Domestic goose egg yolk vitelline membrane structure and protein characterization

The vitelline membrane (VM) of an avian egg is a multilayered protein structure that surrounds the yolk and plays important roles in bird reproduction. This study presents the first analysis of the structure and protein composition of the VM in domestic geese, comparing two breeds with different origins: Lands (LsD) and Garbonosa (Ga) geese. To characterize the VM structure, histological preparations were stained using the Gordon-Sweet, eosin, Gomori trichrome, and Verhoeff-van Gieson methods. Micrographs were taken for both scanning and transmission electron microscopy. After electrophoresis, one protein band (band 1) from the LsD goose and two protein bands (bands 2 and 3) from the Ga goose were selected from the gels and subjected to detailed proteomic analysis. The VM of the Ga goose was thicker than that of the LsD goose (P < 0.001). In the outer layer of the LsD goose, only one sublayer was observed, while the Ga goose had five sublayers. In the inner layer, the LsD goose had six sublayers, while the Ga goose had twelve. The protein fibers forming the outer layer of the VM in the Ga goose were significantly thicker than those in the LsD goose. Analysis of the selected protein bands showed a higher abundance of all identified proteins in the Ga goose VM: band 1 identified as vitelline membrane outer layer protein 1 (VMO-I), band 2 as zona pellucida sperm-binding protein 1 (ZP1) and zona pellucida sperm-binding protein 3 (ZP3), and band 3 as apovitellenin-1 (APOV1). These proteins play roles in stabilizing the VM (VMO-I), are involved in fertilization (ZP1 and ZP3), and facilitate lipid transport from the blood to the yolk (APOV1). The structural and proteomic differences in the VM between LsD and Ga geese are probably due to their different origins, domestication histories, and varying intensities and directions of selection. The results suggest differences in the natural defense mechanisms of eggs from LsD and Ga geese. These findings provide valuable insights for improving reproduction, particularly for enhancing the efficiency of artificial incubation of goose eggs.