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The Unique Features of Proteins Depicting the Chicken Amniotic Fluid

The bird's egg is subject to many environmental pressures including microbial pressures. To cope, it has various and complementary protection systems to preserve the embryo. Of these, the amniotic fluid plays a major role, thanks to its wealth of antimicrobial molecules.

Venn diagrams representing the specific and overlapping proteins identified in the human (during the whole gestation) and chicken (11th day of incubation) amniotic fluid (AF).. © INRA, Sophie Rehault-Godbert
By Sylvie André
Updated on 10/04/2019
Published on 10/03/2019

In many amniotes, the amniotic fluid is depicted as a dynamic milieu that participates in the protection of the embryo (cushioning, hydration, and immunity).
However, in birds, the protein profile of the amniotic fluid remains unexplored, even though its proteomic signature is predicted to differ compared with that of humans. In fact, unlike humans, chicken amniotic fluid does not collect excretory products and its protein composition strikingly changes at mid-development because of the massive inflow of egg white proteins, which are thereafter swallowed by the embryo to support its growth.

Using GeLC-MS/MS and shotgun strategies, we identified 91 nonredundant proteins delineating the chicken amniotic fluid proteome at day 11 of development, before egg white transfer. These proteins were essentially associated with the metabolism of nutrients, immune response and developmental processes. Forty-eight proteins were common to both chicken and human amniotic fluids, including serum albumin, apolipoprotein A1 and alpha-fetoprotein.

Venn diagrams representing the specific and overlapping proteins identified in the human (during the whole gestation) and chicken (11th day of incubation) amniotic fluid (AF).. © INRA, Sophie Rehault-Godbert
Venn diagrams representing the specific and overlapping proteins identified in the human (during the whole gestation) and chicken (11th day of incubation) amniotic fluid (AF). © INRA, Sophie Rehault-Godbert

We further investigated the effective role of chicken amniotic fluid in innate defense and revealed that it exhibits significant antibacterial activity at day 11 of development. This antibacterial potential is drastically enhanced after egg white transfer, presumably due to lysozyme, avian beta-defensin 11, vitelline membrane outer layer protein 1, and beta-microseminoprotein-like as the most likely antibacterial candidates.
Interestingly, several proteins recovered in the chicken amniotic fluid prior and after egg white transfer are uniquely found in birds (ovalbumin and related proteins X and Y, avian beta-defensin 11) or oviparous species (vitellogenins 1 and 2, riboflavin-binding protein).
This study provides an integrative overview of the chicken amniotic fluid proteome and opens stimulating perspectives in deciphering the role of avian egg-specific proteins in embryonic development, including innate immunity. These proteins may constitute valuable biomarkers for poultry production to detect hazardous situations (stress, infection, etc.), that may negatively affect the development of the chicken embryo.

Contact(s)
Scientific contact(s):

Associated Division(s):
Animal Physiology and Livestock Systems
Associated Centre(s):
Val de Loire

References

Da Silva, M.; Dombre, C.; Brionne, A.; Monget, P.; Chesse, M.; De Pauw, M.; Mills, M.; Combes-Soia, L.; Labas, V.; Guyot, N.; Nys, Y.; Rehault-Godbert, S., 2019. The Unique Features of Proteins Depicting the Chicken Amniotic Fluid. Molecular & Cellular Proteomics, 18 (3): S174-S190 http://dx.doi.org/10.1074/mcp.RA117.000459