Figure - available from: Brain Structure and Function
This content is subject to copyright. Terms and conditions apply.
Photomicrographs of transverse sections of the telencephalon of S. canicula showing the expression pattern of GFAP in embryos (a–k) and juveniles (l–q). a Section of the telencephalon of a S25 embryo showing GFAP immunoreactivity in numerous endfeet in the pial surface of pallium (arrows). b–f Photomicrographs of a S29 embryo. b Photomicrograph at lower magnification showing GFAP immunoreactivity in radial processes extending from the ventricular surface to the pia in the pallium (arrows) and subpallium (arrowheads). c–e Photomicrographs at higher magnification showing an intense GFAP immunolabelling in the midline of the telencephalon (arrows) (c, d), in contrast to the rest of the telencephalon which shows weak immunoreactivity (arrows) (e). f Photomicrograph at higher magnification of the choroid plexus which show an intense GFAP immunoreactivity. g, h Photomicrographs from a S31 embryo at different magnifications. g Transverse section of the telencephalon showing radial processes (arrows), endfeet (arrowheads) and numerous positive cells lining the ventricular zone (empty arrowheads) positive for GFAP. Note the intense immunoreactivity in the choroid plexus (asterisk). g′ Photomicrograph at higher magnification of the ventricular surface showing the basal portion of cells close to the ventricle (arrowheads) immunoreactive to GFAP. h Transverse section of the subpallial midline showing intense immunoreactivity for GFAP at the ventricular and pial zone and numerous radial processes positive for GFAP (arrows); cells GFAP positive are intermingled between radial processes (arrowheads). i–k Photomicrographs from S32 embryos. i Section of the rostral telencephalon showing intense convergent processes (arrows) in the midline of subpallium. j–j′ Photomicrographs at different magnifications of the dorsal pallium showing curvy radial processes (arrows) and numerous cells in the ventricular zone showing GFAP immunoreactivity in the periphery of the cell body (arrowheads in j′). k Photomicrograph at high magnification of the medial pallium showing intense GFAP positive radial processes converging in the pallial midline (arrows). l–q Transverse sections of GFAP immunoreactivity in the telencephalon of juveniles. l Panoramic view of the ventricular zone of the telencephalon showing differences in the expression of GFAP between medial pallium, presumptive ventral pallium and subpallium. Note strong immunoreactivity in the choroid plexus (asterisk). m–o Magnifications of the ventricular zone, pial surface and blood vessels, respectively, showing ventricular positive cells (arrows in m), endfeet in the pial surface (arrows in n) and endfeet around blood vessels (arrows in o). p, q Details of the caudal telencephalon showing the presence of small cells close to blood vessels (empty arrowheads) and endfeet positive for GFAP surrounding blood vessels (arrowheads in p), as well as the presence of numerous endfeet in the roof of the caudal ventricle (arrows in q). Scale bars 200 µm (o), 100 µm (b, g, i, j, p), 50 µM (a, h, j′, m, n, q), 20 µM (c, d, e, f, k), 10 µM (g′, l)
Source publication
Radial glial cells (RGCs) are the first cell populations of glial nature to appear during brain ontogeny. They act as primary progenitor (stem) cells as well as a scaffold for neuronal migration. The proliferative capacity of these cells, both in development and in adulthood, has been subject of interest during past decades. In contrast with mammal...
Citations
... Due to their extremely rich phosphorylation potential, NFs are probably involved also in regulatory mechanisms (22). GFAP is one of the first detected markers of radial glial cells (RDCs) in early, intermediate, and late embryos of dogfish Scyliorhinus canicula L. (23,24). RDCs are supposed to be the predominant glial cells in fish (24). ...
... GFAP is one of the first detected markers of radial glial cells (RDCs) in early, intermediate, and late embryos of dogfish Scyliorhinus canicula L. (23,24). RDCs are supposed to be the predominant glial cells in fish (24). Although the expression and function of NFs and GFAP were previously investigated in vertebrates and fish (21,(23)(24)(25), findings on dendrin expression in nonmammalian vertebrates are still missing. ...
