Treatment of Adult Metachromatic Leukodystrophy Model Mice Using Intrathecal Administration of Type 9 AAV Vector Encoding Arylsulfatase A

Metachromatic leukodystrophy (MLD) is a lysosomal storage disease caused by an arylsulfatase A (ASA) deficiency and characterized by severe neurological symptoms resulting from demyelination within the central and peripheral nervous systems. We investigated the feasibility and efficacy of intrathecal administration of a type 9 adeno-associated viral vector encoding ASA (AAV9/ASA) for the treatment of 6-week-old MLD model mice, which are presymptomatic, and 1-year-old mice, which exhibit neurological abnormalities. Immunohistochemical analysis following AAV9/ASA administration showed ASA expression within the brain, with highest activities in the cerebellum and olfactory bulbs. In mice treated at 1 year, alcian blue staining and quantitative analysis revealed significant decreases in stored sulfatide within the hindbrain but not forebrain. Behaviorally, mice treated at 1 year showed no improvement in their ability to traverse narrow balance beams as compared to untreated mice. By contrast, MLD mice treated at 6 weeks showed significant decreases in stored sulfatide throughout the entire brain and improved ability to traverse narrow balance beams. These findings suggest intrathecal administration of an AAV9/ASA vector is a promising approach to treating genetic diseases of the central nervous system, including MLD, though it may be essential to begin therapy before the onset of neurological symptoms.

Arylsulfatase A Remodeling during Human Sperm In Vitro Capacitation Using Field Emission Scanning Electron Microscopy (FE-SEM)

Capacitation drives sperm biophysical and biochemical changes for sperm-oocyte interactions. It is a well-known fact that the molecular complex arylsulfatase A (ARSA), hyaluronidase sperm adhesion molecule 1 (SPAM1), and heat shock protein 2 (HSPA2) plays a significant role in sperm–zona pellucida (ZP) binding. However, the time-dependent capacitation effects on the sperm surface ARSA presence and specific topographic distributions remain to be elucidated. Here, we quantified the ARSA density and specific membrane domain locations before (US) and after in vitro capacitation (one and four hours; CS1–CS4) in human sperm using high-resolution field emission scanning electron microscopy (FE-SEM) and immunogold labeling. Our results showed a significant and progressive capacitation-mediated increase of labeled spermatozoa from the US (37%) to CS4 (100%) physiological conditions. In addition, surface mapping revealed a close relationship between the ARSA residues and their acrosomal repositioning. Compared with the ARSA surface heterogeneous distribution found in US, the CS1–4 conditions exhibited clustering on the peri-acrosomal region, showing that time-dependent capacitation also induced a ARSA residue dramatic translocation on sperm surfaces. Our findings provide novel insights into the molecular remodeling events preceding sperm-oocyte interactions.

Case Report: Novel Arylsulfatase A (ARSA) Gene Mutations in a Patient With Adult-Onset Metachromatic Leukodystrophy Misdiagnosed as Multiple Sclerosis

Metachromatic leukodystrophy (MLD) is an autosomal recessive hereditary disorder characterized by the accumulation of sulfatide in the central and peripheral nervous systems. Herein, we present the case of an adult patient with MLD who had mild cognitive and psychiatric dysfunctions and severe vision disturbance, who was initially misdiagnosed as multiple sclerosis. Through genetic screening, this patient was later identified to have a full deletion of exon 4 and the novel p.P220L mutation in the arylsulfatase A (ARSA) gene. These mutations are reported for the first time in MLD. These data will help to update the mutation profiles of patients with MLD.

A dual-enzyme cleavable linker for antibody-drug conjugates

A novel enzyme cleavable linker for antibody-drug conjugates is reported. The 3-O-sulfo-β-galactose linker is cleaved sequentially by two lysosomal enzymes – arylsulfatase A and β-galactosidase – to release the payload...

