Biology subjects

Zanin, E.

Publications and source records attributed to Zanin, E..

9 recordsLinked to original sources

bioRxiv2026

Homeostatic regulation of intrinsic neuronal excitability in visual thalamic relay cells induced by brief monocular deprivation

Homeostatic plasticity of intrinsic excitability (IE) in the visual system has been essentially shown at the cortical level but whether thalamic nuclei also express homeostatic plasticity of IE is unknown. We show here that 4 days of monocular deprivation (MD) at eye opening induces a homeostatic change in IE in dorsal lateral geniculate nucleus (dLGN) neurons. Neurons recorded in the dLGN region activated by the deprived eye are more excitable than neurons recorded in the dLGN region activated by the open eye. No significant changes were observed following 7 days of MD, however. Enhanced excitability in neurons from the deprived side after 4 days of MD was associated with a reduced Kv1-dependent LTP-IE, a smaller voltage ramp, and a reduced inter-spike interval, suggesting that Kv1 channels are down-regulated in deprived dLGN neurons. Furthermore, the ankyrin G signal of the axon initial segment was larger in deprived dLGN neurons compared with open ones, indicating that Nav1 channel number also undergoes homeostatic regulation, and Kv1.1 channel signals were lower in deprived neurons compared to open ones. In addition, electrical coupling was found to be strengthened in neurons displaying enhanced IE following either brief (4 days) or long (10 days) MD. These results suggest that homeostatic and Hebbian plasticity in the dLGN share common expression mechanisms involving the regulation of Kv1 channels, Nav1 channels and electrical coupling between relay neurons.

neuroscience↗

bioRxiv2026

SAS-1 and SSNA-1 form dynamic centriolar satellites in C. elegans

Centriolar satellites are dynamic pericentrosomal assemblies that regulate centrosomal protein homeostasis and ciliogenesis. While extensively characterized in vertebrates, their existence and assembly principles in other systems are less well understood. Here, we identify SAS-1 and its interaction partner SSNA-1 as core components of centriolar satellite-like structures in C. elegans. We show that SAS-1 satellites occupy a previously unrecognized centrosomal layer positioned between the pericentriolar material and a specialized endoplasmic reticulum. SAS-1 satellites exhibit many features of biomolecular condensates, such as dose-dependent formation, rapid dynamics, and sensitivity to disruption of weak hydrophobic interactions, while their organization depends on the microtubule cytoskeleton. Mechanistically we identify the unstructured and so far, uncharacterized N-terminal region of SAS-1 being functionally important for embryonic viability, satellite formation and binding to microtubules. Our findings demonstrate that C. elegans possesses bona fide centriolar satellites that share many features with vertebrate satellites, highlighting their evolutionary conservation and importance across species. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=156 SRC="FIGDIR/small/708307v2_ufig1.gif" ALT="Figure 1"> View larger version (64K): org.highwire.dtl.DTLVardef@4ca11org.highwire.dtl.DTLVardef@6e4a1borg.highwire.dtl.DTLVardef@c34132org.highwire.dtl.DTLVardef@ed4029_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2024

PCMD-1 stabilizes the PCM scaffold and facilitates centriole separation

Centrosomes are highly dynamic organelles, and maintaining their stability is crucial for spindle pole integrity and bipolar spindle formation. Centrosomes consist of a pair of centrioles surrounded by the pericentriolar material (PCM). In Caenorhabditis elegans, interactions between the PCM scaffold protein SPD-5 and the regulatory kinase PLK-1 are essential for PCM formation and disassembly. However, how PCM stability is established and maintained remains an open question. Here, we address this question by analyzing the function of PCMD-1, a protein that predominantly localizes to centrioles. Mutations in the predicted PLK-1 binding sites of PCMD-1 result in a reduction of centrosomal PLK-1 and PCMD-1 levels, leading to severe distortion of the PCM scaffold. The disorganization of the PCM is already evident during its formation and results in the assembly of a structurally unstable mitotic centrosome, which is unable to resist the microtubule pulling forces exerted on the spindle pole. As a consequence of a weakened PCM scaffold, the pulling forces are not effectively relayed to the entrapped centriole pair, resulting in delayed centriole separation in late anaphase. Together, these findings show that PCMD-1, which predominantly localizes to centrioles and tethers the PCM scaffold to them, is essential for stabilizing the entire PCM scaffold and ensuring timely centriole separation during PCM disassembly. We propose a model in which PCMD-1 initiates the ordered assembly of the PCM scaffold by biasing the PCM core to a certain intrinsic order around the centrioles. This intrinsic order acts as a seed that propagates throughout the surrounding micron-scale PCM scaffold, providing the necessary strength and structural integrity for the centrosome.

