Ascoli GA, Peng H, Zeng H, Chen J, Tang J, Long F, Zhou J, Tsien RW, Mitra A, Myers E, Gonzalez-Bellido PT, Iannello G, Zhou Z, Hawrylycz M, Xiao H, Bria A, Butler V, Oh SW
[
Nat Commun,
2014]
Three-dimensional (3D) bioimaging, visualization and data analysis are in strong need of powerful 3D exploration techniques. We develop virtual finger (VF) to generate 3D curves, points and regions-of-interest in the 3D space of a volumetric image with a single finger operation, such as a computer mouse stroke, or click or zoom from the 2D-projection plane of an image as visualized with a computer. VF provides efficient methods for acquisition, visualization and analysis of 3D images for roundworm, fruitfly, dragonfly, mouse, rat and human. Specifically, VF enables instant 3D optical zoom-in imaging, 3D free-form optical microsurgery, and 3D visualization and annotation of terabytes of whole-brain image volumes. VF also leads to orders of magnitude better efficiency of automated 3D reconstruction of neurons and similar biostructures over our previous systems. We use VF to generate from images of 1,107 Drosophila GAL4 lines a projectome of a Drosophila brain.
[
Genes Dev,
2002]
Chromosome segregation and X-chromosome gene regulation in Caenorhabditis elegans share the component MIX-1, a mitotic protein that also represses X-linked genes during dosage compensation. MIX-1 achieves its dual roles through interactions with different protein partners. To repress gene expression, MIX-1 acts in an X-chromosome complex that resembles the mitotic condensin complex yet lacks chromosome segregation function. Here we show that MIX-1 interacts with a mitotic condensin subunit, SMC-4, to achieve chromosome segregation. The SMC-4/MIX-1 complex positively supercoils DNA in vitro and is required for mitotic chromosome structure and segregation in vivo. Thus, C. elegans has two condensin complexes, one conserved for mitosis and another specialized for gene regulation. SMC-4 and MIX-1 colocalize with centromere proteins on condensed mitotic chromosomes and are required for the restricted orientation of centromeres toward spindle poles. This cell cycle-dependent localization requires AIR-2/AuroraB kinase. Depletion of SMC-4/MIX-1 causes aberrant mitotic chromosome structure and segregation, but not dramatic decondensation at metaphase. Moreover, SMC-4/MIX-1 depletion disrupts sister chromatid segregation during meiosis II but not homologous chromosome segregation during meiosis 1, although both processes require chromosome condensation. These results imply that condensin is not simply required for compaction, but plays a more complex role in chromosome architecture that is essential for mitotic and meiotic sister chromatid segregation.