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Summary of the gene expression patterns in the adult zebrafish pallium. A.–D. Cross-sections at the levels indicated through the telencephalon. E. Schematic diagram of a cross section through the mouse telencephalon for comparison (modified after 14 ), note that the amygdaloid complex (AC, brown) is derived both from subpallium (grey) and pallium. Light grey areas (Th/Hyp) are part of the diencephalon. Indicated is also a model of the putative homology of the subdivisions in the adult zebrafish pallium to regions in the tetrapod pallium taking the data presented in this paper into account. Additional marker analysis, lineage tracing experiments and functional analyses are necessary to substantiate the proposed homology to pallial nuclei in tetrapods. * in scattered cells, ** in Dlv in the ventricular zone, moving caudally expression in the neuronal layer and ventricular zone, note that Prox1 positive cells are present in Dld shortly before the anterior commissure, n/a = not applicable. The black dashed line indicates the boundary between D and V. The red dashed lines indicate the boundaries between different nuclei in D. AC amygdaloid complex, ACo anterior cortical amygdalar area, BC basal amygdalar complex, BNSM bed nucleus of the stria medullaris, Ce central amygdala, CP Caudateputamen, DG dentate gyrus, EN entopeduncular nucleus, HF hippocampal formation, Hyp hypothalamus, Me medial amygdala, NCx neocortex, pCx piriform cortex, Po preoptic region, Th thalamus, V area ventralis telencephali, Vp postcommissural nucleus of the area ventralis telencephali, Vs supracommisural nucleus of the area ventralis telencephali.
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Background: The telencephalon shows a remarkable structural diversity among vertebrates. In particular, the everted telencephalon of ray-finned fishes has a markedly different morphology compared to the evaginated telencephalon of all other vertebrates. This difference in development has hampered the comparison between different areas of the palliu...
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... The study of the properties of aNSPCs using a salmon model provides new data on the organization of neurogenic zones in various parts of the brain containing the adult-type stem cells, with focus on their development, origin, cell lines, and proliferative dynamics [8,9]. Currently, the molecular signatures of these populations during homeostasis and repair in the vertebrate forebrain are only beginning to be studied [2,[10][11][12]. Outside the telencephalon, the regenerative plasticity of adult stem/progenitor cells and their biological significance remain poorly understood. ...
... The high regenerative and proliferative capacity of the juvenile salmon brain suggests that most aNSPCs are probably multipotent, as they are capable to replace almost all cell lines lost through damage, including NE cells, radial glia, oligodendrocytes, and neurons. To date, this hypothesis has been supported to a large extent by studies on quiescent Müller retinal glia in adult humans [9] and Danio rerio [11,18,19]. However, the unique regenerative profile of certain cell phenotypes in heterogeneous salmon brainstem cell niches is still unclear. ...
... A distinctive feature of the salmon brain is fetalization, or the presence of signs of the embryonic brain structure in juvenile Oncorhynchus keta [8], Oncorhynchus masou [9], and adult Oncorhynchus mykiss individuals [3]. In this regard, the study of the expression of glutamine synthetase (GS), vimentin (Vim), and nestin (Nes), which are molecular markers of aNSPCs in zebrafish [11,12,24,28] and Apteronotus leptorhynchus [35], contributes to extending our knowledge of the nature of aNSPCs in less studied fish models and, therefore, is important for the comparative study of neurogenesis in general. ...
The central nervous system of Pacific salmon retains signs of embryonic structure throughout life and a large number of neuroepithelial neural stem cells (NSCs) in the proliferative areas of the brain, in particular. However, the adult nervous system and neurogenesis studies on rainbow trout, Oncorhynchus mykiss, are limited. Here, we studied the localization of glutamine synthetase (GS), vimentin (Vim), and nestin (Nes), as well as the neurons formed in the postembryonic period, labeled with doublecortin (DC), under conditions of homeostatic growth in adult cerebellum and brainstem of Oncorhynchus mykiss using immunohistochemical methods and Western Immunoblotting. We observed that the distribution of vimentin (Vim), nestin (Nes), and glutamine synthetase (GS), which are found in the aNSPCs of both embryonic types (neuroepithelial cells) and in the adult type (radial glia) in the cerebellum and the brainstem of trout, has certain features. Populations of the adult neural stem/progenitor cells (aNSPCs) expressing GS, Vim, and Nes have different morphologies, localizations, and patterns of cluster formation in the trout cerebellum and brainstem, which indicates the morphological and, obviously, functional heterogeneity of these cells. Immunolabeling of PCNA revealed areas in the cerebellum and brainstem of rainbow trout containing proliferating cells which coincide with areas expressing Vim, Nes, and GS. Double immunolabeling revealed the PCNA/GS PCNA/Vim coexpression patterns in the neuroepithelial-type cells in the PVZ of the brainstem. PCNA/GS coexpression in the RG was detected in the submarginal zone of the brainstem. The results of immunohistochemical study of the DC distribution in the cerebellum and brainstem of trout have showed a high level of expression of this marker in various cell populations. This may indicate: (i) high production of the adult-born neurons in the cerebellum and brainstem of adult trout, (ii) high plasticity of neurons in the cerebellum and brainstem of trout. We assume that the source of new cells in the trout brain, along with PVZ and SMZ, containing proliferating cells, may be local neurogenic niches containing the PCNA-positive and silent (PCNA-negative), but expressing NSC markers, cells. The identification of cells expressing DC, Vim, and Nes in the IX-X cranial nerve nuclei of trout was carried out.
