scholarly journals Intricate structure of the interphase chromocenter revealed by the analysis of a factor involved in species formation

2018 ◽  
Author(s):  
Natalia Y. Kochanova ◽  
Tamas Schauer ◽  
Grusha Primal Mathias ◽  
Andrea Lukacs ◽  
Andreas Schmidt ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Super Resolution ◽  
Pericentric Heterochromatin ◽  
Gene Encoding ◽  
Centromeric Chromatin ◽  
Species Formation ◽  
Higher Eukaryotes ◽  
And Function ◽  
Super Resolution Microscopy

ABSTRACTIn higher eukaryotes centromeres often coalesce into a large intranuclear domain called the chromocenter. Chromocenters are important for the organization of pericentric heterochromatin and a disturbance of their formation results in an upregulation of repetitive elements and causes defects in chromosome segregation. Mutations in the gene encoding for the centromere associated Drosophila speciation factor HMR show very similar phenotypes suggesting a role of HMR in chromocenter architecture and function. We performed confocal and super resolution microscopy as well as proximity based biotinylation experiments of HMR and its associated protein HP1a to generate a molecular map of HMR and HP1a bound chromatin. Our work reveals an intricate internal structure of the centromeric chromatin region, which suggests a role of HMR in separating heterochromatin from centromeric chromatin.

Super-Resolution Microscopy in Studying the Structure and Function of the Cell Nucleus

Acta Naturae ◽  
2017 ◽  
Vol 9 (4) ◽  
pp. 42-51
Author(s):  
S. S. Ryabichko ◽  
◽  
A. N. Ibragimov ◽  
L. A. Lebedeva ◽  
E. N. Kozlov ◽  
...  
Keyword(s):  
Cell Nucleus ◽  
Super Resolution ◽  
Structure And Function ◽  
And Function ◽  
Super Resolution Microscopy

scholarly journals Phosphorylation of Drosophila CENP-A on serine 20 regulates protein turn-over and centromere-specific loading

2019 ◽  
Vol 47 (20) ◽  
pp. 10754-10770 ◽  
Author(s):  
Anming Huang ◽  
Leopold Kremser ◽  
Fabian Schuler ◽  
Doris Wilflingseder ◽  
Herbert Lindner ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Posttranslational Modifications ◽  
Centromeric Chromatin ◽  
Phosphorylated Form ◽  
Specific Loading ◽  
Histone H3 Variant ◽  
Proteasome Pathway ◽  
Turn Over ◽  
Fine Tune

Abstract Centromeres are specialized chromosomal regions epigenetically defined by the presence of the histone H3 variant CENP-A. CENP-A is required for kinetochore formation which is essential for chromosome segregation during mitosis. Spatial restriction of CENP-A to the centromere is tightly controlled. Its overexpression results in ectopic incorporation and the formation of potentially deleterious neocentromeres in yeast, flies and in various human cancers. While the contribution of posttranslational modifications of CENP-A to these processes has been studied in yeast and mammals to some extent, very little is known about Drosophila melanogaster. Here, we show that CENP-A is phosphorylated at serine 20 (S20) by casein kinase II and that in mitotic cells, the phosphorylated form is enriched on chromatin. Importantly, our results reveal that S20 phosphorylation regulates the turn-over of prenucleosomal CENP-A by the SCFPpa-proteasome pathway and that phosphorylation promotes removal of CENP-A from ectopic but not from centromeric sites in chromatin. We provide multiple lines of evidence for a crucial role of S20 phosphorylation in controlling restricted incorporation of CENP-A into centromeric chromatin in flies. Modulation of the phosphorylation state of S20 may provide the cells with a means to fine-tune CENP-A levels in order to prevent deleterious loading to extra-centromeric sites.

scholarly journals Microscope-AOtools: A generalised adaptive optics implementation

