Induction of Stress Granules and Developmental Instability of Offspring Phenotype Due to Hypothermia During First Mouse Embryo Cleavage

Zygotic genome activation (ZGA) represents one of the most vulnerable periods to environmental perturbations. The objective of this study was to investigate the formation of stress granules in mouse embryos in response to temperature reduction during ZGA, preimplantation embryo mortality, and long-term phenotypic outcomes. These outcomes included the evaluation of expression noise in bilateral right/left limbs of offspring as an indicator of developmental instability, behavioral deviation, hippocampal volume, and metabolomics profiling in adult offspring. Exposure to hypothermia during ZGA was associated with an increased number and inter-blastomere variability of stress granules, extended duration of the second embryonic division, and elevated embryonic mortality during the second and third cleavage stages. The embryonic response to hypothermic stress correlated with phenotypic traits indicative of increased pathology risk. Expression noise, serving as an indicator of developmental instability, was reduced in adult offspring derived from two-cell embryos incubated at 35 °C compared to those at 37 °C, while showing no significant difference relative to the control group. These results suggest that embryos surviving hypothermic exposure (35 °C) possess enhanced resilience to the adverse effects commonly associated with embryo transfer procedures. Furthermore, increased hippocampal volume and augmented auditory startle reflex observed in offspring that endured hypothermia during ZGA imply reduced risks of cognitive-related pathologies and reduced risks of pathologies associated with cognitive functions.