scholarly journals Microcephaly models in the developing zebrafish retinal neuroepithelium point to an underlying defect in metaphase progression

Open Biology ◽  
2013 ◽  
Vol 3 (10) ◽  
pp. 130065 ◽  
Author(s):  
Claire Novorol ◽  
Janina Burkhardt ◽  
Kirstin J. Wood ◽  
Anila Iqbal ◽  
Claudio Roque ◽  
...  
Keyword(s):  
Brain Size ◽  
Time Lapse ◽  
Spindle Pole ◽  
Cellular Mechanisms ◽  
Proliferating Cells ◽  
Eye Size ◽  
Ideal System ◽  
Dramatic Rise ◽  
Autosomal Recessive Primary Microcephaly ◽  
Mitotic Defect

Autosomal recessive primary microcephaly (MCPH) is a congenital disorder characterized by significantly reduced brain size and mental retardation. Nine genes are currently known to be associated with the condition, all of which encode centrosomal or spindle pole proteins. MCPH is associated with a reduction in proliferation of neural progenitors during fetal development. The cellular mechanisms underlying the proliferation defect, however, are not fully understood. The zebrafish retinal neuroepithelium provides an ideal system to investigate this question. Mutant or morpholino-mediated knockdown of three known MCPH genes ( stil , aspm and wdr62 ) and a fourth centrosomal gene, odf2 , which is linked to several MCPH proteins, results in a marked reduction in head and eye size. Imaging studies reveal a dramatic rise in the fraction of proliferating cells in mitosis in all cases, and time-lapse microscopy points to a failure of progression through prometaphase. There was also increased apoptosis in all the MCPH models but this appears to be secondary to the mitotic defect as we frequently saw mitotically arrested cells disappear, and knocking down p53 apoptosis did not rescue the mitotic phenotype, either in whole retinas or clones.

scholarly journals Human Microcephaly Protein RTTN Is Required for Proper Mitotic Progression and Correct Spindle Position

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1441
Author(s):  
En-Ju Chou ◽  
Tang K. Tang
Keyword(s):  
Brain Size ◽  
Neurodevelopmental Disorder ◽  
Mitotic Progression ◽  
Centriole Duplication ◽  
Spindle Poles ◽  
Multipolar Spindles ◽  
Mitotic Abnormalities ◽  
Cortical Localization ◽  
Spindle Position ◽  
Autosomal Recessive Primary Microcephaly

Autosomal recessive primary microcephaly (MCPH) is a complex neurodevelopmental disorder characterized by a small brain size with mild to moderate intellectual disability. We previously demonstrated that human microcephaly RTTN played an important role in regulating centriole duplication during interphase, but the role of RTTN in mitosis is not fully understood. Here, we show that RTTN is required for normal mitotic progression and correct spindle position. The depletion of RTTN induces the dispersion of the pericentriolar protein γ-tubulin and multiple mitotic abnormalities, including monopolar, abnormal bipolar, and multipolar spindles. Importantly, the loss of RTTN altered NuMA/p150Glued congression to the spindle poles, perturbed NuMA cortical localization, and reduced the number and the length of astral microtubules. Together, our results provide a new insight into how RTTN functions in mitosis.

scholarly journals Cellular Functions of OCT-3/4 Regulated by Ubiquitination in Proliferating Cells

Cancers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 663
Author(s):  
Kwang-Hyun Baek ◽  
Jihye Choi ◽  
Chang-Zhu Pei
Keyword(s):  
Stem Cells ◽  
Cellular Proliferation ◽  
Critical Role ◽  
Embryonic Stem ◽  
Cell Types ◽  
Ubiquitin Proteasome System ◽  
Specific Cell ◽  
Cellular Mechanisms ◽  
Proliferating Cells ◽  
Proliferation And Differentiation

Octamer-binding transcription factor 3/4 (OCT-3/4), which is involved in the tumorigenesis of somatic cancers, has diverse functions during cancer development. Overexpression of OCT-3/4 has been detected in various human somatic tumors, indicating that OCT-3/4 activation may contribute to the development and progression of cancers. Stem cells can undergo self-renewal, pluripotency, and reprogramming with the help of at least four transcription factors, OCT-3/4, SRY box-containing gene 2 (SOX2), Krüppel-like factor 4 (KLF4), and c-MYC. Of these, OCT-3/4 plays a critical role in maintenance of undifferentiated state of embryonic stem cells (ESCs) and in production of induced pluripotent stem cells (iPSCs). Stem cells can undergo partitioning through mitosis and separate into specific cell types, three embryonic germ layers: the endoderm, the mesoderm, and the trophectoderm. It has been demonstrated that the stability of OCT-3/4 is mediated by the ubiquitin-proteasome system (UPS), which is one of the key cellular mechanisms for cellular homeostasis. The framework of the mechanism is simple, but the proteolytic machinery is complicated. Ubiquitination promotes protein degradation, and ubiquitination of OCT-3/4 leads to regulation of cellular proliferation and differentiation. Therefore, it is expected that OCT-3/4 may play a key role in proliferation and differentiation of proliferating cells.

