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Neuregulin 1 is required for Schwann cell migration. (A-D) nrg1 (A,B,B) and nrg1 type III (C,D,D) mRNA expression at 33 hpf, shown in dorsal (A,C) and lateral (B,D) views. (B,D) Higher magnification of the boxed regions in B,D. Arrowheads mark the PLLg and asterisks mark motoneurons. (E,F)Lateral views of control-injected (E) and nrg1 morpholino-injected (F) zebrafish embryos at 29 hpf. (G-H) Lateral views of control-injected (G,G) and morphant (H,H) embryos carrying the Foxd3:GFP transgene (green) and stained with anti-acetylated tubulin (acTub, red) at 29 hpf. Schwann cells are marked by arrowheads and stellate-shaped pigment cells by asterisks. In lateral views, anterior is to the left and dorsal is up. In dorsal views, anterior is to the left. ALLg, anterior lateral line ganglion; PLLg, posterior lateral line ganglion. Scale bar: 50mm.
Source publication
During peripheral nerve development, each segment of a myelinated axon is matched with a single Schwann cell. Tight regulation of Schwann cell movement, proliferation and differentiation is essential to ensure that these glial cells properly associate with axons. ErbB receptors are required for Schwann cell migration, but the operative ligand and i...
Contexts in source publication
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... PLLn initially grows out within the epidermis above the basement membrane, and Schwann cells are required for the nerve to transition to its mature location beneath this basement membrane ( Raphael et al., 2010). At 5 dpf the nerve is normally located beneath the basement membrane and Schwann cells have begun to myelinate axons ( Fig. 3A,A; n10). In the absence of Schwann cells, erbb mutant nerves remain in the epidermis and become defasciculated ( Raphael et al., 2010). To determine whether nrg1 z26 mutant nerves resemble erbb mutant nerves at the ultrastructural level, we examined transverse sections of the PLLn by transmission electron microscopy (TEM). As in other mutants lacking Schwann cells ( Raphael et al., 2010;Voas et al., 2009), nrg1 z26 nerves fail to transition across the basement membrane and are defasciculated ( Fig. 3B,B; n4). By Foxd3:GFP transgene analysis we observed a small number of 'escaper' Schwann cells in the nrg1 z26 mutants at 2 dpf. In wild-type larvae, more than 75 Foxd3:GFP + Schwann cells stretch from the ganglion to the end of the PLLn, whereas in nrg1 z26 mutants an average of 2.3 Schwann cells reach, on average, somite 3. The greatest number of Schwann cells observed in a mutant nerve was seven, and the farthest somite reached was somite 7 (data not shown; n25 nrg1 z26 mutants). Similarly, by TEM we occasionally observed these escaper Schwann cells along nrg1 z26 mutant nerves at the level of somite 5. These Schwann cells were sufficient to transition the nerve across the basement membrane, but did not myelinate the axons within their bundle ( Fig. 3C,C; n2). These results indicate that mutants for erbb receptors and nrg1 type III have similar ultrastructural ...
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... determine whether Neuregulin 1 (Nrg1) ligands are expressed during Schwann cell migration, we performed in situ hybridization using a probe that recognizes all known zebrafish nrg1 isoforms. During migration (33 hpf), the probe strongly labeled the PLLg, which contains the cell bodies of the neurons that form the PLLn (Fig. 1A,B,B, arrowhead). A probe specific for the type III isoform revealed an almost identical staining pattern (Fig. 1C,D,D). Common region probes and type III-specific probes also detected similar expression patterns at 24 hpf, 48 hpf, 72 hpf and 4 dpf (data not shown). These results indicate that nrg1 type III is expressed at the right time and place to control Schwann cell migration and myelination in ...
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... determine whether Neuregulin 1 (Nrg1) ligands are expressed during Schwann cell migration, we performed in situ hybridization using a probe that recognizes all known zebrafish nrg1 isoforms. During migration (33 hpf), the probe strongly labeled the PLLg, which contains the cell bodies of the neurons that form the PLLn (Fig. 1A,B,B, arrowhead). A probe specific for the type III isoform revealed an almost identical staining pattern (Fig. 1C,D,D). Common region probes and type III-specific probes also detected similar expression patterns at 24 hpf, 48 hpf, 72 hpf and 4 dpf (data not shown). These results indicate that nrg1 type III is expressed at the right time and place to control Schwann cell migration and myelination in ...
