PSAP and sphingolipidosis: Mammalian prosaposin proteins, derived saposin peptides, and synthetic prosaptide analogues exert cyto-trophic and -protective effects on a variety of cell types, at different developmental stages [64,65], and prosaposin deficiency causes a specific type of encephalopathy, a genetic lysosomal storage disease belonging to the group of sphingolipidoses [66] (https://disease-ontology.org/?id=DOID:0111330, accessed on 20 March 2022; https://www.omim.org/entry/611721, accessed on 20 March 2022; https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=139406, accessed on 20 March 2022).