Glial Cells In Central Nervous System Research Articles

The role of microglia in the development of neurodegeneration.

Microglia-mediated central nervous system (CNS) inflammation is one of the key features of various neurodegenerative diseases, including Parkinson's and Alzheimer's diseases. In the last few years, a number of studies have investigated the link between neurodegenerative diseases and CNS glial cells, in particular microglia. Microglial cells are the main resident immune cells and comprise approximately 10-15% of all CNS cells. Microglia at rest regulates CNS homeostasis via phagocytic activity, by removing pathogens and cell detritus. "Resting" microglia cells transform into an activated form and produce inflammatory mediators, thus protecting neurons and providing defense against invading pathogens. Excessive inflammation leads to neuronal damage and neurodegenerative diseases. Various microglial reactions at different stages of the disease can open up new directions for treatment interventions and modification of the inflammatory activity. This review focuses on the potential role of microglia and the dynamic M1/M2 phenotype changes that are critically linked to certain neurodegenerative diseases.

Quantifying the Local Mechanical Properties of Cells in a Fibrous Three-Dimensional Microenvironment

Measurements of the mechanical response of biological cells are critical for understanding injury and disease, for developing diagnostic tools, and for computational models in mechanobiology. Although it is well known that cells are sensitive to the topography of their microenvironment, the current paradigm in mechanical testing of adherent cells is mostly limited to specimens grown on flat two-dimensional substrates. In this study, we introduce a technique in which cellular indentation via optical trapping is performed on cells at a high spatial resolution to obtain their regional mechanical properties while they exist in a more favorable three-dimensional microenvironment. We combine our approach with nonlinear contact mechanics theory to consider the effects of a large deformation. This allows us to probe length scales that are relevant for obtaining overall cell stiffness values. The experimental results herein provide the hyperelastic material properties at both high (∼100 s−1) and low (∼1–10 s−1) strain rates of murine central nervous system glial cells. The limitations due to possible misalignment of the indenter in the three-dimensional space are examined using a computational model.

Enteric Glia: S100, GFAP, and Beyond.

Since several years, the enteric nervous system (ENS) is getting more and more in the focus of gastrointestinal research. While the main interest was credited for years to the enteric neurons and their functional properties, less attention has been paid on the enteric glial cells (EGCs). Although the similarity of EGCs to central nervous system (CNS) astrocytes has been demonstrated a long time ago, EGCs were investigated in more detail only recently. Similar to the CNS, there is not "the" EGC, but also a broad range of diversity. Based on morphology and protein expression, such as glial fibrillary acidic protein (GFAP), S100, or Proteolipid-protein-1 (PLP1), several distinct glial types can be differentiated. Their heterogeneity in morphology, localization, and transcription as well as interaction with surrounding cells indicate versatile functional properties of these cells for gut function in health and disease. Although NG2 is found in a subset of CNS glial cells, it did not colocalize with the glial marker S100 or GFAP in the ENS. Instead, it in part colocalize with PDGFRα, as it does in the CNS, which do stain fibroblast-like cells in the gastrointestinal tract. Moreover, there seem to be species dependent differences. While GFAP is always found in the rodent ENS, this is completely different for the human gut. Only the compromised human ENS shows a significant amount of GFAP-positive glial cells. So, in general we can conclude that the EGC population is species specific and as complex as CNS glia. Anat Rec, 302:1333-1344, 2019. © 2019 Wiley Periodicals, Inc.

Emerging Role of Schwann Cells in Neuropathic Pain: Receptors, Glial Mediators and Myelination

Neuropathic pain caused by nerve injury or disease remains a major challenge for modern medicine worldwide. Most of the pathogenic mechanisms underlying neuropathic pain are centered on neuronal mechanisms. Accumulating evidence suggests that non-neuronal cells, especially glial cells, also play active roles in the initiation and resolution of pain. The preponderance of evidence has implicated central nervous system (CNS) glial cells, i.e., microglia and astrocytes, in the control of pain. The role of Schwann cells in neuropathic pain remains poorly understood. Schwann cells, which detect nerve injury and provide the first response, play a critical role in the development and maintenance of neuropathic pain. The cells respond to nerve injury by changing their phenotype, proliferating and interacting with nociceptive neurons by releasing glial mediators (growth factors, cytokines, chemokines, and biologically active small molecules). In addition, receptors expressed in active Schwann cells have the potential to regulate different pain conditions. In this review article, we will provide and discuss emerging evidence by integrating recent advances related to Schwann cells and neuropathic pain.

