Biology subjects

Min, R.

Publications and source records attributed to Min, R..

4 recordsLinked to original sources

bioRxiv2025

Altered mechanical properties of astrocytes lacking MLC1; implications for the leukodystrophy MLC

Loss of function of the astrocyte protein MLC1 causes Megalencephalic Leukoencephalopathy with subcortical Cysts (MLC), a leukodystrophy characterized by white matter edema and slow neurological deterioration. MLC1 dysfunction leads to swelling of perivascular astrocyte endfeet and an impaired attachment of endfeet to blood vessels. In isolated primary astrocytes, loss of MLC1 hinders recovery of astrocytes from cell swelling, but the cellular function of MLC1 is not completely understood. MLC1 modulates gating of mechanosensitive ion channels involved in volume regulation. The cytoskeleton plays a crucial role in cell volume regulation, and interactions between the cytoskeleton and cell membrane affect the properties of mechanosensitive ion channels. Therefore, we investigated whether primary Mlc1-null mouse astrocytes show a disruption in their mechanical properties. We measured mechanical properties of cultured primary astrocytes with an indentation technique and demonstrated that Mlc1-null astrocytes are softer than wild-type astrocytes. Proteomic analysis confirmed dysregulation of several cytoskeleton-related pathways in Mlc1-null astrocytes. Confocal imaging revealed that organization of the actin cytoskeleton is unaffected. Instead, we observed alterations in focal adhesions, which aid in relaying mechanical forces between the cytoskeleton, cell membrane, and the extracellular matrix (ECM). Together, our findings reveal that the mechanical properties of Mlc1-null astrocytes are altered, and that disrupted cytoskeleton-membrane-ECM interactions potentially play a role in the disease. Modulators of astrocyte mechanobiology might therefore hold promise for MLC therapy development.

neuroscience↗

bioRxiv2024

Effect of seizures on the severity of myelin vacuolization in a mouse model of megalencephalic leukoencephalopathy with subcortical cysts

ObjectiveMegalencephalic leukoencephalopathy with subcortical cysts (MLC) is a white matter disease characterized by myelin vacuolization and swollen perivascular astrocyte processes. Neuronal activity has been implicated as primary cause of myelin vacuolization and astrocyte swelling. Since acute and excessive increases in neuronal activity occur in MLC during seizures, we investigated whether seizure activity leads to the acute development of myelin vacuoles and swollen astrocyte processes. MethodsGlialcam-null mice (an established MLC mouse model) and wild-type mice received repeated i.p. low dose (5 mg / kg) kainic acid (KA) injections until severe seizures developed. Following a 60-minute period of severe seizure activity, mice were terminated and brains were fixed and processed. Brain tissue was analyzed for myelin vacuolization and astrocyte process thickness using H&E and GFAP stains, respectively. ResultsRepeated low-dose injections of KA resulted in prolonged severe seizure activity in mice of both genotypes. Total amount of seizure activity was comparable between Glialcam-null and wild-type mice. KA-induced severe seizure activity did not significantly increase myelin vacuolization in either Glialcam-null or wild-type mice. The width of perivascular astrocyte processes was also not affected by severe seizure activity. InterpretationWe show that (i) repeatedly injecting a low dose of KA provides the opportunity to regulate seizure development and generate severe seizures in both wild-type and seizure-sensitive Glialcam-null mice, and that (ii) the two major pathological features of MLC, myelin vacuolization and swollen astrocyte endfeet, are not acutely aggravated in response to KA-induced severe seizure activity.

neuroscience↗

bioRxiv2023

Astrocyte CB1 receptors are required for inhibitory maturation and ocular dominance plasticity in the mouse visual cortex

Summary and IntroductionNeuronal circuits are shaped by experience. This happens much more readily in the young compared to the adult brain. The unique learning capacity of the young brain is regulated through postnatal critical periods, during which the ability of neuronal networks to re-wire is greatly enhanced1. Endocannabinoids, which signal through the cannabinoid CB1 receptor (CB1R), regulate several forms of neuronal plasticity2. In the developing neocortex, CB1Rs play a key role in the maturation of inhibitory circuits. For example, interfering with CB1R signaling during development disrupts inhibitory maturation in the prefrontal cortex3. In developing primary visual cortex (V1), endocannabinoid-mediated plasticity at inhibitory synapses regulates the maturation of inhibitory synaptic transmission, shifting synapses from an immature state characterized by strong short-term depression to a mature state with reduced short-term depression4,5. This maturation step correlates with the timing of the critical period. While CB1Rs were originally thought to reside mainly on presynaptic axon terminals, recent studies have highlighted an unexpected role for astrocytic CB1Rs in endocannabinoid mediated plasticity6-8. Here, we investigate the impact of cell-type specific removal of CB1Rs from interneurons or astrocytes on development of inhibitory synapses and network plasticity of V1. We show that removing CB1Rs from astrocytes interferes with maturation of inhibitory synaptic transmission in V1. In addition, it strongly reduces ocular dominance (OD) plasticity during the critical period. In contrast, removing interneuron CB1Rs leaves these processes intact. Our results reveal an unexpected role of astrocytic CB1Rs in critical period plasticity in V1, and highlight the involvement of glial cells in the plasticity and synaptic maturation of sensory circuits.

neuroscience↗

bioRxiv2022

Proximity of astrocyte leaflets to the synapse determines memory strength

SummaryAstrocyte distal processes, known as leaflets or perisynaptic astrocyte processes (PAPs), fine-tune synaptic activity by clearing neurotransmitters and limiting extrasynaptic glutamate diffusion. While learning and memory depends on orchestrated synaptic activity of neuronal ensembles within the hippocampus, it is becoming increasingly evident that astrocytes residing in the environment of these synapses play a central role in shaping memories. However, how astroglial synaptic coverage contributes to mnemonic processing remains largely unknown. Here, we targeted astrocyte leaflet structure in vivo by depleting Ezrin, an integral leaflet-structural protein, in astrocytes of the adult hippocampal CA1 using a CRISPR-Cas9 genetic approach. This resulted in significantly smaller astrocyte territories and reduced astroglial synaptic coverage. In addition, using genetically encoded glutamate sensors and whole-cell patch-clamp recordings from pyramidal neurons, we found that Ezrin deletion and the resultant manipulation of leaflet structure boosted extrasynaptic glutamate diffusion and NMDA-receptor activation. Importantly, these cellular phenotypes translated to enhanced fear memory expression that was accompanied by increased activation of CA1 pyramidal neurons in the days after learning occurred. We show that Ezrin is critical for astrocyte morphology as well as for adult hippocampal synapse integrity and function. Our data show that astrocyte leaflet structure gates memory strength by regulating glutamate spillover in the vicinity of memory-related synaptic activity.

neuroscience↗