... (mesencephalon), and hindbrain (rhombencephalon) are clearly distinguishable by 16 hpf (Fig. 2). Structurally, the zebrafish forebrain consists of the olfactory bulb, and the telencephalon including the pallium and subpallium, and diencephalon including the hypothalamus, habenula and pineal body (Cheng et al., 2014;Ganz et al., 2014;Mueller et al., 2011). The midbrain is composed of the optic tectum corresponding to the superior colliculus in mammals and the tegmentum, and the hindbrain includes the cerebellum and the brain stem of the facial and vagal lobes (Heap et al., 2018;Kaslin et al., 2013;Kaslin and Brand, 2016). ...
... In addition, zebrafish shares highly conserved neurotransmitters and neuronal cells with mammals and humans throughout the brain with some regional specificity (Higashijima et al., 2004;Panula et al., 2010). For example, glutamatergic neurons are mainly distributed in the pallium and habenula of the forebrain as well as in the granule cell layer of cerebellum, while cholinergic neurons are in the subpallium (Bae et al., 2009;Ganz et al., 2014;Hibi and Shimizu, 2012;Nathan et al., 2015). Serotonergic neurons are distributed in the dorsal telencephalon along the raphe nuclei and the brain stem, and GABAergic and histaminergic neurons are in the subpallium and the Purkinje cell layer of the cerebellum, and in the posterior neuronal group of the hypothalamus, respectively (Eriksson et al., 1998;Hibi and Shimizu, 2012;Kaslin and Panula, 2001;Lillesaar et al., 2009;Ma, 2003;Mueller et al., 2006;Rink and Wullimann, 2002). ...
Nanomaterials have been widely employed from industrial to medical fields due to their small sizes and versatile characteristics. However, nanomaterials can also induce unexpected adverse effects on health. In particular, exposure of the nervous system to nanomaterials can cause serious neurological dysfunctions and neurodegenerative diseases. A number of studies have adopted various animal models to evaluate the neurotoxic effects of nanomaterials. Among them, zebrafish has become an attractive animal model for neurotoxicological studies due to several advantages, including the well-characterized nervous system, efficient genome editing, convenient generation of transgenic lines, high-resolution in vivo imaging, and an array of behavioral assays. In this review, we summarize recent studies on the neurotoxicological effects of nanomaterials, particularly engineered nanomaterials and nanoplastics, using zebrafish and discuss key findings with advantages and limitations of the zebrafish model in neurotoxicological studies.
... Several studies have been conducted to decipher the organization of the teleost pallium based on anatomical characterization and the expression of molecular markers (Wullimann and Mueller, 2004;Vargas et al., 2009;Mueller, 2011;Harvey-Girard et al., 2012;Ganz et al., 2015). Current knowledge on the functional role of the different pallial regions, is complemented with a series of functional studies involving distinct learning paradigms in combination with the detection of neuronal activity (by different proxies) and/or lesions on specific regions (Portavella et al., 2004;Durán et al., 2010;Trotha et al., 2014;Elliott et al., 2017;Lal et al., 2018;Ausas et al., 2019). ...
... Both of these cognitive functions are processed by the mammalian hippocampus. Furthermore, the zebrafish LP region expresses several molecular markers resembling the ones expressed by the mammalian hippocampus (Mueller and Wullimann, 2009;Ganz et al., 2015). Our results are in agreement with the involvement of the teleost LP in processing spatial information and reveal a rostro-caudal specialization of this structure, being the cLP the only region in which this spatial task heightens the addition of new neurons. ...