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... analyses alone do not distinguish whether Nrg1 type III is required in neurons or in glia. Although we (Fig. 1C,D) and others ( Ho et al., 1995;Meyer et al., 1997) primarily observed nrg1 type III expression in neurons, nrg1 type III expression has been detected in rat Schwann cells ( Rosenbaum et al., 1997) and in adult zebrafish nerve, in which most mRNAs derive from Schwann cells (data not shown). To determine whether Nrg1 type III is required in neurons or Schwann cells, we made genetic chimeras. Wild-type cells labeled with a lineage tracer were transplanted into nrg1 z26 mutant hosts carrying the Foxd3:GFP transgene to mark mutant Schwann cells (Fig. 4A). As a few Schwann cells are seen in nerves of nrg1 z26 mutants (never more than seven Schwann ...
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... determine whether Nrg1 is required for Schwann cell migration, all nrg1 isoforms were knocked down by an antisense morpholino oligonucleotide that targets the common EGF domain ( Holmes et al., 1992;Honjo et al., 2008). Embryos injected with the nrg1 morpholino had comparable morphology to control-injected embryos, but RT-PCR analysis demonstrated that the nrg1 transcripts were improperly spliced ( Fig. 1E,F; see Fig. S1A in the supplementary material). The Foxd3:GFP transgene, which marks a subset of neural crest derivatives, was used to visualize Schwann cells ( Gilmour et al., 2002). Schwann cells are detected as elongated, Foxd3:GFP + cells (Fig. 1, white arrowheads) that are associated with PLLn axons; nearby pigment cells also express GFP but are not associated with the nerve and have a stellate morphology (Fig. 1, white asterisks). There is a dramatic reduction of Schwann cells along the PLLn of morphants ( Fig. 1H,H; n68/68) as compared with control- injected embryos ( Fig. 1G,G; n48/48). Neural crest cells, which are the precursors of Schwann cells, were able to migrate to the ganglion, as has been observed in erbb mutants ( Lyons et al., 2005), but most did not migrate from the ganglion. This indicates that Nrg1 signaling is required for Schwann cells to occupy the PLLn, supporting the possibility that Nrg1 signals direct Schwann cell migration via ErbB ...
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... determine whether Nrg1 is required for Schwann cell migration, all nrg1 isoforms were knocked down by an antisense morpholino oligonucleotide that targets the common EGF domain ( Holmes et al., 1992;Honjo et al., 2008). Embryos injected with the nrg1 morpholino had comparable morphology to control-injected embryos, but RT-PCR analysis demonstrated that the nrg1 transcripts were improperly spliced ( Fig. 1E,F; see Fig. S1A in the supplementary material). The Foxd3:GFP transgene, which marks a subset of neural crest derivatives, was used to visualize Schwann cells ( Gilmour et al., 2002). Schwann cells are detected as elongated, Foxd3:GFP + cells (Fig. 1, white arrowheads) that are associated with PLLn axons; nearby pigment cells also express GFP but are not associated with the nerve and have a stellate morphology (Fig. 1, white asterisks). There is a dramatic reduction of Schwann cells along the PLLn of morphants ( Fig. 1H,H; n68/68) as compared with control- injected embryos ( Fig. 1G,G; n48/48). Neural crest cells, which are the precursors of Schwann cells, were able to migrate to the ganglion, as has been observed in erbb mutants ( Lyons et al., 2005), but most did not migrate from the ganglion. This indicates that Nrg1 signaling is required for Schwann cells to occupy the PLLn, supporting the possibility that Nrg1 signals direct Schwann cell migration via ErbB ...
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... determine whether Nrg1 is required for Schwann cell migration, all nrg1 isoforms were knocked down by an antisense morpholino oligonucleotide that targets the common EGF domain ( Holmes et al., 1992;Honjo et al., 2008). Embryos injected with the nrg1 morpholino had comparable morphology to control-injected embryos, but RT-PCR analysis demonstrated that the nrg1 transcripts were improperly spliced ( Fig. 1E,F; see Fig. S1A in the supplementary material). The Foxd3:GFP transgene, which marks a subset of neural crest derivatives, was used to visualize Schwann cells ( Gilmour et al., 2002). Schwann cells are detected as elongated, Foxd3:GFP + cells (Fig. 1, white arrowheads) that are associated with PLLn axons; nearby pigment cells also express GFP but are not associated with the nerve and have a stellate morphology (Fig. 1, white asterisks). There is a dramatic reduction of Schwann cells along the PLLn of morphants ( Fig. 1H,H; n68/68) as compared with control- injected embryos ( Fig. 1G,G; n48/48). Neural crest cells, which are the precursors of Schwann cells, were able to migrate to the ganglion, as has been observed in erbb mutants ( Lyons et al., 2005), but most did not migrate from the ganglion. This indicates that Nrg1 signaling is required for Schwann cells to occupy the PLLn, supporting the possibility that Nrg1 signals direct Schwann cell migration via ErbB ...
