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BACKGROUND: Traumatic brain injury (TBI) often results in diverse molecular responses, challenging traditional proteomic studies that measure average changes at tissue levels and fail to capture the complexity and heterogeneity of the affected tissues. Spatial proteomics offers a solution by providing insights into sub-region-specific alterations within tissues. This study focuses on the hippocampal sub-regions, analyzing proteomic expression profiles in mice at the acute (1 day) and subacute (7 days) phases of post-TBI to understand subregion-specific vulnerabilities and long-term consequences. METHODS: Three mice brains were collected from each group, including Sham, 1-day post-TBI and 7-day post-TBI. Hippocampal subregions were extracted using Laser Microdissection (LMD) and subsequently analyzed by label-free quantitative proteomics. RESULTS: The spatial analysis reveals region-specific protein abundance changes, highlighting the elevation of FN1, LGALS3BP, HP, and MUG-1 in the stratum moleculare (SM), suggesting potential immune cell enrichment post-TBI. Notably, established markers of chronic traumatic encephalopathy, IGHM and B2M, exhibit specific upregulation in the dentate gyrus bottom (DG2) independent of direct mechanical injury. Metabolic pathway analysis identifies disturbances in glucose and lipid metabolism, coupled with activated cholesterol synthesis pathways enriched in SM at 7-Day post-TBI and subsequently in deeper DG1 and DG2 suggesting a role in neurogenesis and the onset of recovery. Coordinated activation of neuroglia and microtubule dynamics in DG2 suggest recovery mechanisms in less affected regions. Cluster analysis revealed spatial variations post-TBI, indicative of dysregulated neuronal plasticity and neurogenesis and further predisposition to neurological disorders. TBI-induced protein upregulation (MUG-1, PZP, GFAP, TJP, STAT-1, and CD44) across hippocampal sub-regions indicates shared molecular responses and links to neurological disorders. Spatial variations were demonstrated by proteins dysregulated in both or either of the time-points exclusively in each subregion (ELAVL2, CLIC1 in PL, CD44 and MUG-1 in SM, and SHOC2, LGALS3 in DG). CONCLUSIONS: Utilizing advanced spatial proteomics techniques, the study unveils the dynamic molecular responses in distinct hippocampal subregions post-TBI. It uncovers region-specific vulnerabilities and dysregulated neuronal processes, and potential recovery-related pathways that contribute to our understanding of TBI's neurological consequences and provides valuable insights for biomarker discovery and therapeutic targets.
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Zinc Finger MIZ-Type Containing 1 (Zmiz1), also known as ZIMP10 or RAI17, is a transcription cofactor and member of the Protein Inhibitor of Activated STAT (PIAS) family of proteins. Zmiz1 is critical for a variety of biological processes including vascular development. However, its role in the lymphatic vasculature is unknown. In this study, we utilized human dermal lymphatic endothelial cells (HDLECs) and an inducible, lymphatic endothelial cell (LEC)-specific Zmiz1 knockout mouse model to investigate the role of Zmiz1 in LECs. Transcriptional profiling of ZMIZ1-deficient HDLECs revealed downregulation of genes crucial for lymphatic vessel development. Additionally, our findings demonstrated that loss of Zmiz1 results in reduced expression of proliferation and migration genes in HDLECs and reduced proliferation and migration in vitro. We also presented evidence that Zmiz1 regulates Prox1 expression in vitro and in vivo by modulating chromatin accessibility at Prox1 regulatory regions. Furthermore, we observed that loss of Zmiz1 in mesenteric lymphatic vessels significantly reduced valve density. Collectively, our results highlight a novel role of Zmiz1 in LECs and as a transcriptional regulator of Prox1, shedding light on a previously unknown regulatory factor in lymphatic vascular biology.
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Proliferación Celular , Células Endoteliales , Proteínas de Homeodominio , Vasos Linfáticos , Factores de Transcripción , Proteínas Supresoras de Tumor , Animales , Humanos , Ratones , Movimiento Celular/genética , Células Endoteliales/metabolismo , Regulación de la Expresión Génica , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Linfangiogénesis/genética , Vasos Linfáticos/metabolismo , Vasos Linfáticos/citología , Ratones Noqueados , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Proteínas Supresoras de Tumor/genética , Proteínas Supresoras de Tumor/metabolismoRESUMEN
Neurodevelopmental disorders (NDDs) are a class of pathologies arising from perturbations in brain circuit formation and maturation with complex etiological triggers often classified as environmental and genetic. Neuropsychiatric conditions such as autism spectrum disorders (ASD), intellectual disability (ID), and attention deficit hyperactivity disorders (ADHD) are common NDDs characterized by their hereditary underpinnings and inherent heterogeneity. Genetic risk factors for NDDs are increasingly being identified in non-coding regions and proteins bound to them, including transcriptional regulators and chromatin remodelers. Importantly, de novo mutations are emerging as important contributors to NDDs and neuropsychiatric disorders. Recently, de novo mutations in transcriptional co-factor Zmiz1 or its regulatory regions have been identified in unrelated patients with syndromic ID and ASD. However, the role of Zmiz1 in brain development is unknown. Here, using publicly available databases and a Zmiz1 mutant mouse model, we reveal that Zmiz1 is highly expressed during embryonic brain development in mice and humans, and though broadly expressed across the brain, Zmiz1 is enriched in areas prominently impacted in ID and ASD such as cortex, hippocampus, and cerebellum. We investigated the relationship between Zmiz1 structure and pathogenicity of protein variants, the epigenetic marks associated with Zmiz1 regulation, and protein interactions and signaling pathways regulated by Zmiz1. Our analysis reveals that Zmiz1 regulates multiple developmental processes, including neurogenesis, neuron connectivity, and synaptic signaling. This work paves the way for future studies on the functions of Zmiz1 and highlights the importance of combining analysis of mouse models and human data.
