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Multiple sulfatase deficiency (MSD) is a severe, lysosomal storage disorder caused by pathogenic variants in the gene SUMF1, encoding the sulfatase modifying factor formylglycine-generating enzyme. Patients with MSD exhibit functional deficiencies in all cellular sulfatases. The inability of sulfatases to break down their substrates leads to progressive and multi-systemic complications in patients, similar to those seen in single-sulfatase disorders such as metachromatic leukodystrophy and mucopolysaccharidoses IIIA. Here, we aimed to determine if hematopoietic stem cell transplantation with ex vivo SUMF1 lentiviral gene therapy could improve outcomes in a clinically relevant mouse model of MSD. We first tested our approach in MSD patient-derived cells and found that our SUMF1 lentiviral vector improved protein expression, sulfatase activities, and glycosaminoglycan accumulation. In vivo, we found that our gene therapy approach rescued biochemical deficits, including sulfatase activity and glycosaminoglycan accumulation, in affected organs of MSD mice treated post-symptom onset. In addition, treated mice demonstrated improved neuroinflammation and neurocognitive function. Together, these findings suggest that SUMF1 HSCT-GT can improve both biochemical and functional disease markers in the MSD mouse., Competing Interests: Declaration of interests R.C.A.-N. is an advisor to Latus Bio, AskBio, and Orchard Therapeutics. L.A.A. is an advisor to Takeda and Orchard Therapeutics. S.B.R. is a scientific advisory board member of Ionis Pharmaceuticals, Meira GTx, Vifor, and Disc Medicine. He has been or is a consultant for GSK, BMS, Incyte, Cambridge Healthcare Res, Celgene Corporation, Catenion, First Manhattan Co., FORMA Therapeutics, Ghost Tree Capital, Keros Therapeutics, Noble insight, Protagonist Therapeutics, Sanofi Aventis U.S., Slingshot Insight, Spexis AG, Techspert.io, BVF Partners L.P., Rallybio, LLC, venBio Select LLC, ExpertConnect LLC, and LifeSci Capital., (Copyright © 2024 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.)

Biallelic variants in SUMF1 are associated with multiple sulfatase deficiency (MSD), a rare lysosomal storage disorder typically diagnosed in early infancy or childhood, marked by severe neurodegeneration and early mortality. We present clinical and molecular characterisation of three unrelated patients aged 13 to 58 years with milder clinical manifestations due to SUMF1 disease variants, including two adult patients presenting with apparent non-syndromic retinal dystrophy. Whole genome sequencing identified biallelic SUMF1 variants in all three patients; Patient 1 homozygous for a complex allele c.[290G>T;293T>A]; p.[(Gly97Val);(Val98Glu)], Patient 2 homozygous for c.866A>G; p.(Tyr289Cys), and Patient 3 compound heterozygous for c.726-1G>C and p.(Tyr289Cys). Electroretinography indicated a rod-cone dystrophy with additional possible inner retinal dysfunction in all three patients. Biochemical studies confirmed reduced, but not absent, sulfatase enzyme activity in the absence of extra-ocular disease (Patient 1) or only mild systemic disease (Patients 2, 3). These cases are suggestive that non-null SUMF1 genotypes can cause an attenuated clinical phenotype, including retinal dystrophy without systemic complications, in adulthood., (© 2024 The Author(s). Clinical Genetics published by John Wiley & Sons Ltd.)

Sulfatases catalyze essential cellular reactions, including degradation of glycosaminoglycans (GAGs). All sulfatases are post-translationally activated by the formylglycine generating enzyme (FGE) which is deficient in multiple sulfatase deficiency (MSD), a neurodegenerative lysosomal storage disease. Historically, patients were presumed to be deficient of all sulfatase activities; however, a more nuanced relationship is emerging. Each sulfatase may differ in their degree of post-translational modification by FGE, which may influence the phenotypic spectrum of MSD. Here, we evaluate if residual sulfatase activity and accumulating GAG patterns distinguish cases from controls and stratify clinical severity groups in MSD. We quantify sulfatase activities and GAG accumulation using three complementary methods in MSD participants. Sulfatases differed greatly in their tolerance of reduction in FGE-mediated activation. Enzymes that degrade heparan sulfate (HS) demonstrated lower residual activities than those that act on other GAGs. Similarly, HS-derived urinary GAG subspecies preferentially accumulated, distinguished cases from controls, and correlated with disease severity. Accumulation patterns of specific sulfatase substrates in MSD provide fundamental insights into sulfatase regulation and will serve as much-needed biomakers for upcoming clinical trials. This work highlights that biomarker investigation of an ultra-rare disease can simultaneously inform our understanding of fundamental biology and advance clinical trial readiness efforts., (© 2023 SSIEM.)

Background: Multiple sulfatase deficiency (MSD) is a rare lysosomal storage disorder caused due to pathogenic variants in the SUMF1 gene. The SUMF1 gene encodes for formylglycine generating enzyme (FGE) that is involved in the catalytic activation of the family of sulfatases. The affected patients present with a wide spectrum of clinical features including multi-organ involvement. To date, almost 140 cases of MSD have been reported worldwide, with only four cases reported from India. The present study describes two cases of late infantile form of MSD from India and the identification of a novel missense variant in the SUMF1 gene., Case Presentation: In case 1, a male child presented to us at the age of 6 years. The remarkable presenting features included ichthyosis, presence of irritability, poor social response, thinning of corpus callosum on MRI and, speech regression. Clinical suspicion of MSD was confirmed by enzyme analysis of two sulfatase enzymes followed by gene sequencing. We identified a novel missense variant c.860A > T (p.Asn287Ile) in exon 7 of the SUMF1 gene. In case 2, a two and a half years male child presented with ichthyosis, leukodystrophy and facial dysmorphism. We performed an enzyme assay for two sulfatases, which showed significantly reduced activities thereby confirming MSD diagnosis., Conclusion: Overall, present study has added to the existing data on MSD from India. Based on the computational analysis, the novel variant c.860A > T identified in this study is likely to be associated with a milder phenotype and prolonged survival., (© 2023. The Author(s).)

