Enhanced osteoblastic differentiation of parietal bone in a novel murine model of mucopolysaccharidosis type II.

Mucopolysaccharidosis type II (MPS II, OMIM 309900) is an X-linked disorder caused by a deficiency of lysosomal enzyme iduronate-2-sulfatase (IDS). The clinical manifestations of MPS II involve cognitive decline, bone deformity, and visceral disorders. These manifestations are closely associated with IDS enzyme activity, which catalyzes the stepwise degradation of heparan sulfate and dermatan sulfate. In this study, we established a novel Ids-deficient mice and further assessed the enzyme's physiological role. Using DNA sequencing, we found a genomic modification of the Ids genome, which involved the deletion of a 138-bp fragment spanning from intron 2 to exon 3, along with the insertion of an adenine at the 5' end of exon 3 in the mutated allele. Consistent with previous data, our Ids-deficient mice showed an attenuated enzyme activity and an enhanced accumulation of glycosaminoglycans. Interestingly, we noticed a distinct enlargement of the calvarial bone in both neonatal and young adult mice. Our examination revealed that Ids deficiency led to an enhanced osteoblastogenesis in the parietal bone, a posterior part of the calvarial bone originating from the paraxial mesoderm and associated with an enhanced expression of osteoblastic makers, such as Col1a and Runx2. In sharp contrast, cell proliferation of the parietal bone in these mice appeared similar to that of wild-type controls. These results suggest that the deficiency of Ids could be involved in an augmented differentiation of calvarial bone, which is often noticed as an enlarged head circumference in MPS II-affected individuals.

Frequency of iduronate-2-sulfatase gene variants detected in newborn screening for mucopolysaccharidosis type II in Japan.

Mucopolysaccharidosis II (MPS II) is an X-linked, recessive, inborn metabolic disorder caused by defects in iduronate-2-sulfatase (IDS). The age at onset, disease severity, and rate of progression vary significantly among patients. This disease is classified into severe or mild forms depending on neurological symptom involvement. The severe form is associated with progressive cognitive decline while the mild form is predominantly associated with somatic features. Newborn screening (NBS) for MPS II has been performed since December 2016, mainly in Kyushu, Japan, where 197,700 newborns were screened using a fluorescence enzyme activity assay of dried blood spots. We diagnosed one newborn with MPS II with lower IDS activity, elevated urinary glycosaminoglycans, and a novel variant of the IDS gene. In the future, NBS for MPS II is expected to be performed in many regions of Japan and will contribute to the detection of more patients with MPS II, which is crucial to the early treatment of the disorder.

Sustained long-term disease correction in a murine model of MPSII following stem cell gene therapy.

Mucopolysaccharidosis type II (MPSII) is a pediatric lysosomal storage disease caused by deficiencies in the IDS (iduronate-2-sulfatase) gene resulting in accumulation of glycosaminoglycans, multisystem disease, and profound neurodegeneration in severe forms. Although enzyme replacement therapy is available for somatic forms of disease, the inability of native IDS to pass the blood-brain barrier renders it ineffective for the brain. We previously demonstrated the short-term efficacy of a brain-targeted hematopoietic stem cell gene therapy approach to treat MPSII mice using lentiviral IDS fused to the blood-brain-barrier-crossing peptide ApoEII (IDS.ApoEII) in comparison with a lentivirus expressing native IDS and an unmanipulated bone marrow transplant. Here we evaluated the longevity of disease correction for 12-16 months following treatment. We observed sustained IDS enzyme activity in organs of long-term IDS.ApoEII-treated MPSII mice, similar to those analyzed 6 months post-treatment, with continued clearance of storage material in the brain and peripheral organs, maintained correction of astrogliosis, microgliosis, and correction of altered cytokines and chemokines. IDS.ApoEII also significantly reduced retinal atrophy, characteristic of MPSII. Overall, IDS.ApoEII resulted in systemic prevention of the MPSII phenotype, with no observed toxicity following treatment. This provides evidence of the sustained efficacy and safety of this treatment ahead of a recently opened clinical trial.

Gene therapy for cross-correction of somatic organs and the CNS in mucopolysaccharidosis II in rodents and non-human primates.

