Ndst1, also known as N-deacetylase / N-sulfotransferase, is a key enzyme in heparan sulfate (HS) biosynthesis, responsible for N-deacetylation and N-sulfation of N-acetyl-glucosamine residues. This step influences downstream enzymatic modifications, determining the overall structure and sulfation degree of the HS polysaccharide chain. HS is an important extracellular matrix component involved in various signaling pathways, such as Wnt, BMP, and prion-related processes, thus making Ndst1 crucial for normal development and physiological functions [4,7,8]. Genetic models, like knockout (KO) and conditional knockout (CKO) mice, are valuable tools for studying Ndst1 functions.

In conditional knockout mouse studies, neuronal Ndst1-depleted mice infected with extracellular, plaque-forming prions survived longer, showing fewer and smaller parenchymal plaques, shorter fibrils, and increased vascular amyloid, suggesting enhanced aggregate clearance. This indicates that HS sulfate groups (regulated by Ndst1) hinder the transit of extracellular prion protein monomers [1]. In Xenopus embryos, ndst1 overexpression expanded the neural crest region, while translational inhibition reduced the trigeminal and adjacent neural crest regions, and ndst1-knocked-down embryos showed cranial ganglion formation defects. Ndst1 was also found to activate the Wnt signaling pathway at the neurula stage [2]. In murine adipose-derived stem cells, overexpression of NDST1 suppressed osteogenic differentiation, induced chemokine production under TNF-α stimulation, and attenuated the fibrotic response [3]. In HPH-induced RVH rats, increased NDST1 was observed, and in vitro cell experiments showed that inhibiting NDST1 expression enhanced cell viability, reduced apoptosis, and alleviated cardiomyocyte hypertrophy [5]. In Ndst1(-/-) mice, defective lung cell differentiation, increased cell proliferation, and enhanced downstream BMP signaling were found, with exogenous heparin able to rescue BMP signaling and internalization abnormalities [6].

In conclusion, Ndst1 is essential for proper functioning in multiple biological processes including embryonic development, neural patterning, stem cell function, and disease-related pathways such as prion-associated neurodegeneration, hypoxic pulmonary hypertension-induced right ventricular hypertrophy, and fibrotic response. The use of Ndst1 KO/CKO mouse models has significantly contributed to understanding its role in these disease areas, providing insights into potential therapeutic targets.