Fig 5
Purkinje cell maturation. a, b Nissl staining of midsagittal sections at P0 demonstrating coalescence of PCs into a monolayer at P0. GAP-43 (+/+) (a) and GAP-43 (−/−) (b). a Purkinje cells have begun coalescing into a monolayer (asterisk) except in the CeL (arrow). b Increased cell density in the CeL (arrow). c-h Calbindin expression by PCs. GAP-43 (+/+) (c, e, g) and GAP-43 (−/−) (d, f, h). c, d Midsagittal sections at P0. c PCs have begun to coalesce into a monolayer (asterisk) but are excluded from the CeL where the fppd is beginning to invaginate (arrow). d PC migration into the anterior and posterior lobes is inhibited (asterisks) and they invade the CeL (arrow). Scale bar=50 μm. e, f Expression of calbindin by PCs at P8. e PCs flanking primary (fpr) and secondary (fsec, fppd) fissures are elaborating extensive dendritic arbors (arrow). f GAP-43 (−/−) PCs flanking the secondary fppd have stunted dendrites (arrow) and are misaligned. Scale bar= 150 μm. g, h Expression of calbindin by PCs at P21. g PCs flanking the fppd form a monolayer. h PCs flanking the fppd remain aggregated at the fissure flanks (arrows). Scale bar=100 μm
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Growth-associated protein 43 (GAP-43) is required for development of a functional cerebral cortex in vertebrates; however, its role in cerebellar development is not well understood. Recently, we showed that absence of GAP-43 caused defects in proliferation, differentiation, and polarization of cerebellar granule cells. In this paper, we show that a...
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Context 1
... different from (+/+) littermates, (63±7 cells/mm vs. 58±4 cells/ mm, n=6), even though the cerebellum itself was smaller. Likewise, consistent with the delayed migration in the embryonic neuroepithelium, migration of PCs was abnormal: In wild-type cerebella at P0, migrating PCs were beginning to coalesce subjacent to the ML (asterisks Fig. 5a,c), except in the CeL from which they are normally excluded [46] (arrows, Fig. 5a,c). In the absence of GAP-43, this coalescence of PCs was delayed, and they appeared clumped (asterisks, Fig. 5d). PCs also invaded the CeL (arrows, Fig. 5b,d). Hence, early effects of GAP-43 on PC differentiation had persistent postnatal ...
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... even though the cerebellum itself was smaller. Likewise, consistent with the delayed migration in the embryonic neuroepithelium, migration of PCs was abnormal: In wild-type cerebella at P0, migrating PCs were beginning to coalesce subjacent to the ML (asterisks Fig. 5a,c), except in the CeL from which they are normally excluded [46] (arrows, Fig. 5a,c). In the absence of GAP-43, this coalescence of PCs was delayed, and they appeared clumped (asterisks, Fig. 5d). PCs also invaded the CeL (arrows, Fig. 5b,d). Hence, early effects of GAP-43 on PC differentiation had persistent postnatal ...
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... neuroepithelium, migration of PCs was abnormal: In wild-type cerebella at P0, migrating PCs were beginning to coalesce subjacent to the ML (asterisks Fig. 5a,c), except in the CeL from which they are normally excluded [46] (arrows, Fig. 5a,c). In the absence of GAP-43, this coalescence of PCs was delayed, and they appeared clumped (asterisks, Fig. 5d). PCs also invaded the CeL (arrows, Fig. 5b,d). Hence, early effects of GAP-43 on PC differentiation had persistent postnatal ...
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... In wild-type cerebella at P0, migrating PCs were beginning to coalesce subjacent to the ML (asterisks Fig. 5a,c), except in the CeL from which they are normally excluded [46] (arrows, Fig. 5a,c). In the absence of GAP-43, this coalescence of PCs was delayed, and they appeared clumped (asterisks, Fig. 5d). PCs also invaded the CeL (arrows, Fig. 5b,d). Hence, early effects of GAP-43 on PC differentiation had persistent postnatal ...
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... postnatal PC development that could not directly be ascribed to prior impairment of proliferation and migration was also abnormal in GAP-43 (−/−) cerebella. In wild-type cerebella at P8, PCs surrounding the primary and secondary fissures had formed a monolayer and elaborated dendritic arbors (Fig. 5e). In the absence of GAP-43, monolayer formation was delayed and the dendritic arbors of the PCs were stunted compared with wild type and appeared misaligned (arrows, Fig. 5e,f). By P21, PCs flanking the primary fissures, such as the fpr, had formed a monolayer even in the absence of GAP-43 (not shown); however, those surrounding the ...