Immunity Against Bacterial Infection of the Central Nervous System: An Astrocyte Perspective.

Bacterial infection of the central nervous system (CNS) is a severe and life-threatening condition with high mortality, and it may lead to permanent neurological deficits in survivors. Increasing evidence indicates that astrocytes, as the most abundant CNS glial cell population, regulate innate and adaptive immune responses in the CNS under pathological conditions in addition to their role in the maintenance of CNS homeostasis and neuronal function. Following antigen recognition, astrocytes participate in the initiation of innate immune responses, and prompt an adaptive immune response to recruit peripheral immune cells. Investigations have been conducted to understand the immunological role of astrocytes in CNS disease and injury, however, their part in bacterial infections of the CNS has not been fully evaluated. A better understanding will permit the identification of successful therapeutic targets for an improved prognosis and disease outcome.

Neuroinflammation in the central nervous system: Symphony of glial cells.

Neuroinflammation in the central nervous system (CNS) is an important subject of neuroimmunological research. Emerging evidence suggests that neuroinflammation is a key player in various neurological disorders, including neurodegenerative diseases and CNS injury. Neuroinflammation is a complex and well-orchestrated process by various groups of glial cells in CNS and peripheral immune cells. The cross-talks between various groups of glial cells in CNS neuroinflammation is an extremely complex and dynamic process which resembles a well-orchestrated symphony. However, the understanding of how glial cells interact with each other to shape the distinctive immune responses of the CNS remains limited. In this review, we will discuss the joint actions of glial cells in three phases of neuroinflammation, including initiation, progression, and prognosis, the three movements of the symphony, as the role of each type of glial cells in neuroinflammation depends on the nature of inflammatory cues and specific course of diseases. This perspective of glial cells in neuroinflammation might provide helpful clues to the development of the early diagnosis and therapeutic intervention of the various CNS diseases.

Physiological and Pathophysiological Roles of Transient Receptor Potential Channels in Microglia-Related CNS Inflammatory Diseases.

Central nervous system (CNS) inflammation is a potential therapeutic target for neurodegenerative diseases. In recent years, a number of studies have focused on the links between neurodegenerative diseases and CNS glial cells, especially microglia. Microglia are the main resident immune cells in the CNS and represent approximately 10-15% of all CNS cells. Microglia play an important role in maintaining brain homeostasis at rest by surveying the environment, and engulfing apoptotic cells and debris in the healthy brain. However, under certain pathological conditions, microglia can generate neurotoxic factors, such as pro-inflammatory cytokines and molecules like nitric oxide (NO), which lead to CNS inflammatory diseases. In this review, we discuss the evidence that regulation of microglial ion channels may modulate CNS inflammation and subsequent tissue damage in neurological disorders. In particular, we discuss the role of transient receptor potential (TRP) channels in microglia in both acute and chronic inflammatory conditions, and describe the physiological and pathophysiological roles of TRP channels in CNS inflammatory pathways. Additionally, we describe the benefits of stimulation/inhibition of TRP channels in animal models of microglia-related CNS inflammatory diseases.

Understanding Progressive Multifocal Leukoencephalopathy Risk in Multiple Sclerosis Patients Treated with Immunomodulatory Therapies: A Bird's Eye View.

The increased use of newer potent immunomodulatory therapies for multiple sclerosis (MS), including natalizumab, fingolimod, and dimethyl fumarate, has expanded the patient population at risk for developing progressive multifocal leukoencephalopathy (PML). These MS therapies shift the profile of lymphocytes within the central nervous system (CNS) leading to increased anti-inflammatory subsets and decreased immunosurveillance. Similar to MS, PML is a demyelinating disease of the CNS, but it is caused by the JC virus. The manifestation of PML requires the presence of an active, genetically rearranged form of the JC virus within CNS glial cells, coupled with the loss of appropriate JC virus-specific immune responses. The reliability of metrics used to predict risk for PML could be improved if all three components, i.e., viral genetic strain, localization, and host immune function, were taken into account. Advances in our understanding of the critical lymphocyte subpopulation changes induced by these MS therapies and ability to detect viral mutation and reactivation will facilitate efforts to develop these metrics.

