Biology subjects

Schafer, W.

Publications and source records attributed to Schafer, W..

8 recordsLinked to original sources

bioRxiv2026

K2P Channels Regulate Presynaptic Organisation through a Membrane Potential-Independent Mechanism

Neuronal ion channels have well-established effects on synaptic plasticity, in many cases by influencing pathways that depend on membrane excitability. Here we find that a C. elegans two-pore domain potassium (K2P) channel, TWK-40, regulates presynaptic organisation through a membrane potential-independent mechanism. Instead, this mechanism depends on TWK-40's effects on intracellular potassium levels. Loss-of-function mutations in TWK-40 lead to excessive presynaptic protein accumulation, while gain-of-function mutations lead to depleted presynaptic components and cause synaptic transmission deficits. These abnormalities are phenocopied by transporter mutations that mimic TWK-40's effects on intracellular potassium concentration, but not by sodium channel mutations that mimic its effects on membrane excitability. This indicates that cytoplasmic potassium promotes presynaptic assembly. This process depends on the PYK-1 pyruvate kinase, a potassium-sensitive enzyme, and three transcription factors. These findings establish a new pathway linking neuronal potassium homeostasis to the control of presynaptic organisation and synaptic function.

molecular biology↗

bioRxiv2025

A gene expression atlas of a juvenile nervous system

Although the fundamental architecture of metazoan nervous systems is typically established in the embryo, substantial numbers of neurons are added during post-natal development while existing neurons expand in size, refine connectivity, and undergo additional differentiation. To reveal the underlying molecular determinants of postembryonic neurogenesis and maturation, we have produced gene expression profiles of all neuron types and their progenitors in the first larval stage (L1) of C. elegans. Comparisons of the L1 profile to the embryo and to the later L4 larval stage identified thousands of differentially expressed genes across individual neurons throughout the nervous system. Key neuropeptide signaling networks, for example, are remodeled during larval development. Gene regulatory network analysis revealed potential transcription factors driving the temporal changes in gene expression across the nervous system, including a broad role for the heterochronic transcription factor lin-14. We utilized available connectomic data of juvenile animals in combination with our neuron-specific atlas to identify potential molecular determinants of membrane contact and synaptic connectivity. These expression data are available through a user-friendly interface at CeNGEN.org for independent investigations of the maturation, connectivity and function of a developing nervous system.

neuroscience↗

bioRxiv2022

The neuropeptidergic connectome of C. elegans

SummaryEfforts are currently ongoing to map synaptic wiring diagrams or connectomes in order to understand the neural basis of brain function. However, chemical synapses represent only one type of functionally important neuronal connection; in particular, extrasynaptic, "wireless" signaling by neuropeptides is widespread and plays essential roles in all nervous systems. By integrating single-cell anatomical and gene expression datasets with a biochemical analysis of receptor-ligand interactions, we have generated a draft connectome of neuropeptide signaling in the C. elegans nervous system. This connectome is characterized by a high connection density, extended signaling cascades, autocrine foci, and a decentralized topology, with a large, highly interconnected core containing three constituent communities sharing similar patterns of input connectivity. Intriguingly, several of the most important nodes in this connectome are little-studied neurons that are specialized for peptidergic neuromodulation. We anticipate that the C. elegans neuropeptidergic connectome will serve as a prototype to understand basic organizational principles of neuroendocrine signaling networks.

neuroscience↗

bioRxiv2022

Physiological insight into the conserved properties of Caenorhabditis elegans acid-sensing DEG/ENaCs

Acid sensing ion channels (ASICs) are members of the diverse family of degenerin/epithelial sodium channels (DEG/ENaCs). They perform a wide range of physiological roles in healthy organisms, including in gut function and synaptic transmission, but also play important roles in disease, as acidosis is a hallmark of painful inflammatory and ischaemic conditions. We performed a screen for acid-sensitivity on all 30 subunits of the C. elegans DEG/ENaC family using Two-Electrode Voltage Clamp (TEVC) in Xenopus oocytes. We found two groups of acid-sensing DEG/ENaCs characterised by being inhibited or activated by increasing proton concentrations. Three of these acid-sensitive C. elegans DEG/ENaCs were activated by acidic pH, making them functionally similar to the vertebrate ASICs. We also identified four new members of the acid-inhibited DEG/ENaC group, giving a total of seven additional acid-sensitive channels. We observed sensitivity to the anti-hypertensive drug amiloride as well as modulation by the trace element zinc. Acid-sensitive DEG/ENaCs were found to be expressed in both neurons and non-neuronal tissue, highlighting the likely functional diversity of these channels. Our findings provide a framework to exploit the C. elegans channels as models to study the function of these acid-sensing channels in vivo, as well as to study them as potential targets for anti-helminthic drugs.