cell biology↗

bioRxiv2023

Dynein directs prophase centrosome migration to control the stem cell division axis in the developing C. elegans epidermis

The microtubule motor dynein is critical for the assembly and positioning of mitotic spindles. In C. elegans, these dynein functions have been extensively studied in the early embryo but remain poorly explored in other developmental contexts. Here we use a hypomorphic dynein mutant to investigate the motors contribution to asymmetric stem cell-like divisions in the larval epidermis. Live imaging of seam cell divisions that precede formation of the seam syncytium shows that mutant cells properly assemble but frequently mis-orient their spindle. Mis-oriented divisions misplace daughter cells from the seam cell row, generate anucleate compartments due to aberrant cytokinesis, and disrupt asymmetric cell fate inheritance. Consequently, the seam becomes disorganized and populated with extra cells that have lost seam identity, leading to fatal epidermal rupture. We show that dynein orients the spindle through the cortical GOA-1Gi-LIN-5NuMA pathway, which directs the migration of prophase centrosomes along the anterior-posterior axis. Spindle mis-orientation in the dynein mutant can be rescued by stretching cells, implying that dynein-dependent cortical cues and elongated cell shape jointly ensure correct asymmetric division of epithelial stem cells.

cell biology↗

bioRxiv2023

Spatially distinct inputs modulate the amount of active Mitotic-phase GAP to locally restrict RhoA signaling for successful cell division

At the end of mitosis a contractile ring consisting of filamentous actin (F-actin) assembles at the cell equator and ring constriction equally partitions the cellular content. Inhibitory and stimulatory signaling cascades spatially limit RhoA activity to a narrow central zone to promote F-actin polymerization only at the cell equator. While the stimulatory signal is well-characterized, the mechanisms by which inhibitory signals restrict active RhoA to a narrow equatorial zone and prevent improper RhoA activity at the cell poles are not known. Here, we identify two regulatory inputs that control the activation and cortical targeting of the Mitotic-phase GTPase activating protein (MP-GAP) for RhoA which limits RhoA activity both at the cell poles and at the cell equator. We show that at cell poles, MP-GAP is a direct phosphorylation target of spindle-pole associated Aurora A kinase. We identify three Aurora A target residues in a region of MP-GAP that binds directly to its catalytic GAP domain suggesting the Aurora A phosphorylation releases MP-GAP autoinhibition. We show that phosphorylation of these sites is required to keep RhoA activity low at the cell poles. At the cell equator, F-actin facilitates MP-GAP enrichment, which opposes RhoA GEF activity and thereby accelerates RhoA flux through the GTPase cycle for the formation of a narrow equatorial zone of active RhoA. Thus, the amount of active MP-GAP is modulated by two distinct regulatory inputs that function in spatially restricted locations: Aurora A phosphorylation relieves MP-GAP autoinhibition to limit RhoA activity at the cell poles, while F-actin polymerization promotes MP-GAP targeting to prevent distribution of active RhoA in a broad zone at the cell equator. By determining the mechanism of spatially confining RhoA activity at the equator and the cell poles during cytokinesis, our work has broad implications to how Rho activity zones are formed and maintained during cytokinesis and how defects in their formation impact animal development and disease.

cell biology↗

bioRxiv2023

Visual activity enhances neuronal excitability in thalamic relay neurons

The dorsal lateral geniculate nucleus (dLGN) has long been held to act as a basic relay for visual information travelling from the retina to cortical areas, but recent findings suggest a largely underestimated functional plasticity of dLGN neurons. However, the cellular mechanisms supporting this functional plasticity have not been yet explored. In particular, it remains to elucidate whether intrinsic neuronal excitability change upon visual stimuli. We show here that monocular deprivation for 10 days reduces the intrinsic excitability of dorsal LGN relay cells. Furthermore, dLGN neurons exhibit long-term potentiation of their intrinsic excitability (LTP-IE) when suprathreshold afferent retinal inputs are stimulated at 40 Hz or when spikes are induced with direct somatic current injection to reproduce patterns of retinal activity. LTP-IE is observed after eye opening and requires calcium influx mediated by L-type calcium channels. It involves activation of PKA and is expressed through the down-regulation of Kv1 potassium channels. In conclusion, our study provides the first evidence for intrinsic plasticity in dLGN relay cells, thus further pointing the role of thalamic neurons in activity-dependent visual plasticity and amblyopia.

