Biology subjects

Medeiros, A. T.

Publications and source records attributed to Medeiros, A. T..

4 recordsLinked to original sources

bioRxiv2024

Synaptic gene expression is coordinated across development by conserved chromatin regulators

Synapses are the primary sites of communication in the nervous system. Synapse formation requires the simultaneous expression of hundreds of proteins across cells. Through genomic and functional studies in Drosophila, we investigated the regulatory mechanisms underlying the spatiotemporal coordination of synaptic gene expression during neurodevelopment. We find that chromatin opening is coordinated across hundreds of synaptic genes immediately preceding transcription, whereas repression of these genes outside developmental periods of synaptogenesis is regulated by distinct mechanisms. We identify the conserved DEAF1 transcription factor (TF) as a direct repressor of synaptic genes. Disruption of DEAF1 or pioneer TF CLAMP, which promotes DEAF1 binding, increases synaptic gene expression across neuronal subtypes, leading to excess synapse formation. DEAF1, which is linked to syndromic intellectual disability, is also sufficient to block synaptogenesis. These findings reveal the importance of coordinated synaptic gene repression in sculpting neuronal connectivity and broaden our understanding of gene regulation in neurodevelopment.

neuroscience↗

bioRxiv2023

Molecular and organizational diversity intersect to generate functional synaptic heterogeneity within and between excitatory neuronal subtypes

Synaptic heterogeneity is a hallmark of nervous systems that enables complex and adaptable communication in neural circuits. To understand circuit function, it is thus critical to determine the factors that contribute to the functional diversity of synapses. We investigated the contributions of voltage-gated calcium channel (VGCC) abundance, spatial organization, and subunit composition to synapse diversity among and between synapses formed by two closely related Drosophila glutamatergic motor neurons with distinct neurotransmitter release probabilities (Pr). Surprisingly, VGCC levels are highly predictive of heterogeneous Pr among individual synapses of either low- or high-Pr inputs, but not between inputs. We find that the same number of VGCCs are more densely organized at high-Pr synapses, consistent with tighter VGCC-synaptic vesicle coupling. We generated endogenously tagged lines to investigate VGCC subunits in vivo and found that the 2{delta}-3 subunit Straightjacket along with the CAST/ELKS active zone (AZ) protein Bruchpilot, both key regulators of VGCCs, are less abundant at high-Pr inputs, yet positively correlate with Pr among synapses formed by either input. Consistently, both Straightjacket and Bruchpilot levels are dynamically increased across AZs of both inputs when neurotransmitter release is potentiated to maintain stable communication following glutamate receptor inhibition. Together, these findings suggest a model in which VGCC and AZ protein abundance intersects with input-specific spatial and molecular organization to shape the functional diversity of synapses.

neuroscience↗

bioRxiv2020

α-Synuclein-112 impairs synaptic vesicle recycling consistent with its enhanced membrane binding properties

Synucleinopathies are neurological disorders associated with -synuclein overexpression and aggregation. While it is well established that overexpression of wild type -synuclein (-syn-140) leads to cellular toxicity and neurodegeneration, much less is known about other naturally occurring -synuclein splice isoforms. In this study we provide the first detailed examination of the synaptic effects caused by one of these splice isoforms, -synuclein-112 (-syn-112). -Syn-112 is produced by an in-frame excision of exon 5, resulting in deletion of amino acids 103-130 in the C-terminal region. -Syn-112 is upregulated in the substantia nigra, frontal cortex, and cerebellum of parkinsonian brains and is correlated with susceptibility to sporadic Parkinsons disease (PD), dementia with Lewy bodies (DLB) and multiple systems atrophy (MSA). We report here that -syn-112 binds strongly to anionic phospholipids when presented in highly-curved liposomes, similar to -syn-140. However, -syn-112 bound significantly stronger to all phospholipids tested, including the phosphoinositides. -Syn-112 also dimerized and trimerized on isolated synaptic membranes, while -syn-140 remained largely monomeric. When introduced acutely to lamprey synapses, -syn-112 robustly inhibited synaptic vesicle recycling. Interestingly, -syn-112 produced effects on the plasma membrane and clathrin-mediated synaptic vesicle endocytosis that were phenotypically intermediate between those caused by monomeric and dimeric -syn-140. These findings indicate that -syn-112 exhibits enhanced phospholipid binding and oligomerization in vitro and consequently interferes with synaptic vesicle recycling in vivo in ways that are consistent with its biochemical properties. This study provides additional evidence suggesting that impaired vesicle endocytosis is a cellular target of excess -synuclein and advances our understanding of potential mechanisms underlying disease pathogenesis in the synucleinopathies.

neuroscience↗

bioRxiv2019

Hsc70 Ameliorates the Vesicle Recycling Defects Caused by Excess -Synuclein at Synapses

-Synuclein overexpression and aggregation are linked to Parkinsons disease (PD), dementia with Lewy bodies (DLB), and several other neurodegenerative disorders. In addition to effects in the cell body, -synuclein accumulation occurs at presynapses where the protein is normally localized. While it is generally agreed that excess -synuclein impairs synaptic vesicle trafficking, the underlying mechanisms are unknown. We show here that acute introduction of excess human -synuclein at a classic vertebrate synapse, the lamprey reticulospinal synapse, selectively impaired the uncoating of clathrin-coated vesicles (CCVs) during synaptic vesicle recycling, leading to a severe depletion of synaptic vesicles. Furthermore, human -synuclein and lamprey {gamma}-synuclein both interact in vitro with Hsc70, the chaperone protein that uncoats CCVs at synapses. After introducing excess -synuclein to lamprey axons, Hsc70 availability was reduced at the synapses, suggesting Hsc70 sequestration as a possible mechanism underlying the synaptic vesicle trafficking defects. In support of this hypothesis, increasing the levels of exogenous Hsc70 together with -synuclein ameliorated the CCV uncoating and vesicle recycling defects. These experiments identify a reduction in Hsc70 availability at synapses, and consequently its function, as the mechanism by which -synuclein induces synaptic vesicle recycling defects. To our knowledge, this is the first report of a viable chaperone-based strategy for reversing the toxic impacts of excess -synuclein at synapses, which may be of value for ameliorating synaptic defects in PD and other synuclein-linked diseases.\n\nSIGNIFICANCE STATEMENTSynaptic defects caused by -synuclein overexpression are linked to cognitive deficits in PD and other diseases. However, the mechanisms by which excess -synuclein impairs synaptic vesicle trafficking are unknown. Data presented here demonstrate that acute introduction of excess -synuclein at a classical vertebrate synapse selectively inhibits CCV uncoating, leading to impaired vesicle recycling. Furthermore, increasing -synuclein reduced synaptic levels of Hsc70, the clathrin uncoating ATPase. Subsequently increasing Hsc70 restored CCV uncoating and improved vesicle recycling. This study identifies a novel molecular mechanism underlying the -synuclein-induced synaptic defects and presents one viable strategy for reversing them.

neuroscience↗