Biology subjects

Renda, F.

Publications and source records attributed to Renda, F..

8 recordsLinked to original sources

bioRxiv2026

Hierarchy of spindle forces in prometaphase

Dramatic movements characterize rapid assembly of mitotic spindle in prometaphase: chromosomes congress to the spindle equator, while spindle poles segregate rapidly elongating the spindle. Direct biophysical measurements of forces driving these movements are lacking, but the forces could be learned from the rapid pole and chromosome movements. We analyzed 3D trajectories of chromosomes and spindle poles in the wild-type and PRC1-depleted cells during early prometaphase and reconstructed the spindle forces. This analysis posits that (i) chromosomes do not interact with each other, except for a short-range steric repulsion, (ii) effective pole-chromosome forces are repulsive at short and attractive at long distances, (iii) dominant forces of spindle poles segregation are interpolar in origin. The important implication of these results is that the pole-pole segregation is robust, largely insensitive to regional variations inside the cell and to complex process of chromosome congression.

biophysics↗

bioRxiv2025

De novo Golgi biogenesis requires coordinated transactivation of a Golgi regulon

The Golgi apparatus expands during differentiation and high secretory demand, yet the transcriptional control of its biogenesis remains poorly defined. Here, we developed a targeted enzymatic ablation method to eliminate the Golgi and trigger de novo organelle formation. Single-cell RNA-seq of cells rebuilding Golgi revealed an orchestrated induction of a broad Golgi gene network coinciding with structural and functional organelle maturation. This gene set spans all Golgi sub-compartments and functions, including glycosylation, trafficking, and ion transport, thus supporting the concept of a unified Golgi regulon, enabling the simultaneous expression of components required for the organelle structural and functional integrity. Through promoter analysis and RNAi screening, we identified CREB3L1 as a key transcriptional regulator critical for Golgi gene activation and organelle reformation. These findings indicate that CREB3L1-dependent transcriptional mechanisms orchestrate a complete Golgi biogenesis program that may be essential for organelle regeneration and for secretory pathway plasticity during physiological remodeling.

cell biology↗

bioRxiv2025

The kinetochore corona orchestrates chromosome congression through transient microtubule interactions

For proper segregation of chromosomes and successful cytokinesis, chromosomes must first congress - gather in a tight plate near the spindle equator. Molecular mechanism(s) of congression are not fully understood. Here we combine live cell microscopy, perturbations of microtubule motor activities, correlative light/electron microscopy, and computational modeling, to quantitatively characterize the early-prometaphase movements that bring the scattered chromosomes to the equator in human RPE1 cells. We find that the early-prometaphase movements are predominantly directed toward the spindle center and not the spindle poles. Centromere velocity of the centripetal movements is not constant with centromeres moving faster at larger distances from the spindle center. We also detect that numerous short microtubules appear at kinetochores at the earliest stages of spindle assembly and prior to chromosome congression. Computational modeling reveals that a mechanism based on brief, stochastic, minus-end directed interactions between the short microtubules protruding from the kinetochores and long appropriately curved microtubules within the spindle accurately predicts the observed distance-velocity function. Further, the model predicts that insufficient numbers of microtubules protruding from the kinetochores decreases the velocity and randomizes directionality of congression movements. These predictions match changes in the chromosome behavior observed in cells with suppressed nucleation of microtubules at the kinetochore corona (RPE1 Rod{Delta}/{Delta}). In contrast, predictions of computational models based on continuous pulling forces at kinetochores differ significantly from the experimental observations. Together, live-cell observations and modeling reveal a novel mechanism that enables the efficient and synchronized arrival of chromosomes to the spindle equator. Significance StatementFor equal segregation into daughter cells, chromosomes, scattered in a large volume at the onset of cell division, must congress into a narrow plate near the equator of the mitotic spindle. Molecular mechanisms of congression remain obscure. Here we use live-cell microscopy and structural analyses to quantitatively characterize chromosome behavior during congression in human cells. From these quantifications we derive a computational model that accurately predicts directionality and velocity of chromosome movements and suggests that the force for these movements arises from stochastic, transient, minus-end directed interactions between short microtubules protruding from the kinetochores and long appropriately shaped microtubules within the spindle. The model also accurately predicts changes in chromosome behavior in cells with functionally deficient kinetochores.