2020 ◽  
Author(s):  
Nicholas Hall ◽  
Josh Titlow ◽  
Martin J. Booth ◽  
Ian M. Dobbie
Keyword(s):  
Image Quality ◽  
Adaptive Optics ◽  
Super Resolution ◽  
Biological Imaging ◽  
New Techniques ◽  
Reduce Image Quality ◽  
Set Up ◽  
And Function ◽  
Microscopy Techniques ◽  
Super Resolution Microscopy

AbstractMicroscope-AOtools is a software package which allows for a simple, robust and generalised implementation of adaptive optics (AO) elements. It contains all the necessary methods for set-up, calibration, and aberration correction which are simple to use and function in a robust manner. Aberrations arising from sources such as sample hetero-geneity and refractive index mismatches are constant problems in biological imaging. These aberrations reduce image quality and the achievable depth of imaging, particularly in super-resolution microscopy techniques. AO technology has been proven to be effective in correcting for these aberrations and thereby improving the image quality. However, it has not been widely adopted by the biological imaging community due, in part, to difficulty in set-up and operation of AO, particularly by non-specialist users. Microscope-AOtools offers a robust, easy-to-use implementation of the essential methods for set-up and use of AO techniques. These methods are constructed in a generalised manner that can utilise a range of adaptive optics elements, wavefront sensing techniques and sensorless AO correction methods. Furthermore, the methods are designed to be easily extensible as new techniques arise, leading to a streamlined pipeline for new AO technology and techniques to be adopted by the wider microscopy community.

scholarly journals Platelet SHARPIN regulates platelet adhesion and inflammatory responses through associations with αIIbβ3 and LUBAC

2022 ◽  
Author(s):  
Ana Kasirer-Friede ◽  
Emilia Peuhu ◽  
Johanna Ivaska ◽  
Sanford J. Shattil
Keyword(s):  
Inflammatory Responses ◽  
Super Resolution ◽  
Cytoplasmic Tail ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Littermate Control ◽  
Protein Substrates ◽  
Pathway Activation ◽  
Super Resolution Microscopy

Platelets form hemostatic plugs to prevent blood loss and they modulate immunity and inflammation in several ways. A key event during hemostasis is activation of integrin αIIbβ3 through direct interactions of the β3 cytoplasmic tail with talin and kindlin-3. Recently, we showed that human platelets express the adapter molecule, SHARPIN, that can associate directly with the αIIb cytoplasmic tail and can separately promote NF-κB pathway activation as a member of the Met-1 linear ubiquitination activation complex (LUBAC). Here we investigated the role of SHARPIN in platelets after crossing Sharpin flox/flox (fl/fl) mice with PF4-Cre or GPIbα-Cre mice to selectively delete SHARPIN in platelets. SHARPIN-null platelets adhered to immobilized fibrinogen through αIIbβ3, and they spread more extensively than littermate control platelets in a manner dependent on feedback stimulation by platelet adenosine diphosphate (ADP) (P < 0.01). SHARPIN-null platelets showed increased colocalization of αIIbβ3 with talin as assessed by super-resolution microscopy and increased binding of soluble fibrinogen in response to sub-maximal concentrations of ADP (P < 0.05). However, mice with SHARPIN-null platelets showed compromised thrombus growth on collagen and slightly prolonged tail bleeding times. Platelets lacking SHARPIN also showed reduced NF-κB activation and linear ubiquitination of protein substrates upon challenge with classical platelet agonists. Furthermore, the loss of platelet SHARPIN resulted in significant reduction in inflammation in murine models of colitis and peritonitis (P < 0.01). Thus, SHARPIN plays differential and context-dependent roles in platelets to regulate important inflammatory and integrin adhesive functions of these anucleate cells.

scholarly journals Detyrosinated microtubules spatially constrain lysosomes facilitating lysosome–autophagosome fusion

2018 ◽  
Vol 218 (2) ◽  
pp. 632-643 ◽  
Author(s):  
Nitin Mohan ◽  
Elena M. Sorokina ◽  
Ione Vilanova Verdeny ◽  
Angel Sandoval Alvarez ◽  
Melike Lakadamyali
Keyword(s):  
Epithelial Cells ◽  
Functional Diversity ◽  
Super Resolution ◽  
Live Cell ◽  
Small Subset ◽  
Post Translational Modifications ◽  
Super Resolution Microscopy ◽  
Small Subpopulation ◽  
Dependent Mechanism

