Biology subjects

Wojcik, S. M.

Publications and source records attributed to Wojcik, S. M..

6 recordsLinked to original sources

bioRxiv2023

Transcriptional networks predating cognition-associated pyramidal lineages are restructured by erythropoietin

Recombinant human erythropoietin (rhEPO) has potent procognitive effects, hematopoiesis-independent, but underlying mechanisms and physiological role of brain-expressed EPO have remained obscure. Here, we provide encyclopedic transcriptional hippocampal profiling of mice treated with rhEPO. Based on [~]108,000 single nuclei, we unmask multiple pyramidal lineages with their comprehensive molecular signatures. By temporal profiling and gene regulatory analysis, we build a developmental trajectory of CA1 pyramidal neurons derived from multiple predecessor lineages and elucidate gene regulatory networks underlying their fate determination. With EPO as tool, we discover novel populations of newly differentiating pyramidal neurons, overpopulating to [~]200% upon rhEPO with upregulation of genes crucial for neurodifferentiation, dendrite growth, synaptogenesis, memory formation, and cognition. Using a Cre-based approach to visually distinguish pre-existing from newly formed pyramidal neurons for patch-clamp recordings, we learn that rhEPO treatment differentially affects excitatory and inhibitory inputs. Our findings provide mechanistic insight into how EPO modulates neuronal functions and networks.

neuroscience↗

bioRxiv2022

Modelling non-local neural information processing in the brain

The representation of the surrounding world emerges through integration of sensory information and actions. We present a novel neural model which implements non-local, parallel information processing on a neocolumnar architecture with lateral interconnections. Information is integrated into a holographic wave interference pattern. We compare the simulated in silico pattern with observed in vivo invasive and non-invasive electrophysiological data in human and non-human primates. Our model replicates the modulation of neural high-frequency activity during visual perception showing that phase-locked low and high-frequency oscillations self-organize efficiently and carry high information content. The simulation further models how criticality (high content) of information processing emerges given a sufficiently high number of correlated neurons. Non-local information processing, forming one holographic wave pattern, suggests a platform for emergence of conscious perception. One sentence summarySimulated non-local information processing on a neocolumnar architecture models well multiple electrophysiological observations of brain activity, including high-frequency activity during visual perception in primates.

neuroscience↗

bioRxiv2020

Molecular and functional architecture of striatal dopamine release sites

Dopamine controls striatal circuit function, but its transmission mechanisms are not well understood. We recently showed that dopamine secretion requires RIM, suggesting that it occurs at active zone-like sites similar to conventional synapses. Here, we establish using a systematic conditional gene knockout approach that Munc13 and Liprin-, active zone proteins for vesicle priming and release site organization, are important for dopamine secretion. Correspondingly, RIM zinc finger and C2B domains, which bind to Munc13 and Liprin-, respectively, are needed to restore dopamine release in RIM knockout mice. In contrast, and different from conventional synapses, the active zone scaffolds RIM-BP and ELKS, and the RIM domains that bind to them, are expendable. Hence, dopamine release necessitates priming and release site scaffolding by RIM, Munc13, and Liprin-, but other active zone proteins are dispensable. Our work establishes that molecularly simple but efficient release site architecture mediates fast dopamine exocytosis.

neuroscience↗

bioRxiv2020

Synaptotagmin-7 places dense-core vesicles at the cell membrane to promote Munc13-2- and Ca2+-dependent priming

The functional consequences of the co-expression of synaptotagmin-1 and synaptotagmin-7 are unclear. We show that when present separately, synaptotagmin-1 and synaptotagmin-7 act as standalone fast and slow Ca2+-sensors for vesicle fusion in mouse chromaffin cells. When present together, synaptotagmin-7 stimulates Ca2+-dependent vesicle priming and inhibits depriming. The priming effect of Synaptotagmin-7 extends to the Readily Releasable Pool, whose fusion is executed by synaptotagmin-1, indicating synergistic action of the two Ca2+-sensors, although they are only partially colocalized. Synaptotagmin-7 promotes ubMunc13-2-dependent priming and the absence of synaptotagmin-7 renders phorbolesters less effective in stimulating priming, although synaptotagmin-7 independent priming is also observed. Morphologically, synaptotagmin-7 places vesicles in close membrane apposition (< 6 nm); in its absence vesicles accumulate out of reach of the fusion complex (20-40 nm). We suggest that a synaptotagmin-7-dependent movement toward the membrane is involved in Munc13-2/phorbolester/Ca2+-dependent priming and sets the stage for fast and slow exocytosis triggering.

neuroscience↗

bioRxiv2019

Physiological and pathophysiological homeostasis of astroglial channel proteins by Nedd4-2

Nedd4-2 is an E3 ubiquitin ligase, missense mutation of which is related to familial epilepsy, indicating its critical role in regulating neuronal network activity. However, Nedd4-2 substrates involved in neuronal network function have yet to be identified. Using mouse lines lacking Nedd4-1 and Nedd4-2, we identified astrocytic channel proteins inwardly rectifying K+ channel 4.1 (Kir4.1) and Connexin43 as Nedd4-2 substrates. We found that the expression of Kir4.1 and Connexin43 is increased upon conditional deletion of Nedd4-2 in astrocytes, leading to an elevation of astrocytic membrane ion permeability and gap junction activity, with a consequent reduction of {gamma}-oscillatory neuronal network activity. Interestingly, our biochemical data demonstrate that missense mutations found in familial epileptic patients produce gain-of-function of Nedd4-2 gene product. Our data reveal a process of coordinated astrocytic ion channel proteostasis that controls astrocyte function and astrocyte-dependent neuronal network activity, and elucidate a potential mechanism by which aberrant Nedd4-2 function leads to epilepsy.\n\nCONDENSED TITLEUbiquitination of Astrocytic Channels by Nedd4-2\n\nSUMMARYUbiquitination is a key regulatory machinery for protein expression. Our present work provides evidence that astrocytic ion channel proteostasis coordinated by an E3 ubiquitin ligase Nedd4-2 is of particular importance for the maintenance of neuronal network activity.

neuroscience↗

bioRxiv2018

Mammalian vesicular glutamate transporter VGLUT1 reduces synaptic vesicle superpool size and spontaneous release frequency.

Glutamate secretion at excitatory synapses is tightly regulated to allow for the precise tuning of synaptic strength. Vesicular Glutamate Transporters (VGLUT) accumulate glutamate into synaptic vesicles (SV) and thereby regulate quantal size. Further, the number of release sites and the release probability of SVs maybe regulated by the organization of active zone proteins and SV clusters. In the present work, we uncover a mechanism mediating an increased SV clustering through a tripartite interaction of VGLUT1, endophilinA1 and intersectin1. This strengthening of SV clusters results in a combined reduction of axonal SV super-pool size and miniature excitatory events frequency. Our findings support a model in which clustered vesicles are held together through multiple weak interactions between SH3 domains and proline rich sequences of synaptic proteins. In mammals, VGLUT1 gained a poly-proline sequence that recruits endophilinA1 and turns the transporter into a dual regulator of quantal release parameters at excitatory synapses.

neuroscience↗