Molecular Genetic Study Of Embryonic (Fetal) Arrest In Early Pregnancy

Background and objective:The main underlying cause of missed abortion(MA)is chromosomal abnormality.Due to the development in genomics and detection methods,exploring the genetic pathogenesis of MA is becoming an increasing focus of current research direction.Whole-exome sequencing(WES)technology was used to detect MA product of conception(POC)with normal chromosomes and bioinformatics analysis was used to identify genes important in early embryonic(fetal)development,providing new methods by which to study the mechanisms underlying MA.There are few reports on using WES to identify MA-related genes.Our study was divided into two parts.Part 1:Screening of MA villi using conventional karyotyping and next generation sequencing(NGS)Objective:To compare conventional karyotyping and NGS copy number variation analysis(CNVA)for characterizing POC after MA and discuss the advantages,limitations,and uniformity of the two methods in detecting POC chromosomal abnormalities.Methods:Sixty-nine MA POC samples were collected and analyzed by conventional karyotyping and NGS.Results:? The diagnostic success rate of conventional karyotyping was lower than that of NGS-CNVA.? The detection rate of chromosome abnormalities in all samples by conventional karyotyping was significantly lower than that by NGS.? Abnormalities in chromosome number were the most commonly type of chromosomal abnormalities found in the MA specimens,where most were in autosomal chromosomes.? The coincidence rate of the results from these two methods reached 93.33%.?There were 12 MA cases involving normal chromosomes detected by these two methods.Conclusion:Both conventional karyotyping and NGS have advantages and disadvantages when detecting POC chromosomes.The consistency in the detection results was high.Diagnostic efficiency could be improved by combining these two methods.Part 2:Identifying genetic mutations in POC with normal karyotypes using WESObjective:Use WES to identify genetic deficiencies in MA POC with normal chromosome and an unknown cause of MA.Methods:? DNA was extracted from villi with normal chromosomes from unexplained MA and WES was performed.? Genes associated with abnormal embryonic development,embryonic lethality,and MA in past genetic murine studies were selected using the Mouse Genome Informatics(MGI)database.? The WES data were analyzed and verified.? Thirty-six rare mutations involving 32 genes were screened using bioinformatics analysis tools.? The LDB1 heterozygous mutation c.662C>T mutation was analyzed as a pathogenic allele using multiple prediction tools.This mutation is extremely rare and was predicted to be a highly pathogenic variant associated with embryonic death.LDB1 mutations in POC may be associated with MA.DIDO1?LIAS?ATE1?OTX2?NF1?PTCH1?TRIM28?GAS1?INTS1?SRRT and CREBBP were also found to be the candidate genes for MA.Conclusion:Using WES combined with bioinformatics analysis of MA POC with normal chromosomes,genetic mutations were found to potentially be a cause of embryonic(fetal)death in early pregnancy.