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... abnormal in GAP-43 (−/−) cerebella. In wild-type cerebella at P8, PCs surrounding the primary and secondary fissures had formed a monolayer and elaborated dendritic arbors (Fig. 5e). In the absence of GAP-43, monolayer formation was delayed and the dendritic arbors of the PCs were stunted compared with wild type and appeared misaligned (arrows, Fig. 5e,f). By P21, PCs flanking the primary fissures, such as the fpr, had formed a monolayer even in the absence of GAP-43 (not shown); however, those surrounding the affected secondary fissures, such as the fppd, remained aggregated especially at the fissure flanks (arrows, Fig. ...
Context 7
... were stunted compared with wild type and appeared misaligned (arrows, Fig. 5e,f). By P21, PCs flanking the primary fissures, such as the fpr, had formed a monolayer even in the absence of GAP-43 (not shown); however, those surrounding the affected secondary fissures, such as the fppd, remained aggregated especially at the fissure flanks (arrows, Fig. ...
Citations
... In addition, we observed a decrease to Neuromodulin (GAP43) in all BPA-treated groups, a nervous system-specific protein required in mitotic neural progenitors (Brittis et al., 1995;Esdar et al., 1999). GAP43 is uniformly expressed in proliferating areas of the developing embryonic brain, while a lack of GAP43 expression results in suppressed neural progenitor proliferation (Kanazir et al., 1996;Mani et al., 2001;Mishra et al., 2008). Interestingly, the absence of GAP43 expression induces aberrations to the Frontiers in Cell and Developmental Biology frontiersin.org ...
Bisphenol A (BPA) exposure is associated with a plethora of neurodevelopmental abnormalities and brain disorders. Previous studies have demonstrated BPA-induced perturbations to critical neural stem cell (NSC) characteristics, such as proliferation and differentiation, although the underlying molecular mechanisms remain under debate. The present study evaluated the effects of a repeated-dose exposure of environmentally relevant BPA concentrations during the in vitro 3D neural induction of human induced pluripotent stem cells (hiPSCs), emulating a chronic exposure scenario. Firstly, we demonstrated that our model is suitable for NSC differentiation during the early stages of embryonic brain development. Our morphological image analysis showed that BPA exposure at 0.01, 0.1 and 1 µM decreased the average spheroid size by day 21 (D21) of the neural induction, while no effect on cell viability was detected. No alteration to the rate of the neural induction was observed based on the expression of key neural lineage and neuroectodermal transcripts. Quantitative proteomics at D21 revealed several differentially abundant proteins across all BPA-treated groups with important functions in NSC proliferation and maintenance (e.g., FABP7, GPC4, GAP43, Wnt-8B, TPPP3). Additionally, a network analysis demonstrated alterations to the glycolytic pathway, potentially implicating BPA-induced changes to glycolytic signalling in NSC proliferation impairments, as well as the pathophysiology of brain disorders including intellectual disability, autism spectrum disorders, and amyotrophic lateral sclerosis (ALS). This study enhances the current understanding of BPA-related NSC aberrations based mostly on acute, often high dose exposures of rodent in vivo and in vitro models and human GWAS data in a novel human 3D cell-based model with real-life scenario relevant prolonged and low-level exposures, offering further mechanistic insights into the ramifications of BPA exposure on the developing human brain and consequently, later life neurological disorders.
... It was obvious that GAP43, NF200, and MBP were significantly expressed at the site of injury, whereas GFAP was inhibited in the SHH-RMSCs group as indicated in the results of immunohistochemistry and immunofluorescence. GAP43 and NF200 are specific proteins in the nervous system, which are closely related to nerve growth (Al-Chalabi and Miller, 2003;Shen et al., 2008;Harauz and Boggs, 2013). GFAP is the marker of astrocytes that proliferate rapidly during nerve injury. ...
Purpose: Spinal cord injury (SCI) has a damaging impact on patients, amid being a worldwide problem with no effective treatment. Herein, we reported a method for functional therapy of SCI in rats, wherein we combined thermo-sensitive hydrogel with Sonic Hedgehog (SHH) expressed in rat bone-marrow derived mesenchymal stem cells (RMSCs).