Mucopolysaccharidosis II (MPS II) is a rare lysosomal storage disease characterized by deficient activity of iduronate-2-sulfatase (I2S), leading to pathological accumulation of glycosaminoglycans (GAGs) in tissues. We used iduronate-2-sulfatase knockout (Ids KO) mice to investigate if liver-directed recombinant adeno-associated virus vectors (rAAV8-LSP-hIDSco) encoding human I2S (hI2S) could cross-correct I2S deficiency in Ids KO mouse tissues, and we then assessed the translation of mouse data to non-human primates (NHPs). Treated mice showed sustained hepatic hI2S production, accompanied by normalized GAG levels in somatic tissues (including critical tissues such as heart and lung), indicating systemic cross-correction from liver-secreted hI2S. Brain GAG levels in Ids KO mice were lowered but not normalized; higher doses were required to see improvements in brain histology and neurobehavioral testing. rAAV8-LSP-hIDSco administration in NHPs resulted in sustained hepatic hI2S production and therapeutic hI2S levels in cross-corrected somatic tissues but no hI2S exposure in the central nervous system, perhaps owing to lower levels of liver transduction in NHPs than in mice. Overall, we demonstrate the ability of rAAV8-LSP-hIDSco to cross-correct I2S deficiency in mouse somatic tissues and highlight the importance of showing translatability of gene therapy data from rodents to NHPs, which is critical for supporting translation to clinical development.

Multifaceted Approach for Quantification and Enzymatic Activity of Iduronate-2-Sulfatase to Support Developing Gene Therapy for Hunter Syndrome.

Mucopolysaccharidosis type II, commonly called Hunter syndrome, is a rare X-linked recessive disease caused by the deficiency of the lysosomal enzyme iduronate-2-sulphatase (I2S). A deficiency of I2S causes an abnormal glycosaminoglycans accumulation in the body's cells. Although enzyme replacement therapy is the standard therapy, adeno-associated viruses (AAV)-based gene therapy could provide a single-dose solution to achieve a prolonged and constant enzyme level to improve patient's quality of life. Currently, there is no integrated regulatory guidance to describe the bioanalytical assay strategy to support gene therapy products. Herein, we describe the streamlined strategy to validate/qualify the transgene protein and its enzymatic activity assays. The method validation for the I2S quantification in serum and method qualification in tissues was performed to support the mouse GLP toxicological study. Standard curves for I2S quantification ranged from 2.00 to 50.0 µg/mL in serum and 6.25 to 400 ng/mL in the surrogate matrix. Acceptable precision, accuracy, and parallelism in the tissues were demonstrated. To assess the function of the transgene protein, fit-for-purpose method qualification for the I2S enzyme activity in serum was performed. The observed data indicated that the enzymatic activity in serum increased dose-dependently in the lower I2S concentration range. The highest I2S transgene protein was observed in the liver among tissue measured, and its expression level was maintained up to 91 days after the administration of rAAV8 with a codon-optimized human I2S. In conclusion, the multifaceted bioanalytical method for I2S and its enzymatic activity were established to assess gene therapy products in Hunter syndrome.

Generation and characterization of an immunodeficient mouse model of mucopolysaccharidosis type II.

Mucopolysaccharidosis type II (Hunter syndrome, MPS II) is an inherited X-linked recessive disease caused by deficiency of iduronate-2-sulfatase (IDS), resulting in the accumulation of the glycosaminoglycans (GAG) heparan and dermatan sulfates. Mouse models of MPS II have been used in several reports to study disease pathology and to conduct preclinical studies for current and next generation therapies. Here, we report the generation and characterization of an immunodeficient mouse model of MPS II, where CRISPR/Cas9 was employed to knock out a portion of the murine IDS gene on the NOD/SCID/Il2rγ (NSG) immunodeficient background. IDS-/- NSG mice lacked detectable IDS activity in plasma and all analyzed tissues and exhibited elevated levels of GAGs in those same tissues and in the urine. Histopathology revealed vacuolized cells in both the periphery and CNS of NSG-MPS II mice. This model recapitulates skeletal disease manifestations, such as increased zygomatic arch diameter and decreased femur length. Neurocognitive deficits in spatial memory and learning were also observed in the NSG-MPS II model. We anticipate that this new immunodeficient model will be appropriate for preclinical studies involving xenotransplantation of human cell products intended for the treatment of MPS II.

Clinical characteristics and genotypes of 201 patients with mucopolysaccharidosis type II in China: A retrospective, observational study.

