ORCID Profile
0000-0003-3664-154X
Current Organisation
Max Planck Institute for Cell Biology and Genetics
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Biochemistry and Cell Biology | Biochemistry and Cell Biology not elsewhere classified | Structural Biology (incl. Macromolecular Modelling) | Synthetic Biology
ANZSRC Socio-Economic Objective (SEO)
Related Links
Publications
Adaptation to environmental temperature in divergent clades of the nematode Pristionchus pacificus.
Publisher: Wiley
Date: 30-06-2022
DOI: 10.1111/EVO.14520
Abstract: Because of ongoing climate change, populations of organisms are being subjected to stressful temperatures more often. This is especially problematic for ectothermic organisms, which are likely to be more sensitive to changes in temperature. Therefore, we need to know if ectotherms have adapted to environmental temperature and, if so, what are the evolutionary mechanisms behind such adaptation. Here, we use the nematode Pristionchus pacificus as a case study to investigate thermal adaptation on the Indian Ocean island of La Réunion, which experiences a range of temperatures from coast to summit. We study the evolution of high-temperature tolerance by constructing a phylogenetic tree of strains collected from many different thermal niches. We show that populations of P. pacificus at low altitudes have higher fertility at warmer temperatures. Most likely, this phenotype has arisen recently and at least twice independently, consistent with parallel evolution. We also studied low-temperature tolerance and showed that populations from high altitudes have increased their fertility at cooler temperatures. Together, these data indicate that P. pacificus strains on La Réunion are subject to ergent selection, adapting to hot and cold niches at the coast and summit of the volcano. Precisely defining these thermal niches provides essential information for models that predict the impact of future climate change on these populations.
A High-Resolution C. elegans Essential Gene Network Based on Phenotypic Profiling of a Complex Tissue
Publisher: Elsevier BV
Date: 04-2011
Variation of the enhanced biologically damaging solar UV due to clouds
Publisher: Springer Science and Business Media LLC
Date: 20-05-2004
DOI: 10.1039/B402035A
Abstract: The variation of the biologically damaging solar UV (UVBE) enhanced by clouds above that of clear sky UVBE has been investigated. This was undertaken for summer through to winter for SZA of 5 to 60 degrees employing an integrated automatic cloud and spectral UV measurement system that recorded the solar UV spectra and the sky images at five minute intervals. The UVBE calculated with action spectra with higher relative effectiveness in the UVA produced the lower percentage of cloud enhanced cases. The DNA UVBE provided the highest percentage of cloud enhanced cases compared to the total number of UV scans with 2.2% cloud enhanced cases. As a comparison, the plant and fish melanoma UVBE provided the lowest percentage of cloud enhanced cases with 0.6 to 0.8% cloud enhanced cases. For the cases of cloud enhanced UVBE, the average ratio of the measured UVBE to calculated cloud free UVBE for the photokeratitis, cataracts, plant, generalized plant damage and fish melanoma action spectra was 1.21 to 1.25. In comparison, the highest value of 1.4 was for the DNA action spectrum.
The Distribution of Active Force Generators Controls Mitotic Spindle Position
Publisher: American Association for the Advancement of Science (AAAS)
Date: 25-07-2003
Abstract: During unequal cell isions a mitotic spindle is eccentrically positioned before cell cleavage. To determine the basis of the net force imbalance that causes spindle displacement in one-cell Caenorhabditis elegans embryos, we fragmented centrosomes with an ultraviolet laser. Analysis of the mean and variance of fragment speeds suggests that the force imbalance is due to a larger number of force generators pulling on astral microtubules of the posterior aster relative to the anterior aster. Moreover, activation of heterotrimeric guanine nucleotide– binding protein (Gprotein) α subunits is required to generate these astral forces.