MeCP2 in central nervous system glial cells: current updates

avMethyl‑CpG binding protein 2 (MeCP2) is an epigenetic regulator, which preferentially binds to methylated CpG dinucleotides in DNA. MeCP2 mutations have been linked to Rett syndrome, a neurodevelopmental disorder characterized by severe intellectual disability in females. Earlier studies indicated that loss of MeCP2 function in neuronal cells was the sole cause of Rett syndrome. Subsequent studies have linked MeCP2 expression in CNS glial cells to Rett syndrome pathogenesis. In this review, we have discussed the role of MeCP2 in glial subtypes, astrocytes, oligodendrocytes and microglia, and how loss of MeCP2 function in these cells has a profound influence on both glial and neuronal function.

Roles of Glial Cells in Sculpting Inhibitory Synapses and Neural Circuits.

Glial cells are essential for every aspect of normal neuronal development, synapse formation, and function in the central nervous system (CNS). Astrocytes secrete a variety of factors that regulate synaptic connectivity and circuit formation. Microglia also modulate synapse development through phagocytic activity. Most of the known actions of CNS glial cells are limited to roles at excitatory synapses. Nevertheless, studies have indicated that both astrocytes and microglia shape inhibitory synaptic connections through various mechanisms, including release of regulatory molecules, direct contact with synaptic terminals, and utilization of mediators in the extracellular matrix. This review summarizes recent investigations into the mechanisms underlying CNS glial cell-mediated inhibitory synapse development.

Expression and Differential Responsiveness of Central Nervous System Glial Cell Populations to the Acute Phase Protein Serum Amyloid A

Acute-phase response is a systemic reaction to environmental/inflammatory insults and involves hepatic production of acute-phase proteins, including serum amyloid A (SAA). Extrahepatically, SAA immunoreactivity is found in axonal myelin sheaths of cortex in Alzheimer’s disease and multiple sclerosis (MS), although its cellular origin is unclear. We examined the responses of cultured rat cortical astrocytes, microglia and oligodendrocyte precursor cells (OPCs) to master pro-inflammatory cytokine tumour necrosis factor (TNF)-α and lipopolysaccaride (LPS). TNF-α time-dependently increased Saa1 (but not Saa3) mRNA expression in purified microglia, enriched astrocytes, and OPCs (as did LPS for microglia and astrocytes). Astrocytes depleted of microglia were markedly less responsive to TNF-α and LPS, even after re-addition of microglia. Microglia and enriched astrocytes showed complementary Saa1 expression profiles following TNF-α or LPS challenge, being higher in microglia with TNF-α and higher in astrocytes with LPS. Recombinant human apo-SAA stimulated production of both inflammatory mediators and its own mRNA in microglia and enriched, but not microglia-depleted astrocytes. Co-ultramicronized palmitoylethanolamide/luteolin, an established anti-inflammatory/ neuroprotective agent, reduced Saa1 expression in OPCs subjected to TNF-α treatment. These last data, together with past findings suggest that co-ultramicronized palmitoylethanolamide/luteolin may be a novel approach in the treatment of inflammatory demyelinating disorders like MS.

Static Magnetic Field Stimulation Enhances Oligodendrocyte Differentiation and Secretion of Neurotrophic Factors

The cellular-level effects of low/high frequency oscillating magnetic field on excitable cells such as neurons are well established. In contrast, the effects of a homogeneous, static magnetic field (SMF) on Central Nervous System (CNS) glial cells are less investigated. Here, we have developed an in vitro SMF stimulation set-up to investigate the genomic effects of SMF exposure on oligodendrocyte differentiation and neurotrophic factors secretion. Human oligodendrocytes precursor cells (OPCs) were stimulated with moderate intensity SMF (0.3 T) for a period of two weeks (two hours/day). The differential gene expression of cell activity marker (c-fos), early OPC (Olig1, Olig2. Sox10), and mature oligodendrocyte markers (CNP, MBP) were quantified. The enhanced myelination capacity of the SMF stimulated oligodendrocytes was validated in a dorsal root ganglion microfluidics chamber platform. Additionally, the effects of SMF on the gene expression and secretion of neurotrophic factors- BDNF and NT3 was quantified. We also report that SMF stimulation increases the intracellular calcium influx in OPCs as well as the gene expression of L-type channel subunits-CaV1.2 and CaV1.3. Our findings emphasize the ability of glial cells such as OPCs to positively respond to moderate intensity SMF stimulation by exhibiting enhanced differentiation, functionality as well as neurotrophic factor release.