cell biology↗

bioRxiv2024

The environmental impact of pharmaceuticals: an evidence-mapping review of recent data on aquatic concentrations and predictable effects

Pharmaceuticals are recognised among emerging contaminants, particularly in water. They have the potential to alter ecosystem dynamics, with notable examples including hormone-induced feminization of male fish and disruptions to oogenesis in invertebrates. To assess the risk posed by pharmaceuticals, it is essential to understand their amount (via Measured Environmental Concentrations - MEC) and their actual effects on target species (via Predicted No Effect Concentrations - PNEC). Recently, many studies have aimed to collect MEC data from around the world, but a comprehensive overview is still lacking. Thus, the objective of this study is to provide a comprehensive overview by examining recently published literature on MEC data for a wide range of pharmaceuticals. Additionally, to enable risk assessment, this study also reviewed the published literature on PNEC data and integrated it with existing databases. A total of 315 substances were selected for MEC data extraction, with the inclusion of 56 articles. The most frequently monitored locations were Cadiz Bay in Spain (90 samples), the River Thames in the UK (51), and Hrd[e]jovice in the Czech Republic (49). Most MEC samples were collected from surface water (N=325), influent wastewater treatment plants (WWTP) (205), and effluent WWTP (118). Based on PNEC values, risk analysis identified 81 pharmaceuticals as high-risk, with the highest risk values for propranolol (risk quotient [RQ]: 29,450,000), diclofenac (395,920), and 17alpha-ethinylestradiol (95,946). Additionally, the ATC classes with the most high-risk substances were anti-infectives (J), nervous system agents (N), cardiovascular agents (C), antineoplastic agents (L), analgesics (M), and sex hormones (G). The findings of this study highlight the widespread impact of pharmaceuticals across the globe and the involvement of multiple therapeutic classes. To move beyond the current point-in-time overview, which is limited to specific locations and sampling periods, systems for continuous monitoring of pharmaceuticals should be developed. This could involve the creation of resource-efficient methods and the integration of sampling data with estimation models. Furthermore, these results could serve as a starting point for developing and implementing actions to prevent and mitigate the environmental impact of pharmaceuticals.

ecology↗

bioRxiv2021

Genetic control of kinetochore-driven microtubule growth in Drosophila mitosis

Centrosome-containing cells assemble their spindles exploiting three main classes of microtubules (MTs): MTs nucleated by the centrosomes, MTs generated near the chromosomes/kinetochores, and MTs nucleated within the spindle by the augmin-dependent pathway. Mammalian and Drosophila cells lacking the centrosomes generate MTs at kinetochores and eventually form functional bipolar spindles. However, the mechanisms underlying kinetochore-driven MT formation are poorly understood. One of the ways to elucidate these mechanisms is the analysis of spindle reassembly following MT depolymerization. Here, we used an RNA interference (RNAi)-based reverse genetics approach to dissect the process of kinetochore-driven MT regrowth (KDMTR) after colcemid-induced MT depolymerization. This MT depolymerization procedure allows a clear assessment of KDMTR, as colcemid disrupts centrosome-driven MT regrowth but allows KDMTR. We examined KDMTR in normal Drosophila S2 cells and in S2 cells subjected to RNAi against conserved genes involved in mitotic spindle assembly: mast/orbit/chb (CLASP1), mei-38 (TPX2), mars (HURP), dgt6 (HAUS6), Eb1 (MAPRE1/EB1), Patronin (CAMSAP2), asp (ASPM) and Klp10A (KIF2A). RNAi-mediated depletion of Mast/Orbit, Mei-38, Mars, Dgt6 and Eb1 caused a significant delay in KDMTR, while loss of Patronin had a milder negative effect on this process. In contrast, Asp or Klp10A deficiency increased the rate of KDMTR. These results coupled with the analysis of GFP-tagged proteins (Mast/Orbit, Mei-38, Mars, Eb1, Patronin and Asp) localization during KDMTR suggested a model for kinetochore-dependent spindle reassembly. We propose that kinetochores capture the plus ends of MTs nucleated in their vicinity and that these MTs elongate at kinetochores through the action of Mast/Orbit. The Asp protein binds the MT minus ends since the beginning of KDMTR, preventing excessive and disorganized MT regrowth. Mei-38, Mars, Dgt6, Eb1 and Patronin positively regulate polymerization, bundling and stabilization of regrowing MTs until a bipolar spindle is reformed. Author summaryThe mitotic spindle is a microtubule (MT)-based molecular machine that mediates precise chromosome segregation during cell division. Both Drosophila and human cells assemble their spindles exploiting two main classes of MTs: MTs nucleated by the centrosomes (MT nucleating organelles) and MTs generated at or near the kinetochores (the chromosome-associated structures that bind the spindle MTs). Cells of both species can assemble a functional mitotic spindle in the complete absence of centrosomes, but the mechanisms underlying this process are still poorly understood. We used Drosophila S2 cells as model system to analyze spindle reassembly following colcemid-induced MT depolymerization. MT regrowth (MTR) after colcemid treatment was particularly informative as this drug disrupts the MT nucleating ability of the centrosomes but allows kinetochore-driven MTR (KDMTR). We analyzed KDMTR in normal cells and in cells subjected to RNA interference (RNAi)-mediated depletion of 8 different evolutionarily conserved proteins involved in spindle assembly, and identified proteins that either promote or delay KDMTR. These results coupled with the analysis of proteins localization during spindle reassembly allowed us to integrate the current model on the role of kinetochore-driven MT growth in spindle formation.