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... determine whether Nrg1 is required for Schwann cell migration, all nrg1 isoforms were knocked down by an antisense morpholino oligonucleotide that targets the common EGF domain ( Holmes et al., 1992;Honjo et al., 2008). Embryos injected with the nrg1 morpholino had comparable morphology to control-injected embryos, but RT-PCR analysis demonstrated that the nrg1 transcripts were improperly spliced ( Fig. 1E,F; see Fig. S1A in the supplementary material). The Foxd3:GFP transgene, which marks a subset of neural crest derivatives, was used to visualize Schwann cells ( Gilmour et al., 2002). Schwann cells are detected as elongated, Foxd3:GFP + cells (Fig. 1, white arrowheads) that are associated with PLLn axons; nearby pigment cells also express GFP but are not associated with the nerve and have a stellate morphology (Fig. 1, white asterisks). There is a dramatic reduction of Schwann cells along the PLLn of morphants ( Fig. 1H,H; n68/68) as compared with control- injected embryos ( Fig. 1G,G; n48/48). Neural crest cells, which are the precursors of Schwann cells, were able to migrate to the ganglion, as has been observed in erbb mutants ( Lyons et al., 2005), but most did not migrate from the ganglion. This indicates that Nrg1 signaling is required for Schwann cells to occupy the PLLn, supporting the possibility that Nrg1 signals direct Schwann cell migration via ErbB ...
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... determine whether Nrg1 is required for Schwann cell migration, all nrg1 isoforms were knocked down by an antisense morpholino oligonucleotide that targets the common EGF domain ( Holmes et al., 1992;Honjo et al., 2008). Embryos injected with the nrg1 morpholino had comparable morphology to control-injected embryos, but RT-PCR analysis demonstrated that the nrg1 transcripts were improperly spliced ( Fig. 1E,F; see Fig. S1A in the supplementary material). The Foxd3:GFP transgene, which marks a subset of neural crest derivatives, was used to visualize Schwann cells ( Gilmour et al., 2002). Schwann cells are detected as elongated, Foxd3:GFP + cells (Fig. 1, white arrowheads) that are associated with PLLn axons; nearby pigment cells also express GFP but are not associated with the nerve and have a stellate morphology (Fig. 1, white asterisks). There is a dramatic reduction of Schwann cells along the PLLn of morphants ( Fig. 1H,H; n68/68) as compared with control- injected embryos ( Fig. 1G,G; n48/48). Neural crest cells, which are the precursors of Schwann cells, were able to migrate to the ganglion, as has been observed in erbb mutants ( Lyons et al., 2005), but most did not migrate from the ganglion. This indicates that Nrg1 signaling is required for Schwann cells to occupy the PLLn, supporting the possibility that Nrg1 signals direct Schwann cell migration via ErbB ...
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... determine whether Nrg1 is required for Schwann cell migration, all nrg1 isoforms were knocked down by an antisense morpholino oligonucleotide that targets the common EGF domain ( Holmes et al., 1992;Honjo et al., 2008). Embryos injected with the nrg1 morpholino had comparable morphology to control-injected embryos, but RT-PCR analysis demonstrated that the nrg1 transcripts were improperly spliced ( Fig. 1E,F; see Fig. S1A in the supplementary material). The Foxd3:GFP transgene, which marks a subset of neural crest derivatives, was used to visualize Schwann cells ( Gilmour et al., 2002). Schwann cells are detected as elongated, Foxd3:GFP + cells (Fig. 1, white arrowheads) that are associated with PLLn axons; nearby pigment cells also express GFP but are not associated with the nerve and have a stellate morphology (Fig. 1, white asterisks). There is a dramatic reduction of Schwann cells along the PLLn of morphants ( Fig. 1H,H; n68/68) as compared with control- injected embryos ( Fig. 1G,G; n48/48). Neural crest cells, which are the precursors of Schwann cells, were able to migrate to the ganglion, as has been observed in erbb mutants ( Lyons et al., 2005), but most did not migrate from the ganglion. This indicates that Nrg1 signaling is required for Schwann cells to occupy the PLLn, supporting the possibility that Nrg1 signals direct Schwann cell migration via ErbB ...
