What makes up neuroglia

NG2-expressing glial precursor cells are a new potential oligodendroglioma cell initiating population in N-ethyl-N-nitrosourea-induced gliomagenesis. Linking oligodendrocyte and myelin dysfunction to neurocircuitry abnormalities in schizophrenia. Prog Neurobiol. Mitochondria, oligodendrocytes and inflammation in bipolar disorder: evidence from transcriptome studies points to intriguing parallels with multiple sclerosis. Neurobiol Dis. Association between Alzheimer's disease pathogenesis and early demyelination and oligodendrocyte dysfunction.

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I Accept Show Purposes. Your central nervous system CNS is made up of your brain and the nerves of your spinal column. Astrocytes The most common type of glial cell in the central nervous system is the astrocyte, which is also called astroglia.

These include: Forming the blood-brain barrier BBB : The BBB is like a strict security system, only letting in substances that are supposed to be in your brain while keeping out things that could be harmful. This filtering system is essential for keeping your brain healthy. Regulating neurotransmitters : Neurons communicate via chemical messengers called neurotransmitters. This reuptake process is the target of numerous medications, including anti-depressants.

Cleaning up : Astrocytes also clean up what's left behind when a neuron dies, as well as excess potassium ions, which are chemicals that play an important role in nerve function. An active region gets more than an inactive one. Synchronizing the activity of axons : Axons are long, thread-like parts of neurons and nerve cells that conduct electricity to send messages from one cell to another.

Brain energy metabolism and homeostasis : Astrocytes regulate metabolism in the brain by storing glucose from the blood and provide this as fuel for neurons.

This is one of their most important roles. Astrocyte dysfunction has been potentially linked to numerous neurodegenerative diseases, including: Amyotrophic lateral sclerosis ALS or Lou Gehrig's disease Huntington's chorea Parkinson's disease. Oligodendrocytes Oligodendrocytes come from neural stem cells. Microglia As their name suggests, microglia are tiny glial cells.

Along with Alzheimer's, illnesses that may be linked to microglial dysfunction include: Fibromyalgia Chronic neuropathic pain Autism spectrum disorders Schizophrenia Microglia are believed to have many jobs beyond that, including roles in learning-associated plasticity and guiding the development of the brain, in which they have an important housekeeping function. Ependymal Cells Ependymal cells are primarily known for making up a membrane called the ependyma, which is a thin membrane lining the central canal of the spinal cord and the ventricles passageways of the brain.

Radial Glia Radial glia are believed to be a type of stem cell , meaning that they create other cells. Schwann Cells Schwann cells are named for physiologist Theodor Schwann, who discovered them. Diseases involving Schwann cells include: Guillain-Barre' syndrome Charcot-Marie-Tooth disease Schwannomatosis Chronic inflammatory demyelinating polyneuropathy Leprosy We've had some promising research on transplanting Schwann cells for spinal cord injury and other types of peripheral nerve damage.

Satellite Cells Satellite cells get their name from the way they surround certain neurons, with several satellites forming a sheath around the cellular surface. They're also believed to help transport several neurotransmitters and other substances, including: Glutamate GABA Norepinephrine Adenosine triphosphate Substance P Capsaicin Acetylcholine Satellite cells are linked to chronic pain involving peripheral tissue injury, nerve damage, and a systemic heightening of pain hyperalgesia that can result from chemotherapy.

In a similar way, there are also no studies where mature and myelinating oligodendrocytes have been specifically depleted from the adult brain under pathological conditions. Probably these experiments are also very unlikely to be performed in the future, as oligodendrocytes were not shown to react to different kinds of injury besides providing new myelin during tissue repair, but remain rather stable.

Furthermore, the death of oligodendrocytes induces global demyelination as well as axonal defects already under healthy conditions Vanderluit et al. Summarizing this section, nothing has been published regarding ablation studies of oligodendrocyte lineage cells under pathological conditions. However, as especially for NG2-glia the already established methods have proven to be effective, very promising studies during pathological conditions will likely be investigated in the future.

This review summarizes the tremendous work of the last decades on the various ablation approaches in all types of glial cells in the adult brain see also Tables 1 — 4. Although these methods especially under healthy conditions seem quite similar at first sight, the nature of the cells requires different methodologies. Using the DTA or DTR-system under a cell type specific promoter is a commonly shared and frequently used approach between all glial cell populations.

