Quantitative proteomics and bioinformatic analysis provide new insight into protein function during avian eggshell biomineralization.

Abstract

The calcitic avian eggshell protects the developing embryo and, moreover, ensures that the nutritious table egg remains free of pathogens. The eggshell is formed by nucleation upon a fibrous scaffold (the eggshell membranes) followed by an interaction between the growing mineral crystals and the shell organic matrix. This interaction leads to a highly ordered shell microstructure and texture which contribute to its exceptional mechanical properties. Shell mineralization occurs in three distinct phases of calcification (initiation, growth and termination), which are associated with distinct populations of matrix proteins that are secreted into the acellular uterine fluid as modulators of the process. The recent development of high-throughput methods has led to the identification of many proteins in the shell, but little is known concerning their role in shell formation. In order to determine precisely the importance of particular proteins relative to eggshell mineralization, this project used qualitative and quantitative proteomics of the uterine fluid constituents, coupled with bioinformatic analysis, to predict the functional role of proteins secreted at each of the three main stages of shell calcification. Besides its relevance to food production and to hen reproduction, eggshell calcification is furthermore a relevant model for studying calcium carbonate biomineralization on a two-dimensional membrane support. Better understanding of this process will provide insight into the fabrication of ceramics at ambient pressure and temperature.