... RDCs are supposed to be the predominant glial cells in fish (24). Although the expression and function of NFs and GFAP were previously investigated in vertebrates and fish (21,(23)(24)(25), findings on dendrin expression in nonmammalian vertebrates are still missing. According to present data, there are no records of dendrin presence in the fish brain. ...
Background and purpose: Dendrin is a brain and renal protein that is supposed to be involved in cytoskeletal modifications at the synapse and a part of the slit diaphragm and podocytes. Here, we aimed to investigate dendrin expression in dogfish brain since this newly discovered protein was never reported in fish. We compared the expression of dendrin to those of glial (GFAP) and neuronal (NF) proteins, which have already been described in the dogfish brain. Materials and methods: Histological and immunofluorescent techniques were performed on tissue samples. The obtained data were statistically analyzed. Results: Our results have shown that dendrin is expressed in all observed parts of the dogfish brain. In the forebrain, both observed parts (telencephalon and olfactory lobes) expressed dendrin. Regarding the percentage area of dendrin expression, it is expressed more in olfactory lobes than in the telencephalon. Compared with GFAP and NF expression, the expression of dendrin significantly differs in both parts of the forebrain. The highest dendrin expression was noticed in the midbrain. In dogfish midbrain, the difference in expression of dendrin in comparison to those of GFAP and NF was even more significant. The percentage area of dendrin expression in the hindbrain (cerebellum and medulla oblongata) was smaller than those in the forebrain and midbrain, contrary the percentage area of intermediate filaments GFAP and NF were significantly higher. Conclusion: These results are the first report on dendrin expression in the dogfish brain opening the path for future studies on its role and function.
... BLBP played a role in glial and neuronal differentiation. 9 BLBP, also known as fatty acid-binding protein 7, is a member of the family of fatty acid-binding proteins, which are involved in the cellular internal transportation of fatty acids. [10][11][12] As a transporter of fatty acids, the major functions of BLBP are the facilitation of cellular internal transportation of polyunsaturated fatty acids, 13 especially docosahexaenoic acids. ...
Current studies suggest that the abnormal alteration of brain lipid binding protein (BLBP) might participate in the pathogenesis of amyotrophic lateral sclerosis (ALS). However, the detailed understanding of ALS pathogenesis been yet to be elucidated. Therefore, this research intended to explore the potential effects of BLBP in ALS. The observation and analysis of BLBP-altered features in various anatomical areas and different spinal segments was conducted at the pre-onset, onset, and progression stages of Tg(SOD1*G93A)1Gur (TG) mice and the same periods of age-matched SOD1 wild-type (WT) mice by fluorescence immunohistochemistry and western blotting. BLBP-positive cells were comprehensively distributed in various spinal anatomical areas, especially in both the anterior and posterior horn, around the central canal and in anterior, lateral, and posterior funiculi. Overall, BLBP expression tended to increase from the pre-onset to the onset to the progression stages of the same periods of age-matched WT mice. Furthermore, in TG mice, BLBP expression in the entire spinal cord significantly increased from onset to the progression stage. BLBP was expressed in neurons, astrocytes, and radial glial cells, and at the early and late stages of neural precursor cells (NPCs) and was predominantly distributed outside the cell nucleus. The increase of BLBP-positive cells was closely related to neural cell reduction in TG mice. The distribution and increased expression of BLBP among the cervical, thoracic, and lumbar segments of the spinal cord might participate in the development of ALS and exert potential effects in the pathogenesis of ALS by regulating NPCs.
... GFAP (a type-III intermediate filament protein) and the glutamate transporter GLAST are markers of astroglial or astroglia-like cells, including RGCs [118][119][120][121]. GFAP is present in NPCs, astrocytes (CNS), non-myelinating Schwann cells (PNS), and enteric glial cells [119,120]. ...