genetics↗

bioRxiv2020

Tension promotes kinetochore-microtubule release in response to Aurora B activity

Aurora B kinase regulates kinetochore-microtubule interactions to ensure accurate chromosome segregation in cell division. Tension provides a signal to discriminate attachment errors from bi-oriented kinetochores with sisters correctly attached to opposite spindle poles. Current models focus on tension as an input to locally regulate Aurora B activity. Here we show that the outcome of Aurora B activity depends on tension. Using an optogenetic approach to manipulate Aurora B at individual kinetochores, we find that kinase activity promotes microtubule release when tension is high. Conversely, when tension is low, Aurora B activity promotes depolymerization of kinetochore-microtubule bundles while maintaining attachment. We propose that tension is a signal inducing distinct error-correction mechanisms, with release or depolymerization advantageous for typical errors characterized by high or low tension, respectively.

cell biology↗

bioRxiv2019

kSHREC ‘Delta’ reflects the shape of kinetochore rather than intrakinetochore tension

Distance between fluorescent spots formed by various kinetochore proteins ( Delta) is proposed to reflect the level of intrakinetochore tension (IKT). However, larger-scale changes in the kinetochore architecture may also affect Delta. To test this possibility, we measure Delta in long kinetochores of Indian muntjac (IM) whose shape, size, and orientation are discernable in conventional light microscopy. We find that architecture of IM kinetochores and the value of Delta change minimally when microtubule-mediated forces are suppressed by Taxol. In contrast, large decreases of Delta observed in Taxol-treated human cells coincide with prominent changes in length and shape of the kinetochore. We also find that inner and outer kinetochore proteins intermix within a common spatial compartment instead of forming separate thin layers. These observations, supported by computational modelling, suggest that changes in Delta reflect changes in the kinetochore shape rather than the level of IKT.

cell biology↗

bioRxiv2017

Ultrastructural analysis of intracellular membrane and microtubule behavior during mitosis of Drosophila S2 cells

S2 cells are one of the most widely used Drosophila melanogaster cell lines for molecular dissection of mitosis using RNA interference (RNAi). However, a detailed and complete description of S2 cell mitosis at the ultrastructural level is still missing. Here, we analyzed by transmission electron microscopy (TEM) a random sample of 144 cells undergoing mitosis, focusing on intracellular membrane and microtubule (MT) behavior. This unbiased approach allowed us to discover that S2 cells exhibit a characteristic behavior of intracellular membranes, involving the formation of a quadruple nuclear membrane in early prometaphase and its disassembly during late prometaphase. After nuclear envelope disassembly, the mitotic apparatus becomes encased by a discontinuous network of ER membranes that associate with mitochondria preventing their diffusion into the spindle area. We also observed a peculiar metaphase spindle organization. We found that kinetochores with attached k-fibers are almost invariably associated with lateral MT bundles that can be either interpolar bundles or k-fibers connected to a different kinetochore. This spindle organization is likely to favor chromosome alignment at metaphase and subsequent segregation during anaphase. In summary, we describe several previously unknown features of membrane and microtubule organization during S2 cell mitosis. The genetic determinants of these mitotic features of can now be investigated using an RNAi-based approach, which is particularly easy and efficient in S2 cells

cell biology↗