Adult neurogenesis could be considered as a homeostatic mechanism that accompanies the continuous growth of teleost fish. As an alternative but not excluding hypothesis, adult neurogenesis would provide a form of plasticity necessary to adapt the brain to environmental challenges. The zebrafish pallium is a brain structure involved in the processing of various cognitive functions and exhibits extended neurogenic niches throughout the periventricular zone. The involvement of neuronal addition as a learning-related plastic mechanism has not been explored in this model, yet. In this work, we trained adult zebrafish in a spatial behavioral paradigm and evaluated the neurogenic dynamics in different pallial niches. We found that adult zebrafish improved their performance in a cue-guided rhomboid maze throughout five daily sessions, being the fish able to relearn the task after a rule change. This cognitive activity increased cell proliferation exclusively in two pallial regions: the caudal lateral pallium (cLP) and the rostral medial pallium (rMP). To assessed whether learning impinges on pallial adult neurogenesis, mitotic cells were labeled by BrdU administration, and then fish were trained at different periods of adult-born neuron maturation. Our results indicate that adult-born neurons are being produced on demand in rMP and cLP during the learning process, but with distinct critical periods among these regions. Next, we evaluated the time course of adult neurogenesis by pulse and chase experiments. We found that labeled cells decreased between 4 and 32 dpl in both learning-sensitive regions, whereas a fraction of them continues proliferating over time. By modeling the population dynamics of neural stem cells (NSC), we propose that learning increases adult neurogenesis by two mechanisms: driving a chained proliferation of labeled NSC and rescuing newborn neurons from death. Our findings highlight adult neurogenesis as a conserved source of brain plasticity and shed light on a rostro-caudal specialization of pallial neurogenic niches in adult zebrafish.
... In this regard, expression in zebrafish is similar to the cortex of mammals (neocortex and hippocampus), which expresses neurogranin in numerous principal neurons (Represa et al., 1990;Singec et al., 2004). Neurogranin has been related to synaptic plasticity and learning in higher brain regions (Díez-Guerra, 2010;Pak et al., 2000;Zhong et al., 2009Zhong et al., , 2015, but to date no functional stud- (Folgueira et al., 2004b(Folgueira et al., , 2012Ganz et al., 2014;Nieuwenhuys, 2009;Northcutt, 2008Northcutt, , 2011Porter & Mueller, 2020;N. Yamamoto et al., 2007;Yáñez et al., 2021). ...
We studied the expression of neurogranin in the brain and some sensory organs (barbel taste buds, olfactory organ and retina) of adult zebrafish. Database analysis shows zebrafish has two paralog neurogranin genes (nrgna and nrgnb) that translate into three peptides with a conserved IQ-domain, as in mammals. Western blots of zebrafish brain extracts using an anti-neurogranin antiserum revealed three separate bands, confirming the presence of three neurogranin peptides. Immunohistochemistry shows neurogranin-like expression in the brain and sensory organs (taste buds, neuromasts and olfactory epithelium), not being able to discern its three different peptides. In the retina, the most conspicuous positive cells were bipolar neurons. In the brain, immunopositive neurons were observed in all major regions (pallium, subpallium, preoptic area, hypothalamus, diencephalon, mesencephalon and rhombencephalon, including the cerebellum), a more extended distribution than in mammals. Interestingly, dendrites, cell bodies and axon terminals of some neurons were immunopositive, thus zebrafish neurogranins may play presynaptic and postsynaptic roles. Most positive neurons were found in primary sensory centers (viscerosensory column and medial octavolateral nucleus) and integrative centers (pallium, subpallium, optic tectum and cerebellum), which have complex synaptic circuitry. However, we also observed expression in areas not related to sensory or integrative functions, such as in CSF-contacting cells associated with the hypothalamic recesses, which exhibited high neurogranin-like immunoreactivity. Together, these results reveal important differences with the patterns reported in mammals, suggesting divergent evolution from the common ancestor.
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... Высокая регенеративная и пролиферативная способности мозга молоди лососевых позволяет предполагать, что большинство взрослых стволовых клеток/клеток-предшественников, вероятно, являются мультипотентными, поскольку они, способны заменять практически все клеточные линии, утраченные в результате повреждения, в том числе нейроэпителиальные клетки, радиальную глию, олигодендроциты и нейроны [2][3][4]. На сегодняшний день эта гипотеза, по-видимому, подтверждается в значительной степени покоящейся Мюллеровской глией сетчатки у взрослого человека [6] и исследованиями, проведенными на данио [7]. Тем не менее, уникальный регенеративный профиль индивидуальных клеточных фенотипов в гетерогенных нишах стволовых клеток мозга лососевых рыб, остается пока не ясен. ...
