Characterization of an IDS pathogenic variant in a family with mucopolysaccharidosis type Ⅱ / 中华内分泌代谢杂志

Objective:To identify the genetic variation in a mucopolysaccharidosis type Ⅱ(MPS Ⅱ)family, and conduct a functional study of iduronate-2-sulfatase(IDS): c.323A>C.Methods:A five-generation MPS Ⅱ family of 83 individuals including 4 patients from northern China was collected. Urine mucopolysaccharide and Alder-Reilly body were tested to assist the clinical diagnosis of MPS Ⅱ. IDS enzyme activity was detected on core family members. By the whole exome sequencing of a MPS Ⅱ patient in this family and bioinformatics analysis, the variant was screened and further identified by PCR-Sanger sequencing. Finally, to validate the function of the variant in vitro, the wild-type IDS overexpression plasmid(pCMV-hIDS-WT)and the IDS overexpression plasmid carrying the mutation site(pCMV-hIDS-c.323A>C)were transfected into COS-7 cells and the IDS activity was detected. Results:The proband(Ⅳ3)and Ⅳ4 were diagnosed as MPS Ⅱ by urine mucopolysaccharide, Alder-Reilly body, and IDS enzyme activity tests. Ⅳ3, Ⅳ4, Ⅲ19, and Ⅲ32 were determined to carry IDS: c.323A>C missense variant through the whole-exome sequencing, and diagnosed as MPS Ⅱ. Meanwhile, Ⅱ2, Ⅱ4, Ⅱ8, Ⅱ12, Ⅱ14, Ⅲ5, Ⅲ7, Ⅳ14 in the MPS Ⅱ family carried IDS: c.323A>C missense variant, and were excluded as MPS Ⅱ. The in vitro experiment in COS-7 cells showed that the missense mutation led to a significant decrease in IDS enzyme activity. Conclusion:The variant IDS: c.323A>C: p.Y108S significantly decreases the activity of IDS enzyme in vivo and in vitro, and it is identified as a pathogenic variant for MPS Ⅱ.

Advance in diagnosis and treatment of mucopolysaccharidosis type Ⅱ / 国际儿科学杂志

Mucopolysaccharidosis type Ⅱ(MPS Ⅱ)is a rare and life-threatening X-linked recessive disease.Due to the deficiency of the enzyme iduronate-2-sulfatase(IDS), heparan sulphate and dermatan sulphate can not degrade and accumulate in lysosomes.It leads to progressive pathological dysfunction in multiple cells, tissues and organs.The clinical manifestations of patients are highly heterogeneous.This disease is generally categorized in two clinical subtypes according to the neurological involvement: severe and attenuated forms.The severe form is characterized by progressive neurologic impairment.The gold standard for the diagnosis is confirmed by the measurement of IDS enzyme activity in blood leukocytes or skin fibroblasts.Enzyme replacement therapy can improve many of the signs and symptoms and overall wellbeing in patients with MPSⅡ.Haematopoietic stem cell transplantation can be carefully chosen.

Quantification of the iduronate-2-sulfatase activity in prenatal diagnosis of mucopolysaccharidosis type Ⅱ / 中华实用儿科临床杂志

Objective:To evaluate the activity of iduronate-2-sulfatase (IDS) in fetal villi and peripheral blood plasma of pregnant women at high risk of mucopolysaccharidosis type Ⅱ (MPS Ⅱ), and to discuss the application of gene analysis in prenatal diagnosis of MPS Ⅱ.Methods:The enzymatic testing and gene analysis results of 23 pregnant women at high risk of MPS Ⅱ, who underwent prenatal diagnosis in Guangzhou Women and Children′s Medical Center from February 2013 to December 2020, were analyzed retrospectively.The IDS activity in fetal villi (30 cases) and plasma (28 cases) was detected by artificial substrate fluorescence.The IDS activity in fetal villi (28 cases) and plasma (34 cases) of normal pregnant women was taken as control.Meanwhile, the fetal villi of both pregnant women at high risk of MPS Ⅱ and normal pregnant women were also analyzed by gene testing and for fetal sex identification.Data were compared between groups by the independent samples t test. Results:The normal reference values of the IDS activity in fetal villi and plasma of normal pregnant women were(71.2±23.4) nmol/(mg·4 h) and (611.1±114.5) nmol/(mL·4 h), respectively.Among the 30 cases of high-risk fetal villi, the IDS activity in fetal villi of 8 affected male fetuses was (1.7±0.3) nmol/(mg·4 h), which was significantly lower than that of 11 unaffected male fetuses (83.2±6.3) nmol/(mg·4 h) and that of 9 non-carrier female fetuses (80.0±7.5) nmol/(mg·4 h) ( t=10.8, 8.8; all P<0.01). Meanwhile, the IDS activity was measured in the maternal peripheral plasma of 28 pregnant women at high risk of MPS Ⅱ.Among them, the IDS activity in 8 affected male fetuses was(225.4±20.5) nmol/(mL·4 h), which was significantly lower than that in non-affected male fetuses[(451.0±15.1) nmol/(mL·4 h)] and that in non-carrier female fetuses[(467.7±45.3)nmol/(mL·4 h)]. Eight known pathogenic mutations were found in 30 cases at high risk of MPS Ⅱ of fetal villi, and the mutation types were c. 1048A>C, c.212G>A, c.514C>T, c.257C>T, c.425C>T, and c. 998C>T.Of the 8 cases, 6 affected male fetuses had significantly reduced IDS activities, and the other 2 female carriers had normal IDS enzyme activities. Conclusions:The IDS activity in fetal villi and peripheral plasma of pregnant woman is consistent with the gene analysis results.The IDS activity has an important reference value for the prenatal diagnosis of MPS Ⅱ in the first trimester.When no genetic mutations are found in the probands or the pathogenicity of the new mutation remains unclear, the IDS activity in fetal villi can be detected separately for the prenatal diagnosis of MPS Ⅱ.

A Missense Mutation of IDS Gene in A Chinese Child with Mucopolysaccharidosis Type Ⅱ / 现代检验医学杂志

Objective To study the clinical characteristics and iduronate-2-sulfatase (IDS)gene mutation of one child patient with mucopolysaccharidosis type Ⅱ (MPS Ⅱ).Methods All the 9 exons of IDS gene were amplified by polymerase chain reaction (PCR)technlogy.The PCR products were screened by direct gene Sanger sequencing.Results A missense muta-tion (c.445T>C)on exon 4 was found after the analysis of the gene sequencing results of PCR products in this patient’s IDS gene.Thi smutation leaded to the 149th codon TCT encoded serine into a CCT encoding proline (p.Ser149Pro).Mean-while,the IDS gene in the parents were widetpye,so this was a de novo mutation.Conclusion The de novo mutation of IDS gene is the cause of our patient with?mucopolysaccharidosis,one novel mutation (p.Ser149Pro)was identified.

Mucopolysaccharidosis type Ⅱ: a progress on molecular genetics / 国际儿科学杂志

Mucopolysaccharidosis type Ⅱ is a rare single gene inherited disorder. In the earlier studies, more attention was paid to the molecular analysis of the hot spots of the mutations. With the detection of more and more novel mutations,more studies are trying to analyze the effect on splicing of different types of mutations and the genotype-phenotype correlations. This review will introduce the progress on molecular genetics, the gene mutation,analysis of the female patients and the genotype-phenotype correlations. With the study of these progress,it suggested that more attention should be paid to the possibility of gene-pseudogen recombinations, trying to study the effect on splicing from the cDNA level, which will benefit the investigation of the genotype-phenotype correlations.