Dynamics of perineuronal nets over amphibian metamorphosis

Edwards, Jacob A.; Risch, Makayla; Hoke, Kim L.

doi:10.1002/cne.25055

Cited by 3 publications

(2 citation statements)

References 73 publications

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“…Recently, WFA was shown to bind both non-reducing terminal and internal N-acetylgalactosamine residues to recognize heparin and to specifically interact with non-sulfated tetrasaccharides of the O-O type (Nadanaka et al, 2020). WFA has been applied to reveal PNs in numerous mammalian species and even in amphibians (Edwards et al, 2021), chicken (Morawski et al, 2009) and seasonally altered in canary birds (Cornez et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Update on Perineuronal Net Staining With Wisteria floribunda Agglutinin (WFA)

Härtig

Meinicke

Michalski

et al. 2022

Front. Integr. Neurosci.

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As chemically specialized forms of the extracellular matrix in the central nervous system, polyanionic perineuronal nets (PNs) contain diverse constituents, including chondroitin sulfate proteoglycans (CSPGs), hyaluronic acid, and tenascins. They are detectable by various histological approaches such as colloidal iron binding and immunohistochemical staining to reveal, for instance, the CSPGs aggrecan, neurocan, phosphacan, and versican. Moreover, biotin, peroxidase, or fluorescein conjugates of the lectins Vicia villosa agglutinin and soybean agglutinin enable the visualization of PNs. At present, the N-acetylgalactosamine-binding Wisteria floribunda agglutinin (WFA) is the most widely applied marker for PNs. Therefore, this article is largely focused on methodological aspects of WFA staining. Notably, fluorescent WFA labeling allows, after its conversion into electron-dense adducts, electron microscopic analyses. Furthermore, the usefulness of WFA conjugates for the oftentimes neglected in vivo and in vitro labeling of PNs is emphasized. Subsequently, we discuss impaired WFA-staining sites after long-lasting experiments in vitro, especially in autoptic brain samples with long postmortem delay and partial enzymatic degradation, while immunolabeling of aggrecan and CSPG link proteins under such conditions has proven more robust. In some hippocampal regions from perfusion-fixed mice, more PNs are aggrecan immunoreactive than WFA positive, whereas the retrosplenial cortex displays many WFA-binding PNs devoid of visible aggrecan immunoreactivity. Additional multiple fluorescence labeling exemplarily revealed in ischemic tissue diminished staining of WFA-binding sites and aquaporin 4 and concomitantly upregulated immunolabeling of neurofilament, light chains, and collagen IV. Finally, we briefly discuss possible future staining approaches based on nanobodies to facilitate novel technologies revealing details of net morphology.

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Section: Introductionmentioning

confidence: 99%

Update on Perineuronal Net Staining With Wisteria floribunda Agglutinin (WFA)

Härtig

Meinicke

Michalski

et al. 2022

Front. Integr. Neurosci.

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“…The perineuronal net (PNN) is a key regulator of plasticity and conserved across species (1)(2)(3)(4). It stabilises existing synapses at the end of critical period during development and restricts new synapses onto the enwrapped neurons (5,6).…”

Section: Introductionmentioning

confidence: 99%

An in vitro neuronal model replicating the in vivo maturation and heterogeneity of perineuronal nets

Dickens

Goodenough

Kwok

2022

Preprint

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The perineuronal net (PNN) is a condensed form of extracellular matrix (ECM) that enwraps specific populations of neurons and regulates plasticity. To create a PNN, only three classes of components are needed: membrane bound hyaluronan by its synthetic enzyme hyaluronan synthases (HASs), a link protein and a CSPG. However, there is redundancy within the classes as multiple HAS isoforms, link proteins and CSPGs have been found in the PNN in vivo. The effect of this heterogeneity has on PNN function is unresolved. Currently, the most common way to address this question is through the creation and study of PNN component in knockout animals. Here, we reported the development of a primary neuronal culture model which reproduces the in vivo maturation and heterogeneity of PNNs. This model accurately replicated mature cortical PNNs, both in terms of the heterogeneity in PNN composition and its maturation. PNNs transitioned from an immature punctate morphology to the reticular morphology as observed in the mature CNS. We also observed a small population of PNNs that were mature at an earlier time point and a distinct composition, highlighting further heterogeneity. This model will provide a valuable tool for the study of PNN biology, their roles in diseases and the development of PNN focused plasticity treatment.

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Lectin binding and gel secretion within Lorenzinian electroreceptors of Polyodon

et al. 2022

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We imaged the carbohydrate-selective spatial binding of 8 lectins in the ampullary organs (AOs) of electroreceptors on the rostrum of freshwater paddlefish (Polyodon spathula), by fluorescence imaging and morphometry of frozen sections. A focus was candidate sites of secretion of the glycoprotein gel filling the lumen of AOs. The rostrum of Polyodon is an electrosensory appendage anterior of the head, covered with >50,000 AOs, each homologous with the ampulla of Lorenzini electroreceptors of marine rays and sharks. A large electrosensory neuroepithelium (EN) lines the basal pole of each AO’s lumen in Polyodon; support cells occupy most (97%) of an EN’s apical area, along with electrosensitive receptor cells. (1) Lectins WGA or SBA labeled the AO gel. High concentrations of the N-acetyl-aminocarbohydrate ligands of these lectins were reported in canal gel of ampullae of Lorenzini, supporting homology of Polyodon AOs. In cross sections of EN, WGA or SBA labeled cytoplasmic vesicles and organelles in support cells, especially apically, apparently secretory. Abundant phalloidin+ microvilli on the apical faces of support cells yielded the brightest label by lectins WGA or SBA. In parallel views of the apical EN surface, WGA labeled only support cells. We concluded that EN support cells massively secrete gel from their apical microvilli (and surface?), containing amino carbohydrate ligands of WGA or SBA, into the AO lumen. (2) Lectins RCA120 or ConA also labeled EN support cells, each differently. RCA120-fluorescein brightly labeled extensive Golgi tubules in the apical halves of EN cells. ConA did not label microvilli, but brightly labeled small vesicles throughout support cells, apparently non-secretory. (3) We demonstrated “sockets” surrounding the basolateral exteriors of EN receptor cells, as candidate glycocalyces. (4) We explored whether additional secretions may arise from non-EN epithelial cells of the interior ampulla wall. (5) Model: Gel is secreted mainly by support cells in the large EN covering each AO’s basal pole. Secreted gel is pushed toward the pore, and out. We modeled gel velocity as increasing ~11x, going distally in AOs (toward the narrowed neck and pore), due to geometrical taper of the ampulla wall. Gel renewal and accelerated expulsion may defend against invasion of the AO lumen by microbes or small parasites. (6) We surveyed lectin labeling of accessory structures, including papilla cells in AO necks, striated ectoderm epidermis, and sheaths on afferent axons or on terminal glia.

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Dynamics of perineuronal nets over amphibian metamorphosis

Cited by 3 publications

References 73 publications

Update on Perineuronal Net Staining With Wisteria floribunda Agglutinin (WFA)

Update on Perineuronal Net Staining With Wisteria floribunda Agglutinin (WFA)

An in vitro neuronal model replicating the in vivo maturation and heterogeneity of perineuronal nets

Lectin binding and gel secretion within Lorenzinian electroreceptors of Polyodon

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