Multiple sulfatase deficiency (MSD, MIM #272200) results from pathogenic variants in the SUMF1 gene that impair proper function of the formylglycine-generating enzyme (FGE). FGE is essential for the posttranslational activation of cellular sulfatases. MSD patients display reduced or absent sulfatase activities and, as a result, clinical signs of single sulfatase disorders in a unique combination. Up to date therapeutic options for MSD are limited and mostly palliative. We performed a screen of FDA-approved drugs using immortalized MSD patient fibroblasts. Recovery of arylsulfatase A activity served as the primary readout. Subsequent analysis confirmed that treatment of primary MSD fibroblasts with tazarotene and bexarotene, two retinoids, led to a correction of MSD pathophysiology. Upon treatment, sulfatase activities increased in a dose- and time-dependent manner, reduced glycosaminoglycan content decreased and lysosomal position and size normalized. Treatment of MSD patient derived induced pluripotent stem cells (iPSC) differentiated into neuronal progenitor cells (NPC) resulted in a positive treatment response. Tazarotene and bexarotene act to ultimately increase the stability of FGE variants. The results lay the basis for future research on the development of a first therapeutic option for MSD patients., (© 2023 The Authors. Published under the terms of the CC BY 4.0 license.)

Multiple sulfatase deficiency (MSD) is an ultrarare lysosomal storage disorder due to deficiency of all known sulfatases. MSD is caused by mutations in the Sulfatase Modifying Factor 1 (SUMF1) gene encoding the enzyme responsible for the post-translational modification and activation of all sulfatases. Most MSD patients carry hypomorph SUMF1 variants resulting in variable degrees of residual sulfatase activities. In contrast, Sumf1 null mice with complete deficiency in all sulfatase enzyme activities, have very short lifespan with significant pre-wean lethality, owing to a challenging preclinical model. To overcome this limitation, we genetically engineered and characterized in mice two commonly identified patient-based SUMF1 pathogenic variants, namely p.Ser153Pro and p.Ala277Val. These pathogenic missense variants correspond to variants detected in patients with attenuated MSD presenting with partial-enzyme deficiency and relatively less severe disease. These novel MSD mouse models have a longer lifespan and show biochemical and pathological abnormalities observed in humans. In conclusion, mice harboring the p.Ser153Pro or the p.Ala277Val variant mimic the attenuated MSD and are attractive preclinical models for investigation of pathogenesis and treatments for MSD., (© 2022 SSIEM.)

Multiple Sulfatase Deficiency (MSD, MIM#272200) is an ultra-rare lysosomal storage disorder arising from mutations in the SUMF1 gene, which encodes the formylglycine-generating enzyme (FGE). FGE is necessary for the activation of sulfatases, a family of enzymes that are involved in the degradation of sulfated substrates such as glycosaminoglycans and sulfolipids. SUMF1 mutations lead to functionally impaired FGE and individuals with MSD demonstrate clinical signs of single sulfatase deficiencies, including metachromatic leukodystrophy (MLD) and several mucopolysaccharidosis (MPS) subtypes. Comprehensive information related to the natural history of MSD is missing. We completed a systematic literature review and a meta-analysis on data from published cases reporting on MSD. As available from these reports, we extracted clinical, genetic, biochemical, and brain imaging information. We identified 75 publications with data on 143 MSD patients with a total of 53 unique SUMF1 mutations. The mean survival was 13 years (95% CI 9.8-16.2 years). Seventy-five clinical signs and 11 key clusters of signs were identified. The most frequently affected organs systems were the nervous, skeletal, and integumentary systems. The most frequent MRI features were abnormal myelination and cerebral atrophy. Individuals with later onset MSD signs and survived longer than those with signs at birth. Less severe mutations, low disease burden and achievement of independent walking positively correlated with longer survival. Despite the limitations of our approach, we were able to define clinical characteristics and disease outcomes in MSD. This work will provide the foundation of natural disease history data needed for future clinical trial design., (© 2020 The Authors. Journal of Inherited Metabolic Disease published by John Wiley & Sons Ltd on behalf of SSIEM.)

Multiple sulfatase deficiency (MSD) is an ultra-rare neurodegenerative disorder caused by pathogenic variants in SUMF1. This gene encodes formylglycine-generating enzyme (FGE), a protein required for sulfatase activation. The clinical course of MSD results from additive effect of each sulfatase deficiency, including metachromatic leukodystrophy (MLD), several mucopolysaccharidoses (MPS II, IIIA, IIID, IIIE, IVA, VI), chondrodysplasia punctata, and X-linked ichthyosis. While it is known that affected individuals demonstrate a complex and severe phenotype, the genotype-phenotype relationship and detailed clinical course is unknown. We report on 35 cases enrolled in our retrospective natural history study, n = 32 with detailed histories. Neurologic function was longitudinally assessed with retrospective scales. Biochemical and computational modeling of novel SUMF1 variants was performed. Genotypes were classified based on predicted functional change, and each individual was assigned a genotype severity score. The median age at symptom onset was 0.25 years; median age at diagnosis was 2.7 years; and median age at death was 13 years. All individuals demonstrated developmental delay, and only a subset of individuals attained ambulation and verbal communication. All subjects experienced an accumulating systemic symptom burden. Earlier age at symptom onset and severe variant pathogenicity correlated with poor neurologic outcomes. Using retrospective deep phenotyping and detailed variant analysis, we defined the natural history of MSD. We found that attenuated cases can be distinguished from severe cases by age of onset, attainment of ambulation, and genotype. Results from this study can help inform prognosis and facilitate future study design., (© 2020 The Authors. Journal of Inherited Metabolic Disease published by John Wiley & Sons Ltd on behalf of SSIEM.)