... GFAP (a type-III intermediate filament protein) and the glutamate transporter GLAST are markers of astroglial or astroglia-like cells, including RGCs [118][119][120][121]. GFAP is present in NPCs, astrocytes (CNS), non-myelinating Schwann cells (PNS), and enteric glial cells [119,120]. Interestingly, primary astrocyte cultures contain GFAP-expressing cells that can act as multipotent NPCs when transferred to neurogenic conditions [122]. However, GFAP-expressing NPCs are phenotypically and functionally distinct from non-neurogenic astrocytes [122]. ...
Neural progenitor cells (NPCs) are multipotent neural stem cells (NSCs) capable of self-renewing and differentiating into neurons, astrocytes and oligodendrocytes. In the postnatal/adult brain, NPCs are primarily located in the subventricular zone (SVZ) of the lateral ventricles (LVs) and subgranular zone (SGZ) of the hippocampal dentate gyrus (DG). There is evidence that NPCs are also present in the postnatal/adult hypothalamus, a highly conserved brain region involved in the regulation of core homeostatic processes, such as feeding, metabolism, reproduction, neuroendocrine integration and autonomic output. In the rodent postnatal/adult hypothalamus, NPCs mainly comprise different subtypes of tanycytes lining the wall of the 3rd ventricle. In the postnatal/adult human hypothalamus, the neurogenic niche is constituted by tanycytes at the floor of the 3rd ventricle, ependymal cells and ribbon cells (showing a gap-and-ribbon organization similar to that in the SVZ), as well as suprachiasmatic cells. We speculate that in the postnatal/adult human hypothalamus, neurogenesis occurs in a highly complex, exquisitely sophisticated neurogenic niche consisting of at least four subniches; this structure has a key role in the regulation of extrahypothalamic neurogenesis, and hypothalamic and extrahypothalamic neural circuits, partly through the release of neurotransmitters, neuropeptides, extracellular vesicles (EVs) and non-coding RNAs (ncRNAs).
... More recently, a method for genetic manipulation has become available [47]. Over the years, S. canicula proved to be a valid and good model for the study of a lot of biological processes, such as brain development [48][49][50], lifelong tooth cycling [44,51], retina function and development [52][53][54], and the immune system [55][56][57][58]. We therefore decided to investigate the distribution of neurotrophin genes by in situ hybridization in the brain of the small spotted catshark. ...
Neurotrophins (NTFs) are structurally related neurotrophic factors essential for differentiation , survival, neurite outgrowth, and the plasticity of neurons. Abnormalities associated with neurotrophin-signaling (NTF-signaling) were associated with neuropathies, neurodegenerative disorders , and age-associated cognitive decline. Among the neurotrophins, brain-derived neurotrophic factor (BDNF) has the highest expression and is expressed in mammals by specific cells throughout the brain, with particularly high expression in the hippocampus and cerebral cortex. Whole genome sequencing efforts showed that NTF signaling evolved before the evolution of Vertebrates; thus, the shared ancestor of Protostomes, Cyclostomes, and Deuterostomes must have possessed a single ortholog of neurotrophins. After the first round of whole genome duplication that occurred in the last common ancestor of Vertebrates, the presence of two neurotrophins in Agnatha was hypothesized, while the monophyletic group of cartilaginous fishes, or Chondrichthyans, was situated immediately after the second whole genome duplication round that occurred in the last common ancestor of Gnathostomes. Chondrichthyans represent the outgroup of all other living jawed vertebrates (Gnathostomes) and the sister group of Osteichthyans (comprehensive of Actinopterygians and Sarcopterygians). We were able to first identify the second neurotrophin in Agnatha. Secondly, we expanded our analysis to include the Chondrichthyans, with their strategic phylogenetic position as the most basal extant Gnathostome taxon. Results from the phylogenetic analysis confirmed the presence of four neurotrophins in the Chondrichthyans, namely the orthologs of the four mammalian neurotrophins BDNF, NGF, NT-3, and NT-4. We then proceeded to study the expression of BDNF in the adult brain of the Chondrichthyan Scyliorhinus canicula. Our results showed that BDNF is highly expressed in the S. canicula brain and that its expression is highest in the Telencephalon, while the Mesencephalic and Diencephalic areas showed expression of BDNF in isolated and well-defined cell groups. NGF was expressed at much lower levels that could be detected by PCR but not by in situ hybridization. Our results warrant further investigations in Chondrichthyans to characterize the putative ancestral function of neurotrophins in Vertebrates.
