Fat-containing cells are eliminated during Dictyostelium development

Abstract

Triacylglycerol is a universal storage molecule for metabolic energy in living organisms. However, Dictyostelium amoebae, that have accumulated storage fat from added fatty acids do not progress though the starvation period preceding the development of the durable spore. Mutants deficient in genes of fat metabolism, such as fcsA, encoding a fatty acid activating enzyme, or dgat1 and dgat2, specifying proteins that synthesize triacylglycerol, strongly increase their chances to contribute to the spore fraction of the developing fruiting body, but lose the ability to produce storage fat efficiently. Dictyostelium seipin, an orthologue of a human protein, that in patients causes the complete loss of adipose tissue when mutated, does not quantitatively affect fat storage in the amoeba. Dictyostelium seiP knockout mutants have lipid droplets that are enlarged in size but reduced in number. These mutants are as vulnerable as the wildtype when exposed to fatty acids during their vegetative growth phase, and do not efficiently enter the spore head in Dictyostelium development.