Mucopolysaccharidosis type II (MPS II) is an X-linked recessive lysosomal storage disease caused by a disease-associated variant in the IDS gene, which encodes iduronate 2-sulfatase (IDS). We aimed to characterize the clinical characteristics and genotypes of the largest cohort of Chinese patients with MPS II and so gain a deeper understanding of natural disease progression. Patients with confirmed MPS II and without treatment were included. The disease was classified as severe in patients with neurological impairment, and as attenuated in patients aged >6 years without neurological impairment. Of the 201 male patients, 78.1% had severe MPS II. Cognitive regression occurred before age 6 years in 94.3% of patients. Of 122 IDS variants identified, 37 were novel. Among the large gene alteration types identified, only the frequency of IDS-IDS2 recombination was significantly higher in severe versus attenuated MPS II (P = 0.032). Some identified point variants could inform the understanding of genotype-phenotype correlations. In conclusion, this study showed that classification of the disease as attenuated should only be made in patients aged >6 years. Our findings expand the understanding of the genotype-phenotype relationship, inform the diagnostic process, and provide an indication of the likely prognosis.

The Etiological Study of Three Hunter Syndrome Families in Southern China / 中山大学学报(医学科学版)

ObjectiveTo reveal the molecular pathogenesis of Hunter syndrome in three families in southern China and to clarify the correlation between phenotype and genotype， so as to lay a foundation for future prenatal or preimplantation genetic diagnosis. MethodsOn the basis of initial clinical diagnosis and pedigree analysis， qualitative detection of glycosaminoglycans in urine was performed first， and then anticoagulant blood samples were collected from the children and their relatives. DNA was extracted and the IDS gene sequence was analyzed by PCR and Sanger sequencing. Various methods such as RT-PCR and bioinformatics analysis were used to identify the pathogenicity of the new variants. ResultsThe urine test results of the patients in the three families were all strongly positive（++）. Probands were all male， with hemizygous mutations in IDS gene from their mothers， and the mutation sites were c.615_622delCATACAGT， c.847_848delGT and IVS7 ds+1 G>A， respectively. The cross-species conservation analysis showed that the amino acid of IDS gene mutation site was highly conserved during species evolution. Compared with the normal protein， mutant proteins exhibited significant differences in the predicted results of advanced structure. The variants identified in the three families were classified as pathogenic by ACMG criteria. ConclusionsThe three probands were diagnosed with Hunter syndrome. The c.615_622del（p.Il206Valfs*18）， c.847_848del（p.Val283Alafs*57） and IVS7 ds+1 G>A （p.G336Dfs*12） of IDS gene are all novel pathogenic mutations， which are the underlying causes of morbidity in children. This study has further enriched the mutation spectrum of IDS gene.

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.

Phenotypic Correction of Murine Mucopolysaccharidosis Type II by Engraftment of Ex Vivo Lentiviral Vector-Transduced Hematopoietic Stem and Progenitor Cells.

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is an X-linked recessive lysosomal disease caused by deficiency of iduronate-2-sulfatase (IDS). The absence of IDS results in the accumulation of the glycosaminoglycans (GAGs) heparan sulfate and dermatan sulfate. Currently, the only approved treatment option for MPS II is enzyme replacement therapy (ERT), Elaprase. However, ERT is demanding for the patient and does not ameliorate neurological manifestations of the disease. Using an IDS-deficient mouse model that phenocopies the human disease, we evaluated hematopoietic stem and progenitor cells (HSPCs) transduced with a lentiviral vector (LVV) carrying a codon-optimized human IDS coding sequence regulated by a ubiquitous MNDU3 promoter (MNDU3-IDS). Mice treated with MNDU3-IDS LVV-transduced cells showed supraphysiological levels of IDS enzyme activity in plasma, peripheral blood mononuclear cells, and in most analyzed tissues. These enzyme levels were sufficient to normalize GAG storage in analyzed tissues. Importantly, IDS levels in the brains of MNDU3-IDS-engrafted animals were restored to 10-20% than that of wild-type mice, sufficient to normalize GAG content and prevent emergence of cognitive deficit as evaluated by neurobehavioral testing. These results demonstrate the potential effectiveness of ex vivo MNDU3-IDS LVV-transduced HSPCs for treatment of MPS II.

Twenty years of Colombian experience with enzymatic screening in patients with features of mucopolysaccharidosis.