Background: Multiple sulfatase deficiency (MSD, MIM #272200) is an ultrarare congenital disorder caused by SUMF1 mutation and often misdiagnosed due to its complex clinical presentation. Impeded by a lack of natural history, knowledge gained from individual case studies forms the source for a reliable diagnosis and consultation of patients and parents., Methods: We collected clinical records as well as genetic and metabolic test results from two MSD patients. The functional properties of a novel SUMF1 variant were analyzed after expression in a cell culture model., Results: We report on two MSD patients-the first neonatal type reported in Israel-both presenting with this most severe manifestation of MSD. Our patients showed uniform clinical symptoms with persistent pulmonary hypertension, hypotonia, and dysmorphism at birth. Both patients were homozygous for the same novel SUMF1 mutation (c.1043C>T, p.A348V). Functional analysis revealed that the SUMF1-encoded variant of formylglycine-generating enzyme is highly instable and lacks catalytic function., Conclusion: The obtained results confirm genotype-phenotype correlation in MSD, expand the spectrum of clinical presentation and are relevant for diagnosis including the extremely rare neonatal severe type of MSD., (© 2020 The Authors. Molecular Genetics & Genomic Medicine published by Wiley Periodicals, Inc.)

Multiple Sulfatase Deficiency (MSD) is an inborn error of metabolism caused by pathogenic variants in the SUMF1 gene encoding the formylglycine-generating enzyme (FGE) that activates all known sulfatases. FGE deficiency results in widespread tissue accumulation of multiple sulphated substrates. Through a systematic analysis of published cases, we retrieved 80 MSD cases and reviewed the disease clinical, biochemical, and genetic findings. Leukodystrophy, neurosensorial hearing loss, and ichthyosis were the most frequent findings at diagnosis. Of 51 reported pathogenic variants, 20 were likely gene disruptive and the remaining were missense variants. No correlations between class of variants and clinical severity or degree of enzyme deficiency were detected. However, cases harboring variants located at N-terminal always had severe neonatal presentations. Moreover, cases with neonatal onset showed the lowest overall survival rate compared to late-infantile and juvenile onsets. Using GnomAD, carrier frequency for pathogenic SUMF1 variants was estimated to be ~1/700 and the disease prevalence was approximately 1/2,000,000. In summary, MSD is an ultra-rare multisystem disorder with mainly neurologic, hearing and skin involvements. Although the collected data were retrospective and heterogenous, the quantitative data inform the disease natural history and are important for both counseling and design of future interventional studies., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Multiple sulfatase deficiency (MSD, MIM #272200) is an ultra-rare disease comprising pathophysiology and clinical features of mucopolysaccharidosis, sphingolipidosis and other sulfatase deficiencies. MSD is caused by impaired posttranslational activation of sulfatases through the formylglycine generating enzyme (FGE) encoded by the sulfatase modifying factor 1 ( SUMF1 ) gene, which is mutated in MSD. FGE is a highly conserved, non-redundant ER protein that activates all cellular sulfatases by oxidizing a conserved cysteine in the active site of sulfatases that is necessary for full catalytic activity. SUMF1 mutations result in unstable, degradation-prone FGE that demonstrates reduced or absent catalytic activity, leading to decreased activity of all sulfatases. As the majority of sulfatases are localized to the lysosome, loss of sulfatase activity induces lysosomal storage of glycosaminoglycans and sulfatides and subsequent cellular pathology. MSD patients combine clinical features of all single sulfatase deficiencies in a systemic disease. Disease severity classifications distinguish cases based on age of onset and disease progression. A genotype- phenotype correlation has been proposed, biomarkers like excreted storage material and residual sulfatase activities do not correlate well with disease severity. The diagnosis of MSD is based on reduced sulfatase activities and detection of mutations in SUMF1 . No therapy exists for MSD yet. This review summarizes the unique FGE/ sulfatase physiology, pathophysiology and clinical aspects in patients and their care and outlines future perspectives in MSD., Competing Interests: Authors declare no conflicts of interest.

Metachromatic Leukodystrophy (MLD) and Multiple Sulfatase Deficiency (MSD) are rare and ultra-rare lysosomal storage diseases. Due to enzyme defects, patients are unable to split the sulfategroup from the respective substrates. In MSD all sulfatases are affected due to a defect of the Sulfatase Modifying Factor 1 (SUMF1) gene coding for the formylglycine generating enzyme (FGE) necessary for the modification of the active site of sulfatases. In MLD mutations in the arylsulfatase A (ARSA) gene cause ARSA deficiency with subsequent accumulation of 3-sulfogalactocerebroside especially in oligodendrocytes. The clinical consequence is demyelination and a devastating neurological disease. Enzyme replacement therapy (ERT) with recombinant human arylsulfatase A (rhARSA), gene therapy, and stem cell transplantation are suggested as new therapeutic options. The aim of our study was to characterize rhARSA concerning its substrate specificity using analytical isotachophoresis (ITP). Substrate specificity could be demonstrated by sulfate splitting from the natural substrates 3-sulfogalactocerebroside and ascorbyl-2-sulfate and the artificial substrate p-nitrocatecholsulfate, whereas galactose-6-sulfate, a substrate of galactose-6‑sulfurylase, was totally resistant. In contrast, leukocyte extracts of healthy donors were able to split sulfate also from galactose-6-sulfate. The ITP method allows therefore a rapid and simple differentiation between samples of MLD and MSD patients and healthy donors. Therefore, the isotachophoretic diagnostic assay from leukocyte extracts described here provides a fast and efficient way for the diagnosis of MLD and MSD patients and an elegant system to differentiate between these diseases in one assay., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Multiple sulfatase deficiency is an autosomal recessive lysosomal storage disorder due to a deficiency in formylglycine-generating enzyme, which is encoded by the Sulfatase Modifying Factor 1 ( SUMF1) gene. Clinically, the disorder is variable. The most common characteristics are developmental regression, intellectual disability, ichthyosis, and periventricular white matter disease. Herein, we report 6 Saudi patients with multiple sulfatase deficiency caused by a novel homozygous missense mutation in the SUMF1 gene (NM_182760.3; c.785A>G [p.Gln262Arg]). The patients are 2 females and 4 males between 5 and 13 years of age, with an age of onset of 1 to 3 years. All patients are consanguineous and suffer from developmental regression, intellectual disability, ichthyosis, and periventricular white matter disease. This cohort differs from previous cohorts because of the absence of organomegaly and skeletal abnormalities.

