Researchers led by Kyushu University and Japan’s National Institute of Genetics report that mouse embryos undergo nuclear softening and deformation at the two-cell stage. They say this physical change accompanies major zygotic gene activation, when roughly 2,000 genes needed for early development switch on simultaneously.
Nature also describes the finding as a distinct, transient nuclear state that supports the start of the zygotic transcription program. While the Phys.org report emphasizes the link between nuclear softening and the two-cell-stage timing of gene activation, Nature frames the result more broadly as an early-life physical state that enables zygotic transcription. Both accounts attribute the observation to a coordinated transition in embryo nuclei that occurs at the beginning of developmental gene expression.