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Specific and highly diverse connectivity between functionally specialized regions of the nervous system is controlled at multiple scales, from anatomically organized connectivity following macroscopic axon tracts to individual axon target-finding and synapse formation. Identifying mechanisms that enable entire subpopulations of related neurons to project their axons with regional specificity within stereotyped tracts to form appropriate long-range connectivity is key to understanding brain development, organization, and function. Here, we investigate how axons of the cerebral cortex form precise connections between the two cortical hemispheres via the corpus callosum. We identify topographic principles of the developing trans-hemispheric callosal tract that emerge through intrinsic guidance executed by growing axons in the corpus callosum within the first postnatal week in mice. Using micro-transplantation of regionally distinct neurons, subtype-specific growth cone purification, subcellular proteomics, and in utero gene manipulation, we investigate guidance mechanisms of transhemispheric axons. We find that adhesion molecule levels instruct tract topography and target field guidance. We propose a model in which transcallosal axons in the developing brain perform a "handshake" that is guided through co-fasciculation with symmetric contralateral axons, resulting in the stereotyped homotopic connectivity between the brain's hemispheres.
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Episodic memories are thought to be stabilized through the coordination of cortico-hippocampal activity during sleep. However, the timing and mechanism of this coordination remain unknown. To investigate this, we studied the relationship between hippocampal reactivation and slow-wave sleep up and down states of the retrosplenial cortex (RTC) and prefrontal cortex (PFC). We found that hippocampal reactivations are strongly correlated with specific cortical states. Reactivation occurred during sustained cortical Up states or during the transition from up to down state. Interestingly, the most prevalent interaction with memory reactivation in the hippocampus occurred during sustained up states of the PFC and RTC, while hippocampal reactivation and cortical up-to-down state transition in the RTC showed the strongest coordination. Reactivation usually occurred within 150-200 msec of a cortical Up state onset, indicating that a buildup of excitation during cortical Up state activity influences the probability of memory reactivation in CA1. Conversely, CA1 reactivation occurred 30-50 msec before the onset of a cortical down state, suggesting that memory reactivation affects down state initiation in the RTC and PFC, but the effect in the RTC was more robust. Our findings provide evidence that supports and highlights the complexity of bidirectional communication between cortical regions and the hippocampus during sleep.
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Hipocampo , Consolidación de la Memoria , Hipocampo/fisiología , Sueño/fisiología , Corteza Prefrontal/fisiología , Giro del Cíngulo , Cognición , Consolidación de la Memoria/fisiologíaRESUMEN
Identities of distinct neuron subtypes are specified during embryonic development, then maintained during post-natal maturation. In cerebral cortex, mechanisms controlling early acquisition of neuron-subtype identities have become increasingly understood. However, mechanisms controlling neuron-subtype identity stability during post-natal maturation are largely unexplored. We identify that Tle4 is required for both early acquisition and post-natal stability of corticothalamic neuron-subtype identity. Embryonically, Tle4 promotes acquisition of corticothalamic identity and blocks emergence of core characteristics of subcerebral/corticospinal projection neuron identity, including gene expression and connectivity. During the first post-natal week, when corticothalamic innervation is ongoing, Tle4 is required to stabilize corticothalamic neuron identity, limiting interference from differentiation programs of developmentally related neuron classes. We identify a deacetylation-based epigenetic mechanism by which TLE4 controls Fezf2 expression level by corticothalamic neurons. This contributes to distinction of cortical output subtypes and ensures identity stability for appropriate maturation of corticothalamic neurons.
