Transcriptomics and Live Imaging to Define Functional Phenotypes of Microglia in Pathological Human Tissue

Established and emerging techniques for the study of microglia: visualization, depletion, and fate mapping

The central nervous system (CNS) is an essential hub for neuronal communication. As a major component of the CNS, glial cells are vital in the maintenance and regulation of neuronal network dynamics. Research on microglia, the resident innate immune cells of the CNS, has advanced considerably in recent years, and our understanding of their diverse functions continues to grow. Microglia play critical roles in the formation and regulation of neuronal synapses, myelination, responses to injury, neurogenesis, inflammation, and many other physiological processes. In parallel with advances in microglial biology, cutting-edge techniques for the characterization of microglial properties have emerged with increasing depth and precision. Labeling tools and reporter models are important for the study of microglial morphology, ultrastructure, and dynamics, but also for microglial isolation, which is required to glean key phenotypic information through single-cell transcriptomics and other emerging approaches. Strategies for selective microglial depletion and modulation can provide novel insights into microglia-targeted treatment strategies in models of neuropsychiatric and neurodegenerative conditions, cancer, and autoimmunity. Finally, fate mapping has emerged as an important tool to answer fundamental questions about microglial biology, including their origin, migration, and proliferation throughout the lifetime of an organism. This review aims to provide a comprehensive discussion of these established and emerging techniques, with applications to the study of microglia in development, homeostasis, and CNS pathologies.

Microglial Potassium Channels: From Homeostasis to Neurodegeneration

The growing interest in the role of microglia in the progression of many neurodegenerative diseases is developing in an ever-expedited manner, in part thanks to emergent new tools for studying the morphological and functional features of the CNS. The discovery of specific biomarkers of the microglia phenotype could find application in a wide range of human diseases, and creates opportunities for the discovery and development of tailored therapeutic interventions. Among these, recent studies highlight the pivotal role of the potassium channels in regulating microglial functions in physiological and pathological conditions such as Alzheimer's Disease, Parkinson's Disease, and Amyotrophic Lateral Sclerosis. In this review, we summarize the current knowledge of the involvement of the microglial potassium channels in several neurodegenerative diseases and their role as modulators of microglial homeostasis and dysfunction in CNS disorders.

Investigating microglia during motor neuron degeneration using a zebrafish model

Many different types of pathologies can arise in the central nervous system (CNS), such as neurodegeneration. The incidence of neurodegenerative diseases continues to increase, yet the pathogenesis underlying most neurodegenerative diseases, notably in amyotrophic lateral sclerosis (ALS), remains elusive. Neuronal support cells, or glia, are known to play a crucial role in ALS. Microglia are the resident immune cells of the CNS and also have neurotrophic support functions. These cells have a disease-modifying function in ALS, yet this role is not well understood. A likely reason for this is that the intact CNS is particularly challenging to access for investigation in patients and in most animal models, which has impeded research in this field. The zebrafish is emerging as a robust model system to investigate cells in vivo, and offer distinct advantages over other vertebrate models for investigating neurodegenerative diseases. Live imaging in vivo is a powerful technique to characterize the role of dynamic cells such as microglia during neurodegeneration, and zebrafish provide a convenient means for live imaging. Here, we discuss the zebrafish as a model for live imaging, provide a brief overview of available high resolution imaging platforms that accommodate zebrafish, and describe our own in vivo studies on the role of microglia during motor neuron degeneration. Live in vivo imaging is anticipated to provide invaluable advancements to defining the pathogenesis underlying neurodegenerative diseases, which may in turn allow for more specifically targeted therapeutics.