Biology subjects

Dammermann, A.

Publications and source records attributed to Dammermann, A..

8 recordsLinked to original sources

bioRxiv2025

Centrosome Softening As A Mechanical Adaptation For Mitosis

Centrosomes are microtubule-organizing centers important for mitotic spindle assembly and chromosome segregation. During mitosis, centrosomes are exposed to mechanical forces via the microtubules they nucleate, yet the material properties underlying their response to these forces remain poorly understood. In this study, we systematically probed the mechanical behavior of C. elegans centrosomes, both in vitro and in vivo. Using microtubule perturbations and quantitative live cell imaging, we found that centrosomes become increasingly deformed during mitosis. Centrosome deformation is independent of cortical pulling forces but instead results from microtubule polymerization within the pericentriolar material. This deformation impacts centrosome size: as microtubule number decreases with cell volume in early cleavage divisions, centrosome size scales proportionately. To directly measure centrosome elasticity, we employed atomic force microscopy (AFM) on isolated centrosomes in vitro and Brillouin light scattering microscopy in developing embryos in vivo. Both approaches revealed that centrosomes progressively soften during mitosis. Theoretical modeling predicts that softening serves to dampen spindle force fluctuations, helping to protect kinetochore-microtubule interactions and safeguarding chromosome segregation. Further, softening may enhance centrosomal microtubule nucleation capacity, facilitating mitotic spindle assembly, particularly in large early embryonic cells. We propose that centrosome softening is a mechanical adaptation for mitosis that couples microtubule number to centrosome size through force-dependent deformation. This optimally balances two mitotic requirements: the need for robust microtubule nucleation and the ability to withstand spindle forces, thereby ensuring accurate cell division.

cell biology↗

bioRxiv2025

In vitro approaches to study centriole and cilium function in early mouse embryogenesis

Although centrioles and primary cilia play an essential role in early mammalian development, their specific function during the interval between their initial formation and the subsequent arrest of embryogenesis in embryos deficient in centrioles or cilia remains largely unexplored. Here, we demonstrate that different 3D in vitro model systems recapitulate early centriole and cilium formation in mouse development. Centrioles and cilia are dispensable in 3D in vitro mouse rosettes, a model system that mimics key events of implantation, including polarization and lumenogenesis. In gastruloids, a model system that recapitulates developmental processes up to 8.5 days after fertilization, centriole loss results in early disassembly. In contrast, cells devoid of cilia continue to form elongated, differentiated and polarized gastruloids, with minor differences at 96 h. Finally, we show that in a mutant affecting the centriolar distal appendages, cilia are absent from 2D cultures but are capable of forming in 3D rosettes and gastruloids, highlighting the importance of multifactorial 3D environment setups in developmental studies. SummaryThis study presents the first in vitro analysis of centriole and cilium formation during early mouse embryonic development, using 3D models to mimic implantation, tissue patterning, and axis elongation, offering a controlled platform for investigating their roles in embryogenesis.

developmental biology↗

bioRxiv2024

Centriolar satellites are sites of translation of centrosomal and ciliary proteins

Centriolar satellites are cytoplasmic particles found in the vicinity of centrosomes and cilia whose functional contribution to the formation of these cellular structures has long been unclear. By characterizing the main scaffolding component of satellites, PCM1 or Combover in Drosophila, we show that satellites are not involved in cellular trafficking as previously thought but rather act as sites for the coordinate translation of centrosomal and ciliary proteins through the interaction with a set of RNA binding proteins and proteins involved in quality control. Strikingly, the concentration of satellites near centrosomes and cilia in vertebrates is not a conserved feature and therefore dispensable for satellite function. Such coordinate synthesis may be a general feature in eukaryotic cells to facilitate protein complex formation and cellular compartmentalization. One-Sentence SummaryCentriolar satellites facilitate the coordinate synthesis of centrosomal and ciliary proteins.

cell biology↗

bioRxiv2022

A Phylogenetic Profiling Approach Identifies Novel Ciliogenesis Genes In Drosophila And C. elegans

Cilia are cellular projections that perform sensory and motile functions in eukaryotic cells. A defining feature of cilia is that they are evolutionarily ancient yet not universally conserved. In this study we have used the resulting presence and absence pattern in the genomes of diverse eukaryotes to identify a set of 386 human genes associated with cilium assembly or motility. Comprehensive tissue-specific RNAi in Drosophila and mutant analysis in C. elegans revealed signature ciliary defects for 70-80% of novel genes, a percentage similar to that for known genes within the cluster. Further characterization identified different phenotypic classes, including a set of genes related to the cartwheel component Bld10/Cep135 and two highly conserved regulators of cilium biogenesis. We believe this dataset to define the core set of genes required for cilium assembly and motility across eukaryotes, an invaluable resource for future studies of cilium biology and associated disorders.

cell biology↗

bioRxiv2021

A Modified TurboID Approach Identifies Tissue-Specific Centriolar Components In C. elegans

Proximity-dependent labeling approaches such as BioID have been a great boon to studies of protein-protein interactions in the context of cytoskeletal structures such as centrosomes which are poorly amenable to traditional biochemical approaches like immunoprecipitation and tandem affinity purification. Yet, these methods have so far not been applied extensively to invertebrate experimental models such as C. elegans given the long labeling times required for the original promiscuous biotin ligase variant BirA*. Here, we show that the recently developed variant TurboID successfully probes the interactomes of both stably associated (SPD-5) and dynamically localized (PLK-1) centrosomal components. We further develop an indirect proximity labeling method employing a GFP nanobody-TurboID fusion, which allows the identification of protein interactors in a tissue-specific manner in the context of the whole animal. Critically, this approach utilizes available endogenous GFP fusions, avoiding the need to generate multiple additional strains for each target protein and the potential complications associated with overexpressing the protein from transgenes. Using this method, we identify homologs of two highly conserved centriolar components, Cep97 and Bld10/Cep135, which are present in various somatic tissues of the worm. Surprisingly, neither protein is expressed in early embryos, likely explaining why these proteins have escaped attention until now. Our work expands the experimental repertoire for C. elegans and opens the door for further studies of tissue-specific variation in centrosome architecture.