... The radial glia cells in the medial pallium of Xenopus laevis and Trachemys scripta elegans Analysis of radial glial cells in the MP was performed using two markers: brain lipid binding protein (BLBP) in Xenopus laevis (Figures 3A-D) and glial fibrillary acidic protein GFAP in Trachemys scripta elegans (Figures 3E-G). Both markers are widely described in the literature as markers of radial glia, and each one worked most satisfactorily in these species, although these markers may not initiate their expression simultaneously in all regions of the telencephalon [see Docampo-Seara et al. (2019)]. In X. laevis, the direction of radial glia fibers during pallial development (Figures 3A,B) and in the adult (Figures 3C,D) was perpendicular to the ventricular lining. ...
In all vertebrates, the most dorsal region of the telencephalon gives rise to the pallium, which in turn, is formed by at least four evolutionarily conserved histogenetic domains. Particularly in mammals, the medial pallium generates the hippocampal formation. Although this region is structurally different among amniotes, its functions, attributed to spatial memory and social behavior, as well as the specification of the histogenetic domain, appears to be conserved. Thus, the aim of the present study was to analyze this region by comparative analysis of the expression patterns of conserved markers in two vertebrate models: one anamniote, the amphibian Xenopus laevis ; and the other amniote, the turtle Trachemys scripta elegans , during development and in adulthood. Our results show that, the histogenetic specification of both models is comparable, despite significant cytoarchitectonic differences, in particular the layered cortical arrangement present in the turtle, not found in anurans. Two subdivisions were observed in the medial pallium of these species: a Prox1 + and another Er81/Lmo4 +, comparable to the dentate gyrus and the mammalian cornu ammonis region, respectively. The expression pattern of additional markers supports this subdivision, which together with its functional involvement in spatial memory tasks, provides evidence supporting the existence of a basic program in the specification and functionality of the medial pallium at the base of tetrapods. These results further suggest that the anatomical differences found in different vertebrates may be due to divergences and adaptations during evolution.
... We further performed immunostaining of BLBP [a specific marker of radial glial cells and neonatal cortical astrocytes (Guo et al., 2009;Docampo-Seara et al., 2019)] to address if Npas3 knockdown cells that detained in the deep cortical layers were progenitor cells. Interestingly, we found that most Npas3 knockdown cells that stalled in WM but not layers V and VI were BLBP positive ( Figures 4C,D). ...
The neuronal PAS domain 3 (NPAS3) is a member of the basic helix-loop-helix (bHLH) PAS family of transcription factors and is implicated in psychiatric and neurodevelopmental disorders. NPAS3 is robustly expressed in the cortical ventricle zone (VZ), a transient proliferative zone containing progenitor cells, mainly radial glial cells, destined to give rise to cortical excitatory neurons. However, the role of NPAS3 in corticogenesis remains largely unknown. In this study, we knocked down Npas3 expression in the neural progenitor cells residing in the cortical VZ to investigate the role of Npas3 in cerebral cortical development in mice. We demonstrated that Npas3 knockdown profoundly impaired neuronal radial migration and changed the laminar cell fate of the cells detained in the deep cortical layers. Furthermore, the downregulation of Npas3 led to the stemness maintenance of radial glial cells and increased the proliferation rate of neural progenitor cells residing in the VZ/subventricular zone (SVZ). These findings underline the function of Npas3 in the development of the cerebral cortex and may shed light on the etiology of NPAS3 -related disorders.