This method has the advantage that it does not require specific features like the expression of a uniquely expressed surface receptor that can be targeted by a drug or being a uniquely mitotically active cell population, but can be applied to all cell types in a similar fashion when used with a specific promoter. The side effects of this method also seem to be rather low and the efficiency quite high, wherefore this method is a very good candidate to be used for future ablation studies of any cell type.

The use of cell specific pharmacological drugs is still an applicable and successful method to ablate cells, but has been so far only exploited for microglia Elmore et al. However, although these drugs are supposed to have a very high specificity for a cell type or a surface receptor, there might still be some receptor expression in other cell types, resulting in controversial outcomes of different studies like for instance in the case of the L-AAA-induced astrocyte ablation Saffran and Crutcher, ; Khurgel et al.

The same becomes true for microglia: although there are no controversial reports about the application of PLX to induce myeloid cell death, it is already known that the drug might cross-react with some other receptor-kinases like, e.

For NG2-glia there are until now no cell specific drugs available, probably due to the lack of a unique promising target receptor on those cells. In general, the use of cell specific pharmacological drugs still represents an easy and effective way for cell specific ablation studies that does in addition not require the use of expensive transgenic mouse lines.

However, the risk of also targeting other cell populations and hence inducing potential secondary effects is still high and the experiments should — as always — be interpreted with caution. Another very commonly used but also very cell specific approach is the application of X-irradiation to a specific region of interest.

But this method can mainly be used for the ablation of NG2-glia, as they carry the unique feature of being the only proliferative cells outside the neurogenic niches, while microglia and astrocytes generally survive this treatment as they do not cycle under physiological conditions Xu et al.

In this region, the proportion of slowly cycling NG2-glia was shown to be high in humans Geha et al. However, it has also proven that X-irradiation is not very efficient to ablate NG2-glia, as this method mainly targets actively cycling cells, but NG2-glia were shown to be a very slowly cycling cell population and to have a very long cell cycle due to an extended G1-resting phase Simon et al.

This unique property is also the reason why infusion of the mitotic blocker AraC specifically ablates NG2-glia Robins et al.

This variation could most likely first be explained by the use of different promoters like MBP or MOG that are driving the suicide gene expression. Even when using the same promoter, variations in the recombination rate and hence the ablation efficiency can occur, as the cloning strategy of the transgenic animals and the induction protocols can highly influence the recombination rate.

The application of the systemic prodrug that can either be given by injections or in the chow would increase the variability between the different studies, as one application form might be more efficient than another.

All these arguments do also apply when comparing the area specificity of the ablation approaches that also showed a high variability especially for astrocytes. After injury, the ablation approaches between at least microglia and astrocytes as so far no studies have been performed for cells of the oligodendrocyte lineage , are mainly using the TK as a mediator for apoptosis. Again, these studies proved to be quite efficient, both in terms of ablation efficiency and functional readout; might however be accompanied by some disadvantages.

TK-mediated cell ablation mainly targets proliferating cells, but not those that are quiescent Bush et al. Hence, the analysis of the function of another subpopulation of quiescent astrocytes would require another ablation method. For microglia this bias does not seem to be so pronounced, as a higher proportion of microglia is able to proliferate after a pathological insult Amat et al.

Brain research generally has the tendency to look at different cell types in a very isolated way, as many of these ablation studies also did, both in the healthy and the pathological brain. In those studies that also determined the consequences of the ablation in other cell types, only the cell numbers were quantified but not their function.

However, it is nowadays well accepted that a panglial network exists that is highly connected with each other via connexins May et al. It is, e. The ablation of one cell type in the brain could also elicit a reaction in other cell types even when only on the signaling level. Unpublished data from our lab also indicate a cellular communication between the different glial cell types under pathological conditions: when genetically ablating NG2-glia after cortical stab wound injury, the cellular reactions of both astrocytes and microglia was hampered Schneider and Dimou, unpublished observations , similar to what has already been observed in the spinal cord after a diminished NG2-glia reactivity Rodriguez et al.

Taking these new findings into account, the overall sum of glial ablation studies can already provide insights in the cellular characteristics of these cells and help to better understand their function in both the healthy as well as the pathological brain. However, looking to the future, they could be further exploited to investigate the almost unknown terrain of glial cell interactions in vivo.

SJ structured and wrote the manuscript. LD gave structural and contextual input and corrected the manuscript. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Akiyama, H. Brain microglia constitutively express beta-2 integrins. Amat, J. Phenotypic diversity and kinetics of proliferating microglia and astrocytes following cortical stab wounds.

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Djogo, T. Adult NG2-glia are required for median eminence-mediated leptin sensing and body weight control. Cell Metab. Doetsch, F. Regeneration of a germinal layer in the adult mammalian brain.