cell biology↗

bioRxiv2020

An Acentriolar Centrosome At The C. elegans Ciliary Base

In animal cells the functions of the cytoskeleton are coordinated by centriole-based centrosomes via microtubule-nucleating {gamma}-tubulin complexes embedded in the pericentriolar material or PCM [1]. PCM assembly has been best studied in the context of mitosis, where centriolar SPD-2 recruits PLK-1, which in turn phosphorylates key scaffolding components such as SPD-5 and CNN to promote expansion of the PCM polymer [2-4]. To what extent these mechanisms apply to centrosomes in interphase or in differentiated cells remains unclear [5]. Here, we examine a novel type of centrosome found at the ciliary base of C. elegans sensory neurons, which we show plays important roles in neuronal morphogenesis, cellular trafficking and ciliogenesis. These centrosomes display similar dynamic behavior to canonical, mitotic centrosomes, with a stable PCM scaffold and dynamically localized client proteins. Unusually, however, they are not organized by centrioles, which degenerate early in terminal differentiation [6]. Yet, PCM not only persists but continues to grow with key scaffolding proteins including SPD-5 expressed under control of the RFX transcription factor DAF-19. This assembly occurs in the absence of the mitotic regulators SPD-2, AIR-1 and PLK-1, but requires tethering by PCMD-1, a protein which also plays a role in the initial, interphase recruitment of PCM in early embryos [7]. These results argue for distinct mechanisms for mitotic and non-mitotic PCM assembly, with only the former requiring PLK-1 phosphorylation to drive rapid expansion of the scaffold polymer. ETOC BLURBCentrioles play a critical role in mitotic centrosome assembly. Here, Garbrecht et al. show that pericentriolar material (PCM) persists at the ciliary base of C. elegans sensory neurons after centriole degeneration, where it contributes to neuronal morphogenesis and cellular trafficking. Remarkably, this PCM displays dynamic properties similar to canonical centrosomes, yet its continued assembly and maintenance is independent of known mitotic regulators, suggesting differential mechanisms for mitotic and non-mitotic centrosome assembly. HIGHLIGHTSO_LIPCM persists at the acentriolar ciliary base in C. elegans C_LIO_LIPCM assembles in a SPD-2, AIR-1 and PLK-1-independent manner C_LIO_LIPCMD-1 tethers PCM at the ciliary base in the absence of centrioles C_LIO_LIPCM is required for neuronal morphogenesis and cilium assembly C_LI

cell biology↗

bioRxiv2019

Cep97 Is Required For Centriole Structural Integrity And Cilia Formation In Drosophila

Centrioles are highly elaborate microtubule-based structures responsible for the formation of centrosomes and cilia. Despite considerable variation across species and tissues, within any given tissue their size is essentially constant [1, 2]. While the diameter of the centriole cylinder is set by the dimensions of the inner scaffolding structure of the cartwheel [3], how centriole length is set so precisely and stably maintained over many cell divisions is not well understood. Cep97 and CP110 are conserved proteins that localize to the distal end of centrioles and have been reported to limit centriole elongation in vertebrates [4, 5]. Here, we examine Cep97 function in Drosophila melanogaster. We show that Cep97 is essential for formation of full-length centrioles in multiple tissues of the fly. We further identify the microtubule deacetylase Sirt2 as a Cep97 proximity interactor. Deletion of Sirt2 likewise affects centriole size. Interestingly, so does deletion of the acetylase Atat1, indicating that loss of stabilizing acetyl marks impairs centriole integrity. Cep97 and CP110 were originally identified as inhibitors of cilia formation in vertebrate cultured cells [6] and loss of CP110 is a widely used marker of basal body maturation. In contrast, in Drosophila Cep97 is only transiently removed from basal bodies and loss of Cep97 strongly impairs ciliogenesis. Collectively, our results support a model whereby Cep97 functions as part of a protective cap that acts together with the microtubule acetylation machinery to maintain centriole stability, essential for proper function in cilium biogenesis.

cell biology↗

bioRxiv2017

Accumulation And Functional Architecture Of Deleterious Genetic Variants During The Extinction Of Wrangel Island Mammoths

Woolly mammoths were among the most abundant cold adapted species during the Pleistocene. Their once large populations went extinct in two waves, an end-Pleistocene extinction of continental populations followed by the mid-Holocene extinction of relict populations on St. Paul Island ~5,600 years ago and Wrangel Island ~4,000 years ago. Wrangel Island mammoths experienced an episode of rapid demographic decline coincident with their isolation, leading to a small population, reduced genetic diversity, and the fixation of putatively deleterious alleles, but the functional consequences of these processes are unclear. Here we show that the Wrangel Island mammoth accumulated many putative deleterious mutations that are predicted to cause diverse behavioral and developmental defects. Resurrection and functional characterization of Wrangel Island mammoth genes carrying these substitutions identified both loss and gain of function mutations in genes associated with developmental defects (HYLS1), oligozoospermia and reduced male fertility (NKD1), diabetes (NEUROG3), and the ability to detect floral scents (OR5A1). These results suggest that Wrangel Island mammoths may have suffered adverse consequences from their reduced population sizes and isolation.

genetics↗