Clinical And Genetic Characteristics Of Congenital Disorder Of Glycosylation Caused By PMM2 Gene Mutation

Background Congenital disorders of glycosylation(CDG)is a disease caused by abnormal polysaccharide synthesis and binding to proteins and lipids,which are a group of genetic and metabolic diseases that have attracted extensive attention in recent years.Most of the inheritance patterns are autosomal recessive inheritance,and a few are autosomal dominant and X-linked inheritance.So far,more than 100 types of CDG have been discovered.This disease can almost cause functional damage to multiple organs and systems of the whole body,such as liver,kidney,nerves,heart and blood vessels.PMM2-CDG(CDG Ia)is the most common type of CDG known at present,which is caused by pathogenic mutations of the phosphomannose mutase 2(PMM2)gene.PMM2 is a cytoplasmic enzyme located on chromosome 16p13,which can convert mannose6-phosphate to mannose 1-phosphate.The incidence of this disease is about 1 : 20,000,and the early mortality is high.Currently,p.Arg141 His is the most common mutation type reported in the literature,followed by p.Val231 Met.This disease can involve multiple organs and systems,without definite and effective therapeutic scheme.In this study,the clinical manifestations and genetic characteristics of a patient with PMM2-CDG were analyzed,and the cases with hepatic manifestations reported at home and abroad were reviewed,to further explore the liver manifestations and genetic characteristics of the disease,so as to provide a basis for its diagnosis and genetic counseling.Objectives To investigate the clinical data and genetic characteristics of a case of CDG caused by PMM2 gene mutations,and review the hepatic manifestations and genetic characteristics of relevant cases reported at home and abroad,so as to further enrich the gene library of this disease,provide more data and basis for its diagnosis and genetic counseling,and improve clinicians’ understanding of this disease.Method1.Data collection: The basic,clinical and family data of the subjects were collected.2.Sample collection: With the consent of the patients’ guardians and family members,5ml peripheral venous blood was collected from the child and parents into purple EDTA tubes.3.Sample treatment: Blood DNA was extracted using a DNA extraction kit.4.Construction of DNA library: The DNA library was constructed using a KAPA Library Preparation Kit.5.DNA sample capture: The vacuum concentrated DNA library was eluted by Seq Cap hybrid mix,and then added with heat capture probe-library mixture.Afterwards,the treated binding buffer-resuspended Dynal magnetic beads were added,and resuspended magnetic beads were obtained by further processing.The resuspended magnetic beads were used for PCR amplification.The PCR products were purified using Ampure magnetic beads and quantified by Qubit.6.Sequencing: The captured DNA samples were collected for Illumina Nova Seq high-throughput sequencing.The sequencing data were read and bioinformatically analyzed after qualified by Illumina Sequence Control Software(SCS).7.Sanger sequencing verification: Sanger sequencing was used to verify the sites to be verified of the subject and family members.8.Case analysis: By keyword searching of the literature at home and abroad,and reviewing the relevant cases reported at home and abroad,the hepatic manifestations and related genetic characteristics of PMM2-CDG cases were summarized.Result1.Gene sequencing showed two heterozygous mutations in the PMM2 gene of this child:c.556 G>A(p.G186R)and c.584＿585del AT(p.H195Rfs*4).The child was diagnosed as PMM2-CDG,and parents were healthy,carrying a pathogenic mutation individually.2.In this study,a total of 163 foreign articles were searched,involving 950 reported cases.Among them,hepatic manifestations were found in 288 cases,accounting for 30%.A total of 46 missense mutations were reported,of which c.422G>A(p.Arg141His),c.691G>A(p.Val231Met)and c.357C>A(p.Phe119Leu)had the highest frequencies.Additionally,a total of 12 domestic articles were searched,including 20 reported cases,among which 14 presented hepatic manifestations.In cases with hepatic manifestations,17 mutation sites were detected,including 15 missense mutations,1 frameshift mutation and 1 splicing mutation.One Chinese article and 1 English article with the same sites were searched,involving a total of 3 cases.Conclusion1.The clinical manifestations,auxiliary examination and gene detection results of the patient reported in this study are all consistent with the characteristics of PMM2-CDG,resulting in definite diagnosis.Moreover,this mutation has not been reported before,which further enriches the gene library of this disease.2.This study summarizes the hepatic manifestations and genetic characteristics of PMM2-CDG cases reported at home and abroad,so as to provide a further basis for the diagnosis and improve the medical staff’s understanding of this disease.