The major candidate for multiple sulfatase deficiency is a defective formylglycine-generating enzyme (FGE). Though adequately produced, mutations in FGE stall the activation of sulfatases and prevent their activity. Missense mutations, viz. E130D, S155P, A177P, W179S, C218Y, R224W, N259I, P266L, A279V, C336R, R345C, A348P, R349Q and R349W associated with multiple sulfatase deficiency are yet to be computationally studied. Aforementioned mutants were initially screened through ws-SNPs&GO 3D program. Mutant R345C acquired the highest score, and hence was studied in detail. Discrete molecular dynamics explored structural distortions due to amino acid substitution. Therein, comparative analyses of wild type and mutant were carried out. Changes in structural contours were observed between wild type and mutant. Mutant had low conformational fluctuation, high atomic mobility and more compactness than wild type. Moreover, free energy landscape showed mutant to vary in terms of its conformational space as compared to wild type. Subsequently, wild type and mutant were subjected to single-model analyses. Mutant had lesser intra molecular interactions than wild type suggesting variations pertaining to its secondary structure. Furthermore, simulated thermal denaturation showed dissimilar pattern of hydrogen bond dilution. Effects of these variations were observed as changes in elements of secondary structure. Docking studies of mutant revealed less favourable binding energy towards its substrate as compared to wild type. Therefore, theoretical explanations for structural distortions of mutant R345C leading to multiple sulfatase deficiency were revealed. The protocol of the study could be useful to examine the effectiveness of pharmacological chaperones prior to experimental studies.

Multiple sulfatase deficiency (MSD) is a rare inherited metabolic disease caused by defective cellular sulfatases. Activity of sulfatases depends on post-translational modification catalyzed by formylglycine-generating enzyme (FGE), encoded by the SUMF1 gene. SUMF1 pathologic variants cause MSD, a syndrome presenting with a complex phenotype. We describe the first Polish patient with MSD caused by a yet undescribed pathologic variant c.337G>A [p.Glu113Lys] (i.e. p.E113K) in heterozygous combination with the known deletion allele c.519+5_519+8del [p.Ala149_Ala173del]. The clinical picture of the patient initially suggested late infantile metachromatic leukodystrophy, with developmental delay followed by regression of visual, hearing and motor abilities as the most apparent clinical symptoms. Transient signs of ichthyosis and minor dysmorphic features guided the laboratory workup towards MSD. Since MSD is a rare disease and there is a variable clinical spectrum, we thoroughly describe the clinical outcome of our patient. The FGE-E113K variant, expressed in cell culture, correctly localized to the endoplasmic reticulum but was retained intracellularly in contrast to the wild type FGE. Analysis of FGE-mediated activation of steroid sulfatase in immortalized MSD cells revealed that FGE-E113K exhibited only approx. 15% of the activity of wild type FGE. Based on the crystal structure we predict that the exchange of glutamate-113 against lysine should induce a strong destabilization of the secondary structure, possibly affecting the folding for correct disulfide bridging between C235-C346 as well as distortion of the active site groove that could affect both the intracellular stability as well as the activity of FGE. Thus, the novel variant of the SUMF1 gene obviously results in functionally impaired FGE protein leading to a severe late infantile type of MSD., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Among diseases that cause ichthyosis as one of the symptoms, there are some diseases that induce abnormalities in organs other than the skin. Of these, diseases with characteristic signs are regarded as syndromes. Although these syndromes are very rare, Netherton syndrome, Sjögren-Larsson syndrome, Conradi-Hünermann-Happle syndrome, Dorfman-Chanarin syndrome, ichthyosis follicularis, atrichia and photophobia (IFAP) syndrome, and Refsum syndrome have been described in texts as representative ones. It is important to know the molecular genetics and pathomechanisms in order to establish an effective therapy and beneficial genetic counseling including a prenatal diagnosis., (© 2016 Japanese Dermatological Association.)

Background: Multiple sulfatase deficiency is a rare inherited metabolic disorder caused by mutations in the SUMF1 gene. The disease remains poorly known, often leading to a late diagnosis. This study aimed to provide improved knowledge of the disease, through complete clinical, biochemical, and molecular descriptions of a cohort of unrelated patients. The main objective was to identify prognostic markers, both phenotypic and genotypic, to accelerate the diagnosis and improve patient care., Methods: The phenotypes of ten unrelated patients were fully documented at the clinical and biochemical levels. The long-term follow-up of each patient allowed correlations of the phenotypes to the disease outcomes. Each patient's molecular defects were also identified. Site-directed mutagenesis was used to individually express the mutants and assess their stability. Characterisation of the protein mutants was completed by in silico analyses based on sequence comparisons and structural models., Results: The most severe cases were characterised by the presence of non-neurological symptoms as well as the occurrence of psychomotor regression before 2 years of age. Nine novel SUMF1 mutations were identified. Clinically severe forms were often associated with SUMF1 mutations that strongly affected the protein stability and/or catalytic function as predicted from in silico and western blot analyses., Conclusions: This detailed clinical description and follow-up of a cohort of patients, together with the molecular characterisation of their underlying defects, contribute to improved knowledge of multiple sulfatase deficiency. Predictors of a bad prognosis were the presence of several non-neurological symptoms and the onset of psychomotor regression before 2 years of age. No strict correlation existed between in vitro residual sulfatase activity and disease severity. Genotype-phenotype correlations related to previously reported mutants were strengthened. These and previous observations allow not only improved prediction of the disease outcome but also provision of appropriate care for patients, in the expectation of specific treatment development.

Sulfatases are key enzymatic regulators of sulfate homeostasis with several biological functions including degradation of glycosaminoglycans (GAGs) and other macromolecules in lysosomes. In a severe lysosomal storage disorder, multiple sulfatase deficiency (MSD), global sulfatase activity is deficient due to mutations in the sulfatase-modifying factor 1 (SUMF1) gene, encoding the essential activator of all sulfatases. We identify a novel regulatory layer of sulfate metabolism mediated by a microRNA. miR-95 depletes SUMF1 protein levels and suppresses sulfatase activity, causing the disruption of proteoglycan catabolism and lysosomal function. This blocks autophagy-mediated degradation, causing cytoplasmic accumulation of autophagosomes and autophagic substrates. By targeting miR-95 in cells from MSD patients, we can effectively increase residual SUMF1 expression, allowing for reactivation of sulfatase activity and increased clearance of sulfated GAGs. The identification of this regulatory mechanism opens the opportunity for a unique therapeutic approach in MSD patients where the need for exogenous enzyme replacement is circumvented.

