Loss and Rebirth of the Animal Microtubule Organizing Center: How Maternal Expression of Centrosomal Proteins Cooperates with the Sperm Centriole in Zygotic Centrosome Reformation

BioEssays ◽  
2018 ◽  
Vol 40 (4) ◽  
pp. 1700135 ◽  
Author(s):  
Daigo Inoue ◽  
Joachim Wittbrodt ◽  
Oliver J. Gruss
Keyword(s):  
Microtubule Organizing Center ◽  
Maternal Expression ◽  
Organizing Center ◽  
Centrosomal Proteins

scholarly journals Myogenin controls via AKAP6 non-centrosomal microtubule organizing center formation at the nuclear envelope

2020 ◽  
Author(s):  
Robert Becker ◽  
Silvia Vergarajauregui ◽  
Florian Billing ◽  
Maria Sharkova ◽  
Eleonora Lippolis ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Nuclear Envelope ◽  
Muscle Cells ◽  
Cell Types ◽  
Microtubule Organizing Center ◽  
Anchor Protein ◽  
Organizing Center ◽  
Multiple Cell ◽  
Promoter Studies ◽  
Centrosomal Proteins

AbstractNon-centrosomal microtubule organizing centers (ncMTOC) are pivotal for the function of multiple cell types, but the processes initiating their formation are unknown. Here, we find that the transcription factor myogenin is required in myoblasts for recruiting centrosomal proteins. Moreover, myogenin is sufficient in fibroblasts for ncMTOC formation and centrosome attenuation. Bioinformatics combined with loss- and gain-of-function experiments identified induction of AKAP6 expression as one central mechanism for myogenin-mediated ncMTOC formation. Promoter studies indicate that myogenin preferentially induces the transcription of muscle- and ncMTOC-specific isoforms of Akap6 and Syne1, which encodes nesprin-1α, the ncMTOC anchor protein in muscle cells. Overexpression of AKAP6β and nesprin-1α was sufficient to recruit endogenous centrosomal proteins to the nuclear envelope of myoblasts in the absence of myogenin. Taken together, our results illuminate how mammals transcriptionally control the switch from a centrosomal MTOC to an ncMTOC and identify AKAP6 as a novel ncMTOC component in muscle cells.

scholarly journals AKAP6 orchestrates the nuclear envelope microtubule-organizing center by linking golgi and nucleus via AKAP9

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Silvia Vergarajauregui ◽  
Robert Becker ◽  
Ulrike Steffen ◽  
Maria Sharkova ◽  
Tilman Esser ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Nuclear Envelope ◽  
Ectopic Expression ◽  
Cardiomyocyte Hypertrophy ◽  
Microtubule Organizing Center ◽  
Rat Cardiomyocytes ◽  
Organizing Center ◽  
Centrosomal Proteins ◽  
Human Osteoclasts ◽  
Spectrin Repeats

The switch from centrosomal microtubule-organizing centers (MTOCs) to non-centrosomal MTOCs during differentiation is poorly understood. Here, we identify AKAP6 as key component of the nuclear envelope MTOC. In rat cardiomyocytes, AKAP6 anchors centrosomal proteins to the nuclear envelope through its spectrin repeats, acting as an adaptor between nesprin-1α and Pcnt or AKAP9. In addition, AKAP6 and AKAP9 form a protein platform tethering the Golgi to the nucleus. Both Golgi and nuclear envelope exhibit MTOC activity utilizing either AKAP9, or Pcnt-AKAP9, respectively. AKAP6 is also required for formation and activity of the nuclear envelope MTOC in human osteoclasts. Moreover, ectopic expression of AKAP6 in epithelial cells is sufficient to recruit endogenous centrosomal proteins. Finally, AKAP6 is required for cardiomyocyte hypertrophy and osteoclast bone resorption activity. Collectively, we decipher the MTOC at the nuclear envelope as a bi-layered structure generating two pools of microtubules with AKAP6 as a key organizer.

Three-Dimensional reconstruction of isolated centrosomes by automated electron tomography

1994 ◽  
Vol 52 ◽  
pp. 310-311
Author(s):  
M.B. Braunfeld ◽  
M. Moritz ◽  
B.M. Alberts ◽  
J.W. Sedat ◽  
D.A. Agard
Keyword(s):  
Electron Tomography ◽  
Three Dimensional ◽  
Vital Role ◽  
Complex Nature ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Nucleation Sites ◽  
Dimensional Reconstruction ◽  
Organizing Center ◽  
Resolution Model

