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BioRxiv : the Preprint Server For... May 2024Precise regulation of protein phosphorylation is critical for many cellular processes, and dysfunction in this process has been linked to various neurological disorders...
Precise regulation of protein phosphorylation is critical for many cellular processes, and dysfunction in this process has been linked to various neurological disorders and diseases. Protein phosphatase 1 (PP1) is a ubiquitously expressed serine/threonine phosphatase with three major isoforms, (α, β, γ) and hundreds of known substrates. Previously, we reported that PP1α and PP1γ are essential for the known role of PP1 in synaptic physiology and learning/memory, while PP1β displayed a surprising opposing function. mutations in PP1β cause neurodevelopmental disorders in humans, but the mechanisms involved are currently unknown. A Cre-Lox system was used to delete PP1β specifically in neurons in order to study its effects on developing mice. These animals fail to survive to 3 postnatal weeks, and exhibit deficits in cortical myelination and glutamate release. There was defective compound action potential (CAP) propagation in the optic nerve of the null mice, which was traced to a deficit in the formation of nodes of Ranvier. Finally, it was found that phosphorylation of the PP1β-specific substrate, myosin light chain 2 (MLC2), is significantly enhanced in PP1β null optic nerves. Several novel important roles of PP1β in neurons were discovered, and these data will aid future investigations in delineating the mechanisms by which mutations in PP1β lead to intellectual and developmental delays in patients.
PubMed: 38766050
DOI: 10.1101/2024.05.10.593531 -
Neuroscience Research Mar 2024Neural activity can increase the length of nodes of Ranvier (NOR) and slow impulse transmission; however, little is known about the biologically and clinically important...
Neural activity can increase the length of nodes of Ranvier (NOR) and slow impulse transmission; however, little is known about the biologically and clinically important recovery process. Sensory deprivation promotes neural plasticity in many phenomena, raising the question of whether recovery of NOR morphology is influenced by sensory deprivation. The results show that NOR gap length recovery in mouse optic nerve was not affected significantly by binocular visual deprivation imposed by maintaining mice in 24 hr dark for 30 days compared to mice recovering under normal visual experience. The findings provide insight into the cellular mechanism of NOR plasticity.
PubMed: 38554941
DOI: 10.1016/j.neures.2024.03.005 -
Brain Sciences Nov 2023Diffuse axonal injury (DAI) is a significant feature of traumatic brain injury (TBI) across all injury severities and is driven by the primary mechanical insult and... (Review)
Review
Diffuse axonal injury (DAI) is a significant feature of traumatic brain injury (TBI) across all injury severities and is driven by the primary mechanical insult and secondary biochemical injury phases. Axons comprise an outer cell membrane, the axolemma which is anchored to the cytoskeletal network with spectrin tetramers and actin rings. Neurofilaments act as space-filling structural polymers that surround the central core of microtubules, which facilitate axonal transport. TBI has differential effects on these cytoskeletal components, with axons in the same white matter tract showing a range of different cytoskeletal and axolemma alterations with different patterns of temporal evolution. These require different antibodies for detection in post-mortem tissue. Here, a comprehensive discussion of the evolution of axonal injury within different cytoskeletal elements is provided, alongside the most appropriate methods of detection and their temporal profiles. Accumulation of amyloid precursor protein (APP) as a result of disruption of axonal transport due to microtubule failure remains the most sensitive marker of axonal injury, both acutely and chronically. However, a subset of injured axons demonstrate different pathology, which cannot be detected via APP immunoreactivity, including degradation of spectrin and alterations in neurofilaments. Furthermore, recent work has highlighted the node of Ranvier and the axon initial segment as particularly vulnerable sites to axonal injury, with loss of sodium channels persisting beyond the acute phase post-injury in axons without APP pathology. Given the heterogenous response of axons to TBI, further characterization is required in the chronic phase to understand how axonal injury evolves temporally, which may help inform pharmacological interventions.
PubMed: 38002566
DOI: 10.3390/brainsci13111607 -
Neuroreport Dec 2023In acute inflammatory demyelinating polyneuropathy (AIDP), myelin vesiculation mediated by complement activation contributes to nerve injury. Macrophage infiltration of...
In acute inflammatory demyelinating polyneuropathy (AIDP), myelin vesiculation mediated by complement activation contributes to nerve injury. Macrophage infiltration of the spinal roots has been demonstrated in AIDP, but its pathological significance remains uncertain. The present study aimed to investigate the role of macrophages in the pathogenic sequence of AIDP. A rabbit model of AIDP was induced by immunization with galactocerebroside. Immunostaining was performed to localize the macrophages and myelin injury. The rabbit developed tetraparesis with electrophysiological and pathological features of peripheral nerve demyelination. Immunostaining demonstrated colocalization of IgG antibodies, complement deposition and myelin injury apart from macrophages. Immunostaining and electron microscopy showed myelin injury preceded macrophage infiltration. There was significant disruption of voltage-gated sodium channel clusters at the nodes of Ranvier in the spinal roots. Macrophages acted may as scavengers to remove myelin debris following complement activation-mediated demyelination in the AIDP rabbit. Lesions at the node of Ranvier contribute to conduction failure and muscle weakness.