Multiple Sulfatase Deficiency (MSD; OMIM 272200) is a rare autosomal recessive inborn error of metabolism caused by mutations in the sulfatase modifying factor 1 gene, encoding the formylglycine-generating enzyme (FGE), and resulting in tissue accumulation of sulfatides, sulphated glycosaminoglycans, sphingolipids and steroid sulfates. Less than 50 cases have been published so far. We report a new case of MSD presenting in the newborn period with hypotonia, apnoea, cyanosis and rolling eyes, hepato-splenomegaly and deafness. This patient was compound heterozygous for two so far undescribed SUMF1 mutations (c.191C > A; p.S64X and c.818A > G; p.D273G).

Background: Multiple sulfatase deficiency (MSD) is a rare autosomal recessive inborn error of lysosomal metabolism. The clinical phenotypic spectrum encompasses overlapping features of variable severity and is suggestive of individual single sulfatase deficiencies (i.e., metachromatic leukodystrophy, mucopolysaccharidosis, and X-linked ichthyosis)., Case Report: We describe a 3-year-old male with severe hypotonia, developmental regression and progressive neurodegeneration, coarse facial features, nystagmus (from ocular albinism), and dysmyelinating motor sensory neuropathy. Ethics approval was obtained from the Western University Ontario., Results: Extensive investigative work-up identified deficiencies of multiple sulfatases: heparan sulfate sulfamidase: 6.5 nmoles/mg/protein/17 hour (reference 25.0-75.0), iduronate-2-sulfate sulfatase: 9 nmol/mg/protein/4 hour (reference 31-110), and arylsulfatase A: 3.8 nmoles/hr/mg protein (reference 22-50). The identification of compound heterozygous pathogenic mutations in the SUMF1 gene c.836 C>T (p.A279V) and c.1045C>T (p.R349W) confirmed the diagnosis of MSD., Conclusion: The complex clinical manifestations of MSD and the unrelated coexistence of ocular albinism as in our case can delay diagnosis. Genetic counselling should be provided to all affected families.

Background & Objectives: Multiple suphphatase deficiency (MSD) is an autosomal recessive disorder affecting the post translational activation of all enzymes of the sulphatase family. To date, approximately 30 different mutations have been identified in the causative gene, sulfatase modifying factor 1 (SUMF1). We describe here the mutation analysis of a case of MSD., Methods: The proband was a four year old boy with developmental delay followed by neuroregression. He had coarse facies, appendicular hypertonia, truncal ataxia and ichthyosis limited to both lower limbs. Radiographs showed dysostosis multiplex. Clinical suspicion of MSD was confirmed by enzyme analysis of four enzymes of the sulphatase group., Results: The patient was compound heterozygote for a c.451A>G (p.K151E) substitution in exon 3 and a single base insertion mutation (c.690_691 InsT) in exon 5 in the SUMF1 gene. The bioinformatic analysis of the missense mutation revealed no apparent effect on the overall structure. However, the mutated 151-amino acid residue was found to be adjacent to the substrate binding and the active site residues, thereby affecting the substrate binding and/or catalytic activity, resulting in almost complete loss of enzyme function., Conclusions: The two mutations identified in the present case were novel. This is perhaps the first report of an insertion mutation in SUMF1 causing premature truncation of the protein.

Multiple sulfatase deficiency is a rare autosomal recessive disorder in which affected individuals present a complex phenotype due to the impaired activity of all sulfatases. There are different types of multiple sulfatase deficiency; among them, the neonatal form is the most severe, with a broad range of mucopolysaccharidosis-like symptoms and death within the first year of life. The disorder is caused by homozygous or compound heterozygous mutations in the sulfatase-modifying factor-1 (SUMF1) gene. In this article, we describe a non-ichthyotic neonatal multiple sulfatase deficiency patient with a novel mutation in the SUMF1 gene. The missense mutation c.777C>G, for which the patient was homozygous, had been caused by a p.N259K amino acid substitution. We evaluated the patient using clinical findings, neuroimaging studies and molecular analysis via the literature; we also wanted to note the difficulties in the diagnosis of this rare disease.

Objective: Multiple sulfatase deficiency is a rare autosomal recessively inherited lysosomal storage disorder characterized by the accumulation of sulfated lipids and acid mucopolysaccharides. The aim of this study was to explore the clinical manifestations, enzyme activities and SUMF1 gene mutations in two Chinese patients with multiple sulfatase deficiency., Method: One boy and one girl from two families were studied. Both patients presented with mental retardation, mild coarse facial features, a neurodegenerative course of disease with loss of sensory and motor function after 2 years of age, ichthyosis and skeletal abnormalities (kyphosis or/and scoliosis). Clinical characteristics indicate multiple sulfatase deficiency.Sulfatases activities in blood leucocytes, plasma or cultured fibroblast of the patients were measured.Genomic DNAs were extracted from peripheral blood leukocytes from the patients and their parents. All SUMF1 gene exons and intron-exon boundaries were amplified by PCR and subjected for direct sequencing., Result: In case 1, five sulfatases activities of blood leucocytes and four sulfatases of cultured skin-fibroblasts were analyzed.In case 2, three sulfatases activities of blood leucocytes were tested.Significantly decreased sulfatases activities confirmed the diagnosis of multiple sulfatase deficiency.On SUMF1 gene, c.793_794 insATG (p. P265X)/ c.1045C>T (p.R349W) in case 1 and c.451A>G (p.K151E)/ c.1046G>C (p.R349Q) in case 2 were detected, respectively. Three novel mutations c.793_794insAGT, c.1046G>C and c.451A>G were identified., Conclusions: Multiple sulfatase deficiency usually results in multi-organ damage, especially neurologic, skeletal and skin.Sulfatases assay and SUMF1 gene analysis are necessary for the diagnosis. Two Chinese cases with multiple sulfatase deficiency were firstly reported. Three novel mutations were found.It should be considered that the mutation profile of SUMF1 gene in Chinese patients is different from other populations.