In animal cells, the centrosome functions as the primary microtubule organizing center (MTOC). As such the centrosome plays a vital role in determining a cell's shape, migration, and perhaps most importantly, its division. Despite the obvious importance of this organelle little is known about centrosomal regulation, duplication, or how it nucleates microtubules. Furthermore, no high resolution model for centrosomal structure exists.We have used automated electron tomography, and reconstruction techniques in an attempt to better understand the complex nature of the centrosome. Additionally we hope to identify nucleation sites for microtubule growth.Centrosomes were isolated from early Drosophila embryos. Briefly, after large organelles and debris from homogenized embryos were pelleted, the resulting supernatant was separated on a sucrose velocity gradient. Fractions were collected and assayed for centrosome-mediated microtubule -nucleating activity by incubating with fluorescently-labeled tubulin subunits. The resulting microtubule asters were then spun onto coverslips and viewed by fluorescence microscopy.

Genetic interactions between CDC31 and KAR1, two genes required for duplication of the microtubule organizing center in Saccharomyces cerevisiae.

Genetics ◽  
1994 ◽  
Vol 137 (2) ◽  
pp. 407-422 ◽  
Author(s):  
E A Vallen ◽  
W Ho ◽  
M Winey ◽  
M D Rose
Keyword(s):  
Copy Number ◽  
Gene Dosage ◽  
Spindle Pole Body ◽  
Direct Interaction ◽  
Spindle Pole ◽  
High Copy Number ◽  
Temperature Sensitive ◽  
Microtubule Organizing Center ◽  
Recessive Mutations ◽  
Organizing Center

Abstract KAR1 encodes an essential component of the yeast spindle pole body (SPB) that is required for karyogamy and SPB duplication. A temperature-sensitive mutation, kar1-delta 17, mapped to a region required for SPB duplication and for localization to the SPB. To identify interacting SPB proteins, we isolated 13 dominant mutations and 3 high copy number plasmids that suppressed the temperature sensitivity of kar1-delta 17. Eleven extragenic suppressor mutations mapped to two linkage groups, DSK1 and DSK2. The extragenic suppressors were specific for SPB duplication and did not suppress karyogamy-defective alleles. The major class, DSK1, consisted of mutations in CDC31. CDC31 is required for SPB duplication and encodes a calmodulin-like protein that is most closely related to caltractin/centrin, a protein associated with the Chlamydomonas basal body. The high copy number suppressor plasmids contained the wild-type CDC31 gene. One CDC31 suppressor allele conferred a temperature-sensitive defect in SPB duplication, which was counter-suppressed by recessive mutations in KAR1. In spite of the evidence for a direct interaction, the strongest CDC31 alleles, as well as both DSK2 alleles, suppressed a complete deletion of KAR1. However, the CDC31 alleles also made the cell supersensitive to KAR1 gene dosage, arguing against a simple bypass mechanism of suppression. We propose a model in which Kar1p helps localize Cdc31p to the SPB and that Cdc31p then initiates SPB duplication via interaction with a downstream effector.

scholarly journals Evidence for rapid structural and functional changes of the melanophore microtubule-organizing center upon pigment movements

1979 ◽  
Vol 83 (3) ◽  
pp. 623-632 ◽  
Author(s):  
M Schliwa ◽  
U Euteneuer ◽  
W Herzog ◽  
K Weber
Keyword(s):  
Complete Removal ◽  
Cell System ◽  
The State ◽  
Microtubule Assembly ◽  
Microtubule Organizing Center ◽  
Functional Changes ◽  
Organizing Center ◽  
Pigment Distribution ◽  
And Function ◽  
In Cells

Melanophores of the angelfish, pterophyllum scalare, have previously been shown to display approximately 2,400 microtubules in cells wih pigment dispersed; these microtubules radiate from a presumptive organizing center, the central apparatus (CA), and their number is reduced to approximately 1,000 in the state with aggregated pigment (M. Schliwa and U. Euteneuer, 1978, J. Supramol. Struct. 8:177-190). In an attempt to elucidate the factors controlling this rapid reorganization of the microtubule apparatus, structure and function of the CA have been investigated under different physiological conditions. As a function of the state of pigment distribution, melanophores differ markedly with respect to CA organization. A complex of dense amorphous aggregates and associated fuzzy material, several micrometers in diameter, surrounds the centrioles in cells with pigment dispersed, and numerous microtubules emanate from this complex in a radial fashion. In the aggregated state, on the other hand, few microtubules are observed in the pericentiolar region, and the amount of fibrous material is greatly reduced. These changes in CA morphology as a function of the state of pigment distribution are associated with a marked difference in its capacity to initiatiate the assembly of microtubules from exogenous pure porcine brain tubulin in lysed cell preparations. After complete removal of preexisting microtubules, cells lysed in the dispersed state into a solution of 1-2 mg/ml pure tubulin have numerous microtubules associated with the CA in radial fashion, while cells lysed in the aggregated state nucleate the assembly of only a few microtubules. We conclude that it is the activity of the CA that basically regulates the expression of microtubules. This regulation is achieved through a variation in the capacity to initiate microtubule assembly. Increase or decrease in the amount of dense material, as readily observed in the cell system studied here, seems to be a morphologic expression of such a physiologic function.

