Biology subjects

Jasek, S.

Publications and source records attributed to Jasek, S..

7 recordsLinked to original sources

bioRxiv2025

Neural Connectome of the Ctenophore Statocyst

Ctenophores possess a unique gravity receptor (statocyst) in their aboral organ formed by four clusters of ciliated balancer cells that collectively support a statolith. During reorientation, differential loads on the balancer cilia lead to altered beating of the ciliated comb rows to elicit turns. To study the neural bases of gravity sensing, we used volume electron microscopy (vEM) to image the aboral organ of the ctenophore Mnemiopsis leidyi. We reconstructed 1011 cells, including syncytial neurons that form a nerve net. The syncytial neurons synapse on the balancer cells and also form reciprocal connections with the bridge cells that span the statocyst. High-speed imaging revealed that balancer cilia beat and arrest in a coordinated manner but with differences between the sagittal and tentacular planes of the animal, reflecting nerve-net organisation. Our results suggest a coordinating rather than sensory-motor function for the nerve net and inform our understanding of the diversity of nervous-system organisation across animals.

animal behavior and cognition↗

bioRxiv2024

Whole-body connectome of a segmented annelid larva

Nervous systems coordinate effectors across the body during movements. We know little about the cellular-level structure of synaptic circuits for such body-wide control. Here we describe the whole-body synaptic connectome of a segmented larva of the marine annelid Platynereis dumerilii. We reconstructed and annotated over 9,000 neuronal and non-neuronal cells in a whole-body serial electron microscopy dataset. Differentiated cells were classified into 202 neuronal and 92 non-neuronal cell types. We analyse modularity, multisensory integration, left-right and intersegmental connectivity and motor circuits for ciliated cells, glands, pigment cells and muscles. We identify several segment-specific cell types, demonstrating the heteromery of the annelid larval trunk. At the same time, segmentally repeated cell types across the head, the trunk segments and the pygidium suggest the serial homology of all segmental body regions. We also report descending and ascending pathways, peptidergic circuits and a multi-modal mechanosensory girdle. Our work provides the basis for understanding whole-body coordination in an entire segmented animal.

neuroscience↗

bioRxiv2023

Evolution of the ribbon-like organization of the Golgi apparatus in animal cells

The Golgi ribbon is a structural organization formed by linked Golgi stacks that is believed to be exclusive to vertebrate cells. Its functional contribution to cellular processes is unclear, yet its disruption is associated with several human pathologies. In this study we address the evolutionary origin of the Golgi ribbon, describe a potential molecular mechanism for its emergence and identify a cellular process in which it may be involved. We observed the ribbon-like architecture in the cells of several metazoan taxa, suggesting its early appearance during animal evolution before the emergence of vertebrates. Supported by AlphaFold2 modelling, we propose that the evolution of the complex between two Golgi resident proteins, Golgin-45 and GRASP, led to the tethering of Golgi stacks into the ribbon-like configuration. Finally, we find that the ribbon is assembled during the early embryogenesis of deuterostome animals, a strong indication of its role in development. Overall, our study indicates that the Golgi ribbon is functionally relevant beyond vertebrates and calls for further investigations to decipher its elusive functions. O_FIG O_LINKSMALLFIG WIDTH=89 HEIGHT=200 SRC="FIGDIR/small/528797v2_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@17a404forg.highwire.dtl.DTLVardef@11413b4org.highwire.dtl.DTLVardef@119c036org.highwire.dtl.DTLVardef@19a512f_HPS_FORMAT_FIGEXP M_FIG Graphical abstract C_FIG