Multiple sulfatase deficiency (MSD) is a rare inborn error of metabolism affecting posttranslational activation of sulfatases by the formylglycine generating enzyme (FGE). Due to mutations in the encoding SUMF1 gene, FGE's catalytic capacity is impaired resulting in reduced cellular sulfatase activities. Both, FGE protein stability and residual activity determine disease severity and have previously been correlated with the clinical MSD phenotype. Here, we report a patient with a late infantile severe course of disease. The patient is compound heterozygous for two so far undescribed SUMF1 mutations, c.156delC (p.C52fsX57) and c.390A>T (p.E130D). In patient fibroblasts, mRNA of the frameshift allele is undetectable. In contrast, the allele encoding FGE-E130D is expressed. FGE-E130D correctly localizes to the endoplasmic reticulum and has a very high residual molecular activity in vitro (55% of wildtype FGE); however, it is rapidly degraded. Thus, despite substantial residual enzyme activity, protein instability determines disease severity, which highlights that potential MSD treatment approaches should target protein folding and stabilization mechanisms.

The role of astrocytes in neurodegenerative processes is increasingly appreciated. Here we investigated the contribution of astrocytes to neurodegeneration in multiple sulfatase deficiency (MSD), a severe lysosomal storage disorder caused by mutations in the sulfatase modifying factor 1 (SUMF1) gene. Using Cre/Lox mouse models, we found that astrocyte-specific deletion of Sumf1 in vivo induced severe lysosomal storage and autophagy dysfunction with consequential cytoplasmic accumulation of autophagic substrates. Lysosomal storage in astrocytes was sufficient to induce degeneration of cortical neurons in vivo. Furthermore, in an ex vivo coculture assay, we observed that Sumf1(-/-) astrocytes failed to support the survival and function of wild-type cortical neurons, suggesting a non-cell autonomous mechanism for neurodegeneration. Compared with the astrocyte-specific deletion of Sumf1, the concomitant removal of Sumf1 in both neurons and glia in vivo induced a widespread neuronal loss and robust neuroinflammation. Finally, behavioral analysis of mice with astrocyte-specific deletion of Sumf1 compared with mice with Sumf1 deletion in both astrocytes and neurons allowed us to link a subset of neurological manifestations of MSD to astrocyte dysfunction. This study indicates that astrocytes are integral components of the neuropathology in MSD and that modulation of astrocyte function may impact disease course.

Dysfunctional mitochondria are a well-known disease hallmark. The accumulation of aberrant mitochondria can alter cell homeostasis, thus resulting in tissue degeneration. Lysosomal storage disorders (LSDs) are a group of inherited diseases characterized by the buildup of undegraded material inside the lysosomes that leads to autophagic-lysosomal dysfunction. In LSDs, autophagic stress has been associated to mitochondrial accumulation and dysfunction. However, the mechanisms underlying mitochondrial aberrations and how these are involved in tissue pathogenesis remain largely unexplored. In normal conditions, mitochondrial clearance occurs by mitophagy, a selective form of autophagy, which relies on a parkin-mediated mitochondrial priming and subsequent sequestration by autophagosomes. Here, we performed a detailed analysis of key steps of mitophagy in a mouse model of multiple sulfatase deficiency (MSD), a severe type of LSD characterized by both neurological and systemic involvement. We demonstrated that in MSD liver reduced parkin levels resulted in inefficient mitochondrial priming, thus contributing to the accumulation of giant mitochondria that are located outside autophagic vesicles ultimately leading to cytochrome c release and apoptotic cell death. Morphological and functional changes were also observed in mitochondria from MSD brain but these were not directly associated with neuronal cell loss, suggesting a secondary contribution of mitochondria to neurodegeneration. Together, these data shed new light on the mechanisms underlying mitochondrial dysfunction in LSDs and on their tissue-specific differential contribution to the pathogenesis of this group of metabolic disorders.

Lysosomes are cellular organelles primarily involved in degradation and recycling processes. During lysosomal exocytosis, a Ca²⁺-regulated process, lysosomes are docked to the cell surface and fuse with the plasma membrane (PM), emptying their content outside the cell. This process has an important role in secretion and PM repair. Here we show that the transcription factor EB (TFEB) regulates lysosomal exocytosis. TFEB increases the pool of lysosomes in the proximity of the PM and promotes their fusion with PM by raising intracellular Ca²⁺ levels through the activation of the lysosomal Ca²⁺ channel MCOLN1. Induction of lysosomal exocytosis by TFEB overexpression rescued pathologic storage and restored normal cellular morphology both in vitro and in vivo in lysosomal storage diseases (LSDs). Our data indicate that lysosomal exocytosis may directly modulate cellular clearance and suggest an alternative therapeutic strategy for disorders associated with intracellular storage., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Multiple sulfatase deficiency (MSD), a severe autosomal recessive disease is caused by mutations in the sulfatase modifying factor 1 gene (Sumf1). We have previously shown that in the Sumf1 knockout mouse model (Sumf1(-/-)) sulfatase activities are completely absent and, similarly to MSD patients, this mouse model displays growth retardation and early mortality. The severity of the phenotype makes MSD unsuitable to be treated by enzyme replacement or bone marrow transplantation, hence the importance of testing the efficacy of novel treatment strategies. Here we show that recombinant adeno-associated virus serotype 9 (rAAV9) vector injected into the cerebral ventricles of neonatal mice resulted in efficient and widespread transduction of the brain parenchyma. In addition, we compared a combined, intracerebral ventricles and systemic, administration of an rAAV9 vector encoding SUMF1 gene to the single administrations-either directly in brain, or systemic alone -in MSD mice. The combined treatment resulted in the global activation of sulfatases, near-complete clearance of glycosaminoglycans (GAGs) and decrease of inflammation in both the central nervous system (CNS) and visceral organs. Furthermore, behavioral abilities were improved by the combined treatment. These results underscore that the "combined" mode of rAAV9 vector administration is an efficient option for the treatment of severe whole-body disorders.

