Molecular Determinants of Calcitic Biomineralization.

点击翻译按钮获取中文摘要

Flaws in chicken eggshell (ES) fabrication are a human health and food safety issue; the nutritious table egg is an important source of protein, minerals and vitamins for hundreds of millions of individuals living in poverty worldwide. In this sense, the reproducible nature of calcitic biomineralization of the eggshell is of critical concern to human society. In Canada, it is estimated that about 10,000 annual cases of salmonella poisoning are due to contamination of cracked and imperfect eggshells that find their way into the food chain. Worldwide, foodborne salmonella is responsible for 80.3 million illnesses/yr (1.35 million cases/yr in the United States). In the USA, salmonella poisonings result in 26,500 hospitalizations/yr and 420 deaths/yr. Approximately 18% of salmonella outbreaks are due to consumption of food prepared from contaminated eggs.    My NSERC Discovery research program has an overall aim to investigate the integrated defense strategies that function at the eggshell as a biomineralized barrier in order to maintain the pathogen-free status of the egg.  During 2016-2022 [evidenced in 16 publications and 1 book chapter], our detailed proteomic and transcriptomic studies of eggshell biomineralization in chicken, guinea fowl and duck, in addition to analysis from a broad multi-omics evolutionary perspective, have provided insight into nature's toolkit that is responsible for avian eggshell formation. Our recent publication in Nature Communications emphasizes the critical role that eggshell-specific C-type lectin matrix proteins (ovocleidin-17 in chicken) play in eggshell mineralization. We identified a new vesicular pathway for amorphous calcium carbonate (ACC)-mediated eggshell mineralization and assessed the relevance of a new molecular actor (EDIL3). Moreover, the role of osteopontin in modulating eggshell nanostructure and hardness was confirmed.    However, the eggshell possesses dual functions as both a biomineralized barrier and as a component of the innate immune system. Disentangling immune and biomineralization mechanisms represents a significant challenge to understand how organisms integrate biomineral formation and immune plasticity with the maintenance of critical physical protection. The general goals of my NSERC Discovery research during the next grant cycle are to study the innate immune role of the chorioallantoic membrane (CAM) during ES weakening and microbial challenge, and to further investigate the role of ACC in ES resorption (CAM-mediated demineralization).  We will use transcriptomics (RNA-Seq) and proteomics approaches to investigate the hypotheses that the CAM responds to mechanical and microbial insults by up-regulating its protective mechanisms, and that stabilized ACC is a readily mobilized source of calcium precursor during embryonic growth. These studies will lead to solutions to serious food safety issues such as salmonella contamination of the table egg.