Elusive zebrafish enzyme in lipid secretion

Lipids provide energy and structural components during vertebrate development. Lipoproteins aid in lipid transport throughout the body, and synthesized lipids are also stored in lipid droplets within the cell. Embryos of the model organism zebrafish receive nutrients, including lipids, from a maternally deposited yolk through extraembryonic tissue called the yolk syncytial layer, or YSL. Lipid nutrients are released through the production and secretion of lipoproteins rich in triacylglycerol, or TAG. Scientists want to understand which enzymes direct TAG production to lipoproteins for secretion versus lipid droplets for storage.

In a recent Journal of Biological Chemistry article, Meredith Wilson from Johns Hopkins University and U.S. and U.K. colleagues investigated the fate of TAG in zebrafish lacking certain TAG synthesis enzymes. They found that zebrafish lacking diacylglycerol acyltransferase-2, or Dgat2, can still produce TAG, but the TAG is channeled for YSL storage instead of secretion, as noted by the excessive accumulation of lipid droplets in the YSL that make it look opaque.

The authors concluded that zebrafish have multiple enzymes to ensure TAG production remains intact. Future studies will identify the enzyme that fails to properly channel TAG to lipoprotein formation for secretion in embryonic development.