{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n Heparan sulfate 6‐O‐sulfotransferase 1 (HS6ST1) is a key enzyme that catalyzes the addition of 6‐O sulfate groups onto glucosamine residues of heparan sulfate chains, thereby generating defined sulfation patterns that are critical for modulating growth factor and guidance‐cue signaling in multiple developmental contexts. HS6ST1 activity fine‐tunes fibroblast growth factor (FGF) signaling by affecting the binding affinities between FGF ligands and their receptors, as demonstrated in cell‐based assays and in genetically modified mouse models where reduced 6‐O sulfation led to marked alterations in FGF-dependent responses during lacrimal gland formation and in fibroblast growth factor signaling cascades overall."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": " In the nervous system, HS6ST1 is indispensable for proper neural circuit formation; loss of HS6ST1 function impairs retinal ganglion cell axon guidance by blunting the cellular response to repulsive cues such as Slit proteins"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": ", and mutations that reduce HS6ST1 activity have been linked to idiopathic hypogonadotropic hypogonadism (IHH), with consequent defects in gonadotropin‐releasing hormone neuron development and pubertal timing."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "5", "end_ref": "7"}]}, {"type": "t", "text": " In addition, gene–diabetes interaction studies implicate HS6ST1 variants in modulating the urinary albumin-to-creatinine ratio in diabetic kidney disease."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": " Collectively, these findings underscore the multifunctional role of HS6ST1 in establishing precise heparan sulfate structures that govern key cellular processes such as growth factor signaling, neural guidance, and endocrine regulation during development."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": "\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Noriko Sugaya, Hiroko Habuchi, Naoko Nagai, et al. 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