... Радиальная глия дорсального паллиума конечного мозга была в центре внимания большинства исследований повреждений ЦНС у рыб [8]. Свойства вНСК/НКП интересно исследовать динамически, для различных постравматических периодов, в течение которых могут быть установлены начальный потенциал НСК и возможность участия в репаративном процессе при острой и/или хронической травме [4,7,8]. Сочетание экспериментального моделирования хронической и повторной острой травм может прояснить вопрос, сохраняется ли высокая производительность нейронов при повторной травматизации, что может определять особенные свойства эмбриональных и взрослых НСК и НКП лососей. ...
... Comparative neuroembryology has experienced a rebirth in the context of the evolutionary developmental (evodevo) neurobiology, thanks to studies of expression patterns of highly conserved regulatory genes in the embryonic brain of different species, which allowed visualization of the basic developmental units during embryonic development [Shimamura et al., 1997;Puelles et al., 2000;Murakami et al., 2001Murakami et al., , 2005González et al., 2002a, b;Bachy et al., 2001Bachy et al., , 2002aMueller and Wullimann, 2002;Mueller, 2002, 2004;Wullimann et al., 2005;Brox et al., 2003Brox et al., , 2004Kitagawa et al., 2004;Moreno et al., 2004Moreno et al., , 2008aMoreno et al., , b, 2010Moreno et al., , 2012Mueller et al., 2006Mueller et al., , 2008Eaton et al., 2008;Ferran et al., 2007Ferran et al., , 2009Ferran et al., , 2015Abellán et al., , 2010Abellán et al., , 2014Osório et al., 2010;Domínguez et al., 2010Domínguez et al., , 2013Morona et al., 2011;Quintana-Urzainqui et al., 2012Affaticati et al., 2015;Ganz et al., 2014;Sugahara et al., 2016;Desfilis et al., 2018;Porter and Mueller, 2020]. Early expressed regulatory genes encode transcription factors and signaling proteins, which play key roles in patterning, specification, proliferation, or differentiation, and their expression patterns are highly similar across species at early "phylotypic" embryonic stages [reviewed by Puelles and Medina, 2002;Mueller et al., 2006;Medina, 2007;Osório et al., 2010]. ...
... In contrast, Lhx9 has been found in the ventral pallium of mice [García-López et al., 2008], chickens , lacertid lizards , amphibians [Moreno et al., 2004;Moreno and González, 2006], and teleost and cartilaginous fishes [Peukert et al., 2011;Quintana-Urzainqui et al., 2015]. Thus, the ventral pallium has been incorporated as a basic division of the vertebrate pallium, and is identified or mentioned for discussion by authors from different neuroscience ambits and employing different species, including humans [in addition to references above, see for example: Wullimann and Mueller, 2004;Lindsay et al., 2005;Mueller and Wullimann, 2009;Ganz et al., 2014;Tosches et al., 2018;Porter and Mueller, 2020;Colquitt et al., 2021;Gedman et al., 2021]. ...
... For example, the homology between the mammalian hippocampal formation, the avian hippocampus and parahippocampal area, and the reptilian medial, dorsomedial and dorsal cortices was supported by their topological position next to the choroid tela and their common expression of the transcription factors Lhx2, Lhx9 and Lef1 during development, plus Prox1 in the dentate gyrus-like area that remains through adulthood [Gupta et al., 2012;Abellán et al., 2014;Medina et al., 2017a;Desfilis et al., 2018;Tosches et al., 2018]. Some of these genes were also found in the medial pallium of anamniotes [for example, Moreno et al., 2004;Ganz et al., 2014]. Moreover, experimental studies demonstrated the critical role of these genes in the development of the mammalian hippocampal formation [Lhx2: Porter et al., 1997;Bulchand et al., 2001;Lef1: Galceran et al., 2000;Prox1: Lavado et al., 2010;reviewed by Medina et al., 2017a]. ...