PREPARATION OF MARKED MICROTUBULES FBR THE ASSAY OF THE POLARITY OF MICROTUBULE-BASED MOTORS BY FLUORESCENCE MICROSCOPY
Publisher: Elsevier
Date: 1993
Straight GDP-Tubulin Protofilaments Form in the Presence of Taxol
Publisher: Elsevier BV
Date: 10-2007
DOI: 10.1016/J.CUB.2007.08.063
Abstract: Microtubules exist in dynamic equilibrium, growing and shrinking by the addition or loss of tubulin dimers from the ends of protofilaments. The hydrolysis of GTP in beta-tubulin destabilizes the microtubule lattice by increasing the curvature of protofilaments in the microtubule and putting strain on the lattice. The observation that protofilament curvature depends on GTP hydrolysis suggests that microtubule destabilizers and stabilizers work by modulating the curvature of the microtubule lattice itself. Indeed, the microtubule destabilizer MCAK has been shown to increase the curvature of protofilaments during depolymerization. Here, we show that the atomic force microscopy (AFM) of in idual tubulin protofilaments provides sufficient resolution to allow the imaging of single protofilaments in their native environment. By using this assay, we confirm previous results for the effects of GTP hydrolysis and MCAK on the conformation of protofilaments. We go on to show that taxol stabilizes microtubules by straightening the GDP protofilament and slowing down the transition of protofilaments from straight to a curved configuration.
Growth, fluctuation and switching at microtubule plus ends
Publisher: Springer Science and Business Media LLC
Date: 10-06-2009
DOI: 10.1038/NRM2713
Abstract: Recent experiments suggest that microtubules do not grow steadily but instead elongate at a rate that varies in time. We argue that this variation might arise from fluctuations in the length of a dynamic GTP-tubulin cap at the microtubule end. We propose that these fluctuations can lead to a switch in the dynamics of a microtubule end between growth and shrinkage, and provide insight into how the sensitivity of this switch can be changed by microtubule polymerases, such as XMAP215, and tensile forces, through the stabilization of initial contacts in the cap.
Synergy between XMAP215 and EB1 increases microtubule growth rates to physiological levels
Publisher: Springer Science and Business Media LLC
Date: 12-05-2013
DOI: 10.1038/NCB2744
Abstract: In cells, a complex network of proteins regulates the dynamic growth of microtubules that is essential for ision and migration. In vitro approaches with purified components have so far been unable to reconstitute fast microtubule growth observed in vivo . Here we show that two well-studied plus-end-binding proteins-end-tracking protein EB1 and microtubule polymerase XMAP215-act together to strongly promote microtubule growth to cellular rates. Unexpectedly, the combined effects of XMAP215 and EB1 are highly synergistic, with acceleration of growth well beyond the product of the in idual effects of either protein. The synergistic growth promotion does not rely on any of the canonical EB1 interactions, suggesting an allosteric interaction through the microtubule end. This hypothesis is supported by the finding that taxol and XMAP215, which have non-overlapping binding sites on tubulin, also act synergistically on growth. The increase in growth rates is accompanied by a strong enhancement of microtubule catastrophe by EB1, thereby rendering the fast and dynamic microtubule behaviour typically observed in cells.
Spindle Oscillations during Asymmetric Cell Division Require a Threshold Number of Active Cortical Force Generators
Publisher: Elsevier BV
Date: 11-2006
DOI: 10.1016/J.CUB.2006.09.030
Abstract: Asymmetric ision of the C. elegans zygote is due to the posterior-directed movement of the mitotic spindle during metaphase and anaphase. During this movement along the anterior-posterior axis, the spindle oscillates transversely. These motions are thought to be driven by a force-generating complex-possibly containing the motor protein cytoplasmic dynein-that is located at the cell cortex and pulls on microtubules growing out from the spindle poles. A theoretical analysis indicates that the oscillations might arise from mechanical coordination of the force-generating motors, and this coordination is mediated by the load dependence of the motors' detachment from the microtubules. The model predicts that the motor activity must exceed a threshold for oscillations to occur. We have tested the existence of a threshold by using RNA interference to gradually reduce the levels of dynein light intermediate chain as well as GPR-1 and GPR-2 that are involved in the G protein-mediated regulation of the force generators. We found an abrupt cessation of oscillations as expected if the motor activity dropped below a threshold. Furthermore, we can account for the complex choreography of the mitotic spindle-the precise temporal coordination of the buildup and die-down of the transverse oscillations with the posterior displacement-by a gradual increase in the processivity of a single type of motor machinery during metaphase and anaphase. The agreement between our results and modeling suggests that the force generators themselves have the intrinsic capability of generating oscillations when opposing forces exceed a threshold.