Mucopolysaccharidoses (MPSs) are a group of genetic alterations whose effect is the progressive intralysosomal accumulation of glycosaminoglycans. Affected individuals are deficient in one or more lysosomal enzymes which, depending on the MPS, may cause coarse facial features, short stature, multiple skeletal dysplasia, joint stiffness, or developmental delay. Their diagnosis is mostly performed late or incorrectly, and it represents a challenge since it requires specialized tests only performed in major cities. This makes it difficult for patients to have access to physicians since their geographical location is distant and therefore, the use of samples collected in solid-phase represents an advantage for the study of high-risk populations. In addition, epidemiological information about rare diseases, especially in Latin America, is scarce or inconsistent. Our aim was to report the experience of 20 years of selective screening by assessing enzyme activity and reporting incidence values of MPS in Colombia. This study validated a group of fluorometric endpoint techniques in 8239 patients. The samples were dried blood spots (DBS) collected on filter paper and leukocyte extracts. Reference values in the Colombian population for α-l-iduronidase, iduronate 2-sulfatase, α-N-acetylglucosaminidase, N-acetylglucosamine-6-sulfate sulfatase, ß-galactosidase, arylsulfatase B, and ß-glucuronidase were established in leukocyte extracts, and patients reference ranges were updated in the case of DBS samples. Incidence values were calculated for each MPS and the distribution of cases across the country is also shown. This study offers very useful information for the health system, the scientific community, and it facilitates the diagnosis of these disorders. This is indispensable when seeking to develop new diagnostic or treatment approaches for patients.

Glycosaminoglycan signatures in body fluids of mucopolysaccharidosis type II mouse model under long-term enzyme replacement therapy.

Mucopolysaccharidosis type II (MPS II) is a neurometabolic disorder, due to the deficit of the lysosomal hydrolase iduronate 2-sulfatase (IDS). This leads to a severe clinical condition caused by a multi-organ accumulation of the glycosaminoglycans (GAGs/GAG) heparan- and dermatan-sulfate, whose elevated levels can be detected in body fluids. Since 2006, enzyme replacement therapy (ERT) has been clinically applied, showing efficacy in some peripheral districts. In addition to clinical monitoring, GAG dosage has been commonly used to evaluate ERT efficacy. However, a strict long-term monitoring of GAG content and composition in body fluids has been rarely performed. Here, we report the characterization of plasma and urine GAGs in Ids knock-out (Ids-ko) compared to wild-type (WT) mice, and their changes along a 24-week follow-up, with and without ERT. The concentration of heparan-sulfate (HS), chondroitin-sulfate (CS), and dermatan-sulfate (DS), and of the non-sulfated hyaluronic acid (HA), together with their differentially sulfated species, was quantified by capillary electrophoresis with laser-induced fluorescence. In untreated Ids-ko mice, HS and CS + DS were noticeably increased at all time points, while during ERT follow-up, a substantial decrease was evidenced for HS and, to a minor extent, for CS + DS. Moreover, several structural parameters were altered in untreated ko mice and reduced after ERT, however without reaching physiological values. Among these, disaccharide B and HS 2s disaccharide showed to be the most interesting candidates as biomarkers for MPS II. GAG chemical signature here defined provides potential biomarkers useful for an early diagnosis of MPS II, a more accurate follow-up of ERT, and efficacy evaluations of newly proposed therapies. KEY MESSAGES : Plasmatic and urinary GAGs are useful markers for MPS II early diagnosis and prognosis. CE-LIF allows GAG structural analysis and the quantification of 17 different disaccharides. Most GAG species increase and many structural features are altered in MPS II mouse model. GAG alterations tend to restore to wild-type levels following ERT administration. CS+DS/HS ratio, % 2,4dis CS+DS, and % HS 2s are potential markers for MPS II pathology and ERT efficacy.

A new strategy of desensitization in mucopolysaccharidosis type II disease treated with idursulfase therapy: A case report and review of the literature.

Mucopolysaccharidosis type II (MPS II) is a multisystemic lysosomal storage disorder caused by deficiency of the iduronate 2-sulfatase enzyme. Currently, enzyme replacement therapy (ERT) with recombinant idursulfase is the main treatment available to decrease morbidity and improve quality of life. However, infusion-associated reactions (IARs) are reported and may limit access to treatment. When premedication or infusion rate reductions are ineffective for preventing IARs, desensitization can be applied. To date, only two MPS II patients are reported to have undergone desensitization. We report a pediatric patient with recurrent IARs during infusion successfully managed with gradual desensitization. Our protocol started at 50% of the standard dosage infused at concentrations from 0.0006 to 0.06 mg/ml on weeks 1 and 2, followed by 75% of the standard dosage infused at concentrations from 0.0009 to 0.09 mg/ml on weeks 3 and 4, and full standard dosage thereafter, infused at progressively increasing concentrations until the standard infusion conditions were reached at 3 months. Our experience can be used in the management of MPS II patients presenting IARs to idursulfase infusion, even when general preventive measures are already administered.