Methods: Bone marrow-derived mesenchymal stem cells (BMSCs) were isolated from Sprague-Dawley (SD) female rats. The SHH was optimized and transferred into RMSCs via cationic liposomes, while thermo-sensitive hydrogel was reformed with hyaluronate (HA) and Pluronic F127. Then, a rat model with SCI was established accordingly by male SD rats and randomized into sham, model, RMSCs with hydrogel and SHH-RMSCs with hydrogel. The evaluation of SCI repair based on Basso, Beattie Bresnahanlocomotor rating scale (BBB scale) and inclined plate score. Immunofluorescence, immunohistochemistry and hematoxylin-eosin were utilized to explore the expression of protein (GFAP, GAP43, NF200 and MBP) and histopathology.
Results: It was demonstrated that transfection of SHH with cationic liposomes exhibited more effect in RMSCs than lipofectamine 2000. As shown in SEM, 3.5% HA-F127 demonstrated porous structure. In the MTT and dead/live assay, 3.5% HA-F127 showed good biocompatibility for RMSCs. Both RMSCs and SHH-RMSCs groups could significantly promote BBB and inclined plate scores (p < 0.01) compared with the model. Furthermore, the SHH-RMSC group was significantly improved than RMSC with the expression of related proteins, where NF200, MBP, and GAP43 were principally enhanced with the GFAP expression being virtually down-regulated.
Conclusion: All in all, the results suggested that transplantation of RMSCs with SHH could improve the function of SCI and promote nerve regeneration.
... Our previous study has also shown that Shh can up-regulate Gap43 protein expression in cortical neurons under oxidative stress [15]. Another study has been reported that Gap43 may serve as a key transducer in Shh signaling pathway on cell membrane to exert cell-autonomous functions [16]. Further research is needed to investigate whether Gap43 is involved in Shh induced neurite outgrowth. ...
Neurite outgrowth is the basis for wiring during the development of the nervous system. Dl-3-n-butylphthalide (NBP) has been recognized as a promising treatment to improve behavioral, neurological and cognitive outcomes in ischemic stroke. However, little is known about the effect and mechanism of NBP on the neurite outgrowth. In this study, we used different methods to investigate the potential effects of NBP on the neurite extension and plasticity of immature and mature primary cortical neurons and explored the underlying mechanisms. Our results demonstrated that in immature and mature cortical neurons, NBP promoted the neurite length and intersections, increased neuritic arborization, elevated numbers of neurite branch and terminal points and improved neurite complexity and plasticity of neuronal development processes. Besides, our data revealed that NBP promoted neurite extension and branching partly by activating Shh signaling pathway via increasing Gap43 expression both in immature and mature primary cortical neurons. The present study provided new insights into the contribution of NBP in neuronal plasticity and unveiled a novel pathway to induce Gap43 expression in primary cortical neurons.
... Our study provides supporting evidence showing Chd7-dependent regulation of transcription is involved in the pathogenesis of autism. Moreover, many Chd7-regulated genes identified in this study, such as Gap43, Cadps2 and Reln, function in other brain regions besides cerebellum 21,26,53 . Thus, the molecular network controlled by Chd7 maybe a core network for brain development and function in human. ...
Mutations in chromatin modifier genes are frequently associated with neurodevelopmental diseases. We herein demonstrate that the chromodomain helicase DNA-binding protein 7 (Chd7), frequently associated with CHARGE syndrome, is indispensable for normal cerebellar development. Genetic inactivation of Chd7 in cerebellar granule neuron progenitors leads to cerebellar hypoplasia in mice, due to the impairment of granule neuron differentiation, induction of apoptosis and abnormal localization of Purkinje cells, which closely recapitulates known clinical features in the cerebella of CHARGE patients. Combinatory molecular analyses reveal that Chd7 is required for the maintenance of open chromatin and thus activation of genes essential for granule neuron differentiation. We further demonstrate that both Chd7 and Top2b are necessary for the transcription of a set of long neuronal genes in cerebellar granule neurons. Altogether, our comprehensive analyses reveal a mechanism with chromatin remodellers governing brain development via controlling a core transcriptional programme for cell-specific differentiation.
... Activation of GAP43 has been known to mediate axonal proliferation and regeneration, proliferating neuroepithelium as well as horizontal cell divisions during mammalian neurogenesis. [32][33][34] In the present study, reduced expression of proliferation markers, Ki-67 and p-GAP43, was found in poly(I:C)-treated AS xenografts ( Figure 2). Moreover, no apparent pathological changes of liver and kidney were found in mice after poly(I:C) treatment (Supplementary Figure S5) in histopathology. ...
