Stable Isotope <em>In-Vivo</em> Labeling for Mass-Spectrometry Identification of Paternal Metabolites Transferred from Sperm to Oocyte During Fertilization

Paternal contribution to embryo genetics has so far been limited to allelic sequences for decades. A decade of results suggests, instead, that epigenetic factors-DNA methylation, histone modifications, chromosomal organization, and regulatory RNAs-play crucial roles in paternal inheritance and influence embryonic development and zygote gene expression. Together with nucleic acids, sperm metabolome (lipids, carbohydrates, free amino acids) may act as epigenetic signal. This protocol aims to identify sperm-to-oocyte transferred metabolites by mass spectrometry. The procedure includes stable isotope labeling of sperm cells with ²H2O or U¹³C Glucose to trace, by metabolomics, paternal metabolites transferred to the oocyte during fertilization. The overall goal of the protocol is to reveal the role of paternal sperm metabolome in offspring's susceptibility to dysmetabolism, and it may be adapted to provide insights into how environmental conditions, such as diet and exposure to pollutants, alter paternal metabolic messages, potentially affecting offspring's health and predisposition to diabetes, obesity, and cardiovascular diseases.