Inherited nuclear pore substructures template post-mitotic pore assembly

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Live Imaging of Drosophila Larval Neuroblasts

Stem cells divide asymmetrically to generate two progeny cells with unequal fate potential: a self-renewing stem cell and a differentiating cell. Given their relevance to development and disease, understanding the mechanisms that govern asymmetric stem cell division has been a robust area of study. Because they are genetically tractable and undergo successive rounds of cell division about once every hour, the stem cells of the Drosophila central nervous system, or neuroblasts, are indispensable models for the study of stem cell division. About 100 neural stem cells are located near the surface of each of the two larval brain lobes, making this model system particularly useful for live imaging microscopy studies. In this work, we review several approaches widely used to visualize stem cell divisions, and we address the relative advantages and disadvantages of those techniques that employ dissociated versus intact brain tissues. We also detail our simplified protocol used to explant whole brains from third instar larvae for live cell imaging and fixed analysis applications.     

Microtubule-sliding modules based on kinesins EG5 and PRC1-dependent KIF4A drive human spindle elongation

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Comparison of Methods of Cell Cycle Analysis in Paramecium tetraurelia

ABSTRACT. Four methods are commonly used to study cell cycle processes in Paramecium tetraurelia. These include stage frequency analysis in asynchronous cultures, hand selection of synchronous dividing cells, selection of newly divided cells by elutriation centrifugation, and the sister cell method. We have compared the timing and resolution of stages of oral morphogenesis and micronuclear mitosis with each method. The temporal resolution obtainable with the sister cell method was inadequate to position the timing of morphogenesis stages within the cell cycle. Both the asynchronous method and the hand-selected synchronous samples methods are prone to bias. Elutriation centrifuge synchronization provides large samples with resolution comparable to that of hand selected samples. The elutriation method is the least prone to bias when <5% of the parent culture of Paramecium is selected.     

Lovastatin induces mitotic abnormalities in various cell lines.

We examined the effects of lovastatin, a common anti-atherosclerotic drug and a blocker of the cell cycle, on the process of mitosis. It is known that lovastatin induces an arrest or a retardation of the cell cycle in many cell types not only at the G(1)phase, but also at the G(2)/M transition. After 24-48 h incubation of epithelial PtK(2), T24, HeLa cells and fibroblastic L929 cells in the presence of 1. 0-60.0 microm lovastatin, diverse mitotic perturbations have been observed. The most noteworthy phenomena recorded were prometaphase retardation and chromosome lagging during metaphase and anaphase. After the recovery in lovastatin-free media, the cells continued mitosis without any disturbances. Mevalonic acid prevented the effects of lovastatin. We conclude that the effects were specific for lovastatin-induced inhibition of mevalonic acid synthesis. Immunofluorescence studies with anticentromeric antibodies suggested that one of the possible causes of the lovastatin-induced mitotic disorder could be an interference with the development and function of the centromeres.     

KaryoCreate: A CRISPR-based technology to study chromosome-specific aneuploidy by targeting human centromeres

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Genome instability: Does genetic diversity amplification drive tumorigenesis?

Recent data show that catastrophic events during one cell cycle can cause massive genome damage producing viable clones with unstable genomes. This is in contrast with the traditional view that tumorigenesis requires a long‐term process in which mutations gradually accumulate over decades. These sudden events are likely to result in a large increase in genomic diversity within a relatively short time, providing the opportunity for selective advantages to be gained by a subset of cells within a population. This genetic diversity amplification, arising from a single aberrant cell cycle, may drive a population conversion from benign to malignant. However, there is likely a period of relative genome stability during the clonal expansion of tumors – this may provide an opportunity for therapeutic intervention, especially if mechanisms that limit tolerance of aneuploidy are exploited.     

Collodictyon triciliatum and Diphylleia rotans (= Aulacomonas submarina) Form a New Family of Flagellates (Collodictyonidae) with Tubular Mitochondrial Cristae that is Phylogenetically Distant from other Flagellate Groups

Comparative electron microscopic studies of Collodictyon triciliatum and Diphylleia rotans (=Aulacomonas submarina) showed that they share a distinctive flagellar transitional zone and a very similar flagellarapparatus. In both species, the basic couple of basal bodies and flagella #1 and #2 are connected to the dorsal and ventral roots, respectively. Collodictyon triciliatum has two additional basal bodies and flagella, #3 and #4, situated on each side of the basic couple, each of which also bears a dorsal root. The horseshoe-shaped arrangement of dictyosomes, mitochondria with tubular cristae and the deep ventral groove are very similar to those of Diphylleia rotans. These two genera have very specific features and are placed in a new family, Collodictyonidae, distinct from other eukaryotic groups. Electron microscopic observation of mitotic telophase in Diphylleia rotans revealed two chromosomal masses, surrounded by the nuclear envelope, within the dividing parental nucleus, as in the telophase stage of the heliozoan Actinophrys and the helioflagellate Dimorpha. Spindle microtubules arise from several MTOCs outside the nucleus, and several microtubules penetrate within the dividing nucleus, via pores at the poles. This semi-open type of orthomitosis is reminiscent of that of actinophryids. The SSU rDNA sequence of Diphylleia rotans was compared with that of all the eukaryotic groups that have a slow-evolving rDNA. Diphylleia did not strongly assemble with any group and emerged in a very poorly resolved part of the eukaryotic phylogenetic tree.