Microtubule post-translational modifications impart functional diversity to microtubules by affecting their dynamics, organization, and interaction with proteins. Using super-resolution microscopy, we show that only a small subpopulation of microtubules are detyrosinated in epithelial cells, while acetylated and tyrosinated microtubules comprise the majority of all microtubules. Surprisingly, lysosomes are enriched by approximately threefold on detyrosinated microtubules. Further, their motility on detyrosinated microtubules is impaired, showing shorter runs and more frequent and longer pauses. Lysosome enrichment is mediated through a kinesin-1–dependent mechanism, since knocking down this motor abolishes enrichment. Finally, correlative live-cell and super-resolution microscopy showed that lysosomes interact with autophagosomes on detyrosinated microtubules. Removal of detyrosinated microtubules or knockdown of kinesin-1 leads to a decrease in the percentage of autolysosomes, a fusion intermediate of autophagosomes and lysosomes. Taken together, our data reveal a new role of detyrosinated microtubules as hubs that spatially concentrate lysosomes on a small subset of microtubules and facilitate their interaction and fusion with autophagosomes to initiate autophagy.

scholarly journals FOXL2: a central transcription factor of the ovary

2013 ◽  
Vol 52 (1) ◽  
pp. R17-R33 ◽  
Author(s):  
Adrien Georges ◽  
Aurelie Auguste ◽  
Laurianne Bessière ◽  
Anne Vanet ◽  
Anne-Laure Todeschini ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Forkhead Transcription Factor ◽  
Gene Encoding ◽  
Post Translational Modifications ◽  
Forkhead Box ◽  
Molecular Aspects ◽  
And Function ◽  
Craniofacial Defects ◽  
The Impact

Forkhead box L2 (FOXL2) is a gene encoding a forkhead transcription factor preferentially expressed in the ovary, the eyelids and the pituitary gland. Its germline mutations are responsible for the blepharophimosis ptosis epicanthus inversus syndrome, which includes eyelid and mild craniofacial defects associated with primary ovarian insufficiency. Recent studies have shown the involvement of FOXL2 in virtually all stages of ovarian development and function, as well as in granulosa cell (GC)-related pathologies. A central role of FOXL2 is the lifetime maintenance of GC identity through the repression of testis-specific genes. Recently, a highly recurrent somatic FOXL2 mutation leading to the p.C134W subtitution has been linked to the development of GC tumours in the adult, which account for up to 5% of ovarian malignancies. In this review, we summarise data on FOXL2 modulators, targets, partners and post-translational modifications. Despite the progresses made thus far, a better understanding of the impact of FOXL2 mutations and of the molecular aspects of its function is required to rationalise its implication in various pathophysiological processes.

scholarly journals MeCP2 Is Required for Normal Development of GABAergic Circuits in the Thalamus

2010 ◽  
Vol 103 (5) ◽  
pp. 2470-2481 ◽  
Author(s):  
Zhong-Wei Zhang ◽  
Joseph D. Zak ◽  
Hong Liu
Keyword(s):  
Neurodevelopmental Disorder ◽  
Brain Slices ◽  
Inhibitory Neurons ◽  
Gene Encoding ◽  
Vertebrate Brain ◽  
Gabaergic Synapses ◽  
And Function ◽  
Kinetics Of ◽  
Whole Cell Recordings