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... previous studies (Lyons et al., 2005) supported a role for ErbB receptors in directing Schwann cell migration, it has not been determined whether Nrg1 ligands act to promote Schwann cell motility, direct their migration, or both. To investigate if Nrg1 type III is an instructive signal for migration, we tested whether ectopic expression could misdirect Schwann cell migration. We expressed human NRG1 (hNRG1) type III in all neurons under the control of a pan-neuronal GAL4 driver (Scott et al., 2007). Zebrafish embryos with both the hNRG1typeIII:UAS and the s1101:GAL4 pan- neuronal driver transgenes displayed robust expression of hNRG1 type III in the brain and spinal cord, although there was variability in expression between embryos and within individuals ( Fig. 5B; n18/18). Control embryos that lacked either transgene showed no hNRG1 type III expression ( Fig. 5A; ...
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... the absence of Schwann cells, supernumerary neuromasts form in the posterior lateral line ( Grant et al., 2005). A screen for mutants with supernumerary neuromasts uncovered a mutation, nrg1 z26 , that mapped to the nrg1 locus. Sequence analysis showed that nrg1 z26 mutants harbor a T-to-C transition that converts a cysteine in the CRD to an arginine ( Fig. 2A-D). This cysteine, which is conserved from fish to human, is within the N-terminal transmembrane segment required for membrane localization of Nrg1 type III ( Cabedo et al., 2002;Ho et al., 1995;Wang et al., 2001). The presence of the bulky charged residue in the transmembrane segment is likely to disrupt folding or localization of the mutant Nrg1 type III protein. In genotyping studies, all nrg1 z26 mutants were homozygous for the T-to-C mutation (n134 mutants), confirming that this lesion is tightly linked to the nrg1 z26 mutation. Gross morphology of mutants is normal at 5 dpf (Fig. 2E,F) and a few homozygous mutant adult fish are viable, although small. Schwann cells are absent from the PLLn in nrg1 z26 mutants at all stages examined from 26 hpf to 5 dpf (n156/156). During initial axon outgrowth, Schwann cells are present at the PLLg in nrg1 z26 mutants, but fail to migrate along growing axons ( Fig. 2H; n45/45). A morpholino targeted specifically to the type III isoform knocked down the transcript and similarly reduced Schwann cell migration in otherwise morphologically normal animals (see Fig. S1B,D,F in the supplementary material; n51/51). Taken together, these data indicate that the z26 mutation specifically disrupts the nrg1 type III isoform, and that Nrg1 type III is required for Schwann cell ...
Citations
... Each neuromast consists of hair cells detecting mechanical changes in the environment, surrounded by supporting and mantle cells, which offer protection and serve as progenitors to replace damaged hair cells (Chitnis et al., 2012;Ghysen & Dambly-Chaudiere, 2007). Interneuromast cells, typically maintained in a dormant state by Schwann cells and the posterior lateral line nerve (pLLn), play a crucial role in neuromast regeneration (L opez-Schier & Hudspeth, 2005;Lush & Piotrowski, 2014;Lyons et al., 2005;Perlin et al., 2011). The pLLn releases neuregulin 1-3 (Nrg1-3), activating epidermal growth factor (EGF) receptors on Schwann cells, inhibiting Wnt signaling in interneuromast cells. ...
Macrophages play a pivotal role in the response to injury, contributing significantly to the repair and regrowth of damaged tissues. The external lateral line system in aquatic organisms offers a practical model for studying regeneration, featuring interneuromast cells connecting sensory neuromasts. Under normal conditions, these cells remain dormant, but their transformation into neuromasts occurs when overcoming inhibitory signals from Schwann cells and posterior lateral line nerves. The mechanism enabling interneuromast cells to evade inhibition by Schwann cells remains unclear. Previous observations suggest that macrophages physically interact with neuromasts, nerves, and Schwann cells during regeneration. This interaction leads to the regeneration of neuromasts in a subset of zebrafish with ablated neuromasts. To explore whether macrophages achieve this effect through secreted cytokines, we conducted experiments involving tail amputation in zebrafish larvae and tested the impact of cytokine inhibitors on neuromast regeneration. Most injured larvae remarkably regenerated a neuromast within 4 days post‐amputation. Intriguingly, removal of macrophages and inhibition of the anti‐inflammatory cytokine transforming growth factor‐beta (TGF‐β) significantly delayed neuromast regeneration. Conversely, inhibition of the pro‐inflammatory cytokines interleukin‐6 (IL‐6) and tumor necrosis factor‐alpha (TNF‐α) had minor effects on the regeneration process. This study provides insights into how macrophages activate interneuromast cells, elucidating the pathways underlying neuromast regeneration.