Multiple Sulfatase Deficiency (MSD) is caused by mutations in the sulfatase-modifying factor 1 gene encoding the formylglycine-generating enzyme (FGE). FGE post translationally activates all newly synthesized sulfatases by generating the catalytic residue formylglycine. Impaired FGE function leads to reduced sulfatase activities. Patients display combined clinical symptoms of single sulfatase deficiencies. For ten MSD patients, we determined the clinical phenotype, FGE expression, localization and stability, as well as residual FGE and sulfatase activities. A neonatal, very severe clinical phenotype resulted from a combination of two nonsense mutations leading to almost fully abrogated FGE activity, highly unstable FGE protein and nearly undetectable sulfatase activities. A late infantile mild phenotype resulted from FGE G263V leading to unstable protein but high residual FGE activity. Other missense mutations resulted in a late infantile severe phenotype because of unstable protein with low residual FGE activity. Patients with identical mutations displayed comparable clinical phenotypes. These data confirm the hypothesis that the phenotypic outcome in MSD depends on both residual FGE activity as well as protein stability. Predicting the clinical course in case of molecularly characterized mutations seems feasible, which will be helpful for genetic counseling and developing therapeutic strategies aiming at enhancement of FGE., (© 2011 Macmillan Publishers Limited All rights reserved 1018-4813/11)

A defect in invariant NKT (iNKT) cell selection was hypothesized in lysosomal storage disorders (LSD). Accumulation of glycosphingolipids (GSL) in LSD could influence lipid loading and/or presentation causing entrapment of endogenous ligand(s) within storage bodies or competition of the selecting ligand(s) by stored lipids for CD1d binding. However, when we analyzed the iNKT cell compartment in newly tested LSD animal models that accumulate GSL, glycoaminoglycans or both, we observed a defective iNKT cell selection only in animals affected by multiple sulfatase deficiency, in which a generalized aberrant T-cell development, rather than a pure iNKT defect, was present. Mice with single lysosomal enzyme deficiencies had normal iNKT cell development. Thus, GSL/glycoaminoglycans storage and lysosomal engulfment are not sufficient for affecting iNKT cell development. Rather, lipid ligand(s) or storage compounds, which are affected in those LSD lacking mature iNKT cells, might indeed be relevant for iNKT cell selection.

Multiple Sulfatase Deficiency (MSD) is a rare autosomal recessive disease in which the activities of all sulfatases are reduced; its estimated prevalence is 1:1.4 million births. The disease is caused by mutations in SUMF1, which encodes an enzyme involved in the post-translational modification of sulfatases. The MSD phenotype is a combination of the clinical features found in diseases resulting from a deficiency of the individual sulfatases; i.e., mucopolysaccharidosis II, IIIA, IIID, IVA and VI, metachromatic leukodystrophy, X-linked ichthyosis, and the X-linked recessive form of chondrodysplasia punctata. We describe herein the first case of a Brazilian patient with MSD. The case was initially diagnosed as having mucopolysaccharidosis (MPS), due to skeletal alterations, coarse facial features, and urinary excretion of dermatan sulfate and heparan sulfate. Later, after a detailed biochemical investigation, the diagnosis of MSD was established. The analysis of the SUMF1 showed the patient was a compound heterozygote for two novel mutations (p.R349G and p.F244S). This case illustrates the challenges in the diagnosis of a disease considered rare, such as MSD. We point out that the availability of therapy for certain MPS disorders necessitates correct disease assignment, and the need to exclude the likelihood of MSD.

Multiple sulfatase deficiency (MSD), mucolipidosis (ML) II/III and Niemann-Pick type C1 (NPC1) disease are rare but fatal lysosomal storage disorders caused by the genetic defect of non-lysosomal proteins. The NPC1 protein mainly localizes to late endosomes and is essential for cholesterol redistribution from endocytosed LDL to cellular membranes. NPC1 deficiency leads to lysosomal accumulation of a broad range of lipids. The precise functional mechanism of this membrane protein, however, remains puzzling. ML II, also termed I cell disease, and the less severe ML III result from deficiencies of the Golgi enzyme N-acetylglucosamine 1-phosphotransferase leading to a global defect of lysosome biogenesis. In patient cells, newly synthesized lysosomal proteins are not equipped with the critical lysosomal trafficking marker mannose 6-phosphate, thus escaping from lysosomal sorting at the trans Golgi network. MSD affects the entire sulfatase family, at least seven members of which are lysosomal enzymes that are specifically involved in the degradation of sulfated glycosaminoglycans, sulfolipids or other sulfated molecules. The combined deficiencies of all sulfatases result from a defective post-translational modification by the ER-localized formylglycine-generating enzyme (FGE), which oxidizes a specific cysteine residue to formylglycine, the catalytic residue enabling a unique mechanism of sulfate ester hydrolysis. This review gives an update on the molecular bases of these enigmatic diseases, which have been challenging researchers since many decades and so far led to a number of surprising findings that give deeper insight into both the cell biology and the pathobiochemistry underlying these complex disorders. In case of MSD, considerable progress has been made in recent years towards an understanding of disease-causing FGE mutations. First approaches to link molecular parameters with clinical manifestation have been described and even therapeutical options have been addressed. Further, the discovery of FGE as an essential sulfatase activating enzyme has considerable impact on enzyme replacement or gene therapy of lysosomal storage disorders caused by single sulfatase deficiencies.

Lysosomal storage diseases (LSDs) are characterized by intra-lysosomal accumulation of undegraded metabolites due to the defective activity of lysosomal enzymes. There is a paucity of data, however, relating to the mechanisms that link this accumulation with disease pathology. Several LSDs can be attributed to deficiencies in the activity of sulfatase enzymes. The gene responsible for the post-translational modification that activates sulfatases, sulfatase modifying factor 1 (SUMF1), is defective in the rare autosomal recessive disorder multiple sulfatase deficiency (MSD). A mouse model of MSD (Sumf1 knockout mouse) exhibits a similar phenotype to patients with MSD, with marked lysosomal storage of undegraded metabolites, and increased expression of inflammatory markers and apoptotic markers. Investigation of disease pathology in mouse models of two LSDs (MSD and mucopolysaccharidosis (MPS) Type IIIA) has revealed an increased number of autophagosomes in these animals compared with wild-type mice. This appears to result from impaired autophagosome-lysosome fusion, which may in turn lead to an absence of autophagy. The suggestion that LSDs can be defined as disorders of autophagy implies that there may be some overlap between pathological mechanisms of LSDs and more common neurodegenerative diseases, and this may help provide direction for future therapeutic strategies.