scholarly journals Cell proliferation controls body size growth, tentacle morphogenesis, and regeneration in hydrozoan jellyfish Cladonema pacificum

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7579 ◽  
Author(s):  
Sosuke Fujita ◽  
Erina Kuranaga ◽  
Yu-ichiro Nakajima
Keyword(s):  
Cell Proliferation ◽  
Body Size ◽  
Environmental Changes ◽  
Size Control ◽  
Cellular Mechanisms ◽  
Proliferating Cells ◽  
Size Growth ◽  
Local Cell ◽  
Proliferating Cell

Jellyfish have existed on the earth for around 600 million years and have evolved in response to environmental changes. Hydrozoan jellyfish, members of phylum Cnidaria, exist in multiple life stages, including planula larvae, vegetatively-propagating polyps, and sexually-reproducing medusae. Although free-swimming medusae display complex morphology and exhibit increase in body size and regenerative ability, their underlying cellular mechanisms are poorly understood. Here, we investigate the roles of cell proliferation in body-size growth, appendage morphogenesis, and regeneration using Cladonema pacificum as a hydrozoan jellyfish model. By examining the distribution of S phase cells and mitotic cells, we revealed spatially distinct proliferating cell populations in medusae, uniform cell proliferation in the umbrella, and clustered cell proliferation in tentacles. Blocking cell proliferation by hydroxyurea caused inhibition of body size growth and defects in tentacle branching, nematocyte differentiation, and regeneration. Local cell proliferation in tentacle bulbs is observed in medusae of two other hydrozoan species, Cytaeis uchidae and Rathkea octopunctata, indicating that it may be a conserved feature among hydrozoan jellyfish. Altogether, our results suggest that hydrozoan medusae possess actively proliferating cells and provide experimental evidence regarding the role of cell proliferation in body-size control, tentacle morphogenesis, and regeneration.

scholarly journals Extracellular vesicles from amyloid-β exposed cell cultures induce severe dysfunction in cortical neurons

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Chiara Beretta ◽  
Elisabeth Nikitidou ◽  
Linn Streubel-Gallasch ◽  
Martin Ingelsson ◽  
Dag Sehlin ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Cortical Neurons ◽  
Amyloid Β ◽  
Neuronal Cell ◽  
Time Lapse ◽  
Cellular Mechanisms ◽  
Axonal Swelling ◽  
Tem Analysis ◽  
Neuronal Cell Bodies ◽  
Time Lapse Imaging

AbstractAlzheimer’s disease (AD) is characterized by a substantial loss of neurons and synapses throughout the brain. The exact mechanism behind the neurodegeneration is still unclear, but recent data suggests that spreading of amyloid-β (Aβ) pathology via extracellular vesicles (EVs) may contribute to disease progression. We have previously shown that an incomplete degradation of Aβ42 protofibrils by astrocytes results in the release of EVs containing neurotoxic Aβ. Here, we describe the cellular mechanisms behind EV-associated neurotoxicity in detail. EVs were isolated from untreated and Aβ42 protofibril exposed neuroglial co-cultures, consisting mainly of astrocytes. The EVs were added to cortical neurons for 2 or 4 days and the neurodegenerative processes were followed with immunocytochemistry, time-lapse imaging and transmission electron microscopy (TEM). Addition of EVs from Aβ42 protofibril exposed co-cultures resulted in synaptic loss, severe mitochondrial impairment and apoptosis. TEM analysis demonstrated that the EVs induced axonal swelling and vacuolization of the neuronal cell bodies. Interestingly, EV exposed neurons also displayed pathological lamellar bodies of cholesterol deposits in lysosomal compartments. Taken together, our data show that the secretion of EVs from Aβ exposed cells induces neuronal dysfunction in several ways, indicating a central role for EVs in the progression of Aβ-induced pathology.

scholarly journals Reorientation of Mispositioned Spindles in Short Astral Microtubule Mutantspc72Δ Is Dependent on Spindle Pole Body Outer Plaque and Kar3 Motor Protein

2002 ◽  
Vol 13 (4) ◽  
pp. 1366-1380 ◽  
Author(s):  
Dominic Hoepfner ◽  
Florian Schaerer ◽  
Arndt Brachat ◽  
Achim Wach ◽  
Peter Philippsen
Keyword(s):  
Spindle Pole Body ◽  
Time Lapse ◽  
Nuclear Migration ◽  
Spindle Pole ◽  
Astral Microtubule ◽  
Spindle Pole Bodies ◽  
Microtubule Motor ◽  
Microtubule Formation ◽  
Mother Cells