cell biology↗

bioRxiv2021

Desmosomal connectomics of all somatic muscles in an annelid larva

Cells form networks in animal tissues through synaptic, chemical and adhesive links. Invertebrate muscle cells often connect to other cells through desmosomes, adhesive junctions anchored by intermediate filaments. To study desmosomal networks, we skeletonised 853 muscle cells and their desmosomal partners in volume electron microscopy data covering an entire larva of the annelid Platynereis. Muscle cells adhere to each other, to epithelial, glial, ciliated, and bristle-producing cells and to the basal lamina, forming a desmosomal connectome of over 2,000 cells. The aciculae - chitin rods that form an endoskeleton in the segmental appendages - are highly connected hubs in this network. This agrees with the many degrees of freedom of their movement, as revealed by video microscopy. Mapping motoneuron synapses to the desmosomal connectome allowed us to infer the extent of tissue influenced by motoneurons. Our work shows how cellular-level maps of synaptic and adherent force networks can elucidate body mechanics.

animal behavior and cognition↗

bioRxiv2020

Whole-animal connectome and cell-type complement of the three-segmented Platynereis dumerilii larva

Nervous systems coordinate effectors across the body during movements. We know little about the cellular-level structure of synaptic circuits for such body-wide control. Here we describe the whole-body synaptic connectome and cell-type complement of a three-segmented larva of the marine annelid Platynereis dumerilii. We reconstructed and annotated over 1,500 neurons and 6,500 non-neuronal cells in a whole-body serial electron microscopy dataset. The differentiated cells fall into 180 neuronal and 90 non-neuronal cell types. We analyse the modular network architecture of the entire nervous system and describe polysynaptic pathways from 428 sensory neurons to four effector systems - ciliated cells, glands, pigment cells and muscles. The complete somatic musculature and its innervation will be described in a companion paper. We also investigated intersegmental differences in cell-type complement, descending and ascending pathways, and mechanosensory and peptidergic circuits. Our work provides the basis for understanding whole-body coordination in annelids.

neuroscience↗

bioRxiv2018

Neural circuitry of a polycystin-mediated hydrodynamic startle response for predator avoidance

Startle responses triggered by aversive stimuli including predators are widespread across animals. These coordinated whole-body actions require the rapid and simultaneous activation of a large number of muscles. Here we study a startle response in a planktonic larva to understand the whole-body circuit implementation of the behavior. Upon encountering water vibrations, larvae of the annelid Platynereis close their locomotor cilia and simultaneously contract the body and raise the parapodia. The startle response is mediated by collar receptor neurons expressing the polycystins PKD1-1 and PKD2-1. CRISPR-generated PKD1-1 and PKD2-1 mutant larvae do not startle and fall prey to a copepod predator at a higher rate. Reconstruction of the whole-body connectome of the collar-receptor-cell circuitry revealed converging feedforward circuits to the ciliary bands and muscles. The wiring diagram suggests circuit mechanisms for the intersegmental and left-right coordination of the response. Our results reveal how polycystin-mediated mechanosensation can trigger a coordinated whole-body effector response involved in predator avoidance.\n\nShort SummaryThe neuronal circuitry of the Platynereis startle response links polycystin-dependent hydrodynamic sensors to muscle and ciliary effector cells

neuroscience↗

bioRxiv2017

Synaptic and peptidergic connectome of a neurosecretory centre in the annelid brain

Neurosecretory centres in animal brains use peptidergic signalling to influence physiology and behaviour. Understanding neurosecretory centre function requires mapping cell types, synapses, and peptidergic networks. Here we use electron microscopy and gene expression mapping to analyse the synaptic and peptidergic connectome of an entire neurosecretory centre. We mapped 78 neurosecretory neurons in the brain of larval Platynereis dumerilii, a marine annelid. These neurons form an anterior neurosecretory organ expressing many neuropeptides, including hypothalamic peptide orthologues and their receptors. Analysis of peptide-receptor pairs revealed sparsely connected networks linking specific neuronal subsets. We experimentally analysed one peptide-receptor pair and found that a neuropeptide can couple neurosecretory and synaptic brain signalling. Our study uncovered extensive non-synaptic signalling within a neurosecretory centre and its connection to the synaptic brain.

neuroscience↗