Methyl-CpG binding protein 2 (MeCP2) is highly expressed in neurons in the vertebrate brain, and mutations of the gene encoding MeCP2 cause the neurodevelopmental disorder Rett syndrome. This study examines the role of MeCP2 in the development and function of thalamic GABAergic circuits. Whole cell recordings were carried out in excitatory neurons of the ventrobasal complex (VB) of the thalamus and in inhibitory neurons of the reticular thalamic nucleus (RTN) in acute brain slices from mice aged P6 through P23. At P14–P16, the number of quantal GABAergic events was decreased in VB neurons but increased in RTN neurons of Mecp2-null mice, without any change in the amplitude or kinetics of quantal events. There was no difference between mutant and wild-type mice in paired-pulse ratios of evoked GABAergic responses in the VB or the RTN. On the other hand, unitary responses evoked by minimal stimulation were decreased in the VB but increased in the RTN of mutants. Similar changes in the frequency of quantal events were observed at P21–P23 in both the VB and RTN. At P6, however, quantal GABAergic transmission was altered only in the VB not the RTN. Immunostaining of vesicular GABA transporter showed opposite changes in the number of GABAergic synaptic terminals in the VB and RTN of Mecp2-null mice at P18–P20. The loss of MeCP2 had no significant effect on intrinsic properties of RTN neurons recorded at P15–P17. Our findings suggest that MeCP2 differentially regulates the development of GABAergic synapses in excitatory and inhibitory neurons in the thalamus.

scholarly journals Analysis of kinesin motor function at budding yeast kinetochores

2006 ◽  
Vol 172 (6) ◽  
pp. 861-874 ◽  
Author(s):  
Jessica D. Tytell ◽  
Peter K. Sorger
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Motor Function ◽  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Budding Yeast ◽  
Kinesin Motor ◽  
Complex Processes ◽  
Sister Chromatids ◽  
Higher Eukaryotes ◽  
And Function

Accurate chromosome segregation during mitosis requires biorientation of sister chromatids on the microtubules (MT) of the mitotic spindle. Chromosome–MT binding is mediated by kinetochores, which are multiprotein structures that assemble on centromeric (CEN) DNA. The simple CENs of budding yeast are among the best understood, but the roles of kinesin motor proteins at yeast kinetochores have yet to be determined, despite evidence of their importance in higher eukaryotes. We show that all four nuclear kinesins in Saccharomyces cerevisiae localize to kinetochores and function in three distinct processes. Kip1p and Cin8p, which are kinesin-5/BimC family members, cluster kinetochores into their characteristic bilobed metaphase configuration. Kip3p, a kinesin-8,-13/KinI kinesin, synchronizes poleward kinetochore movement during anaphase A. The kinesin-14 motor Kar3p appears to function at the subset of kinetochores that become detached from spindle MTs. These data demonstrate roles for structurally diverse motors in the complex processes of chromosome segregation and reveal important similarities and intriguing differences between higher and lower eukaryotes.

scholarly journals The condensin complex is required for proper spindle assembly and chromosome segregation in Xenopus egg extracts

2003 ◽  
Vol 161 (6) ◽  
pp. 1041-1051 ◽  
Author(s):  
Sarah M. Wignall ◽  
Renée Deehan ◽  
Thomas J. Maresca ◽  
Rebecca Heald
Keyword(s):  
Chromosome Segregation ◽  
Spindle Assembly ◽  
Condensin Complex ◽  
Egg Extracts ◽  
Chromosomal Architecture ◽  
Xenopus Egg ◽  
Sperm Nuclei ◽  
And Function ◽  
Xenopus Egg Extracts

Chromosome condensation is required for the physical resolution and segregation of sister chromatids during cell division, but the precise role of higher order chromatin structure in mitotic chromosome functions is unclear. Here, we address the role of the major condensation machinery, the condensin complex, in spindle assembly and function in Xenopus laevis egg extracts. Immunodepletion of condensin inhibited microtubule growth and organization around chromosomes, reducing the percentage of sperm nuclei capable of forming spindles, and causing dramatic defects in anaphase chromosome segregation. Although the motor CENP-E was recruited to kinetochores pulled poleward during anaphase, the disorganized chromosome mass was not resolved. Inhibition of condensin function during anaphase also inhibited chromosome segregation, indicating its continuous requirement. Spindle assembly around DNA-coated beads in the absence of kinetochores was also impaired upon condensin inhibition. These results support an important role for condensin in establishing chromosomal architecture necessary for proper spindle assembly and chromosome segregation.

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