The pallium is the largest part of the telencephalon in amniotes, and comparison of its subdivisions across species has been extremely difficult and controversial due to its high divergence. Comparative embryonic genoarchitecture studies have greatly contributed to propose models of pallial fundamental divisions, which can be compared across species and be used to extract general organizing principles as well as to ask more focused and insightful research questions. The use of these models is crucial to discern between conservation, convergence or divergence in the neural populations and networks found in the pallium. Here we provide a critical review of the models proposed using this approach, including tetrapartite, hexapartite and double-ring models, and compare them to other models. While recognizing the power of these models for understanding brain architecture, development and evolution, we also highlight limitations and comment on aspects that require attention for improvement. We also discuss on the use of transcriptomic data for understanding pallial evolution and advise for better contextualization of these data by discerning between gene regulatory networks involved in the generation of specific units and cell populations versus genes expressed later, many of which are activity dependent and their expression is more likely subjected to convergent evolution.
... The dorsal telencephalon consists of the medial dorsal telencephalon (sometimes called medial dorsal pallium) and the lateral dorsal telencephalon (sometimes called lateral dorsal pallium). The medial dorsal telencephalon is suggested to have a function homologous to that of the amygdala while the lateral dorsal telencephalon is suggested to be similar to the hippocampus (Ganz et al. 2014;Northcutt 2006;Maximino et al. 2013). The posterior tuberculum in teleost fish is considered to have features suggestive of an ancient basal ganglion, mainly the presence of dopaminergic cells that project to the striatum (Wullimann 2014). ...
Atrazine (ATZ), a commonly used pesticide linked to endocrine disruption, cancer, and altered neurochemistry, frequently contaminates water sources at levels above the US Environmental Protection Agency’s 3 parts per billion (ppb; μg/L) maximum contaminant level. Adult male zebrafish behavior, brain transcriptome, brain methylation status, and neuropathology were examined to test the hypothesis that embryonic ATZ exposure causes delayed neurotoxicity, according to the developmental origins of health and disease paradigm. Zebrafish (Danio rerio) embryos were exposed to 0 ppb, 0.3 ppb, 3 ppb, or 30 ppb ATZ during embryogenesis (1–72 h post fertilization (hpf)), then rinsed and raised to maturity. At 9 months post fertilization (mpf), males had decreased locomotor parameters during a battery of behavioral tests. Transcriptomic analysis identified altered gene expression in organismal development, cancer, and nervous and reproductive system development and function pathways and networks. The brain was evaluated histopathologically for morphometric differences, and decreased numbers of cells were identified in raphe populations. Global methylation levels were evaluated at 12 mpf, and the body length, body weight, and brain weight were measured at 14 mpf to evaluate effects of ATZ on mature brain size. No significant difference in genome methylation or brain size was observed. The results demonstrate that developmental exposure to ATZ does affect neurodevelopment and neural function in adult male zebrafish and raises concern for possible health effects in humans due to ATZ’s environmental presence and persistence.
Graphical abstract
... For regeneration studies in other parts of the teleost CNS, we kindly refer to other publications on the diencephalon (Vijayanathan et al., 2017;Caldwell et al., 2019), cerebellum (Zupanc et al., 1998(Zupanc et al., , 2003(Zupanc et al., , 2006Zupanc and Ott, 1999;Zupanc, 2001, 2002;Ilieş et al., 2012), retina (Hitchcock and Raymond, 2004), and spinal cord (Ghosh and Hui, 2018). Indeed, the teleost telencephalon holds the subpallial and pallial neurogenic niches of the telencephalon, which are thought to be homologous to the mammalian subventricular zone and the subgranular zone -the two main neurogenic niches in adult mammals (Adolf et al., 2006;Grandel et al., 2006;Broglio et al., 2010;Durán et al., 2010;Ganz et al., 2010Ganz et al., , 2014. The NSCs in these neurogenic niches run along the ventricle, also called the ventricular zone (VZ), and cycling NSCs give rise to neurons that typically migrate only one or two cell sizes away from the VZ, ending up in what is called the periventricular zone (PVZ) (Adolf et al., 2006;Grandel et al., 2006). ...
Aging increases the risk for neurodegenerative disease and brain trauma, both leading to irreversible and multifaceted deficits that impose a clear societal and economic burden onto the growing world population. Despite tremendous research efforts, there are still no treatments available that can fully restore brain function, which would imply neuroregeneration. In the adult mammalian brain, neuroregeneration is naturally limited, even more so in an aging context. In view of the significant influence of aging on (late-onset) neurological disease, it is a critical factor in future research. This review discusses the use of a non-standard gerontology model, the teleost brain, for studying the impact of aging on neurorepair. Teleost fish share a vertebrate physiology with mammals, including mammalian-like aging, but in contrast to mammals have a high capacity for regeneration. Moreover, access to large mutagenesis screens empowers these teleost species to fill the gap between established invertebrate and rodent models. As such, we here highlight opportunities to decode the factor age in relation to neurorepair, and we propose the use of teleost fish, and in particular killifish, to fuel new research in the neuro-gerontology field.
