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Elife 2023 Apr 25;12. doi: 10.7554/eLife.84360.
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Mitotic chromosomes scale to nuclear-cytoplasmic ratio and cell size in Xenopus.

Zhou CY , Dekker B , Liu Z , Cabrera H , Ryan J , Dekker J , Heald R .

During the rapid and reductive cleavage divisions of early embryogenesis, subcellular structures such as the nucleus and mitotic spindle scale to decreasing cell size. Mitotic chromosomes also decrease in size during development, presumably to scale coordinately with mitotic spindles, but the underlying mechanisms are unclear. Here we combine in vivo and in vitro approaches using eggs and embryos from the frog Xenopus laevis to show that mitotic chromosome scaling is mechanistically distinct from other forms of subcellular scaling. We found that mitotic chromosomes scale continuously with cell, spindle, and nuclear size in vivo. However, unlike for spindles and nuclei, mitotic chromosome size cannot be reset by cytoplasmic factors from earlier developmental stages. In vitro, increasing nuclear-cytoplasmic (N/C) ratio is sufficient to recapitulate mitotic chromosome scaling, but not nuclear or spindle scaling, through differential loading of maternal factors during interphase. An additional pathway involving importin α scales mitotic chromosomes to cell surface area/volume ratio (SA/V) during metaphase. Finally, single-chromosome immunofluorescence and Hi-C data suggest that mitotic chromosomes shrink during embryogenesis through decreased recruitment of condensin I, resulting in major rearrangements of DNA loop architecture to accommodate the same amount of DNA on a shorter chromosome axis. Together, our findings demonstrate how mitotic chromosome size is set by spatially and temporally distinct developmental cues in the early embryo.

PubMed ID: 37096661
PMC ID: PMC10260010
Article link: Elife
Grant support: [+]

Species referenced: Xenopus laevis
GO keywords: metaphase [+]
Antibodies: H1-8 Ab1 H3 Ab45 Tubb Ab1

GEO Series: GSE217111: NCBI

Article Images: [+] show captions
References [+] :
Abdennur, Cooler: scalable storage for Hi-C data and other genomically labeled arrays. 2020, Pubmed