Biology subjects

Pereda, A. E.

Publications and source records attributed to Pereda, A. E..

5 recordsLinked to original sources

bioRxiv2026

Electrical and chemical synapses share similar organizational principle

Electrical transmission is mediated by intercellular channels that cluster into structures known as gap junctions (GJ). In vertebrates, GJ channels are encoded by the gene family of connexin (Cx) proteins that assemble as hexamers, termed hemichannels, in the pre- and postsynaptic membranes, and that subsequently dock to form GJ channels. Auditory contacts on the fish Mauthner cells serve as model to study the properties and organization of vertebrate electrical synapses. Electrical transmission at these synapses is mediated by multiple co-existing GJs at which the presence of intercellular channels is regulated by a molecular scaffold. Zebrafish contain four homologs of the neuronal Cx36: Cx35.5 and Cx35.1 (gjd2a and b, respectively), and Cx34.1 and Cx34.7 (gjd1a and b). Cx mutations suggested that GJs are formed by heterotypic channels made of presynaptic Cx35.5 and postsynaptic Cx34.1. Using transgenic fish in which Cxs were tagged, we found that a second Cx, Cx34.7, is present together with Cx34.1 on the postsynaptic side at some but not all GJs at these terminals. When exogenously expressed, both Cx34.1 and Cx34.7 formed heterotypic functional channels with Cx35.5, each with substantially different voltage-dependent properties, indicating they can serve differential functions. However, we previously demonstrated that electrical transmission is lost in Cx34.1 but not Cx34.7 null mutants, suggesting that Cx34.7 cannot compensate for the loss of Cx34, despite the intrinsic ability of Cx34.1 and Cx34.7 to create functional channels. The findings reveal an unanticipated functional organization in the electrical synapse, where Cx34.1 is obligatory and Cx34.7 accessory, roles that appear to be defined by the postsynaptic molecular scaffold, with two postsynaptic Cxs possibly assembling under specific functional contexts. Thus, our results indicate that electrical synapses share an organizational motif with chemical synapses, akin to how they combine postsynaptic receptor types to modify synaptic function.

neuroscience↗

bioRxiv2023

The components of an electrical synapse as revealed by expansion microscopy of a single synaptic contact

Most nervous systems combine both transmitter-mediated and direct cell-cell communication, known as chemical and electrical synapses, respectively. Chemical synapses can be identified by their multiple structural components. Electrical synapses are, on the other hand, generally defined by the presence of a gap junction (a cluster of intercellular channels) between two neuronal processes. However, while gap junctions provide the communicating mechanism, it is unknown whether electrical transmission requires the contribution of additional cellular structures. We investigated this question at identifiable single synaptic contacts on the zebrafish Mauthner cells, at which gap junctions coexist with specializations for neurotransmitter release and where the contact defines the anatomical limits of a synapse. Expansion microscopy of these contacts revealed a detailed map of the incidence and spatial distribution of proteins pertaining to various synaptic structures. Multiple gap junctions of variable size were identified by the presence of their molecular components. Remarkably, most of the synaptic contacts surface was occupied by interleaving gap junctions and components of adherens junctions, suggesting a close functional association between these two structures. In contrast, glutamate receptors were confined to small peripheral portions of the contact, indicating that most of the synaptic area works as an electrical synapse. Thus, our results revealed the overarching organization of an electrical synapse that operates with not one, but multiple gap junctions, in close association with structural and signaling molecules known to be components of AJs. The relationship between these intercellular structures will aid in establishing the boundaries of electrical synapses found throughout animal connectomes and provide insight into the structural organization and functional diversity of electrical synapses.

neuroscience↗

bioRxiv2022

Neurobeachin controls the asymmetric subcellular distribution of electrical synapse proteins