... A recent study identified the expression pattern of conserved genes in the pallium of adult zebrafish in order to define pallial subdivisions and to determine their homologs in tetrapods [20,21]. They suggested that the Dm corresponds to the pallial amygdala in mammals, the Dc is the homolog of the cortex and the Dl (ventral and dorsal parts) could be the homolog of the hippocampus [22]. ...
Traumatic brain injury (TBI) remains the leading cause of long-term disability, which annually involves millions of individuals. Several studies on mammals reported that neurotrophins could play a significant role in both protection and recovery of function following neurodegenerative
diseases such as stroke and TBI. This protective role of neurotrophins after an event of TBI has also been reported in the zebrafish model. Nevertheless, reparative mechanisms in mammalian brain are limited, and newly formed neurons do not survive for a long time. In contrast, the brain of adult fish has high regenerative properties after brain injury. The evident differences in regenerative properties between mammalian and fish brain have been ascribed to remarkable different adult neurogenesis
processes. However, it is not clear if the specific role and time point contribution of each neurotrophin and receptor after TBI is conserved during vertebrate evolution. Therefore, in this review, I reported
the specific role and time point of intervention for each neurotrophic factor and receptor after an event of TBI in zebrafish and mammals.
... Interestingly, the telencephalon contains several neurogenic niches (estimated to 16 according to Byrd and Brunjes, 2001;Adolf et al., 2006;Grandel et al., 2006;Kishimoto et al., 2011Kishimoto et al., , 2013. Among these, the Vv of the subpallium is considered to be homologous of the SVZ of the lateral ventricle of mammals, and the Dl and/or Dp of the pallium to be the equivalent of the SGZ of the DG (see below for description of these neurogenic niches) (Broglio et al., 2005;März et al., 2010;Grandel and Brand, 2013;Ganz et al., 2014). However, these homologies between fish and rodents would benefit from further investigation in order to ascertain such evolutionary comparisons. ...
... The work from Ganz et al. (2014) aimed at identifying the expression pattern of conserved genes in the pallium of adult zebrafish in order to define pallial subdivisions and to determine their homologs in tetrapods (Ganz et al., 2014). They suggested that the Dm corresponds to the pallial amygdala in mammals, the Dc is the homolog of the cortex and the Dl (ventral and dorsal parts) could Frontiers in Neuroscience | www.frontiersin.org 2 September 2020 | Volume 14 | Article 568930 FIGURE 1 | Schematic representation of evagination and eversion in vertebrates. ...
... The work from Ganz et al. (2014) aimed at identifying the expression pattern of conserved genes in the pallium of adult zebrafish in order to define pallial subdivisions and to determine their homologs in tetrapods (Ganz et al., 2014). They suggested that the Dm corresponds to the pallial amygdala in mammals, the Dc is the homolog of the cortex and the Dl (ventral and dorsal parts) could Frontiers in Neuroscience | www.frontiersin.org 2 September 2020 | Volume 14 | Article 568930 FIGURE 1 | Schematic representation of evagination and eversion in vertebrates. ...
In contrast to mammals, the adult zebrafish brain shows neurogenic activity in a multitude of niches present in almost all brain subdivisions. Irrespectively, constitutive neurogenesis in the adult zebrafish and mouse telencephalon share many similarities at the cellular and molecular level. However, upon injury during tissue repair, the situation is entirely different. In zebrafish, inflammation caused by traumatic brain injury or by induced neurodegeneration initiates specific and distinct neurogenic programs that, in combination with signaling pathways implicated in constitutive neurogenesis, quickly, and efficiently overcome the loss of neurons. In the mouse brain, injury-induced inflammation promotes gliosis leading to glial scar formation and inhibition of regeneration. A better understanding of the regenerative mechanisms occurring in the zebrafish brain could help to develop new therapies to combat the debilitating consequences of brain injury, stroke, and neurodegeneration. The aim of this review is to compare the properties of neural progenitors and the signaling pathways, which control adult neurogenesis and regeneration in the zebrafish and mammalian telencephalon.