Genotype-phenotype spectrum of 130 unrelated Indian families with Mucopolysaccharidosis type II.

MPS II is an X linked recessive lysosomal storage disorder with multi-system involvement and marked molecular heterogeneity. In this study, we explored the clinical and molecular spectrum of 144 Indian patients with MPS II from 130 unrelated families. Clinical information was collected on a predesigned clinical proforma. Sanger method was employed to sequence all the exons and exon/intron boundaries of the IDS gene. In cases where causative variation was not detected by Sanger sequencing, MLPA and RFLP were performed to identify large deletions/duplications and complex rearrangements. Cytogenetic microarray was done in one patient to see the breakpoints and extent of deletion. In one patient with no detectable likely pathogenic or pathogenic variation, whole-genome sequencing was also performed. Novel variants were systematically assessed by in silico prediction software and protein modelling. The pathogenicity of variants was established based on ACMG criteria. An attempt was also made to establish a genotype-phenotype correlation. Positive family history was present in 31% (41/130) of patients. Developmental delay and intellectual disability were the main reasons for referral. Macrocephaly, coarse facies and dysostosis were present in almost all patients. Hepatosplenomegaly, joint contractures and short stature were the characteristic features, seen in 87% (101/116), 67.8% (74/109) and 41.4% (41/99) patients respectively. Attenuated phenotype was seen in 32.6% (47/144) patients, while severe phenotype was seen in 63% (91/144) patients. The detection rate for likely pathogenic or pathogenic variants in our cohort is 95.5% (107/112) by Sanger sequencing, MLPA and RFLP. We also found two variants of unknown significance, one each by Sanger sequencing and WGS. Total of 71 variants were identified by Sanger sequencing and 29 of these variants were found to be novel. Amongst the novel variants, there was a considerable proportion (51%) of frameshift variants (15/29). Almost half of the causative variants were located in exon 3,8 and 9. A significant genotype-phenotype correlation was also noted for both known and novel variants. This information about the genotype spectrum and phenotype will be helpful for diagnostic and prognostic purposes.

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 1-year and 4-month-old child with mucopolysaccharidoses type II: A clinical case report from Ethiopia.

Mucopolysaccharidoses (MPSs) are a class of lysosomal storage disorders resulting in progressive disease manifestations and are caused by pathogenic variants in genes coding for enzymes needed to degrade glycosaminoglycans. While most of the seven MPSs are autosomal recessive disorders, MPS II, also known as Hunter syndrome, is inherited in an X-linked recessive manner and is the most common MPS. Here, we report a 1-year and 4-month-old boy who presented with delayed developmental milestones, back deformity, and left scrotal swelling noticed by parents at one year of age. He has coarse facial appearance with macrocephaly, widened wrists, congenital dermal melanocytosis on his back, kyphotic deformity in the thoracolumbar area and left-sided inguinal hernia all consistent with a suspected MPS II diagnosis. The MPS II diagnosis was subsequently confirmed with genetic testing of the IDS gene. To our knowledge, this is the first case of MPS II reported from Ethiopia. This case shows the importance of early clinical recognition of genetic conditions and the utility of genetic testing for confirmation. The diagnosis provided important surveillance and natural history information for the patient's providers and family.

A molecular genetics view on Mucopolysaccharidosis Type II.

Mucopolysaccharidosis Type II (MPS II) is an X-linked recessive genetic disorder that primarily affects male patients. With an incidence of 1 in 100,000 male live births, the disease is one of the orphan diseases. MPS II symptoms are caused by mutations in the lysosomal iduronate-2-sulfatase (IDS) gene. The mutations cause a loss of enzymatic performance and result in the accumulation of glycosaminoglycans (GAGs), heparan sulfate and dermatan sulfate, which are no longer degradable. This inadvertent accumulation causes damage in multiple organs and leads either to a severe neurological course or to an attenuated course of the disease, although the exact relationship between mutation, extent of GAG accumulation and disease progression is not yet fully understood. This review is intended to present current diagnostic procedures and therapeutic interventions. In times when the genetic profile of patients plays an increasingly important role in the assessment of therapeutic success and future drug design, we chose to further elucidate the impact of genetic diversity within the IDS gene on disease phenotype and potential implications in current diagnosis, prognosis and therapy. We report recent advances in the structural biological elucidation of I2S enzyme that that promises to improve our future understanding of the molecular damage of the hundreds of IDS gene variants and will aid damage prediction of novel mutations in the future.