Neuroblastoma (NB) is the deadliest pediatric solid tumor due to its pleomorphic molecular characteristics. In the innate immune system, toll-like receptor 3 (TLR3) recognizes viral double-stranded RNAs to initiate immune signaling. Positive TLR3 expression indicates a favorable prognosis in NB patients, and is associated with MYCN-non-amplified. However, TLR3-mediated innate immune responses remain elusive in NB. In this study, we attempted to dissect the molecular mechanism underlying TLR3-agonist polyinosinic-polycytidylic acid [poly(I:C)] treatment in NB in vivo. We established NB xenograft models in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice with MYCN-amplified SK-N-DZ (DZ) cells or MYCN-non-amplified SK-N-AS (AS) cells. Poly(I:C) treatment led to significant tumor regression in AS xenografts, but not in DZ xenografts. Through immunohistochemical analysis, significant suppression of tumor proliferation, downregulation of c-Myc expression, and upregulation of TLR3 expression were found in the treatment group. Poly(I:C) inducing activation of TLR3/IRF3-mediated innate immunity associated with downregulation of c-Myc can be found in MYCN-non-amplified SK-N-AS cells, but not in MYCN-amplified BE(2)-M17 cells. Knockdown of TLR3 disturbed poly(I:C)-induced suppression of c-Myc and upregulation of p-IRF3 in AS cells. Furthermore, poly(I:C) treatment upregulated active NF-κB, mitochondrial antioxidant manganese superoxide dismutase and 8-hydroxydeoxyguanosine, which works with reactive oxygen species (ROS) generation and DNA damage. Upregulation of active caspase 3 and cleaved poly [ADP-ribose] polymerase 1 were found in poly(I:C)-treated AS xenografts, which indicates the induction of apoptosis. Thus, our results suggest that c-Myc overexpression may increase sensitivity to poly(I:C)-induced tumor growth arrest and ROS-mediated apoptosis in NB. This study demonstrates that c-Myc protein expression has an important role in TLR3-induced innate immune responses, providing future treatment recommendations.Laboratory Investigation advance online publication, 16 May 2016; doi:10.1038/labinvest.2016.57.
... An animal study discovered that the CB was enlarged and produced new neuronlike glomus cells in hypoxia [30]. Meanwhile, studies further demonstrated that GAP-43 was also expressed in proliferating neuroblasts, and that neuronal differentiation was inhibited both in vitro and in vivo by the absence of GAP-43 expression, suggesting that GAP-43 was required for appropriate cell fate commitment during neurogenesis [31,32]. The results of the present study suggested that the changes in GAP-43 expression under different PO 2 conditions may regulate the differentiation of CB cells under these conditions. ...
Adaptive changes in the carotid body (CB) including the expression of the growth-associated protein-43 (GAP-43) have been studied in response to low, but not high, oxygen exposure. Expression of GAP-43 in the CB of rats under different atmospheric pressures and oxygen partial pressure (PO2) conditions was investigated. Mature male Sprague-Dawley rats were exposed to intermittent hypobaric hypoxia (IHH, 0, 1, 2 and 3 weeks), intermittent hyperbaric oxygen (IHBO2, 0, 1, 5 and 10 days, sacrificed six hours or 24 hours after the last HBO2 exposure), and intermittent hyperbaric normoxia (IHN, same treatment pattern as IHBO2). GAP-43 was highly expressed (mainly in type I cells) in the CB of normal rats. IHH u-regulated GAP-43 expression in the CB with significant differences (immunohistochemical staining [IHC]: F(3,15)=40.64, P < 0.01; western blot [WB]: F(3,16) = 53.52, P < 0.01) across the subgroups. GAP-43 expression in the CB was inhibited by IHBO2 (controls vs. IHBO2 groups, IHC: F(6,30) = 15.85, P < 0.01; WB: F(6,29) = 15.95, P < 0.01). No detectable changes in GAP-43 expression were found for IHN. These findings indicated that different PO2 conditions, but not air pressures, played an important role in the plasticity of the CB, and that GAP-43 might be a viable factor for the plasticity of the CB.