We present serial clinical, magnetic resonance imaging (MRI) and neurophysiological findings of a patient with multiple sulphatase deficiency (MSD), who was first admitted at the age of 9 months, because of psychomotor retardation. MRI demonstrated extensive diffuse symmetrical high signal in the deep white matter of both cerebral hemispheres, as well as of the subcortical white matter and the brainstem, while there was additional enlargement of sulci and subdural spaces and mild atrophy. Assay of arylsulphatase A activity in white blood cell homogenates at the age of 29 months disclosed a marked deficiency of the enzyme, compatible with the diagnosis of early-infantile metachromatic leukodystrophy. During the course of a later admission, the presence of ichthyosis pointed out to the possible diagnosis of MSD; further assays of sulphatases in plasma, leukocytes as well as in cultured fibroblasts, combined with an abnormal excretion of mucopolysaccharides and sulphatides in urine confirmed the diagnosis. Molecular analysis identified a homozygous disease-causing mutation (R349W) of the SUMF1 gene. Serial neurophysiological and MRI studies demonstrated the progressive nature of the disorder (regarding both central and peripheral nervous system), correlating with the clinical deterioration (spastic quadriplegia, optic atrophy and epilepsy) with subsequent death at the age of 4 years.

Multiple sulfatase deficiency (MSD) is an inherited lysosomal storage disease that affects post-translational activation of all of the sulfatases. Since biochemical and clinical findings are variable, the diagnosis is difficult in most of the cases. Missense, nonsense, microdeletion and splicing mutations in SUMF1 gene were found in all of the MSD patients analyzed. Here, we present clinical findings of two consanguineous patients with multiple sulfatase deficiency. They were found to be homozygous for a novel missense mutation c.739G > C causing a p.G247R amino acid substitution in the SUMF1 protein.

Most lysosomal storage disorders (LSDs) are caused by deficiencies of lysosomal hydrolases. While LSDs were among the first inherited diseases for which the underlying biochemical defects were identified, the mechanisms from enzyme deficiency to cell death are poorly understood. Here we show that lysosomal storage impairs autophagic delivery of bulk cytosolic contents to lysosomes. By studying the mouse models of two LSDs associated with severe neurodegeneration, multiple sulfatase deficiency (MSD) and mucopolysaccharidosis type IIIA (MPSIIIA), we observed an accumulation of autophagosomes resulting from defective autophagosome-lysosome fusion. An impairment of the autophagic pathway was demonstrated by the inefficient degradation of exogenous aggregate-prone proteins (i.e. expanded huntingtin and mutated alpha-synuclein) in cells from LSD mice. This impairment resulted in massive accumulation of polyubiquitinated proteins and of dysfunctional mitochondria which are the putative mediators of cell death. These data identify LSDs as 'autophagy disorders' and suggest the presence of common mechanisms in the pathogenesis of these and other neurodegenerative diseases.

Multiple Sulfatase Deficiency (MSD) is a rare inborn autosomal-recessive disorder, which mainly combines clinical features of metachromatic leukodystrophy, mucopolysaccharidosis and X-linked ichthyosis. The clinical course ranges from neonatal severe to mild juvenile cases. MSD is caused by mutations in the SUMF1 gene encoding the formylglycine-generating enzyme (FGE). FGE posttranslationally activates sulfatases by generating formylglycine in their catalytic sites. We analyzed the functional consequences of missense mutations p.A177P, p.W179S, p.A279V and p.R349W with regard to FGE's subcellular localization, enzymatic activity, protein stability, intracellular retention and resulting sulfatase activities. All four mutations did not affect localization of FGE in the endoplasmic reticulum of MSD fibroblasts. However, they decreased its specific enzymatic activity to less than 1% (p.A177P and p.R349W), 3% (p.W179S) or 23% (p.A279V). Protein stability was severely decreased for p.A279V and p.R349W, and almost comparable to wild type for p.A177P and p.W179S. The patient with the mildest clinical phenotype carries the mutation p.A279V leading to decreased FGE protein stability, but high residual enzymatic activity and only slightly reduced sulfatase activities. In contrast, the most severely affected patient carries the mutation p.R349W leading to drastically decreased protein stability, very low residual enzymatic activity and considerably reduced sulfatase activities. Our functional studies provide novel insight into the molecular defect underlying MSD and reveal that both residual enzyme activity and protein stability of FGE contribute to the clinical phenotype. The application of improved functional assays to determine these two molecular parameters of FGE mutants may enable the prediction of the clinical outcome in the future., ((c) 2007 Wiley-Liss, Inc.)

Sulfatases catalyze the hydrolysis of sulfate ester bonds from a wide variety of substrates and are implicated in several human inherited diseases. Multiple sulfatase deficiency (MSD) is a rare autosomal recessive disorder characterized by the simultaneous deficiency of all known sulfatases. MSD is caused by mutations in the Sulfatase Modifying Factor 1 (SUMF1) gene encoding the alpha-formylglycine generating enzyme (FGE), which is responsible for the post-translational modification of sulfatases. In all MSD patients, residual sulfatase activities are detectable, at variable levels. To correlate the nature of the residual sulfatase activities detected in MSD patients with residual FGE activity, four FGE mutants (i.e. p.S155P, p.R224W, p.R345C, p.R349W) found in homozygosis in MSD patients were analyzed. Using viral-mediated gene delivery, these mutants were over-expressed in mouse embryonic fibroblasts (MEFs) from a recently developed Sumf1 KO mouse line which is completely devoid of all sulfatase activities. The results obtained indicate that mutant SUMF1 cDNAs encode stable SUMF1 proteins which are of the appropriate molecular weight and are properly localized in the endoplasmic reticulum. Expression of these cDNAs in Sumf1-/- MEFs results in partial rescue of sulfatase activities. These data indicate that MSD is due to hypomorphic SUMF1 mutations and suggest that complete loss of SUMF1 function is likely to be lethal in humans., ((c) 2007 Wiley-Liss, Inc.)