{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nSGSH (N‐sulfoglucosamine sulfohydrolase) is a lysosomal enzyme that plays a critical role in the degradation of heparan sulfate—an essential glycosaminoglycan. Impairment of SGSH activity due to mutations in its gene disrupts heparan sulfate turnover, leading to its progressive accumulation in lysosomes and ultimately causing the neurodegenerative disorder mucopolysaccharidosis type IIIA (Sanfilippo syndrome type A). This enzyme deficiency chiefly manifests with severe central nervous system degeneration, establishing SGSH as a key factor in maintaining neuronal health."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": "Dissection of the molecular basis of MPS IIIA has uncovered a wide spectrum of mutations—including missense, nonsense, and frameshift types—that dramatically reduce or abrogate SGSH enzymatic activity. Detailed expression studies and pulse-chase analyses have revealed that many mutant SGSH proteins are rapidly degraded or misprocessed, compromising their lysosomal delivery. High-resolution crystal structure data of glycosylated SGSH have further elucidated its conserved active-site architecture—including the catalytic formylglycine residue and key substrate-binding features—which explains how certain mutations (for example, p.Ser298Pro) correlate with a milder, slowly progressive clinical phenotype and have important implications for genetic counseling."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "4", "end_ref": "7"}]}, {"type": "t", "text": "These mechanistic insights into SGSH function have paved the way for emerging therapeutic and diagnostic strategies. Preclinical studies using recombinant human SGSH delivered via enzyme replacement or gene therapy have demonstrated significant restoration of SGSH activity, efficient clearance of accumulated substrates, and reduced neuropathology in animal models of MPS IIIA. Complementary to these advances, development of sensitive enzymatic activity assays based on dried blood spots holds promise for earlier diagnosis and improved monitoring of treatment response."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "8", "end_ref": "10"}]}, {"type": "t", "text": ""}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "G Yogalingam, J J Hopwood "}, {"type": "b", "children": [{"type": "t", "text": "Molecular genetics of mucopolysaccharidosis type IIIA and IIIB: Diagnostic, clinical, and biological implications."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Hum Mutat (2001)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1002/humu.1189"}], "href": "https://doi.org/10.1002/humu.1189"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "11668611"}], "href": "https://pubmed.ncbi.nlm.nih.gov/11668611"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Serap Emre, Mugen Terzioglu, Aysegul Tokatli, et al. 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"}, {"type": "b", "children": [{"type": "t", "text": "The mutation p.Ser298Pro in the sulphamidase gene (SGSH) is associated with a slowly progressive clinical phenotype in mucopolysaccharidosis type IIIA (Sanfilippo A syndrome)."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Hum Mutat (2008)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1002/humu.20738"}], "href": "https://doi.org/10.1002/humu.20738"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "18407553"}], "href": "https://pubmed.ncbi.nlm.nih.gov/18407553"}]}, {"type": "r", "ref": 5, "children": [{"type": "t", "text": "Nicole Muschol, Sandra Pohl, Ann Meyer, et al. 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