The Unique Features of Proteins Depicting the Chicken Amniotic Fluid

Abstract

SUMMARYIn 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 to human's. In fact, unlike humans, chicken amniotic fluid does not collect excretory products and its protein composition strikingly changes at mid-development due to 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 non-redundant 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. We further investigated the effective role of the 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 betadefensin 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, riboflavinbinding protein). This study provides an integrative overview of the chicken amniotic fluid proteome and opens stimulating perspectives in deciphering the role of the avian egg-specific proteins in embryonic development, including innate immunity. These proteins may constitute Proteomic specificities of the chicken amniotic fluid 3 valuable biomarkers for poultry production to detect hazardous situations (stress, infection, etc.), that may negatively affect the development of the chicken embryo. Proteomic specificities of the chicken amniotic fluid4

Dynamics of Structural Barriers and Innate Immune Components during Incubation of the Avian Egg: Critical Interplay between Autonomous Embryonic Development and Maternal Anticipation

“…Direct transfer of gut proteins to the allantoic sac is also likely to occur [83]. EW anti- Listeria monocytogenes and anti- Streptococcus uberis activities are maintained during embryonic development up to ED12 [84], and EW antibacterial proteins have been shown to be active even after their transfer into the amniotic sac [20]. …”

“…Following EW transfer, its antibacterial proteins may also contribute to protect the embryo before and after hatching, like the vernix caseosa in humans [125]. Interestingly, several proteins recovered in the AmF prior and after EW transfer are uniquely found in birds (OVAL and its related proteins OVAX and OVAY, and also AvBD11) or oviparous species (vitellogenin [VTG]1, VTG2, and riboflavin-binding protein [RBP]) [20]. …”

“…However, unlike in mammals, chicken AmF does not collect excretory products and its protein composition strikingly changes at mid-development due to the massive inflow of EW proteins, which are thereafter swallowed by the embryo to support its growth. Proteomics has identified 91 nonredundant proteins delineating the chicken AmF proteome at ED11, before EW transfer [20]. These proteins are essentially associated with the metabolism of nutrients, immune response, and developmental processes.…”

“…1). These acellular structures serve as a source of nutrients and energy as well as physical, chemical, and molecular defenses to protect the chicken embryo against physical shock and microbial infection in the course of its 21-day development [20-22] (Fig. 2).…”

Reproductive Proteomics Comes of Age

“…protective, nutritive, and immune functions, but the overall protein composition is complex and poorly understood. Da Silva et al (31) use LC-MS/MS to identify doz-ens of proteins present in the chicken amniotic fluid proteome before the influx of massive amounts of egg white proteins. Importantly, they found that 48 of these were common to both chicken and humans amniotic fluids defining a target set of high-quality proteins with potentially conserved function in developing egg and fetus.…”