Yolk represents the last growth stage of a single cell, the oocyte, which contains, besides
bona fide cytoplasm, endocytosed serum-derived lipoproteins and minor components
essential for normal embryo development. Transport of bulk lipoproteins, micronutrients, and
morphogens to oocytes in parallel with maintenance of somatic homeostasis is achieved by
ligand targeting via cell-specific expression of receptors and subtle differences in ligand
structure. Lipoprotein metabolism is the prime example of these regulatory principles, in …