An emergent disease-associated motor neuron state precedes cell death in a mouse model of ALS.

To uncover molecular determinants of motor neuron degeneration and selective vulnerability in amyotrophic lateral sclerosis (ALS), we generated longitudinal single-nucleus transcriptomes and chromatin accessibility profiles of spinal motor neurons from the SOD1-G93A ALS mouse model. Vulnerable alpha motor neurons showed thousands of molecular changes, marking a transition into a novel cell state we named 'disease-associated motor neurons' (DAMNs). We identified transcription factor regulatory networks that govern how healthy cells transition into DAMNs as well as those linked to vulnerable and resistant motor neuron subtypes.

GPCR signaling gates astrocyte responsiveness to neurotransmitters and control of neuronal activity.

How astrocytes regulate neuronal circuits is a fundamental question in neurobiology. Specifically, how astrocytes respond to different neurotransmitters in vivo and how they affect downstream circuit modulation are questions that remain to be fully elucidated. Here, we report a mechanism in by which G protein-coupled adrenergic signaling in astrocytes can control-or "gate"-their ability to respond to other neurotransmitters.

Adrenergic signaling gates astrocyte responsiveness to neurotransmitters and control of neuronal activity.

How astrocytes regulate neuronal circuits is a fundamental, unsolved question in neurobiology. Nevertheless, few studies have explored the rules that govern when astrocytes respond to different neurotransmitters and how they affect downstream circuit modulation. Here, we report an unexpected mechanism in by which G-protein coupled adrenergic signaling in astrocytes can control, or "gate," their ability to respond to other neurotransmitters.

Why you always in a mood? Pumpin' polyP, actin' brand new.

What causes neurons to die in neurodegenerative disease? In this issue of Neuron, Arredondo et al., 2022 report an unexpected culprit that may drive neuronal death in amyotrophic lateral sclerosis-an evolutionarily ancient energy-storage polymer called polyphosphate (polyP).

Neurotoxic reactive astrocytes induce cell death via saturated lipids.

Astrocytes regulate the response of the central nervous system to disease and injury and have been hypothesized to actively kill neurons in neurodegenerative disease. Here we report an approach to isolate one component of the long-sought astrocyte-derived toxic factor. Notably, instead of a protein, saturated lipids contained in APOE and APOJ lipoparticles mediate astrocyte-induced toxicity.

Monitoring phagocytic uptake of amyloid β into glial cell lysosomes in real time.

Phagocytosis by glial cells is essential to regulate brain function during health and disease. Therapies for Alzheimer's disease (AD) have primarily focused on targeting antibodies to amyloid β (Aβ) or inhibitng enzymes that make it, and while removal of Aβ by phagocytosis is protective early in AD it remains poorly understood. Impaired phagocytic function of glial cells during later stages of AD likely contributes to worsened disease outcome, but the underlying mechanisms of how this occurs remain unknown.

Single-cell transcriptomic analysis of the adult mouse spinal cord reveals molecular diversity of autonomic and skeletal motor neurons.

The spinal cord is a fascinating structure that is responsible for coordinating movement in vertebrates. Spinal motor neurons control muscle activity by transmitting signals from the spinal cord to diverse peripheral targets. In this study, we profiled 43,890 single-nucleus transcriptomes from the adult mouse spinal cord using fluorescence-activated nuclei sorting to enrich for motor neuron nuclei.

Knockout of reactive astrocyte activating factors slows disease progression in an ALS mouse model.

Reactive astrocytes have been implicated in the pathogenesis of neurodegenerative diseases, including a non-cell autonomous effect on motor neuron survival in ALS. We previously defined a mechanism by which microglia release three factors, IL-1α, TNFα, and C1q, to induce neurotoxic astrocytes. Here we report that knocking out these three factors markedly extends survival in the SOD1 ALS mouse model, providing evidence for gliosis as a potential ALS therapeutic target.

CD49f Is a Novel Marker of Functional and Reactive Human iPSC-Derived Astrocytes.

New methods for investigating human astrocytes are urgently needed, given their critical role in the central nervous system. Here we show that CD49f is a novel marker for human astrocytes, expressed in fetal and adult brains from healthy and diseased individuals. CD49f can be used to purify fetal astrocytes and human induced pluripotent stem cell (hiPSC)-derived astrocytes.

Astrocytes and microglia: Models and tools.

Glial cells serve as fundamental regulators of the central nervous system in development, homeostasis, and disease. Discoveries into the function of these cells have fueled excitement in glial research, with enthusiastic researchers addressing fundamental questions about glial biology and producing new scientific tools for the community. Here, we outline the pros and cons of in vivo and in vitro techniques to study astrocytes and microglia with the goal of helping researchers quickly identify the best approach for a given research question in the context of glial biology.

Play It Again, SAM: Macrophages Control Peripheral Fat Metabolism.

Macrophages and other immune cells are increasingly recognized to have unique and nontraditional functions in various tissues of the body. In a recent issue of Nature Medicine, Pirzgalska et al. [1] characterized a unique set of tissue-specialized macrophages that modulate the connection between the nervous system and subcutaneous fat.

Neurotoxic reactive astrocytes are induced by activated microglia.

Reactive astrocytes are strongly induced by central nervous system (CNS) injury and disease, but their role is poorly understood. Here we show that a subtype of reactive astrocytes, which we termed A1, is induced by classically activated neuroinflammatory microglia. We show that activated microglia induce A1 astrocytes by secreting Il-1α, TNF and C1q, and that these cytokines together are necessary and sufficient to induce A1 astrocytes.