Epitranscriptomic modifications in embryonic development: insights into natural and ART-induced mechanisms and implications.

backgroundMammalian embryo development involves a complex process governed by multiple layers of cellular and molecular regulation mechanisms. ART is widely used around the world to assist fertility in humans, with ∼12 million babies being born by ART in the last 40 years. These technologies are also used extensively for reproductive purposes in other mammalian species that have many analogies with human reproductive biology. Epitranscriptomic marks, including RNA modifications such as N6-methyladenosine (m6A) and N1-methyladenosine (m1A), modulate gene expression during gametogenesis and embryo development, and their dynamics are regulated by genes encoding m6A writers (METTL3, METTL14, and WTAP), readers (YTHDF2, YTHDC1-2, and PRRC2A), and erasers (ALKBH5 and FTO). However, the impact of ART on these epigenetic modifications remains poorly understood. OBJECTIVE AND RATIONALE: This narrative review explores the role of epitranscriptomic modifications in both naturally and ART-conceived embryos. It examines how RNA modifications regulate gametogenesis and early embryonic development and how ART-induced cellular stress might perturb these regulatory layers, potentially affecting gametogenesis, embryo competence, and offspring health. Understanding the interaction between ART and epitranscriptomic regulation is crucial for optimizing ART procedures and safeguarding offspring health. SEARCH

methodsThe PubMed and Scopus literature databases were utilized to search for peer-reviewed articles and reviews using terms such as 'epitranscriptomic', 'RNA modification', 'gametogenesis', 'embryo development', 'mammalian development', 'in vitro fertilization', 'ART', and 'assisted reproductive technologies' in combination or individually. All relevant publications until the current year have been critically evaluated and discussed. OUTCOMES: Epitranscriptomic modifications, particularly m6A, have emerged as key regulators of RNA metabolism during gametogenesis and early embryo development. Evidence from both human and animal studies indicates that ART-related stressors, such as oxidative imbalance, hormonal stimulation, and cryopreservation, can disturb RNA methylation at the epitranscriptomic marks m1A and 5-methylcytosine by modulating the expression and activity of m6A writers, erasers, and readers, independently of global transcriptional changes. These alterations can affect embryo competence, placental function, lineage specification, and subsequent offspring development. Moreover, m6A-associated factors participate in stress adaptation and developmental signalling beyond their canonical methylation activity. Collectively, these findings underscore the remarkable sensitivity of the embryonic transcriptome to in vitro manipulation and highlight epitranscriptomic marks as both predictive biomarkers and mechanistic targets for improving the safety, efficacy, and long-term outcomes of assisted reproduction. WIDER IMPLICATIONS: Understanding how ARTs influence the epitranscriptome and its downstream effects is crucial for improving reproductive outcomes. In vitro manipulation, fertilization, and embryo culture can influence RNA regulation in gametes, causing reduced cell differentiation, and, in early embryos, contributing to recurrent implantation failure, decidualization failure, and pregnancy loss. This review aims to share with the scientific community insights into the critical role of epitranscriptomic modifications during gametogenesis and embryogenesis, as well as the potential consequences of in vitro procedures, to guide safer and more effective ART practices. REGISTRATION NUMBER: N/A.