Brain cell type-specific endocytosis of arylsulfatase A identifies limitations of enzyme-based therapies for metachromatic leukodystrophy

Enzyme replacement therapies, allogeneic bone marrow transplantation and gene therapies are treatment options for lysosomal storage diseases caused by inherited deficiencies of soluble lysosomal enzymes. Independent from the approach, the enzyme must be delivered to lysosomes of deficient patient cells. Little is known about the dissemination of enzyme within a tissue where cells compete for uptake via different receptor systems, binding affinities and endocytic rates. To evaluate dissemination and lysosomal targeting of a lysosomal enzyme in the CNS, we analysed receptor-mediated endocytosis of arylsulfatase A (ASA) by different types of brain-derived cell lines and primary murine brain cells. For ASA expressed by chinese hamster ovary cells for enzyme replacement therapy of metachromatic leukodystrophy, endocytic rates decline from microglia to neurons and astrocytes and to oligodendrocytes. Only immature oligodendrocytes endocytose significant amounts of enzyme. Uptake by non-microglial cells is due to mannose 6-phosphate receptors, whereas several receptor systems participate in endocytosis by microglial cells. Interestingly, ASA expressed by microglial cells cannot be taken up in a mannose 6-phosphate dependent manner. The resulting failure to correct non-microglial cells corroborates in vivo data and indicates that therapeutic effects of allogeneic bone marrow transplantation and hematopoietic stem cell gene therapy on metachromatic leukodystrophy are independent of metabolic cross-correction of neurons, astrocytes and oligodendrocytes by receptor-mediated endocytosis.

Arylsulfatase A (ASA) in Parkinson’s Disease: From Pathogenesis to Biomarker Potential

Parkinson’s disease (PD), the second most common neurodegenerative disorder after Alzheimer’s disease, is a clinically heterogeneous disorder, with obscure etiology and no disease-modifying therapy to date. Currently, there is no available biomarker for PD endophenotypes or disease progression. Accumulating evidence suggests that mutations in genes related to lysosomal function or lysosomal storage disorders may affect the risk of PD development, such as GBA1 gene mutations. In this context, recent studies have revealed the emerging role of arylsulfatase A (ASA), a lysosomal hydrolase encoded by the ARSA gene causing metachromatic leukodystrophy (MLD) in PD pathogenesis. In particular, altered ASA levels have been detected during disease progression, and reduced enzymatic activity of ASA has been associated with an atypical PD clinical phenotype, including early cognitive impairment and essential-like tremor. Clinical evidence further reveals that specific ARSA gene variants may act as genetic modifiers in PD. Recent in vitro and in vivo studies indicate that ASA may function as a molecular chaperone interacting with α-synuclein (SNCA) in the cytoplasm, preventing its aggregation, secretion and cell-to-cell propagation. In this review, we summarize the results of recent preclinical and clinical studies on the role of ASA in PD, aiming to shed more light on the potential implication of ASA in PD pathogenesis and highlight its biomarker potential.

Co-occurrence of Metachromatic Leukodystrophy in Phelan-McDermid Syndrome

Phelan-McDermid syndrome or 22q13.3 deletion syndrome is a rare neurodevelopmental disorder characterized by neonatal hypotonia, severe speech delay, moderate to profound intellectual disability, and minor dysmorphic features. Regression of developmental milestones is often recognized as characteristic of this syndrome. We report a 6-year-old patient with Phelan-McDermid syndrome who presented with rapid neurologic deterioration secondary to metachromatic leukodystrophy due to a mutation of the arylsulfatase A gene ( ARSA) on the other allele of 22q13.3. Metachromatic leukodystrophy was diagnosed later after clinical deterioration. Currently, there are no guidelines for screening Phelan-McDermid syndrome patients for metachromatic leukodystrophy. We propose screening for urine sulfatides at the time of Phelan-McDermid syndrome diagnosis to identify patients with pre-symptomatic or early symptomatic metachromatic leukodystrophy as it is important to facilitate discussion of treatment options and prognosis and provide medical surveillance for associated complications.