs of 33,43 in the jaw,and no permanent tooth germs were found in the remaining missing areas,and 22 permanent teeth were congenitally missing.The patient(III4),male,4 years old,was in the deciduous dentition stage,with 10 erupted deciduous teeth at the position of 51,53,55,61,63,65,73,75,83,85.And the crown of 51,53,61,63,73,83 were conical.The X-ray showed that there were permanent tooth germs of 16,26,36,46,12,22,33,43 in the jaw,and no permanent tooth germs were found in the remaining missing areas,and 20 permanent teeth were congenitally missing.A 32-year-old female carrier had sparse hair,the sweat gland secretion was normal.The results of oral examination showed that deciduous teeth 52 were retained,12,22 were missing,52,23 were conical teeth.The X-ray showed that there were no 12,22 permanent tooth germs.A 67-year-old female carrier had congenital missing teeth,conical teeth,sparse hair and other mild clinical manifestations.Other members of the family were normal.2.According to the collected data of the family,the genetic map of the family was drawn,and it can be seen that the family was consistent with the characteristics of recessive inheritance of X chromosome: all patients were males in the families,the females in the families were recessive carries,and parents of the male patient had normal phenotypes,and the disease-causing gene comes from the mother.3.The target region sequencing and sanger sequencing results revealed one missense mutationat(c.463C>T)in exon 3 of EDA gene of the proband(III3).The results showed that there was a change from arginine to cysteine at 155 th amino acid in the ectodysplasin-A(p.Arg155Cys).The same mutation was found in the proband's brother(III4)(EDA: c.463 C>T).Meanwhile there were heterozygous double peaks of nucleotide C and T in the mother(II4)and single peak of nucleotide C at the same position in the father(II3).None of the 100 healthy people had the same mutation in EDA gene.Conclusions1.The family has 11 members in 3 generations,including 2 patients(?3,?4),and the genetic diagnosis were XLHED.2.There was one missense mutation(c.463C>T)in exon 3 of EDA gene of the pedigree's patient,and EDA gene was the pathogenic gene of the HED pedigree.