physiology↗

bioRxiv2021

Distinct roles for two Caenorhabditis elegans acid-sensing ion channels in an ultradian clock

Biological clocks are fundamental to an organisms health, controlling periodicity of behavior and metabolism. Here, we identify two acid-sensing ion channels, with very different proton sensing properties, and describe their role in an ultradian clock, the defecation motor program (DMP) of the nematode Caenorhabditis elegans. An ACD-5-containing channel, on the apical membrane of the intestinal epithelium, is essential for maintenance of luminal acidity, and thus the rhythmic oscillations in lumen pH. In contrast, the second channel, composed of FLR-1, ACD-3 and/or DEL-5, located on the basolateral membrane, controls the intracellular Ca2+ wave and forms a core component of the master oscillator that controls timing and rhythmicity of the DMP. flr-1 and acd-3/del-5 mutants show severe developmental and metabolic defects. We thus directly link the proton-sensing properties of these channels to their physiological roles in pH regulation and Ca2+ signaling, the generation of an ultradian oscillator, and its metabolic consequences. One-Sentence SummaryTwo acid-sensing DEG/ENaC channels play distinct roles in controlling different aspects of rhythmic proton and Ca2+ oscillations in the C. elegans intestine.

physiology↗

bioRxiv2020

Deorphanisation of novel biogenic amine-gated ion channels identifies a new serotonin receptor for learning

Pentameric ligand-gated ion channels (LGCs) play conserved, critical roles in fast synaptic transmission, and changes in LGC expression and localisation are thought to underlie many forms of learning and memory. The C. elegans genome encodes a large number of LGCs without a known ligand or function. Here, we deorphanize five members of a family of Cys-loop LGCs by characterizing their diverse functional properties that are activated by biogenic amine neurotransmitters. To analyse the neuronal function of these LGCs, we show that a novel serotonin-gated cation channel, LGC-50, is essential for aversive olfactory learning. lgc-50 mutants show a specific defect in learned olfactory avoidance of pathogenic bacteria, a process known to depend on serotonergic neurotransmission. Remarkably, the expression of LGC-50 in neuronal processes is enhanced by olfactory conditioning; thus, the regulated expression of these receptors at synapses appears to represent a molecular cornerstone of the learning mechanism.

neuroscience↗

bioRxiv2019

Automated analysis of sleep in adult C. elegans with closed-loop assessment of state-dependent neural activity

Sleep, a state of quiescence associated with growth and restorative processes, is conserved across species. Invertebrates including the nematode Caenorhabditis elegans exhibit sleep-like states during development and periods of satiety and stress. Here we describe two methods to study behavior and associated neural activity during sleep and awake states in adult C. elegans. A large microfluidic device facilitates population-wide assessment of long-term sleep behavior over 12 h, including effects of fluid flow, oxygen, feeding, odors, and genetic perturbations. Smaller devices allow simultaneous recording of sleep behavior and neuronal activity, and a closed-loop sleep detection system delivers chemical stimuli to individual animals to assess sleep-dependent changes to neural responses. Sleep increased the arousal threshold to aversive chemical stimulation, yet sensory neuron (ASH) and first-layer interneuron (AIB) responses were unchanged. This localizes adult sleep-dependent neuromodulation within interneurons presynaptic to the AVA premotor interneurons, rather than afferent sensory circuits.

neuroscience↗

bioRxiv2019

Distinct roles for innexin gap junctions and hemichannels in mechanosensation

Mechanosensation is central to a wide range of functions, including tactile and pain perception, hearing, proprioception, and control of blood pressure, but identifying the molecules underlying mechanotransduction has proved challenging. In Caenorhabditis elegans, the avoidance response to gentle body touch is mediated by 6 touch receptor neurons (TRNs), and is dependent on MEC-4, a DEG/ENaC channel. We show that hemichannels containing the innexin protein UNC-7 are also essential for gentle touch in the TRNs, as well as harsh touch in both the TRNs and the PVD nociceptors. UNC-7 and MEC-4 do not colocalize, suggesting that their roles in mechanosensory transduction are independent. Heterologous expression of unc-7 in touch-insensitive chemosensory neurons confers ectopic touch sensitivity, indicating a direct role for UNC-7 hemichannels in mechanosensation. The unc-7 touch defect can be rescued by the homologous mouse gene Panx1 gene, thus, innexin/pannexin proteins may play broadly conserved roles in neuronal mechanotransduction.

neuroscience↗