... In particular, apart from astrocytes, S100β expression has been also observed in oligodendrocytes [17], ependymocytes [18], vascular Glial cells types and relevant visualization markers. a) Radial glia -GFAP expression [77], EAAT-1 [78], GS [77]; b) Bergmann glia -expression of S100β [79], EAAT-1 [80], GS [81], Vimentin [82], CD44 [41]; c) Müller glia -expression of EAAT-1 [83], GS [84]; d) astrocytes -expression of GFAP, S100β, EAAT-1, vimentin, AQP4, ALDH1L1 [85], GS [86], Cx43 [87], Cx30 [88], aldolase C [89], SOX9 [37], NDRG2 [90]; e) oligodendrocytes -expression of S100β [56], EAAT-2 [91], GS [92], ALDH1L1 [93], CD44 [94]; f) ependymocytes -expression of S100β [95], EAAT-2 [96], GS [77], AQP4 [97], SOX9 [98]; g) CD44 + fibrous astrocyte [75]; h) CD44 + protoplasmic astrocyte [75] endothelium, lymphocytes [19] as well as neurons [58] (figure). S100a10 is a member of S100 protein family expressed in multiple organs (heart, kidneys, liver, lungs, spleen, gastrointestinal tract), including brain, where it plays an important role in transmembrane trafficking, vesicle secretion, and endocytosis [59]. ...
... In particular, apart from astrocytes, S100β expression has been also observed in oligodendrocytes [17], ependymocytes [18], vascular Glial cells types and relevant visualization markers. a) Radial glia -GFAP expression [77], EAAT-1 [78], GS [77]; b) Bergmann glia -expression of S100β [79], EAAT-1 [80], GS [81], Vimentin [82], CD44 [41]; c) Müller glia -expression of EAAT-1 [83], GS [84]; d) astrocytes -expression of GFAP, S100β, EAAT-1, vimentin, AQP4, ALDH1L1 [85], GS [86], Cx43 [87], Cx30 [88], aldolase C [89], SOX9 [37], NDRG2 [90]; e) oligodendrocytes -expression of S100β [56], EAAT-2 [91], GS [92], ALDH1L1 [93], CD44 [94]; f) ependymocytes -expression of S100β [95], EAAT-2 [96], GS [77], AQP4 [97], SOX9 [98]; g) CD44 + fibrous astrocyte [75]; h) CD44 + protoplasmic astrocyte [75] endothelium, lymphocytes [19] as well as neurons [58] (figure). S100a10 is a member of S100 protein family expressed in multiple organs (heart, kidneys, liver, lungs, spleen, gastrointestinal tract), including brain, where it plays an important role in transmembrane trafficking, vesicle secretion, and endocytosis [59]. ...
... In particular, apart from astrocytes, S100β expression has been also observed in oligodendrocytes [17], ependymocytes [18], vascular Glial cells types and relevant visualization markers. a) Radial glia -GFAP expression [77], EAAT-1 [78], GS [77]; b) Bergmann glia -expression of S100β [79], EAAT-1 [80], GS [81], Vimentin [82], CD44 [41]; c) Müller glia -expression of EAAT-1 [83], GS [84]; d) astrocytes -expression of GFAP, S100β, EAAT-1, vimentin, AQP4, ALDH1L1 [85], GS [86], Cx43 [87], Cx30 [88], aldolase C [89], SOX9 [37], NDRG2 [90]; e) oligodendrocytes -expression of S100β [56], EAAT-2 [91], GS [92], ALDH1L1 [93], CD44 [94]; f) ependymocytes -expression of S100β [95], EAAT-2 [96], GS [77], AQP4 [97], SOX9 [98]; g) CD44 + fibrous astrocyte [75]; h) CD44 + protoplasmic astrocyte [75] endothelium, lymphocytes [19] as well as neurons [58] (figure). S100a10 is a member of S100 protein family expressed in multiple organs (heart, kidneys, liver, lungs, spleen, gastrointestinal tract), including brain, where it plays an important role in transmembrane trafficking, vesicle secretion, and endocytosis [59]. ...