scholarly journals Murine Cytomegalovirus Capsid Assembly Is Dependent on US22 Family Gene M140 in Infected Macrophages

2009 ◽  
Vol 83 (15) ◽  
pp. 7449-7456 ◽  
Author(s):  
Laura K. Hanson ◽  
Jacquelyn S. Slater ◽  
Victoria J. Cavanaugh ◽  
William W. Newcomb ◽  
Lisa L. Bolin ◽  
...  
Keyword(s):  
Dna Cleavage ◽  
Early Gene ◽  
Murine Cytomegalovirus ◽  
Genome Replication ◽  
Microtubule Organizing Center ◽  
Viral Dna ◽  
Dnase Treatment ◽  
Organizing Center ◽  
Significant Impairment ◽  
The Stability

ABSTRACT Macrophages are an important target cell for infection with cytomegalovirus (CMV). A number of viral genes that either are expressed specifically in this cell type or function to optimize CMV replication in this host cell have now been identified. Among these is the murine CMV (MCMV) US22 gene family member M140, a nonessential early gene whose deletion (RVΔ140) leads to significant impairment in virus replication in differentiated macrophages. We have now determined that the defect in replication is at the stage of viral DNA encapsidation. Although the rate of RVΔ140 genome replication and extent of DNA cleavage were comparable to those for revertant virus, deletion of M140 resulted in a significant reduction in the number of viral capsids in the nucleus, and the viral DNA remained sensitive to DNase treatment. These data are indicative of incomplete virion assembly. Steady-state levels of both the major capsid protein (M86) and tegument protein M25 were reduced in the absence of the M140 protein (pM140). This effect may be related to the localization of pM140 to an aggresome-like, microtubule organizing center-associated structure that is known to target misfolded and overexpressed proteins for degradation. It appears, therefore, that pM140 indirectly influences MCMV capsid formation in differentiated macrophages by regulating the stability of viral structural proteins.

Peroxynitrite Deteriorates Oocyte Quality through Disassembly of Microtubule Organizing Center

2015 ◽  
Vol 87 ◽  
pp. S114
Author(s):  
Sana Khan ◽  
Faten Shaeib ◽  
Mili Thakur ◽  
Roohi Jeelani ◽  
Husam M Abu-Soud
Keyword(s):  
Oocyte Quality ◽  
Microtubule Organizing Center ◽  
Organizing Center

scholarly journals Protease-Dependent Uncoating of a Complex Retrovirus

2005 ◽  
Vol 79 (14) ◽  
pp. 9244-9253 ◽  
Author(s):  
Jacqueline Lehmann-Che ◽  
Marie-Lou Giron ◽  
Olivier Delelis ◽  
Martin Löchelt ◽  
Patricia Bittoun ◽  
...  
Keyword(s):  
Nuclear Import ◽  
Viral Genome ◽  
Productive Infection ◽  
Wild Type Virus ◽  
Target Cells ◽  
Wild Type ◽  
Microtubule Organizing Center ◽  
Viral Protease ◽  
Virus Life Cycle ◽  
Organizing Center

ABSTRACT Although retrovirus egress and budding have been partly unraveled, little is known about early stages of the replication cycle. In particular, retroviral uncoating, a process during which incoming retroviral cores are altered to allow the integration of the viral genome into host chromosomes, is poorly understood. To get insights into these early events of the retroviral cycle, we have used foamy complex retroviruses as a model. In this report, we show that a protease-defective foamy retrovirus is noninfectious, although it is still able to bud and enter target cells efficiently. Similarly, a retrovirus mutated in an essential viral protease-dependent cleavage site in the central part of Gag is noninfectious. Following entry, wild-type and mutant retroviruses are able to traffic along microtubules towards the microtubule-organizing center (MTOC). However, whereas nuclear import of Gag and of the viral genome was observed for the wild-type virus as early as 8 hours postinfection, incoming capsids and genome from mutant viruses remained at the MTOC. Interestingly, a specific viral protease-dependent Gag cleavage product was detected only for the wild-type retrovirus early after infection, demonstrating that cleavage of Gag by the viral protease at this stage of the virus life cycle is absolutely required for productive infection, an unprecedented observation among retroviruses.

Sign in / Sign up

Export Citation Format

Share Document