Topics: Animals; Rabbits; Myelin Sheath; Guillain-Barre Syndrome; Macrophages; Peripheral Nervous System Diseases; Spinal Nerve Roots
PubMed: 37942737
DOI: 10.1097/WNR.0000000000001964 -
Frontiers in Neuroscience 2023
PubMed: 37937068
DOI: 10.3389/fnins.2023.1277251 -
Journal of Neuroinflammation Oct 2023Homozygous CD59-deficient patients manifest with recurrent peripheral neuropathy resembling Guillain-Barré syndrome (GBS), hemolytic anemia and recurrent strokes....
BACKGROUND
Homozygous CD59-deficient patients manifest with recurrent peripheral neuropathy resembling Guillain-Barré syndrome (GBS), hemolytic anemia and recurrent strokes. Variable mutations in CD59 leading to loss of function have been described and, overall, 17/18 of patients with any mutation presented with recurrent GBS. Here we determine the localization and possible role of membrane-bound complement regulators, including CD59, in the peripheral nervous systems (PNS) of mice and humans.
METHODS
We examined the localization of membrane-bound complement regulators in the peripheral nerves of healthy humans and a CD59-deficient patient, as well as in wild-type (WT) and CD59a-deficient mice. Cross sections of teased sciatic nerves and myelinating dorsal root ganglia (DRG) neuron/Schwann cell cultures were examined by confocal and electron microscopy.
RESULTS
We demonstrate that CD59a-deficient mice display normal peripheral nerve morphology but develop myelin abnormalities in older age. They normally express myelin protein zero (P0), ankyrin G (AnkG), Caspr, dystroglycan, and neurofascin. Immunolabeling of WT nerves using antibodies to CD59 and myelin basic protein (MBP), P0, and AnkG revealed that CD59 was localized along the internode but was absent from the nodes of Ranvier. CD59 was also detected in blood vessels within the nerve. Finally, we show that the nodes of Ranvier lack other complement-membrane regulatory proteins, including CD46, CD55, CD35, and CR1-related gene-y (Crry), rendering this area highly exposed to complement attack.
CONCLUSION
The Nodes of Ranvier lack CD59 and are hence not protected from complement terminal attack. The myelin unit in human PNS is protected by CD59 and CD55, but not by CD46 or CD35. This renders the nodes and myelin in the PNS vulnerable to complement attack and demyelination in autoinflammatory Guillain-Barré syndrome, as seen in CD59 deficiency.
Topics: Mice; Humans; Animals; Membrane Proteins; Ranvier's Nodes; Guillain-Barre Syndrome; Complement System Proteins; CD59 Antigens; CD55 Antigens
PubMed: 37875972
DOI: 10.1186/s12974-023-02920-9 -
Cell Reports Oct 2023The Contactin-associated protein 1 (Cntnap1) mouse mutants fail to establish proper axonal domains in myelinated axons. Human CNTNAP1 mutations are linked to...
The Contactin-associated protein 1 (Cntnap1) mouse mutants fail to establish proper axonal domains in myelinated axons. Human CNTNAP1 mutations are linked to hypomyelinating neuropathy-3, which causes severe neurological deficits. To understand the human neuropathology and to model human CNTNAP1 and CNTNAP1 mutations, we generated Cntnap1 and Cntnap1 mouse mutants, respectively. Both Cntnap1 mutants show weight loss, reduced nerve conduction, and progressive motor dysfunction. The paranodal ultrastructure shows everted myelin loops and the absence of axo-glial junctions. Biochemical analysis reveals that these Cntnap1 mutant proteins are nearly undetectable in the paranodes, have reduced surface expression and stability, and are retained in the neuronal soma. Postnatal transgenic expression of Cntnap1 in the mutant backgrounds rescues the phenotypes and restores the organization of axonal domains with improved motor function. This study uncovers the mechanistic impact of two human CNTNAP1 mutations in a mouse model and provides proof of concept for gene therapy for CNTNAP1 patients.
Topics: Humans; Mice; Animals; Myelin Sheath; Axons; Charcot-Marie-Tooth Disease; Neuroglia; Disease Models, Animal; Ranvier's Nodes; Cell Adhesion Molecules, Neuronal
PubMed: 37862170
DOI: 10.1016/j.celrep.2023.113274 -
Scientific Reports Sep 2023Major depressive disorder (MDD) and chronic unpredictable stress (CUS) in animals feature comparable cellular and molecular disturbances that involve neurons and glial...