One-step purification of assembly-competent tubulin from diverse eukaryotic sources
Publisher: American Society for Cell Biology (ASCB)
Date: 15-11-2012
Abstract: We have developed a protocol that allows rapid and efficient purification of native, active tubulin from a variety of species and tissue sources by affinity chromatography. The affinity matrix comprises a bacterially expressed, recombinant protein, the TOG1/2 domains from Saccharomyces cerevisiae Stu2, covalently coupled to a Sepharose support. The resin has a high capacity to specifically bind tubulin from clarified crude cell extracts, and, after washing, highly purified tubulin can be eluted under mild conditions. The eluted tubulin is fully functional and can be efficiently assembled into microtubules. The method eliminates the need to use heterologous systems for the study of microtubule-associated proteins and motor proteins, which has been a major issue in microtubule-related research.
XMAP215 polymerase activity is built by combining multiple tubulin-binding TOG domains and a basic lattice-binding region.
Publisher: Proceedings of the National Academy of Sciences
Date: 31-01-2011
Abstract: XMAP215/Dis1 family proteins positively regulate microtubule growth. Repeats at their N termini, called TOG domains, are important for this function. While TOG domains directly bind tubulin dimers, it is unclear how this interaction translates to polymerase activity. Understanding the functional roles of TOG domains is further complicated by the fact that the number of these domains present in the proteins of different species varies. Here, we take advantage of a recent crystal structure of the third TOG domain from Caenorhabditis elegans , Zyg9, and mutate key residues in each TOG domain of XMAP215 that are predicted to be important for interaction with the tubulin heterodimer. We determined the contributions of the in idual TOG domains to microtubule growth. We show that the TOG domains are absolutely required to bind free tubulin and that the domains differentially contribute to XMAP215’s overall affinity for free tubulin. The mutants’ overall affinity for free tubulin correlates well with polymerase activity. Furthermore, we demonstrate that an additional basic region is important for targeting to the microtubule lattice and is critical for XMAP215 to function at physiological concentrations. Using this information, we have engineered a “bonsai” protein, with two TOG domains and a basic region, that has almost full polymerase activity.
Microtubule polymerases and depolymerases
Publisher: Elsevier BV
Date: 02-2007
DOI: 10.1016/J.CEB.2006.12.009
Abstract: The variety of shapes and sizes of the microtubule cytoskeleton is as great as the number of different cell types. This large variety is a consequence of the dynamic properties of microtubules, which allow them to adopt distributions of arbitrary size and form. How is the distribution of microtubule lengths controlled? Recent work suggests that the length distribution is controlled, at least in part, by the activity of microtubule polymerases and depolymerases, which accelerate microtubule growth and shrinkage. Specifically, biochemical and single-molecule studies have shown how MCAK (kinesin-13) and Kip3p (kinesin-8) accelerate depolymerization and how XMAP215 may accelerate growth. Studies on the yeast Dam1 complex have shown how proteins can couple a cellular structure, the kinetochore, to the ends of polymerizing and depolymerizing microtubules.
Parallel adaptation to higher temperatures in divergent clades of the nematodePristionchus pacificus
Publisher: Cold Spring Harbor Laboratory
Date: 29-12-2016
DOI: 10.1101/096727
Abstract: Studying the effect of temperature on fertility is particularly important in the light of ongoing climate change. We need to know if organisms can adapt to higher temperatures and, if so, what are the evolutionary mechanisms behind such adaptation. Such studies have been h ered by the lack different populations of sufficient sizes with which to relate the phenotype of temperature tolerance to the underlying genotypes. Here, we examined temperature adaptation in populations of the nematode Pristionchus pacificus , in which in idual strains are able to successfully reproduce at 30°C. Analysis of the frequency of heat tolerant strains in different temperature zones on La Réunion supports that this trait is subject to natural selection. Reconstruction of ancestral states along the phylogeny of highly differentiated P. pacificus clades suggests that heat tolerance evolved multiple times independently. This is further supported by genome wide association studies showing that heat tolerance is a polygenic trait and that different loci are used by in idual P. pacificus clades to develop heat tolerance. More precisely, analysis of allele frequencies indicated that most genetic markers that are associated with heat tolerance are only polymorphic in in idual clades. While in some P. pacificus clades, parallel evolution of heat tolerance can be explained by ancestral polymorphism or by gene flow across clades, we observe at least one clearly distinct and independent scenario where heat tolerance emerged by de novo mutation. Thus, temperature tolerance evolved at least two times independently in the evolutionary history of this species. Our data suggest that studies of wild populations of P. pacificus will reveal distinct cellular mechanisms driving temperature adaptation.