... Nrg1 type III is a critical signal that controls Schwann cell specification [6], migration [7], proliferation [8], apoptosis, and myelination [9] in developing nerves through multiple signaling pathways, such as PI3K/Akt, MAPK/Erk, and calcineurin/NFATc4 [10][11][12][13]. In cultured Schwann cells, Nrg1 type III is identified as the unique signal responsible for activating NF-κB, a critical factor for the cells to differentiate into the myelinating phenotype [6,14]. ...
Nrg1 (Neuregulin 1) type III, a susceptible gene of schizophrenia, exhibits a critical role in the central nervous system and is essential at each stage of Schwann’s cell development. Nrg1 type III comprises double-pass transmembrane domains, with the N-terminal and C-terminal localizing inside the cells. The N-terminal transmembrane helix partially overlaps with the cysteine-rich domain (CRD). In this study, Nrg1 type III constructs with different tags were transformed into cultured cells to verify whether CRD destroyed the transmembrane helix formation. We took advantage of immunofluorescent and immunoprecipitation assays on whole cells and analyzed the N-terminal distribution. Astonishingly, we found that a novel form of Nrg1 type III, about 10% of Nrg1 type III, omitted the N-terminal transmembrane helix, with the N-terminal positioning outside the membrane. The results indicated that the novel single-pass transmembrane status was a minor form of Nrg1 type III caused by N-terminal processing, while the major form was a double-pass transmembrane status.
... During peripheral nervous system development, Schwann cells (SC) migrate along the axons, proliferate, and undergo substantial cytoskeletal remodeling to stretch and associate with axons. [1][2][3][4][5] They also execute dramatic rearrangements needed for radial sorting and axon wrapping allowing them to extend their processes along a unique and specific abaxonal-adaxonal axis. 4,[6][7][8][9][10][11][12][13] The myelin sheath of compacted SC membrane is therefore adjacent to the axon (adaxonal surface) while most of the cytoplasm is close to the outer surface where the basement membrane is formed (abaxonal surface). ...
Background
Schwann cells (SCs) are specialized glial cells of the peripheral nervous system that produce myelin and promote fast action potential propagation. In order to myelinate, SCs engage in a series of events that include migration and division along axons, followed by extensive cytoskeletal rearrangements that ensure axonal ensheathment and myelination. SCs are polarized and extend their processes along an abaxonal‐adaxonal axis. Here, we investigate the role of the apical polarity proteins, Pals1a, and aPKCλ, in SC behavior during zebrafish development.
Results
We analyzed zebrafish nok and has mutants deficient for pals1a and aPKCλ function respectively. Using live imaging, transmission electron microscopy and whole mount immunostaining, we show that SCs can migrate and divide appropriately, exhibit normal radial sorting, express myelin markers and ensheath axons on time in has and nok mutants.
Conclusions
Pals1a and aPKCλ are not essential for SC migration, division or myelination in zebrafish.
... [23][24][25] In the PNS, the transmembrane isoform Nrg1 type III is the key axonal signal that controls the proliferation, migration, and myelination of ErbB-expressing Schwann cells. 18,26,27 In CNS myelination, the function of the Nrg1 type III isoform is much more limited; myelin is present but reduced in the brain of ErbB receptor mutants. 28,29 However, these and other studies 20 report normal myelination in the spinal cord in Nrg1 and ErbB mutants, despite evidence from pioneering in vitro and ex vivo studies 30,31 that established Nrg1 signals as regulators of development, migration, or proliferation of oligodendrocytes, the myelinating cells of the CNS. ...
... 34 To broadly assess myelination in these mutants, we performed in situ hybridization on whole mount embryos for myelin basic protein (mbp), a marker of myelinating glia. In the PNS, animals homozygous for mutations in the EGF exon or type III-specific exon lacked mbp expression, in accord with previous studies of zebrafish and mouse mutants, 18,27 whereas mpb expression in the PNS appeared normal in the type I and type II homozygous mutants (Figures S1D-S1I). All nrg1 mutants expressed mbp in the CNS (Figures S1D-S1I), consistent with previous analyses. ...
