Cynthia Bailey

eLife assessment This is a valuable paper that identifies a potential challenge for embryos during fertilization: holding sperm contents in the fertilized embryos away from the oocyte meiotic spindle so that they don't get ejected into the polar body during meiotic chromosome segregation. The authors identify proteins involved in cytoplasmic streaming and maintaining the grouping of paternal organelles as being critical for this process.

Abstract Microtubule-based spindle formation is essential to faithful chromosome segregation during cell division. In many animal species, the oocyte meiotic spindle forms without centrosomes, unlike most mitotic cells. Even in mitotic cells, centrosomes are sometimes dispensable for bipolar spindle formation. In some systems, Ran-GEF on chromatin initiates spindle assembly. We found that in C.