The slippery slope antedating syngamy: pronuclear activity in preparation for the first cleavage

Nucleolus precursor bodies (NPB) are aggregations of intrapronuclear material observed in the pronuclei of fertilized human eggs. They derive from and evolve into nucleoli of the growing oocyte and the early embryo, respectively. Decades-old observations suggest that the patterns of their distribution represent a morphological marker of embryo developmental competence. Recent time-lapse microscopy (TLM) data now indicate that the vectorial characteristics of NPB movement can predict blastocyst formation, euploidy, and implantation. Since distributions of NPB and chromatin coincide, chromatin rearrangement in preparation for the first mitotic cleavage is emerging as a crucial process of early development.

Automated summary

Nucleolus precursor bodies (NPB) are intrapronuclear aggregations observed in fertilized human eggs, with recent data indicating their movement characteristics can predict embryo developmental competence. Chromatin rearrangement is emerging as a crucial process in early development as NPB and chromatin distributions coincide.