neuroscience↗

bioRxiv2022

Anillin forms linear structures and facilitates furrow ingression after septin and formin depletion

During cytokinesis a contractile ring consisting of unbranched filamentous actin (F-actin) and myosin II filaments assembles and constricts at the cell equator. Unbranched F-actin is de novo generated by formin and without formin cleavage furrow ingression fails. In C. elegans depletion of septin restores cleavage furrow ingression in formin (CYK-1) mutants. How the cleavage furrow ingresses without a detectable unbranched F-actin ring is not known. We report, that in this setting anillin (ANI-1) is essential for furrow ingression and forms a meshwork of linear structures, which circumferentially align around the cell equator. Although equatorial ANI-1 recruitment is facilitated by septins, the formation of linear ANI-1 structures is septin independent. Analysis of ANI-1 deletion mutants reveals that its disordered linker region is required for linear structure formation and furrow ingression. We also found that myosin II (NMY-2) decorates linear ANI-1 structures and promotes their circumferential alignment. NMY-2 also interacts with various lipids and forms membrane localized clusters in absence of F-actin and anillin binding. This suggests that NMY-2 represents an independent link between the F-actin / ANI-1 network and the plasma membrane. Collectively, our data reveals a compensatory mechanism, mediated by ANI-1 linear structures and membrane-bound NMY-2, that promotes furrow formation and ingression when formins are depleted and therefore unbranched F-actin polymerization is compromised.

cell biology↗

bioRxiv2020

PCMD-1 bridges the centrioles and the PCM scaffold in C. elegans

Correct cell division relies on the formation of a bipolar spindle. In animal cells, microtubule nucleation at the spindle poles is facilitated by the pericentriolar material (PCM), which assembles around a pair of centrioles. Although centrioles are essential for PCM assembly, proteins that anchor the PCM to the centrioles are less known. Here we investigate the molecular function of PCMD-1 in bridging the PCM and the centrioles in Caenorhabditis elegans. We demonstrate that centrosomal recruitment of PCMD-1 is dependent on the outer centriolar protein SAS-7. While the most C-terminal part of PCMD-1 is sufficient to target it to the centrosome, the coiled-coil domain promotes its accumulation by facilitating self-interaction. We reveal that PCMD-1 is bridging the centrioles and PCM scaffold through protein-protein interactions with the PCM scaffold protein SPD-5, the mitotic kinase PLK-1 and the centriolar protein SAS-4. Using an ectopic translocation assay, we show that PCMD-1 is able to selectively recruit downstream PCM scaffold components to an ectopic location in the cell, indicating that PCMD-1 is sufficient to anchor the PCM scaffold proteins to the centrioles. Our work suggests that PCMD-1 is an essential functional bridge between the centrioles and the PCM.

cell biology↗

bioRxiv2017

TPXL-1 Activates Aurora A to Clear Contractile Ring Components from the Polar Cortex During Cytokinesis

During cytokinesis, a signal from the bundled microtubules that form between the separating anaphase chromosomes promotes the accumulation of contractile ring components at the cell equator, while a signal from the centrosomal microtubule asters inhibits accumulation of contractile ring components at the cell poles. However, the molecular identity of the inhibitory signal has remained unknown. To identify molecular components of the aster-based inhibitory signal, we developed a means to monitor the removal of contractile ring proteins from the polar cortex after anaphase onset. Using this assay, we show that polar clearing is an active process that requires activation of Aurora A kinase by TPXL-1. TPXL-1 concentrates on astral microtubules coincident with polar clearing in anaphase, and its ability to recruit Aurora A and activate its kinase activity are essential for clearing. In summary, our data identify Aurora A kinase as an aster-based inhibitory signal that restricts contractile ring components to the cell equator during cytokinesis.\n\nSUMMARYDuring cytokinesis, centrosomal asters inhibit cortical contractility at the cell poles. Mangal et al. provide molecular insight into this phenomenon, showing that TPXL-1, which localizes to astral microtubules, activates Aurora A kinase to clear contractile ring proteins from the polar cortex.

cell biology↗