... This microenvironment is comprised of local cell types, cell signals, extracellular matrix and microvasculature. Indeed, the SEZ and SGZ niches are highly vascularized by a network of specialized capillaries (Goldberg and Hirschi, 2009) and NSCs closely interact with the microvasculature (Palmer et al., 2000; Mirzadeh et al., 2008; Shen et al., 2008; Tavazoie et al., 2008). This microvasculature has been shown to be essential in maintaining the function of the neurogenic niches, namely by regulating the proliferation and quiescence of NSCs (Palmer et al., 2000; Shen et al., 2004 Shen et al., , 2008 Tavazoie et al., 2008; Culver et al., 2013), as well as NSCs self-renewal and neurogenesis through soluble factors secreted by the endothelial cells (Shen et al., 2004; Ramírez-Castillejo et al., 2006; Gómez-Gaviro et al., 2012). ...
... Indeed, the SEZ and SGZ niches are highly vascularized by a network of specialized capillaries (Goldberg and Hirschi, 2009) and NSCs closely interact with the microvasculature (Palmer et al., 2000; Mirzadeh et al., 2008; Shen et al., 2008; Tavazoie et al., 2008). This microvasculature has been shown to be essential in maintaining the function of the neurogenic niches, namely by regulating the proliferation and quiescence of NSCs (Palmer et al., 2000; Shen et al., 2004 Shen et al., , 2008 Tavazoie et al., 2008; Culver et al., 2013), as well as NSCs self-renewal and neurogenesis through soluble factors secreted by the endothelial cells (Shen et al., 2004; Ramírez-Castillejo et al., 2006; Gómez-Gaviro et al., 2012). Noteworthy is the recent report of the existence of MSCs in the brain microvasculature (Paul et al., 2012), which paves way for the usage of MSCs secretome to modulate the neurogenic niches cells. ...
Neural stem cells (NSCs) and mesenchymal stem cells (MSCs) share few characteristics apart from self-renewal and multipotency. In fact, the neurogenic and osteogenic stem cell niches derive from two distinct embryonary structures; while the later originates from the mesoderm, as all the connective tissues do, the first derives from the ectoderm. Therefore, it is highly unlikely that stem cells isolated from one niche could form terminally differentiated cells from the other. Additionally, these two niches are associated to tissues/systems (e.g., bone and central nervous system) that have markedly different needs and display diverse functions within the human body. Nevertheless they do share common features. For instance, the differentiation of both NSCs and MSCs is intimately associated with the bone morphogenetic protein family. Moreover, both NSCs and MSCs secrete a panel of common growth factors, such as nerve growth factor (NGF), glial derived neurotrophic factor (GDNF), and brain derived neurotrophic factor (BDNF), among others. But it is not the features they share but the interaction between them that seem most important, and worth exploring; namely, it has already been shown that there are mutually beneficially effects when these cell types are co-cultured in vitro. In fact the use of MSCs, and their secretome, become a strong candidate to be used as a therapeutic tool for CNS applications, namely by triggering the endogenous proliferation and differentiation of neural progenitors, among other mechanisms. Quite interestingly it was recently revealed that MSCs could be found in the human brain, in the vicinity of capillaries. In the present review we highlight how MSCs and NSCs in the neurogenic niches interact. Furthermore, we propose directions on this field and explore the future therapeutic possibilities that may arise from the combination/interaction of MSCs and NSCs.
... In undifferentiated neurons, the response of GAP-43 to extracellular signals plays an important role in guiding the axonal path, whereas its deficiency causes severe defects in cytoarchitecture. The presence of GAP-43 is also required in mitotic neuroblasts [3,10,15] and its absence causes an unsuitable onset of neural differentiation [20,38,39,24]. Shen et al. demonstrated that the expression of GAP-43 in multipotent precursors is necessary for both neurogenic and gliogenic commitment, while its absence alters neuronal and astrocyte differentiation [38]. ...
Growth-associated protein 43 (GAP-43) is a neuronal phosphoprotein associated with initial axonal outgrowth and synaptic remodeling and recent work also suggests its involvement in cell cycle control. The complex expression of GAP-43 features transcriptional and posttranscriptional components. However, in some conditions, GAP-43 gene expression is controlled primarily by the interaction of stabilizing or destabilizing RNA-binding proteins (RBPs) with adenine and uridine (AU)-rich instability elements (AREs) in its 3́UTR. Like GAP-43, many proteins involved in cell proliferation are encoded by ARE-containing mRNAs, some of which codify cell-cycle-regulating proteins including cyclin D1. Considering that GAP-43 and cyclin D1 mRNA stabilization may depend on similar RBPs, this study evaluated the participation of GAP-43 in cell cycle control and its underlying mechanisms, particularly the possible role of its 3'UTR, using GAP-43-transfected NIH-3T3 fibroblasts. Our results show an arrest in cell cycle progression in the G0/G1 phase. This arrest may be mediated by the competition of GAP-43 3'UTR with cyclin D1 3'UTR for the binding of Hu proteins such as HuR, which may lead to a decrease in cyclin D1 expression. These results might lead to therapeutic applications involving the use of sequences in the B region of GAP-43 3'UTR to slow down cell cycle progression.