Dynamics and mechanics of the microtubule plus end
Publisher: Springer Science and Business Media LLC
Date: 04-2003
DOI: 10.1038/NATURE01600
Membrane Invaginations Reveal Cortical Sites that Pull on Mitotic Spindles in One-Cell C. elegans Embryos
Publisher: Public Library of Science (PLoS)
Date: 20-08-2010
Different low-complexity regions of SFPQ play distinct roles in the formation of biomolecular condensates
Publisher: Cold Spring Harbor Laboratory
Date: 30-11-2022
DOI: 10.1101/2022.11.30.518278
Abstract: Demixing of proteins and nucleic acids into condensed liquid phases is rapidly emerging as a ubiquitous mechanism governing the organisation of molecules within the cell. Long disordered low complexity regions (LCRs) are a common feature of proteins that form biomolecular condensates. RNA-binding proteins with prion-like composition have been highlighted as drivers of liquid demixing to form condensates such as nucleoli, paraspeckles and stress granules. Splicing factor proline- and glutamine-rich (SFPQ) is an RNA- and DNA-binding protein essential for DNA repair and paraspeckle formation. Here, we show that the shorter C-terminal LCR of SFPQ is the main region responsible for the condensation of SFPQ in vitro and in the cell. In contrast, we find that, unexpectedly, the longer N-terminal prion-like LCR of SFPQ attenuates condensation, suggesting a more regulatory role in preventing aberrant condensate formation in the cell. Our data add nuance to the emerging understanding of biomolecular condensate formation, by providing the first ex le of a common multifunctional nucleic acid-binding protein with an extensive prion-like region that serves to regulate rather than drive condensate formation.
Yeast kinesin-8 depolymerizes microtubules in a length-dependent manner
Publisher: Springer Science and Business Media LLC
Date: 13-08-2006
DOI: 10.1038/NCB1462
Abstract: The microtubule cytoskeleton and the mitotic spindle are highly dynamic structures, yet their sizes are remarkably constant, thus indicating that the growth and shrinkage of their constituent microtubules are finely balanced. This balance is achieved, in part, through kinesin-8 proteins (such as Kip3p in budding yeast and KLP67A in Drosophila) that destabilize microtubules. Here, we directly demonstrate that Kip3p destabilizes microtubules by depolymerizing them--accounting for the effects of kinesin-8 perturbations on microtubule and spindle length observed in fungi and metazoan cells. Furthermore, using single-molecule microscopy assays, we show that Kip3p has several properties that distinguish it from other depolymerizing kinesins, such as the kinesin-13 MCAK. First, Kip3p disassembles microtubules exclusively at the plus end and second, remarkably, Kip3p depolymerizes longer microtubules faster than shorter ones. These properties are consequences of Kip3p being a highly processive, plus-end-directed motor, both in vitro and in vivo. Length-dependent depolymerization provides a new mechanism for controlling the lengths of subcellular structures.
XMAP215 Is a Processive Microtubule Polymerase
Publisher: Elsevier BV
Date: 2008
EB1 recognizes the nucleotide state of tubulin in the microtubule lattice.
Publisher: Public Library of Science (PLoS)
Date: 23-10-2009
Site-Specific Cryo-focused Ion Beam Sample Preparation Guided by 3D Correlative Microscopy
Publisher: Elsevier BV
Date: 02-2016
XMAP215 activity sets spindle length by controlling the total mass of spindle microtubules
Publisher: Springer Science and Business Media LLC
Date: 25-08-2013
DOI: 10.1038/NCB2834
Abstract: Metaphase spindles are microtubule-based structures that use a multitude of proteins to modulate their morphology and function. Today, we understand many details of microtubule assembly, the role of microtubule-associated proteins, and the action of molecular motors. Ultimately, the challenge remains to understand how the collective behaviour of these nanometre-scale processes gives rise to a properly sized spindle on the micrometre scale. By systematically engineering the enzymatic activity of XMAP215, a processive microtubule polymerase, we show that Xenopus laevis spindle length increases linearly with microtubule growth velocity, whereas other parameters of spindle organization, such as microtubule density, lifetime and spindle shape, remain constant. We further show that mass balance can be used to link the global property of spindle size to in idual microtubule dynamic parameters. We propose that spindle length is set by a balance of non-uniform nucleation and global microtubule disassembly in a liquid-crystal-like arrangement of microtubules.
Related Organisations
Related Funding Activities
Discovery Projects - Grant ID: DP220103667
Start Date: 03-2022
End Date: 03-2025
Amount: $650,573.00
Funder: Australian Research Council
View Funded Activity