Unexpected central role of the androgen receptor in the spontaneous regeneration of myelin.

Lost myelin can be replaced after injury or during demyelinating diseases in a regenerative process called remyelination. In the central nervous system (CNS), the myelin sheaths, which protect axons and allow the fast propagation of electrical impulses, are produced by oligodendrocytes. The abundance and widespread distribution of oligodendrocyte progenitors (OPs) within the adult CNS account for this remarkable regenerative potential. Here, we report a key role for the male gonad, testosterone, and androgen receptor (AR) in CNS remyelination. After lysolecithin-induced demyelination of the male mouse ventral spinal cord white matter, the recruitment of glial fibrillary acidic protein-expressing astrocytes was compromised in the absence of testes and testosterone signaling via AR. Concomitantly, the differentiation of OPs into oligodendrocytes forming myelin basic protein (MBP)+ and proteolipid protein-positive myelin was impaired. Instead, in the absence of astrocytes, axons were remyelinated by protein zero (P0)+ and peripheral myelin protein 22-kDa (PMP22)+ myelin, normally only produced by Schwann cells in the peripheral nervous system. Thus, testosterone favors astrocyte recruitment and spontaneous oligodendrocyte-mediated remyelination. This finding may have important implications for demyelinating diseases, psychiatric disorders, and cognitive aging. The testosterone dependency of CNS oligodendrocyte remyelination may have roots in the evolutionary history of the AR, because the receptor has evolved from an ancestral 3-ketosteroid receptor through gene duplication at the time when myelin appeared in jawed vertebrates.

CXCR3 signaling in glial cells ameliorates experimental autoimmune encephalomyelitis by restraining the generation of a pro-Th17 cytokine milieu and reducing CNS-infiltrating Th17 cells.

BackgroundExperimental autoimmune encephalomyelitis (EAE) is a mouse model of multiple sclerosis (MS). It has been shown that Th17 cells are critical for EAE pathogenesis. Mice lacking CXCR3 develop aggravated EAE compared with wild-type (WT) mice. This study investigated the effect of CXCR3 on Th17 expansion during EAE and further addressed the underlying mechanism.MethodsBoth active EAE and adoptive-transfer EAE experiments were employed for studying EAE pathogenesis in WT and CXCR3−/− mice. Demyelination and leukocyte infiltration in the spinal cord of mice were analyzed by luxol fast blue staining and flow cytometry analysis, respectively. Glial cells expressing CXCR3 in the spinal cord were analyzed by immunofluorescence staining. Cytokine and chemokine levels in the spinal cord were analyzed using quantitative real-time PCR and enzyme-linked immunosorbent assay (ELISA). The glial cell line U87MG was employed for studying the CXCR3 signaling-mediated mechanism regulating Th17 expansion.ResultsCXCR3−/− mice exhibited more severe EAE and had significantly increased central nervous system (CNS)-infiltrating Th17 cells compared with WT mice. Adoptive-transfer experiments showed that CXCR3−/− recipient mice that received Th17 cells polarized from splenocytes of myelin oligodendrocyte glycoprotein (MOG)-immunized CXCR3−/− mice or MOG-immunized WT mice always developed more severe EAE and had significantly increased CNS-infiltrating Th17 cells compared with WT recipient mice that received Th17 cells from the same origin. Furthermore, during EAE, the number of activated glial cells was increased in the CNS of MOG-immunized CXCR3−/− mice, and CXCR3-deficient glial cells expressed increased levels of cytokine genes required for Th17 expansion and recruitment. Finally, we found that extracellular signal-regulated kinase (ERK) activation elicited by CXCR3 signaling in U87MG cells attenuated the activation of NF-κB, a key transcription factor critical for the induction of IL-23 and CCL20, which are required for Th17 cell expansion and recruitment, respectively.ConclusionsThis study demonstrates a previously unrecognized role of CXCR3 signaling in glial cells in negatively regulating Th17 cell expansion during EAE. Our results demonstrate that, in addition to its well-known role in the recruitment of immune cells, CXCR3 in CNS glial cells plays a critical role in restraining the pro-Th17 cytokine/chemokine milieu during EAE, thereby diminishing Th17 cell expansion in the CNS and suppressing disease development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0536-4) contains supplementary material, which is available to authorized users.

AstroGenesis: And there was leptin on the sixthday.

