Abstract
Purpose :
Gangliosides are a family of complex, sialic acid-containing glycosphingolipids (GSLs) that are integral components of cell surface microdomains. They are crucial for signal transduction, cell-cell interaction, adhesion, and are implicated in phagocytosis. Gangliosides are highly abundant and diverse in all neuronal derived tissue, and dysfunction in their metabolism can drive multiple neurological disorders. Macular Telangiectasia (MacTel) is a neurodegenerative disease affecting the retina and leading to progressive vision loss. MacTel patients have low circulating serine, a key metabolite in the synthesis of sphingolipids, including GSLs. In this study we investigate perturbation of ganglioside metabolism as a potential contributor to retinal pathology.
Methods :
High resolution LC-MS was performed on serum from 205 MacTel patients and 151 healthy controls for broad spectrum GSL analysis to profile systemic patient GSL diversity and abundance. Mice were fed a custom serine and glycine free diet or an isonitrogenous control diet. hfRPE (Lonza) were differentiated for 2 weeks as per Lonza’s protocol prior to experimental treatment. hfRPE were grown in custom medias deprived of serine and glycine before harvesting for LC-MS analysis. For phagocytosis assays, uptake of fluorophore labelled outer segments was assessed by flow cytometry.
Results :
Analysis of MacTel patient plasma demonstrated significant alterations in complex GSL diversity compared to control participants. Analysis of mouse retinal tissues demonstrated that GSLs have increased complexity in the neural retina compared to the RPE/choroid. Upon serine and glycine starvation in the mice, RPE GSLs were significantly altered, but retinal levels were unchanged. When hfRPE were cultured in serine- and glycine-depleted media, their GSLs were significantly reduced. They also had reduced phagocytic capacity.
Conclusions :
Retinal tissues have distinct GSL profiles suggesting the function of GSLs may be tissue-specific. In vivo and in vitro models indicate that serine and glycine are necessary for maintaining GSL levels and for proper phagocytic function in the RPE, possibly through a GSL dependent mechanism. These data suggest that the altered GSL levels observed in MacTel patient serum is driven by low serine and glycine levels, potentially contributing to retinal pathology.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.