title: Quantitative microscopy uncovers ploidy changes during mitosis in liveDrosophilaembryos and their effect on nuclear size.
abstract: Time-lapse microscopy is a powerful tool to investigate cellular and developmental dynamics. InDrosophila melanogaster, it can be used to study division cycles in embryogenesis. To obtain quantitative information from 3D time-lapse data and track proliferating nuclei from the syncytial stage until gastrulation, we developed an image analysis pipeline consisting of nuclear segmentation, tracking, annotation and quantification. Image analysis ofmaternal-haploid(mh) embryos revealed that a fraction of haploid syncytial nuclei fused to give rise to nuclei of higher ploidy (2n, 3n, 4n). Moreover, nuclear densities inmhembryos at the mid-blastula transition varied over threefold. By tracking synchronized nuclei of different karyotypes side-by-side, we show that DNA content determines nuclear growth rate and size in early interphase, while the nuclear to cytoplasmic ratio constrains nuclear growth during late interphase.mhencodes theDrosophilaortholog of human Spartan, a protein involved in DNA damage tolerance. To explore the link betweenmhand chromosome instability, we fluorescently tagged Mh protein to study its subcellular localization. We show Mh-mKO2 localizes to nuclear speckles that increase in numbers as nuclei expand in interphase. In summary, quantitative microscopy can provide new insights into well-studied genes and biological processes.
authors.affiliation: Imaging Informatics Division, Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), Singapore 138671, Republic of Singapore.
authors.forename: Wee Choo
authors.initials: WC
authors.lastname: Puah
authors.affiliation: Imaging Informatics Division, Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), Singapore 138671, Republic of Singapore.
authors.forename: Rambabu
authors.initials: R
authors.lastname: Chinta
authors.affiliation: Imaging Informatics Division, Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), Singapore 138671, Republic of Singapore mwasser07@gmail.com.
authors.forename: Martin
authors.identifier: http://orcid.org/0000-0002-8753-2346
authors.initials: M
authors.lastname: Wasser
keywords: Drosophila; Live imaging; Maternal haploid; Mitosis; Quantitative microscopy; Spartan