In the central nervous system (CNS), the hypothalamus plays a fundamental role in controlling food intake and energy expenditure as well as glucose homeostasis. Alterations in this control can lead to obesity, glucose intolerance and type 2 diabetes in both rodents and humans [1]. The past two decades have witnessed major advances in our understanding of the control of energy balance by hypothalamic neuronal populations. These neurons respond to peripherally-derived metabolic signals to elicit adaptive behavioral and physiological responses in order to maintain body weight. Leptin, the most notorious adipose-derived hormone, targets neurons of the hypothalamus, notably orexigenic agouti-related protein (AgRP) and anorexigenic proopiomelanocortin (POMC) neurons of the arcuate nucleus (ARC), to decrease feeding and increase energy expenditure. Leptin binding to its receptor (LepR) in ARC neurons regulates neuronal activity and synaptic plasticity by activating signaling pathways that include phosphonositide 3-kinase (PI3K), extracellular signal-regulated kinases (ERK), AMP-activated protein kinase and signal transducer and activator of transcription 3 (STAT3) [1]. Leptin deficiency or loss-offunction mutations in the LepR lead to hyperphagia and obesity in both rodents and humans illustrating the critical role of leptin signaling in central control of energy homeostasis. In addition to the wellestablished actions of leptin on metabolic neurocircuits, nonneuronal cells of the hypothalamus have recently emerged as new targets and mediators of leptin effects on energy balance [2,3]. In this issue of Molecular Metabolism, Rottkamp et al. add a brand new element to the leptin signaling puzzle with demonstration that leptin enhances astrocytes proliferation in the hypothalamus during postnatal development [4]. During CNS development, neurons and glial cells are sequentially generated. Neurogenesis occurs during prenatal brain development and most neurons of the adult brain are already produced at birth. In contrast, glial cells are generated after the end of the first postnatal week and account for more than half of brain cells in adults. Astrocytes, the most abundant glial cells in the brain, provide anatomical and metabolic support for neurons. In addition, they regulate several neuronal processes including proliferation, differentiation and synaptogenesis. Recent evidence suggests that hypothalamic astrocytes

SnapShot: Astrocytes in Health and Disease

Astrocytes are central nervous system (CNS) glial cells with many important functions for normal development and neural functioning. They help control extracellular ion and neurotransmitter concentrations; provide neurotrophic support; are implicated in synapse formation, function, and pruning; and help maintain the blood-brain barrier. Following injury and in disease, they undergo rapid and chronic alterations in function that can either promote or hinder recovery, depending on the disease.

Glial cells of the central nervous system of Bothrops jararaca (Reptilia, Ofidae): an ultrastructural study

Abstract Although ultrastructural characteristics of mature neuroglia in the central nervous system (CNS) are very well described in mammals, much less is known in reptiles, especially serpents. In this context, two specimens of Bothrops jararaca were euthanized for morphological analysis of CNS glial cells. Samples from telencephalon, mesencephalon and spinal cord were collected and processed for light and transmission electron microscopy investigation. Astrocytes, oligodendrocytes, microglial cells and ependymal cells, as well as myelin sheaths, presented similar ultrastructural features to those already observed in mammals and tended to maintain their general aspect all over the distinct CNS regions observed. Morphological similarities between reptilian and mammalian glia are probably linked to their evolutionary conservation throughout vertebrate phylogeny.

Glia Inhibitor Blocks Ventilatory Acclimatization to Chronic Sustained Hypoxia

Neuroglial communication in the central nervous system (CNS) is proving to be an important component of neuronal signaling both in normal conditions as well as stressed or injured states. We investigated the role of CNS glial cells in neural control of ventilation during chronic hypoxia. To assess this, rats received daily administration of either minocycline, a selective microglia inhibitor, (45mg/kg) or saline (i.p.) beginning one day before and during 7 days of exposure to hypoxia (PO2 = 80 Torr). Normoxic controls, which received daily injections of either minocycline (45mg/kg) or saline, were not exposed to hypoxic conditions. Ventilation was recorded using barometric pressure plethysmography in unrestrained rats both before and after exposure to hypoxia. Daily administration of minocycline significantly (p < 0.01) decreased ventilation in normoxia and the hypoxic ventilatory response but not the hypercapnic ventilatory response, following exposure to chronic hypoxic conditions. Breathing frequency and ventilation were significantly lower in chronically hypoxic rats treated with minocycline compared to saline. Minocycline did not have an effect in normoxic conditions. Activation of microglia and astrocytes is being quantified in the NTS using immunohistochemistry. These results suggest a role for glial signaling in the physiological acclimatization during hypoxia.Supported by NIH RO1 HL‐081823

Reprogramming of HUVECs into induced pluripotent stem cells (HiPSCs), generation and characterization of HiPSC-derived neurons and astrocytes.