Copyright © 2015. Published by Elsevier Inc.
... The microenvironment of the neurogenic niche is composed of, and maintained by, several components, including local cell types, cell signals from more distal sources, the extracellular matrix and the microvasculature. Of these, the microvasculature has been argued to be one of the most important structures in maintaining the functional role of the neurogenic niche [10,[34][35][36][37], especially in setting the balance between proliferation and quiescence of NSCs. Indeed, the SVZ and SGZ appear to be highly vascularized by a dense network of specialized capillaries [38]. ...
... Indeed, the SVZ and SGZ appear to be highly vascularized by a dense network of specialized capillaries [38]. It has been shown in vitro that endothelial cells (ECs) can stimulate NSC self-renewal and neurogenesis through secreted soluble factors [35,39,40] and that NSCs closely interact with the microvasculature [10,34,36,41]. Additionally, the blood flow and hemodynamics of this intricate network affect NSC proliferation and can also act as a scaffold during migration [34,[42][43][44][45][46]. ...
... It has been shown in vitro that endothelial cells (ECs) can stimulate NSC self-renewal and neurogenesis through secreted soluble factors [35,39,40] and that NSCs closely interact with the microvasculature [10,34,36,41]. Additionally, the blood flow and hemodynamics of this intricate network affect NSC proliferation and can also act as a scaffold during migration [34,[42][43][44][45][46]. In addition, microglia, the brain resident macrophages, have a significant role in the regulation and maintenance of neurogenesis in the SGZ [47]. ...
Experimental evidence has demonstrated that several aspects of adult neural stem cells (NSCs), including their quiescence, proliferation, fate specification and differentiation, are regulated by epigenetic mechanisms. These control the expression of specific sets of genes, often including those encoding for small non-coding RNAs, indicating a complex interplay between various epigenetic factors and cellular functions.
Previous studies had indicated that in addition to the neuropathology in Alzheimer’s disease (AD), plasticity-related changes are observed in brain areas with ongoing neurogenesis, like the hippocampus and subventricular zone. Given the role of stem cells e.g. in hippocampal functions like cognition, and given their potential for brain repair, we here review the epigenetic mechanisms relevant for NSCs and AD etiology. Understanding the molecular mechanisms involved in the epigenetic regulation of adult NSCs will advance our knowledge on the role of adult neurogenesis in degeneration and possibly regeneration in the AD brain.
... At the cellular level the axon pathfinding is abnormal during the development and the growth cones are morphologically abnormal with reduced F-actin in vitro (Strittmatter et al. 1995;Shen et al. 2002). In addition the neuronal proliferation is also affected (Mani et al. 2001;Shen et al. 2008). Reflecting these structural defects GAP-43 knockout mice also show functional defects including memory impairment and sensorimotor disorder (Metz and Schwab 2004;Rekart et al. 2005). ...
Brain development is composed of several processes, which are chronologically and mechanistically overlapping each other. However, the process of the earliest neural circuit formation in the rostral brain is less understood compared with other processes in brain development, in part because of the lack of appropriate molecular markers. Accordingly, the identification of molecular markers for nerve cells may accelerate the detailed analysis of neural development. Growth associated protein 43 (GAP-43) is a major growth cone protein that regulates F-actin dynamics, and it has been often used as a marker for developing neurons. To test whether GAP-43 can be used as a general marker for developing neurons in chick early embryos, we analyzed the expression pattern of GAP-43 protein in the brain. While the majority of the neurons were GAP-43 positive, the earliest neurons in the dorsal mesencephalon (future tectum) were GAP-43 negative. However, a subset of the GAP-43 negative neurons became positive at later stages. Such a difference in the expression of GAP-43 protein may contribute to the precise patterning of the neural circuits in the mesencephalon in the subsequent development. The earliest neurons in the telencephalon, which belong to the terminal nerve (TN), were also GAP-43 positive. Since the development of TN is poorly understood compared to other cranial nerves, GAP-43 could help the detailed analysis of the development of TN as the marker.