... All nrg1 mutants expressed mbp in the CNS (Figures S1D-S1I), consistent with previous analyses. 20,26,27 To analyze myelin sheath formation at higher resolution, we visualized oligodendrocytes and their myelin sheaths by crossing our nrg1 EGF and isoform-specific lines to the stable transgenic reporter cldnk:GFP-CAAX, 35 which expresses membrane-bound GFP in all myelinating oligodendrocytes ( Figure 1C). We analyzed myelin sheath formation in the dorsal spinal cord at 3.5 dpf (days post fertilization), when individual oligodendrocytes can be imaged. ...
The signaling mechanisms neurons use to modulate myelination of circuits in the central nervous system (CNS) are only partly understood. Through analysis of isoform-specific neuregulin1 (nrg1) mutants in zebrafish, we demonstrate that nrg1 type II is an important regulator of myelination of two classes of spinal cord interneurons. Surprisingly, nrg1 type II expression is prominent in unmyelinated Rohon-Beard sensory neurons, whereas myelination of neighboring interneurons is reduced in nrg1 type II mutants. Cell-type-specific loss-of-function studies indicate that nrg1 type II is required in Rohon-Beard neurons to signal to other neurons, not oligodendrocytes, to modulate spinal cord myelination. Together, our data support a model in which unmyelinated neurons express Nrg1 type II proteins to regulate myelination of neighboring neurons, a mode of action that may coordinate the functions of unmyelinated and myelinated neurons in the CNS.
... Active cell proliferation was observed near the cutting edge at 2 dpa and quantified in a scatter plot on the right. Hudspeth, 2005;Lyons et al., 2005;Perlin et al., 2011;Lush and Piotrowski, 2014). During the migration of the 2 nd pLLp, the intercalary neuromast formation also occurs by blocking the contact between INCs and SWCs (Ledent, 2002;Ghysen and Dambly-Chaudière, 2007;Nuñez et al., 2009). ...
... Electroablation might cause an instant injury of the underlying SWCs and pLLn. As in our case, the diminishing signal of pLLn in the nearby region of a cutting site might indicate a lower expression of Neuregulin 1 type III (Nrg1-3), which is involved in the migration, proliferation, and differentiation of SWCs (Perlin et al., 2011) via the receptor, ErbB2 or ErbB3, of SWCs (Lyons et al., 2005;Rojas-Muñoz et al., 2009). This tripartite relationship is well-established to explain precocious intercalary neuromast formation with the interruption of this ErbB/Neuregulin pathway (Lush and Piotrowski, 2014). ...
In the zebrafish lateral line system, interneuromast cells (INCs) between neuromasts are kept quiescent by underlying Schwann cells (SWCs). Upon severe injuries that cause the complete loss of an entire neuromast, INCs can occasionally differentiate into neuromasts but how they escape from the inhibition by SWCs is still unclear. Using a genetic/chemical method to ablate a neuromast precisely, we found that a small portion of larvae can regenerate a new neuromast. However, the residual regeneration capacity was hindered by inhibiting macrophages. Using in toto imaging, we further discovered heterogeneities in macrophage behavior and distribution along the lateral line. We witnessed the crawling of macrophages between the injured lateral line and SWCs during regeneration and between the second primordium and the first mature lateral line during development. It implies that macrophages may physically alleviate the nerve inhibition to break the dormancy of INCs during regeneration and development in the zebrafish lateral line.
... Trunk neuromast number and positioning changes as the zebrafish grows in length, initially starting with 5-6 primary neuromasts (deposited from 20 to 40 hpf) that eventually expand into nearly 600 neuromasts in adults (Ghysen and Dambly-Chaudière, 2007). Developing SCs can impact the number of neuromasts, as is evident by inappropriate neuromast formation in erbb pathway and sox10 mutants which lack SCs (Grant et al., 2005;Lush and Piotrowski, 2014;Perlin et al., 2011;Rojas-Muñoz et al., 2009). To determine if excess SCs also affect neuromast formation, we labeled neuromasts with an acetylated α-Tubulin antibody and quantified the number of truncal neuromasts. ...