Major depressive disorder (MDD) and chronic unpredictable stress (CUS) in animals feature comparable cellular and molecular disturbances that involve neurons and glial cells in gray and white matter (WM) in prefrontal brain areas. These same areas demonstrate disturbed connectivity with other brain regions in MDD and stress-related disorders. Functional connectivity ultimately depends on signal propagation along WM myelinated axons, and thus on the integrity of nodes of Ranvier (NRs) and their environment. Various glia-derived proteoglycans interact with NR axonal proteins to sustain NR function. It is unclear whether NR length and the content of associated proteoglycans is altered in prefrontal cortex (PFC) WM of human subjects with MDD and in experimentally stressed animals. The length of WM NRs in histological sections from the PFC of 10 controls and 10 MDD subjects, and from the PFC of control and CUS rats was measured. In addition, in WM of the same brain region, five proteoglycans, tenascin-R and NR protein neurofascin were immunostained or their levels measured with western blots. Analysis of covariance and t-tests were used for group comparisons. There was dramatic reduction of NR length in PFC WM in both MDD and CUS rats. Proteoglycan BRAL1 immunostaining was reduced at NRs and in overall WM of MDD subjects, as was versican in overall WM. Phosphacan immunostaining and levels were increased in both in MDD and CUS. Neurofascin immunostaining at NRs and in overall WM was significantly increased in MDD. Reduced length of NRs and increased phosphacan and neurocan in MDD and stressed animals suggest that morphological and proteoglycan changes at NRs in depression may be related to stress exposure and contribute to connectivity alterations. However, differences between MDD and CUS for some NR related markers may point to other mechanisms affecting the structure and function of NRs in MDD.
Topics: Humans; Rats; Animals; Depressive Disorder, Major; White Matter; Ranvier's Nodes; Receptor-Like Protein Tyrosine Phosphatases, Class 5; Prefrontal Cortex; Versicans
PubMed: 37775676
DOI: 10.1038/s41598-023-43627-4 -
European Journal of Translational... Jul 2023Chronic Ataxic Neuropathy with anti-Disialosyl IgM Antibodies (CANDA) is a rare form of immune-mediated sensory ataxic neuropathy. We describe the case of a 45-year-old...
Chronic Ataxic Neuropathy with anti-Disialosyl IgM Antibodies (CANDA) is a rare form of immune-mediated sensory ataxic neuropathy. We describe the case of a 45-year-old man, who was diagnosed with CANDA in October 2018. Since then, he has been treated with monthly courses of intravenous immunoglobulin administration (IV Ig) and, in October 2022, he underwent plasmapheresis, reporting a sudden worsening of clinical and motor picture. After a new IV Ig cycle admission, the patient was hospitalized to perform intensive rehabilitation, involving two individual sessions per day (90 minutes each) for 5 days a week. During hospitalization it was registered a relevant improvement in the muscle strength of the lower limbs (LLs). Furthermore, progressive improvements were recorded both in patient's motor performance and in his level of autonomy in activities of daily living. These results had a positive impact on his quality of life and made it possible to reduce the frequency of IV Ig treatments. This is the first case in literature reporting the combined effect of rehabilitation treatment and medical therapy in CANDA neuropathy.
PubMed: 37522810
DOI: 10.4081/ejtm.2023.11557 -
Molecular and Cellular Neurosciences Sep 2023Collapsin response mediator protein 2 (CRMP2) is a member of a protein family, which is highly involved in neurodevelopment, but most of its members become heavily...
Collapsin response mediator protein 2 (CRMP2) is a member of a protein family, which is highly involved in neurodevelopment, but most of its members become heavily downregulated in adulthood. CRMP2 is an important factor in neuronal polarization, axonal formation and growth cone collapse. The protein remains expressed in adulthood, but is more region specific. CRMP2 is present in adult corpus callosum (CC) and in plastic areas like prefrontal cortex and hippocampus. CRMP2 has been implicated as one of the risk-genes for Schizophrenia (SZ). Here, a CRMP2 conditional knockout (CRMP2-cKO) mouse was used as a model of SZ to investigate how it could affect the white matter and therefore brain connectivity. Multielectrode electrophysiology (MEA) was used to study the function of corpus callosum showing an increase in conduction velocity (CV) measured as Compound Action Potentials (CAPs) in acute brain slices. Light- and electron-microscopy, specifically Serial Block-face Scanning Electron Microscopy (SBF-SEM), methods were used to study the structure of CC in CRMP2-cKO mice. A decrease in CC volume of CRMP2-cKO mice as compared to controls was observed. No differences were found in numbers nor in the size of CC oligodendrocytes (OLs). Similarly, no differences were found in myelin thickness or in node of Ranvier (NR) structure. In contrast, abnormally smaller axons were measured in the CRMP2-cKO mice. Using these state-of-the-art methods it was possible to shed light on specific parts of the dysconnectivity aspect of deletion of CRMP2 related to SZ and add details to previous findings helping further understanding the disease. This paper substantiates the white matter changes in the absence of CRMP2 and ties it to the role it plays in this complex disorder.
Topics: Animals; Mice; Axons; Brain; Corpus Callosum; Mice, Knockout; Myelin Sheath; Neurons
PubMed: 37479154
DOI: 10.1016/j.mcn.2023.103882