The subcellular positioning of synapses and their specialized molecular compositions form the fundamental basis of neural circuits. Like chemical synapses, electrical synapses are constructed from an assortment of adhesion, scaffolding, and regulatory molecules, yet little is known about how these molecules localize at specified subcellular neuronal compartments. Here we investigated the relationship between the autism- and epilepsy-associated gene Neurobeachin, neuronal gap junction channelforming Connexins, and the scaffold ZO1. Using the zebrafish Mauthner circuit we found Neurobeachin localizes to the electrical synapse independent of ZO1 and Connexins. By contrast, we show Neurobeachin is required postsynaptically for the robust localization of ZO1 and Connexins. We demonstrate Neurobeachin binds ZO1 but not Connexins. Finally, we find Neurobeachin is required to restrict postsynaptic electrical synapse proteins to dendrites. These findings reveal a mechanism for the asymmetric synaptic localization of electrical synapse components providing a basis for the subcellular specialization of neuronal gap junctions.

neuroscience↗

bioRxiv2020

Electrical synaptic transmission requires a postsynaptic scaffolding protein

Electrical synaptic transmission relies on neuronal gap junctions containing channels constructed by Connexins. While at chemical synapses neurotransmitter-gated ion channels are critically supported by scaffolding proteins, it is unknown if channels at electrical synapses require similar scaffold support. Here we investigated the functional relationship between neuronal Connexins and Zonula Occludens 1 (ZO1), an intracellular scaffolding protein localized to electrical synapses. Using model electrical synapses in zebrafish Mauthner cells, we demonstrated that ZO1 is required for robust synaptic Connexin localization, but Connexins are dispensable for ZO1 localization. Disrupting this hierarchical ZO1/Connexin relationship abolishes electrical transmission and disrupts Mauthner-cell-initiated escape responses. We found that ZO1 is asymmetrically localized exclusively postsynaptically at neuronal contacts where it functions to assemble intercellular channels. Thus, forming functional neuronal gap junctions requires a postsynaptic scaffolding protein. The critical function of a scaffolding molecule reveals an unanticipated complexity of molecular and functional organization at electrical synapses.

neuroscience↗

bioRxiv2020

A forward genetic screen identifies Dolk as a regulator of startle magnitude through the potassium channel subunit Kv1.1

The acoustic startle response is an evolutionary conserved avoidance behavior. Disruptions in startle behavior, in particular startle magnitude, are a hallmark of several human neurological disorders. While the neural circuitry underlying startle behavior has been studied extensively, the repertoire of genes and genetic pathways that regulate this locomotor behavior has not been explored using an unbiased genetic approach. To identify such genes, we took advantage of the stereotypic startle behavior in zebrafish larvae and performed a forward genetic screen coupled with whole genome analysis. This identified mutants in eight genes critical for startle behavior, including two genes encoding proteins associated with human neurological disorders, Dolichol kinase (Dolk), a broadly expressed regulator of the glycoprotein biosynthesis pathway, and the potassium Shaker-like channel subunit Kv1.1. We demonstrate that Kv1.1 acts independently of supraspinal inputs to regulate locomotion, suggesting its site of action is within spinal circuitry. Moreover, we show that Kv1.1 protein is mis-localized in dolk mutants, suggesting they act in a common genetic pathway to regulate movement magnitude. Combined, our results identify a diverse set of eight genes all associated with human disorders that regulate zebrafish startle behavior and reveal a previously unappreciated role for Dolk and Kv1.1 in regulating movement magnitude via a common genetic pathway. Author summaryUnderlying all animal behaviors are neural circuits, which are controlled by numerous molecular pathways that direct neuron development and activity. To identify and study these molecular pathways that control behavior, we use a simple vertebrate behavior, the acoustic startle response, in the larval zebrafish. In response to an intense noise, larval zebrafish will quickly turn and swim away to escape. From a genetic screen, we have identified a number of mutants that behave in abnormal ways in response to an acoustic stimulus. We cloned these mutants and identified eight genes that regulate startle behavior. All eight genes are associated with human disorders, and here we focus on two genes, dolk and kcna1a, encoding Dolk, a key regulator of protein glycosylation, and the potassium channel Kv1.1, respectively. We demonstrate that loss of dolk or kcna1a causes larval zebrafish to perform exaggerated swim movements and that Dolk is required for Kv1.1 protein localization to axons of neurons throughout the nervous system, providing strong evidence that dolk and kcna1a act in a common molecular pathway. Combined, our studies provide new insights into the genetic regulation of startle behavior.

neuroscience↗