Efficient neurotransmission is essential for organism survival and is enhanced by myelination. However, the genes that regulate myelin and myelinating glial cell development have not been fully characterized. Data from our lab and others demonstrates that cd59, which encodes for a small GPI-anchored glycoprotein, is highly expressed in developing zebrafish, rodent, and human oligodendrocytes (OLs) and Schwann cells (SCs), and that patients with CD59 dysfunction develop neurological dysfunction during early childhood. Yet, the function of Cd59 in the developing nervous system is currently undefined. In this study, we demonstrate that cd59 is expressed in a subset of developing SCs. Using cd59 mutant zebrafish, we show that developing SCs proliferate excessively and nerves may have reduced myelin volume, altered myelin ultrastructure, and perturbed node of Ranvier assembly. Finally, we demonstrate that complement activity is elevated in cd59 mutants and that inhibiting inflammation restores SC proliferation, myelin volume, and nodes of Ranvier to wildtype levels. Together, this work identifies Cd59 and developmental inflammation as key players in myelinating glial cell development, highlighting the collaboration between glia and the innate immune system to ensure normal neural development.
... Despite the efficiency of constitutive gene targeting in zebrafish, cell-type specific analyses of gene function is more technically challenging. A long-standing method to assess cell autonomous vs. non-autonomous gene function in zebrafish has been the creation of genetic chimeras by cell transplantation, which has been used to assess the roles of various factors in zebrafish glia, but is a method most suited to the analysis of single cell behaviour, given its chimeric nature (Lyons et al., 2009;Monk et al., 2009;Perlin et al., 2011;Mensch et al., 2015). Another approach widely used in the field is the expression of specific genes under the control of cell type specific drivers, e.g., the expression of wild-type genes on a mutant background, or the expression of dominant negative or constitutively active forms of genetic regulators, which has also provided insight into glial function in zebrafish (Supplementary Table 1). ...
The term glia describes a heterogenous collection of distinct cell types that make up a large proportion of our nervous system. Although once considered the glue of the nervous system, the study of glial cells has evolved significantly in recent years, with a large body of literature now highlighting their complex and diverse roles in development and throughout life. This progress is due, in part, to advances in animal models in which the molecular and cellular mechanisms of glial cell development and function as well as neuron-glial cell interactions can be directly studied in vivo in real time, in intact neural circuits. In this review we highlight the instrumental role that zebrafish have played as a vertebrate model system for the study of glial cells, and discuss how the experimental advantages of the zebrafish lend themselves to investigate glial cell interactions and diversity. We focus in particular on recent studies that have provided insight into the formation and function of the major glial cell types in the central nervous system in zebrafish.
... Here, on the basis of previous studies and our results showing the presence of foxd3 + cells but not of sox10 + cells in the caudal fin fold mesenchyme, we focused our attention on foxd3 + cells to study the role of NC cell derivatives during epimorphic regeneration of the caudal fin fold. Moreover, the transgenic line Tg(foxd3:GFP) has been used in several studies on NC derivatives, including SC, that also demonstrated the pertinence of focusing on foxd3 to address NCdC role in appendage regeneration 48,49 . ...
Fish species, such as zebrafish (Danio rerio), can regenerate their appendages after amputation through the formation of a heterogeneous cellular structure named blastema. Here, by combining live imaging of triple transgenic zebrafish embryos and single-cell RNA sequencing we established a detailed cell atlas of the regenerating caudal fin in zebrafish larvae. We confirmed the presence of macrophage subsets that govern zebrafish fin regeneration, and identified a foxd3-positive cell population within the regenerating fin. Genetic depletion of these foxd3-positive neural crest-derived cells (NCdC) showed that they are involved in blastema formation and caudal fin regeneration. Finally, chemical inhibition and transcriptomic analysis demonstrated that these foxd3-positive cells regulate macrophage recruitment and polarization through the NRG1/ErbB pathway. Here, we show the diversity of the cells required for blastema formation, identify a discrete foxd3-positive NCdC population, and reveal the critical function of the NRG1/ErbB pathway in controlling the dialogue between macrophages and NCdC.
... In the meantime, previous studies indicated that NGRs play important roles in the initiation and development of human tumors including gliomas (17), gastric cancer (18), Schwannoma (19), colon cancer (20), breast cancer (21) and prostate cancer (22) by regulating cancer cell migration and TME, emerging as therapeutic targets in developing novel strategies against cancers. NRG family members, especially NRG1 and NRG3, have been proved to play important roles in brain development, including neural plasticity (23), differentiation (24), and Schwann cell migration (25). Thus, they may have great potential in the treatment of brain gliomas. ...
