Proteomic characterization of eight-day-old equine blastocysts produced in vivo

Abstract

Early embryo development is dependent on molecular signatures brought by the gametes, gene expression and maternal-embryo interactions. The proteome of the embryo reflects its development state and defines its fate. The present study aimed to describe the proteome of 8-day old equine blastocysts produced in vivo. Follicular dynamics of eight mares were monitored by ultrasonography. When a preovulatory follicle was confirmed, mares received GnRH and were inseminated. After eight days, four embryos were recovered. Proteins were extracted from the embryos (pool) and subjected to mass spectrometry. Different search engines were used for protein identification: Peaks, Proteome Discoverer, SearchGUI and PepExplorer. Mass spectrometry and tools of bioinformatics allowed the identification of 1,977 proteins in the embryos. Biological processes of embryo proteins were cellular and metabolic processes. Cellular components were cell, organelle and protein-containing complex. Molecular functions of embryo proteins were involved in binding, catalytic activities and structural molecule activity. Six pathways relevant to embryo development (FDR < 0.05, Panther platform) related to TCA cycle, pyruvate metabolism, glycolysis, purine metabolism, and pentose phosphate pathway. There were pathways involved in cell-cell communication and extracellular matrix (ECM) remodeling and pathways related to intracellular remodeling, like cytoskeleton regulation by Rho GTPase. Analyses were conducted in a pool of embryos from different mares, providing a comprehensive view about the proteome of 8-day old embryos. However, comparisons could not be made among protein syntheses in the phases of early developmental states of the equine embryo. The current study used mass spectrometry and a combination of search engines for the identification of 1,977 proteins in 8-day-old equine embryos generated in vivo. This is the largest atlas of proteins from embryos of the equine species. Knowledge of protein expression by the embryo helps to understand its physiology and metabolic events.