Analysis Of IDS Gene Mutation And Hematopoietic Stem Cell Transplantation For Mucopolysaccharidosis Type Ⅱ

Part One Mutation analysis of the IDS gene in patients with mucopolysaccharidosis type ⅡObjective: Mucopolysaccharidosis Type Ⅱ(MPS Ⅱ,OMIM: 309900)was a rare X-linked recessive genetic disease,which caused the accumulation of mucopolysaccharides in almost all cells,tissues and organs due to the deficiency in the activity of idulos-2-sulfatase(IDS).Make viscera function impaired.The clinical characteristics,leukocyte IDS activity and IDS gene mutation types of 30 children with MPS Ⅱ were retrospectively analyzed.Methods: The activity of IDS in leukocytes was measured by fluorescence substrate method.Genetic testing included family whole-exome sequencing(WES)and copy number variation sequencing(CNV-seq).Results: The clinical manifestations of the 30 patients mainly included:hepatosplenomegaly,flat nose bridge,large tongue,large head,joint stiffness,elliptic vertebrae,osteoporosis,mental retardation,developmental delay,obstructive sleep apnea,adenoid hypertrophy,umbilical hernia,abdominal hernia,etc.The age of diagnosis ranged from 4 months to 13 years,and all were male.Blood leukocyte IDS activity: 0.28±0.49nmol/g/min(reference value: 6.1～20.8nmol/g/min).25 different mutations were identified in IDS genes,including 16 previously reported and 9 novel mutations(6 frameshift:c.815-818 dup AACG,c.1453 dup A,c.1270-1271 del GT,c.1484-1485 ins TA,c.854 del A,c.12-13 del CC,3 missense: c.325T>G,c.140T>C,c.248 T>G).For three of the newly discovered missense mutation in the computer simulations of the protein structure analysis,the results show that mutations in IDS protein sulfatase domain near the active site structure,W109 G tryptophan was replaced by the glycine,L47 P leucine was replaced by the proline,V83 G replaced by glycine,valine expectations changed their electrostatic interaction,may affect the structure of the protein and thus its function.Conclusions: Our study expands the spectrum of MPS II genotype,provides new insights into the molecular mechanisms of MPS II,and contributes to future studies of genotype-phenotypic associations to estimate prognosis and develop new treatment regimens.Part Two Analysis of clinical effect of allogeneic hematopoietic stem cell transplantation in treatment of mucopolysaccharidosis type ⅡObjective: In order to investigate the outcomes of allogeneic hematopoietic stem cell transplantation(HSCT)in children with Mucopolysaccharidosis type Ⅱ(MPS Ⅱ).Methods: A retrospective analysis was performed on 30 cases with MPSⅡ who have undergone allogeneic hematopoietic stem cell transplantation(HSCT)between January 2019 and March 2021.The analysis included recipients’ status,donors’ status,transplant-related complications,time of granulocyte and platelet implantation,enzyme changes,chimerism,transplant-related complications and organ recovery.Results: All the 30 cases were male.The median age at transplantation was 3 years and 7 months(1 year and 4 months to 13 years and 1 month),median length of follow-up was 16 months(4 to 30 months)post HSCT.Five children underwent double unrelated umbilical cord blood stem cell transplantation,22 children underwent single unrelated umbilical cord blood stem cell transplantation,3 children underwent father’s peripheral blood stem cell transplantation.All these 30 children achieved full-donor chimerism and normal enzyme levels at 1 month after transplantation.There were 12 patients with different degrees of transplant-related complications after transplantation,the incidence was 40%(12/40),2 patients developed autoimmune hemolysis,1 patient developed pulmonary infection,and the incidence of grade Ⅰ-Ⅳacute graft-versus-host disease(a GVHD)was 6.7%(2/30),including 1 patient with grade Ⅱ skin a GVHD.1 patient with grade Ⅱ intestinal a GVHD,and no chronic GVHD occurred.Viral activation occurred in 7 patients after transplantation,4 patients with cytomegalovirus(CMV),1 patient with EB viremia,1 patient with BK viral cystitis,and 1 patient with both CMV and BK viruses.The overall survival rate during the follow-up period was 96.7%(29/30).Four months after transplantation,1 patient developed autoimmune hemolysis and died of secondary pulmonary infection,and the symptoms of the other 29 children improved significantly during the follow-up period.Conclusions: HSCT can save the lives of patients with MPS Ⅱ.Standardized follow-up and multidisciplinary team cooperation can help evaluate the long-term effects of transplantation and further improve the quality of life of patients with MPS Ⅱ.In this study,30 cases were followed up to evaluate the advantages of HSCT.Part Three Summarized the genotypes and clinical phenotypes of Chinese Mucopolysaccharidosis type ⅡObjective: To investigate the correlation between genotype and clinical phenotype of MPS Ⅱ.Methods: The related literatures of Chinese patients diagnosed with MPS Ⅱ disease published before January 1,2022 in CNKI,Wanfang,Pub Med and China Biomedical Literature Database were searched.A total of35 literatures were included.The Chinese search terms are "mucopolysaccharidosis type Ⅱ","iduronate-2-sulfatase gene","Hunter’s syndrome".The English search terms are "mucopolysaccharidosis type Ⅱ","MPS Ⅱ"," IDS gene","Hunter syndrome".Results: A total of 35 articles were included,including 274 patients with MPS Ⅱ,272 males and 1 females,the ratio is 136:1.The youngest patient was diagnosed during neonatal screening,and the oldest one was over 30 years old.Point mutations were present in 48.9% of our patients,being missense variants the most frequent.We correlated the IDS pathogenic variants identified with the phenotype(severe and mild forms).7 mutation types caused inconsistency between genotype and clinical phenotype,2mutations occurred in siblings.Neonatal screening is helpful for the earliest detection of MPS Ⅱ patients.Conclusions: This comprehensive study of the large-scale molecular profile of MPS Ⅱ cases in China reveals genotype-phenotypic associations.This study will lead to a better understanding of the disease and prediction of its clinical progression.This study will allows for more refined genetic counseling for affected patients.