Neurodegenerative diseases are characterized by chronic and progressive structural or functional loss of neurons. Limitations related to the animal models of these human diseases have impeded the development of effective drugs. This emphasizes the need to establish disease models using human-derived cells. The discovery of induced pluripotent stem cell (iPSC) technology has provided novel opportunities in disease modeling, drug development, screening, and the potential for “patient-matched” cellular therapies in neurodegenerative diseases. In this study, with the objective of establishing reliable tools to study neurodegenerative diseases, we reprogrammed human umbilical vein endothelial cells (HUVECs) into iPSCs (HiPSCs). Using a novel and direct approach, HiPSCs were differentiated into cells of central nervous system (CNS) lineage, including neuronal, astrocyte and glial cells, with high efficiency. HiPSCs expressed embryonic genes such as nanog, sox2 and Oct-3/4, and formed embryoid bodies that expressed markers of the 3 germ layers. Expression of endothelial-specific genes was not detected in HiPSCs at RNA or protein levels. HiPSC-derived neurons possess similar morphology but significantly longer neurites compared to primary human fetal neurons. These stem cell-derived neurons are susceptible to inflammatory cell-mediated neuronal injury. HiPSC-derived neurons express various amino acids that are important for normal function in the CNS. They have functional receptors for a variety of neurotransmitters such as glutamate and acetylcholine. HiPSC-derived astrocytes respond to ATP and acetylcholine by elevating cytosolic Ca2+ concentrations. In summary, this study presents a novel technique to generate differentiated and functional HiPSC-derived neurons and astrocytes. These cells are appropriate tools for studying the development of the nervous system, the pathophysiology of various neurodegenerative diseases and the development of potential drugs for their treatments.

Leukodystrophy or genetic leukoencephalopathy? Nature does not make leaps.

The importance of classification was first recognized by Aristotle of caused by mutations in the ABCD1 gene that is variably expressed in Stagira, the great Greek philosopher who proposed rigorous classifications in literally every area of human knowledge. Classifications are indispensable for language and convenient for our ordinary mental operations [1], but—as Aristotle also suggested—every classification presents pitfalls and limitations. Nature does not make leaps (natura non facit saltus), and it does not conform to rigorous divisions. Pragmatically speaking, however, one classification may be, if not more correct, at least more useful than another one. In this issue of Molecular Genetics and Metabolism, Vanderver et al. [2] first address an important and controversial topic in neurology, i.e., the definition of the term “leukodystrophy,” and make a conceptual distinction between “leukodystrophies” and “genetic leukoencephalopathies.” Subsequently, they propose a classification of all the inherited white matter (WM) diseases under one of these two groups. This esoteric work—as defined by the authors—was largely performed for epidemiological purposes, including the assessment of the frequency and burden of these diseases as a group, but it also led to a very comprehensive list of inherited disorders characterized by brain WM involvement. What is a “leukodystrophy”? It is true that this question has been rarely discussed in a scholarly way and an approved definition did not exist [2], but this is probably because the answer was assumed to be self-evident. The term “leukodystrophy,” introduced by Bielschowski and Henneberg in 1928 [3], is in its essence a neuropathological term, which reflects the presence of abnormalities in central nervous system (CNS) glial cell types as the primary or fundamental pathological abnormality. Therefore, we should use the term “leukodystrophy” only when the pathology of the disease is (well-)known, and we could admit that subjects with late onset Alexander Disease (AxD), SPG2, or adrenomyeloneuropathy (AMN) meet the criterion for being classified as having a “leukodystrophy.” The pathology of late onset AxD shows the abundant presence of Rosenthal fibers, i.e., the astrocytic inclusions containing a mixture of glial fibrillary acidic protein, ubiquitin and heat shock proteins, which are the key diagnostic feature of the neuropathology in AxD [4]. The pathology of SPG2, which is caused by mutations in the PLP1 gene encoding for the predominant CNS myelin protein, shows diffuse hypomyelination/dysmyelination with some WM tracts preferentially affected [5]. The pathology in AMN, which is