Astrocytes are the most common type of glial cells that provide homeostasis and protection of the central nervous system. Important specific characteristic of astrocytes is manifestation of morphological heterogeneity, which is directly dependent on localization in a particular area of the brain. Astrocytes can integrate into neural networks and keep neurons active in various areas of the brain. Moreover, astrocytes express a variety of receptors, channels, and membrane transporters, which underlie their peculiar metabolic activity, and, hence, determine plasticity of the central nervous system during development and aging. Such complex structural and functional organization of astrocytes requires the use of modern methods for their identification and analysis. Considering the important fact that determining the most appropriate marker for polymorphic and multiple subgroups of astrocytes is of decisive importance for studying their multifunctionality, this review presents markers, modern imaging techniques, and identification of astrocytes, which comprise a valuable resource for studying structural and functional properties of astrocytes, as well as facilitate better understanding of the extent to which astrocytes contribute to neuronal activity.
... In contrast, in anamniotes (fishes and amphibians), the radial ependymoglia represent the predominant glial cell type in the brain during embryogenesis and in adulthood and they express glial markers similar to that found in apical RGCs (Kálmán and Gould 2001;Cuoghi and Mola 2009;Allen and Lyons 2018). The molecular and morphological similarities between ependymoglia and RGCs in anamniotes make it difficult to discriminate between these cell types in late development (see Docampo-Seara et al. 2018). ...
... Numerous GFAP-, BLBP-, and GS-immunoreactive cells lining the OB ventricle with the typical morphology of RGCs with stained radial processes (ependymal cells or tanycytes: Horstmann 1954) were present in embryos and posthatching juveniles. This pattern was similar to that previously reported in the lateral telencephalic ventricles (Docampo-Seara et al. 2018). In all developmental stages analysed, immunoreactive glial cells were observed in all layers of the OB. ...
... In the developing OB of catshark, GFAP immunoreactivity was detected from mid-developmental stages (S31) and its expression persists in the late embryonic period (S32-34), as well as in post-hatching juveniles. Numerous GFAPimmunoreactive cells (present results) with the morphology of RGC lined the OB ventricle of embryos and posthaching juveniles (ependymal cells or tanycytes : Horstmann 1954), and their apical processes are organized as previously reported in the telencephalic hemispheres (Docampo-Seara et al. 2018), but no changes in organization were observed during development. Similarities and differences can be noted between the glia of catshark and mammals. ...
During development of the olfactory bulb (OB), glial cells play key roles in axonal guiding/targeting, glomerular formation and synaptic plasticity. Studies in mammals have shown that radial glial cells and peripheral olfactory glia (olfactory ensheathing cells, OECs) are involved in the development of the OB. Most studies about the OB glia were carried out in mammals, but data are lacking in most non-mammalian vertebrates. In the present work, we studied the development of the OB glial system in the cartilaginous fish Scyliorhinus canicula (catshark) using antibodies against glial markers, such as glial fibrillary acidic protein (GFAP), brain lipid-binding protein (BLBP), and glutamine synthase (GS). These glial markers were expressed in cells with radial morphology lining the OB ventricle of embryos and this expression continues in ependymal cells (tanycytes) in early juveniles. Astrocyte-like cells were also observed in the granular layer and surrounding glomeruli. Numerous GS-positive cells were present in the primary olfactory pathway of embryos. In the developmental stages analysed, the olfactory nerve layer and the glomerular layer were the regions with higher GFAP, BLBP and GS immuno-reactivity. In addition, numerous BLBP-expressing cells (a marker of mammalian OECs) showing proliferative activity were present in the olfactory nerve layer. Our findings suggest that glial cells of peripheral and central origin coexist in the OB of catshark embryos and early juveniles. These results open the path for future studies about the differential roles of glial cells in the catshark OB during embryonic development and in adulthood.