Loss of Function of Mutant IDS Due to Endoplasmic Reticulum-Associated Degradation: New Therapeutic Opportunities for Mucopolysaccharidosis Type II.

Mucopolysaccharidosis type II (MPS II) results from the dysfunction of a lysosomal enzyme, iduronate-2-sulfatase (IDS). Dysfunction of IDS triggers the lysosomal accumulation of its substrates, glycosaminoglycans, leading to mental retardation and systemic symptoms including skeletal deformities and valvular heart disease. Most patients with severe types of MPS II die before the age of 20. The administration of recombinant IDS and transplantation of hematopoietic stem cells are performed as therapies for MPS II. However, these therapies either cannot improve functions of the central nervous system or cause severe side effects, respectively. To date, 729 pathogenetic variants in the IDS gene have been reported. Most of these potentially cause misfolding of the encoded IDS protein. The misfolded IDS mutants accumulate in the endoplasmic reticulum (ER), followed by degradation via ER-associated degradation (ERAD). Inhibition of the ERAD pathway or refolding of IDS mutants by a molecular chaperone enables recovery of the lysosomal localization and enzyme activity of IDS mutants. In this review, we explain the IDS structure and mechanism of activation, and current findings about the mechanism of degradation-dependent loss of function caused by pathogenetic IDS mutation. We also provide a potential therapeutic approach for MPS II based on this loss-of-function mechanism.

Enzyme Replacement Therapy with Pabinafusp Alfa for Neuronopathic Mucopolysaccharidosis II: An Integrated Analysis of Preclinical and Clinical Data.

Enzyme replacement therapy (ERT) improves somatic manifestations in mucopolysaccharidoses (MPS). However, because intravenously administered enzymes cannot cross the blood-brain barrier (BBB), ERT is ineffective against the progressive neurodegeneration and resultant severe central nervous system (CNS) symptoms observed in patients with neuronopathic MPS. Attempts to surmount this problem have been made with intrathecal and intracerebroventricular ERT in order to achieve CNS effects, but the burdens on patients are inimical to long-term administrations. However, since pabinafusp alfa, a human iduronate-2-sulfatase fused with a BBB-crossing anti-transferrin receptor antibody, showed both central and peripheral efficacy in a mouse model, subsequent clinical trials in a total of 62 patients with MPS-II (Hunter syndrome) in Japan and Brazil substantiated this dual efficacy and provided an acceptable safety profile. To date, pabinafusp alfa is the only approved intravenous ERT that is effective against both the somatic and CNS symptoms of patients with MPS-II. This article summarizes the previously obtained preclinical and clinical evidence related to the use of this drug, presents latest data, and discusses the preclinical, translational, and clinical challenges of evaluating, ameliorating, and preventing neurodegeneration in patients with MPS-II.

Production of therapeutic iduronate-2-sulfatase enzyme with a novel single-stranded RNA virus vector.

The Sendai virus vector has received a lot of attention due to its broad tropism for mammalian cells. As a result of efforts for genetic studies based on a mutant virus, we can now express more than 10 genes of up to 13.5 kilo nucleotides in a single vector with high protein expression efficiency. To prove this benefit, we examined the efficacy of the novel ribonucleic acid (RNA) virus vector harboring the human iduronate-2-sulfatase (IDS) gene with 1,653 base pairs, a causative gene for mucopolysaccharidosis type II, also known as a disorder of lysosomal storage disorders. As expected, this novel RNA vector with the human IDS gene exhibited its marked expression as determined by the expression of enhanced green fluorescent protein and IDS enzyme activity. While these cells exhibited a normal growth rate, the BHK-21 transformant cells stably expressing the human IDS gene persistently generated an active human IDS enzyme extracellularly. The human IDS protein produced failed to be incorporated into the lysosome when cells were pretreated with mannose-6-phosphate, demonstrating that this human IDS enzyme has potential for therapeutic use by cross-correction. These results suggest that our novel RNA vector may be applicable for further clinical settings.