Nuclear migration and positioning in Saccharomyces cerevisiae depend on long astral microtubules emanating from the spindle pole bodies (SPBs). Herein, we show by in vivo fluorescence microscopy that cells lacking Spc72, the SPB receptor of the cytoplasmic γ-tubulin complex, can only generate very short (<1 μm) and unstable astral microtubules. Consequently, nuclear migration to the bud neck and orientation of the anaphase spindle along the mother-bud axis are absent in these cells. However,SPC72 deletion is not lethal because elongated but misaligned spindles can frequently reorient in mother cells, permitting delayed but otherwise correct nuclear segregation. High-resolution time-lapse sequences revealed that this spindle reorientation was most likely accomplished by cortex interactions of the very short astral microtubules. In addition, a set of double mutants suggested that reorientation was dependent on the SPB outer plaque and the astral microtubule motor function of Kar3 but not Kip2/Kip3/Dhc1, or the cortex components Kar9/Num1. Our observations suggest that Spc72 is required for astral microtubule formation at the SPB half-bridge and for stabilization of astral microtubules at the SPB outer plaque. In addition, our data exclude involvement of Spc72 in spindle formation and elongation functions.

scholarly journals Kinetochores are transported poleward along a single astral microtubule during chromosome attachment to the spindle in newt lung cells.

1990 ◽  
Vol 110 (1) ◽  
pp. 81-95 ◽  
Author(s):  
C L Rieder ◽  
S P Alexander
Keyword(s):  
Spatial Separation ◽  
Time Lapse ◽  
Spindle Pole ◽  
Variable Number ◽  
Fiber Formation ◽  
Polar Regions ◽  
Microtubule Depolymerization ◽  
Chromosome Attachment ◽  
Kinetochore Region ◽  
Tubulin Immunofluorescence

During mitosis in cultured newt pneumocytes, one or more chromosomes may become positioned well removed (greater than 50 microns) from the polar regions during early prometaphase. As a result, these chromosomes are delayed for up to 5 h in forming an attachment to the spindle. The spatial separation of these chromosomes from the polar microtubule-nucleating centers provides a unique opportunity to study the initial stages of kinetochore fiber formation in living cells. Time-lapse Nomarski-differential interference contrast videomicroscopic observations reveal that late-attaching chromosomes always move, upon attachment, into a single polar region (usually the one closest to the chromosome). During this attachment, the kinetochore region of the chromosome undergoes a variable number of transient poleward tugs that are followed, shortly thereafter, by rapid movement of the chromosome towards the pole. Anti-tubulin immunofluorescence and serial section EM reveal that the kinetochores and kinetochore regions of nonattached chromosomes lack associated microtubules. By contrast, these methods reveal that the attachment and subsequent poleward movement of a chromosome correlates with the association of a single long microtubule with one of the kinetochores of the chromosome. This microtubule traverses the entire distance between the spindle pole and the kinetochore and often extends well past the kinetochore. From these results, we conclude that the initial attachment of a chromosome to the newt pneumocyte spindle results from an interaction between a single polar-nucleated microtubule and one of the kinetochores on the chromosome. Once this association is established, the kinetochore is rapidly transported poleward along the surface of the microtubule by a mechanism that is not dependent on microtubule depolymerization. Our results further demonstrate that the motors for prometaphase chromosome movement must be either on the surface of the kinetochore (i.e., within the corona but not the plate), distributed along the surface of the kinetochore microtubules, or both.

scholarly journals The chromokinesin Kid is necessary for chromosome arm orientation and oscillation, but not congression, on mitotic spindles

2001 ◽  
Vol 154 (6) ◽  
pp. 1135-1146 ◽  
Author(s):  
Aime A. Levesque ◽  
Duane A. Compton
Keyword(s):  
Cultured Cells ◽  
Time Lapse ◽  
Spindle Pole ◽  
Mitotic Spindles ◽  
Differential Interference Contrast Microscopy ◽  
Spindle Poles ◽  
Ejection Force ◽  
Chromosome Congression ◽  
Contrast Microscopy ◽  
Interference Contrast Microscopy

Chromokinesins have been postulated to provide the polar ejection force needed for chromosome congression during mitosis. We have evaluated that possibility by monitoring chromosome movement in vertebrate-cultured cells using time-lapse differential interference contrast microscopy after microinjection with antibodies specific for the chromokinesin Kid. 17.5% of cells injected with Kid-specific antibodies have one or more chromosomes that remain closely opposed to a spindle pole and fail to enter anaphase. In contrast, 82.5% of injected cells align chromosomes in metaphase, progress to anaphase, and display chromosome velocities not significantly different from control cells. However, injected cells lack chromosome oscillations, and chromosome orientation is atypical because chromosome arms extend toward spindle poles during both congression and metaphase. Furthermore, chromosomes cluster into a mass and fail to oscillate when Kid is perturbed in cells containing monopolar spindles. These data indicate that Kid generates the polar ejection force that pushes chromosome arms away from spindle poles in vertebrate-cultured cells. This force increases the efficiency with which chromosomes make bipolar spindle attachments and regulates kinetochore activities necessary for chromosome oscillation, but is not essential for chromosome congression.