Gliomas, including brain lower grade glioma (LGG) and glioblastoma multiforme (GBM), are the most common primary brain tumors in the central nervous system. Neuregulin (NRG) family proteins belong to the epidermal growth factor (EGF) family of extracellular ligands and they play an essential role in both the central and peripheral nervous systems. However, roles of NRGs in gliomas, especially their effects on prognosis, still remain to be elucidated. In this study, we obtained raw counts of RNA-sequencing data and corresponding clinical information from 510 LGG and 153 GBM samples from The Cancer Genome Atlas (TCGA) database. We analyzed the association of NRG1-4 expression levels with tumor immune microenvironment in LGG and GBM. GSVA (Gene Set Variation Analysis) was performed to determine the prognostic difference of NRGs gene set between LGG and GBM. ROC (receiver operating characteristic) curve and the nomogram model were constructed to estimate the prognostic value of NRGs in LGG and GBM. The results demonstrated that NRG1-4 were differentially expressed in LGG and GBM in comparison to normal tissue. Immune score analysis revealed that NRG1-4 were significantly related to the tumor immune microenvironment and remarkably correlated with immune cell infiltration. The investigation of roles of m⁶A (N6-methyladenosine, m⁶A)-related genes in gliomas revealed that NRGs were prominently involved in m⁶A RNA modification. GSVA score showed that NRG family members are more associated with prognosis in LGG compared with GBM. Prognostic analysis showed that NRG3 and NRG1 can serve as potential independent biomarkers in LGG and GBM, respectively. Moreover, GDSC drug sensitivity analysis revealed that NRG1 was more correlated with drug response compared with other NRG subtypes. Based on these public databases, we preliminarily identified the relationship between NRG family members and tumor immune microenvironment, and the prognostic value of NRGs in gliomas. In conclusion, our study provides comprehensive roles of NRG family members in gliomas, supporting modulation of NRG signaling in the management of glioma.
... One potential explanation of the impaired immune response in ErbB3 knockout mice might be related to the contribution of ErbB3 signaling to cell migration. The role of NRG-1/ErbB signaling in the migration of non-immune cells [53][54][55][56], as well as the migration of lymphocytes [57] and primary immune cells [58] of the central nervous system, has been shown previously. In our study, we demonstrated for the first time that NRG-1 stimulated the migration of bone marrow myeloid cells in vitro via activation of ErbB3. ...
Background
Myeloid cells play an important role in a wide variety of cardiovascular disorders, including both ischemic and non-ischemic cardiomyopathies. Neuregulin-1 (NRG-1)/ErbB signaling has recently emerged as an important factor contributing to the control of inflammatory activation of myeloid cells after an ischemic injury. However, the role of ErbB signaling in myeloid cells in non-ischemic cardiomyopathy is not fully understood. This study investigated the role of ErbB3 receptors in the regulation of early adaptive response using a mouse model of transverse aortic constriction (TAC) for non-ischemic cardiomyopathy.
Methods and results
TAC surgery was performed in groups of age- and sex-matched myeloid cell-specific ErbB3-deficient mice (ErbB3MyeKO) and control animals (ErbB3MyeWT). The number of cardiac CD45 immune cells, CD11b myeloid cells, Ly6G neutrophils, and Ly6C monocytes was determined using flow cytometric analysis. Five days after TAC, survival was dramatically reduced in male but not female ErbB3MyeKO mice or control animals. The examination of lung weight to body weight ratio suggested that acute pulmonary edema was present in ErbB3MyeKO male mice after TAC. To determine the cellular and molecular mechanisms involved in the increased mortality in ErbB3MyeKO male mice, cardiac cell populations were examined at day 3 post-TAC using flow cytometry. Myeloid cells accumulated in control but not in ErbB3MyeKO male mouse hearts. This was accompanied by increased proliferation of Sca-1 positive non-immune cells (endothelial cells and fibroblasts) in control but not ErbB3MyeKO male mice. No significant differences in intramyocardial accumulation of myeloid cells or proliferation of Sca-1 cells were found between the groups of ErbB3MyeKO and ErbB3MyeWT female mice. An antibody-based protein array analysis revealed that IGF-1 expression was significantly downregulated only in ErbB3MyeKO mice hearts compared to control animals after TAC.
Conclusion
Our data demonstrate the crucial role of myeloid cell-specific ErbB3 signaling in the cardiac accumulation of myeloid cells, which contributes to the activation of cardiac endothelial cells and fibroblasts and development of an early adaptive response to cardiac pressure overload in male mice.