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Heppner, F. Experimental autoimmune encephalomyelitis repressed by microglial paralysis. The Schwann cells are underlain by the medullary sheath. The medullary sheath is interrupted at intervals by the nodes of Ranvier. Illustration of the Schwann Cells and the Myelin Sheath : Transmission electron micrograph of a myelinated axon.

The myelin layer concentric surrounds the axon of a neuron, showing Schwann cells. The nervous system consists of nervous tissue, which is composed of two principal types of cells called neuron and neuroglia. Nervous tissue, one of the four main tissue types, is composed of neurons and supporting cells called neuroglia.

There are six types of neuroglia—four in the central nervous system and two in the PNS. These glial cells are involved in many specialized functions apart from support of the neurons.

Neuroglia in the CNS include astrocytes, microglial cells, ependymal cells and oligodendrocytes. In the PNS, satellite cells and Schwann cells are the two kinds of neuroglia.

Astrocytes are shaped like a star and are the most abundant glial cell in the CNS. They have many radiating processes which help in clinging to the neurons and capillaries. They support and brace the neurons and anchor them to the nutrient supply lines.

They also help in the guiding the migration of young neurons. Astrocytes control the chemical environment around the neurons. Microglial cells are small and ovoid un shape with thorny processes. They are found in the CNS. When invading microorganism or dead neurons are present, the microglial cells can transform into a phagocytic macrophage and help in cleaning the neuronal debris. Ependymal cells are ciliated and line the central cavities of the brain and spinal cord where they form a fairly permeable barrier between the cerebrospinal fluid that fills these cavities and the tissue cells of the CNS.

It contains a brain, ventral nerve cord, and ganglia clusters of connected neurons. These ganglia can control movements and behaviors without input from the brain. Octopi may have the most complicated of invertebrate nervous systems—they have neurons that are organized in specialized lobes and eyes that are structurally similar to vertebrate species. Compared to invertebrates, vertebrate nervous systems are more complex, centralized, and specialized. While there is great diversity among different vertebrate nervous systems, they all share a basic structure: a CNS that contains a brain and spinal cord and a PNS made up of peripheral sensory and motor nerves.

One interesting difference between the nervous systems of invertebrates and vertebrates is that the nerve cords of many invertebrates are located ventrally whereas the vertebrate spinal cords are located dorsally.

The nervous system is made up of neurons , specialized cells that can receive and transmit chemical or electrical signals, and glia , cells that provide support functions for the neurons by playing an information processing role that is complementary to neurons. A neuron can be compared to an electrical wire—it transmits a signal from one place to another. Glia can be compared to the workers at the electric company who make sure wires go to the right places, maintain the wires, and take down wires that are broken.

Although glia have been compared to workers, recent evidence suggests that also usurp some of the signaling functions of neurons. There is great diversity in the types of neurons and glia that are present in different parts of the nervous system. There are four major types of neurons, and they share several important cellular components. The nervous system of the common laboratory fly, Drosophila melanogaster , contains around , neurons, the same number as a lobster.

This number compares to 75 million in the mouse and million in the octopus. A human brain contains around 86 billion neurons. Despite these very different numbers, the nervous systems of these animals control many of the same behaviors—from basic reflexes to more complicated behaviors like finding food and courting mates.

The ability of neurons to communicate with each other as well as with other types of cells underlies all of these behaviors. Most neurons share the same cellular components.

But neurons are also highly specialized—different types of neurons have different sizes and shapes that relate to their functional roles. Like other cells, each neuron has a cell body or soma that contains a nucleus, smooth and rough endoplasmic reticulum, Golgi apparatus, mitochondria, and other cellular components.

Neurons also contain unique structures, illustrated in Figure Dendrites are tree-like structures that extend away from the cell body to receive messages from other neurons at specialized junctions called synapses. Although some neurons do not have any dendrites, some types of neurons have multiple dendrites. Dendrites can have small protrusions called dendritic spines, which further increase surface area for possible synaptic connections.

Once a signal is received by the dendrite, it then travels passively to the cell body. The cell body contains a specialized structure, the axon hillock that integrates signals from multiple synapses and serves as a junction between the cell body and an axon.

An axon is a tube-like structure that propagates the integrated signal to specialized endings called axon terminals. These terminals in turn synapse on other neurons, muscle, or target organs. Chemicals released at axon terminals allow signals to be communicated to these other cells.

Neurons usually have one or two axons, but some neurons, like amacrine cells in the retina, do not contain any axons.