Somatic nuclear division in the sporidia of Ustilago violacea. II. Observations on living cells with phase-contrast and fluorescence microscopy

1974 ◽  
Vol 20 (5) ◽  
pp. 739-746 ◽  
Author(s):  
N. H. Poon ◽  
A. W. Day
Keyword(s):  
Fluorescence Microscopy ◽  
Acridine Orange ◽  
Phase Contrast ◽  
Nuclear Division ◽  
Spindle Pole Body ◽  
Time Lapse ◽  
Spindle Pole ◽  
Living Cells ◽  
Pole Body ◽  
Orange Fluorescence

Somatic nuclear division in living cells is described under both phase-contrast and acridine orange fluorescence microscopy. The observations confirm a previous description of the division in fixed cells stained with acetic orcein. Acridine orange at the optimum concentration of 75–250 mg/liter complete medium clearly differentiated the nucleolus, chromatinic granules, nucleoplasm, and spindle pole body, as well as indicating changes in RNA content in the cytoplasm during budding. Acridine orange fluorescence was identical in both living and fixed cells. The fluorescence of the spindle pole body indicated that it contains DNA, which may initiate RNA synthesis. Time-lapse phase-contrast observations confirmed that neither the fixation technique nor acridine orange or acetic orcein staining caused noticeable artefacts during division, and provided indisputable evidence for the sequencing of stages. Estimates from the time-lapse observations indicated that the division is quite slow (about 45 min) and that 'prophase' takes about 12 min, 'metaphase' 5 min, and 'anaphase–telophase' about 28 min.

scholarly journals Cell division in two large pennate diatoms Hantzschia and Nitzschia III. A new proposal for kinetochore function during prometaphase.

1980 ◽  
Vol 86 (2) ◽  
pp. 402-416 ◽  
Author(s):  
D H Tippit ◽  
J D Pickett-Heaps ◽  
R Leslie
Keyword(s):  
Electron Microscopy ◽  
Leading Edge ◽  
Time Lapse ◽  
Cell Types ◽  
Spindle Pole ◽  
Large Species ◽  
Conventional View ◽  
Chromosome Movements ◽  
Kinetochore Function

Prometaphase in two large species of diatoms is examined, using the following techniques: (a) time-lapse cinematography of chromosome movements in vivo; (b) electron microscopy of corresponding stages: (c) reconstruction of the microtubules (MTs) in the kinetochore fiber of chromosomes attached to the spindle. In vivo, the chromosomes independently commence oscillations back and forth to one pole. The kinetochore is usually at the leading edge of such chromosome movements; a variable time later both kinetochores undergo such oscillations but toward opposite poles and soon stretch poleward to establish stable bipolar attachment. Electron microscopy of early prometaphase shows that the kinetochores usually laterally associate with MTs that have one end attached to the spindle pole. At late prometaphase, most chromosomes are fully attached to the spindle, but the kinetochores on unattached chromosomes are bare of MTs. Reconstruction of the kinetochore fiber demonstrates that most of its MTs (96%) extend past the kinetochore and are thus apparently not nucleated there. At least one MT terminates at each kinetochore analyzed. Our interpretation is that the conventional view of kinetochore function cannot apply to diatoms. The kinetochore fiber in diatoms appears to be primarily composed of MTs from the poles, in contrast to the conventional view that many MTs of the kinetochore fiber are nucleated by the kinetochore. Similarly, chromosomes appear to initially orient their kinetochores to opposite poles by moving along MTs attached to the poles, instead of orientation effected by kinetochore MTs laterally associating with other MTs in the spindle. The function of the kinetochore in diatoms and other cell types is discussed.

scholarly journals Coevolving avian eye size and brain size in relation to prey capture and nocturnality

2002 ◽  
Vol 269 (1494) ◽  
pp. 961-967 ◽  
Author(s):  
L. Z. Garamszegi ◽  
A. P. Møller ◽  
J. Erritzøe
Keyword(s):  
Prey Capture ◽  
Brain Size ◽  
Eye Size
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