... Glial fibrillary acidic protein is a type III intermediate filament similar to vimentin and desmin that is pretty conserved in the vertebrate lineage with the exception of Lampreys and Anurans [47,48]. In non-mammalian vertebrates, several studies have shown that developmental radial glia express some degree of GFAP from early stages in fish [49][50][51][52], reptiles [53][54][55] and avians [56]. Amphibians offer a more complex picture: we lack data about caudata (newts and salamanders) regarding GFAP expression in developing radial glia (although is present in adult RGCs that remain as the main form of glia in this group [57]. ...
Radial glial cells (RGC) are at the center of brain development in vertebrates, acting as progenitors for neurons and macroglia (oligodendrocytes and astrocytes) and as guides for migration of neurons from the ventricular surface to their final positions in the brain. These cells originate from neuroepithelial cells (NEC) from which they inherit their epithelial features and polarized morphology, with processes extending from the ventricular to the pial surface of the embryonic cerebrum. We have learnt a great deal since the first descriptions of these cells at the end of the nineteenth century. However, there are still questions regarding how and when NEC transform into RGC or about the function of intermediate filaments such as glial fibrillary acidic protein (GFAP) in RGCs and their dynamics during neurogenesis. For example, it is not clear why RGCs in primates, including humans, express GFAP at the onset of cortical neurogenesis while in rodents it is expressed when it is essentially complete. Based on an ultrastructural analysis of GFAP expression and cell morphology of dividing progenitors in the developing neocortex of the macaque monkey, we show that RGCs become the main progenitor in the developing cerebrum by the start of neurogenesis, as all dividing cells show glial features such as GFAP expression and lack of tight junctions. Also, our data suggest that RGCs retract their apical process during mitosis. We discuss our findings in the context of the role and molecular characteristics of RGCs in the vertebrate brain, their differences with NECs and their dynamic behavior during the process of neurogenesis.
... They appear as cells with bipolar morphology in the mouse embryonic brain at E9 and E10 (at the start point of neurogenesis), presumably allowing appropriate migration of newborn neurons and acting as actual neural stem cells (NSCs). In the adult brain, RGCs can be found in particular regions such as lateral ventricles, hypothalamus, and cerebellum [109]. In mice, GFAP mRNA levels are shown to increase twofold from E15 to E17 and tenfold between E17 and the day of birth; however, the GFAP-expressing cells cannot form neurospheres at E12.5, and only some of the neurosphere-forming cells express GFAP at E15.5 [110]. ...
In the current review, we aim to discuss the principles and the perspectives of using the genetic constructs based on AAV vectors to regulate astrocytes’ activity. Practical applications of optogenetic approaches utilizing different genetically encoded opsins to control astroglia activity were evaluated. The diversity of astrocytic cell-types complicates the rational design of an ideal viral vector for particular experimental goals. Therefore, efficient and sufficient targeting of astrocytes is a multiparametric process that requires a combination of specific AAV serotypes naturally predisposed to transduce astroglia with astrocyte-specific promoters in the AAV cassette. Inadequate combinations may result in off-target neuronal transduction to different degrees. Potentially, these constraints may be bypassed with the latest strategies of generating novel synthetic AAV serotypes with specified properties by rational engineering of AAV capsids or using directed evolution approach by searching within a more specific promoter or its replacement with the unique enhancer sequences characterized using modern molecular techniques (ChIP-seq, scATAC-seq, snATAC-seq) to drive the selective transgene expression in the target population of cells or desired brain regions. Realizing these strategies to restrict expression and to efficiently target astrocytic populations in specific brain regions or across the brain has great potential to enable future studies.
