Sexual reproduction involves the fusion of a female gamete, the oocyte, with a sperm, resulting in the formation of an embryo. In most species, oocytes are huge cells that harbor large nuclei. Oocytes accumulate maternal stores (mRNAs and proteins) that will be used during meiotic divisions and the first steps of embryonic development. The oocyte nucleus plays an essential role in this process and therefore is a central player in the acquisition of the developmental potential of the female gamete for further meiotic divisions and early development after fertilization.

The nucleus of Xenopus oocytes has been known for a while to transcriptionally reprogram somatic nuclei, and recently researchers have been working to better understand the molecular mechanisms involved. Understanding genome organization in the oocyte nucleus and its impact on gene expression is currently the subject of intensive research, as illustrated by the discovery of maternal domains in mouse oocytes priming repressed chromatin. But the position of the nucleus itself can instruct developmental cues, like in the Drosophila oocyte, where is determines the future dorso-ventral axis of the embryo. In mouse oocytes, nucleus positioning can also regulate gene expression.

Biophysical approaches were also instructive to decipher some the amazing properties of these very large nuclei, where the presence of actin meshes can stabilize nuclear bodies and regulate oocyte ageing, like in Xenopus; or gather chromosomes to prevent aneuploidy, like in Starfish.

This collection aims at presenting a variety of techniques that have allowed for the broadening of knowledge on this fascinating organelle, the oocyte nucleus, in recent years.