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Corteza Cerebral , Neuronas , Femenino , Embarazo , Interneuronas , Neuronas/metabolismoRESUMEN
Zinc Finger MIZ-Type Containing 1 (Zmiz1), also known as ZIMP10 or RAI17, is a transcription cofactor and member of the Protein Inhibitor of Activated STAT (PIAS) family of proteins. Zmiz1 is critical for a variety of biological processes including vascular development. However, its role in the lymphatic vasculature is unknown. In this study, we utilized human dermal lymphatic endothelial cells (HDLECs) and an inducible, lymphatic endothelial cell (LEC)-specific Zmiz1 knockout mouse model to investigate the role of Zmiz1 in LECs. Transcriptional profiling of Zmiz1-deficient HDLECs revealed downregulation of genes crucial for lymphatic vessel development. Additionally, our findings demonstrated that loss of Zmiz1 results in reduced expression of proliferation and migration genes in HDLECs and reduced proliferation and migration in vitro. We also presented evidence that Zmiz1 regulates Prox1 expression in vitro and in vivo by modulating chromatin accessibility at Prox1 regulatory regions. Furthermore, we observed that loss of Zmiz1 in mesenteric lymphatic vessels significantly reduced valve density. Collectively, our results highlight a novel role of Zmiz1 in LECs and as a transcriptional regulator of Prox1, shedding light on a previously unknown regulatory factor in lymphatic vascular biology.
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Corticothalamic interactions between associative cortices and higher order thalamic nuclei are involved in high-cognitive functions such as decision-making and working memory. Corticothalamic neurons (CTn) in the prefrontal cortex and other associative areas have been much less studied than their counterparts in the primary sensory areas. The availability of characterized transgenic tools to study CTn in associative areas will facilitate their study and contribute to overcome the scarcity of data about their properties, network dynamics, and contribution to cognitive functions. Here, we characterized the Syt6-Cre (KI148Gsat/Mmud) transgenic mouse line, by tracking expression of a Cre-mediated reporter. In this line, Cre-reporter is strongly expressed in the prefrontal, motor, cingulate, and retrosplenial cortices, as well as in other brain areas including the cerebellum and the olfactory tubercle. Cortical expression starts embryonically and reaches the adult expression pattern by postnatal day 15. In the cortex, Cre-reporter is expressed by layer 6-CTn and by layer 5-CTn to a lesser extent. We quantified Syt6-Cre+ CTn axon varicosities to estimate the distribution and density of putative corticothalamic driver and modulator inputs to thalamic nuclei in the medial, midline, intralaminar, anterior, and motor groups. Also, we characterized the effect of optogenetic stimulation of Syt6-Cre+ neurons in the activity of the prefrontal cortex. CTn stimulation in the prefrontal cortex induces an oscillatory activity in the local field potential that resembles the cortical downstates typically observed during slow-wave sleep or quiet wake.
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Corteza Cerebral , Integrasas , Animales , Corteza Cerebral/fisiología , Integrasas/genética , Ratones , Ratones Transgénicos , Vías Nerviosas/fisiología , NeuronasRESUMEN
Mutations in RAC1 allele are implicated in multiple brain tumors, indicating a rigorous control of Rac1 activity is required for neural tissue normal development and homeostasis. To understand how elevated Rac1 activity affects neural crest cells (NCCs) development, we have generated Rac1 CA ;Wnt1-Cre2 mice, in which a constitutively active Rac1 G12V mutant is expressed specifically in NCCs derivatives. Our results revealed that augmented Rac1 activity leads to enlarged midbrain and altered cell density, accompanied by increased NCCs proliferation rate and misrouted cell migration. Interestingly, our experimental data also showed that elevated Rac1 activity in NCCs disrupts regionalization of dopaminergic neuron progenitors in the ventral midbrain and impairs their differentiation. These findings shed light on the mechanisms of RAC1 mutation correlated brain tumor at the cellular and molecular level.
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The mechanism underlying selective motor neuron (MN) death remains an essential question in the MN disease field. The MN disease spinal muscular atrophy (SMA) is attributable to reduced levels of the ubiquitous protein SMN. Here, we report that SMN levels are widely variable in MNs within a single genetic background and that this heterogeneity is seen not only in SMA MNs but also in MNs derived from controls and amyotrophic lateral sclerosis (ALS) patients. Furthermore, cells with low SMN are more susceptible to cell death. These findings raise the important clinical implication that some SMN-elevating therapeutics might be effective in MN diseases besides SMA. Supporting this, we found that increasing SMN across all MN populations using an Nedd8-activating enzyme inhibitor promotes survival in both SMA and ALS-derived MNs. Altogether, our work demonstrates that examination of human neurons at the single-cell level can reveal alternative strategies to be explored in the treatment of degenerative diseases.
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Enfermedades Neuromusculares/metabolismo , Proteínas del Complejo SMN/metabolismo , Esclerosis Amiotrófica Lateral/metabolismo , Animales , Modelos Animales de Enfermedad , Humanos , Ratones , Neuronas Motoras/metabolismo , Atrofia Muscular Espinal/metabolismo , Análisis de la Célula Individual/métodos , Médula Espinal/metabolismoRESUMEN
Corticothalamic projection neurons (CThPN) are a diverse set of neurons, critical for function of the neocortex. CThPN development and diversity need to be precisely regulated, but little is known about molecular controls over their differentiation and functional specialization, critically limiting understanding of cortical development and complexity. We report the identification of a set of genes that both define CThPN and likely control their differentiation, diversity, and function. We selected the CThPN-specific transcriptional coregulator Fog2 for functional analysis. We identify that Fog2 controls CThPN molecular differentiation, axonal targeting, and diversity, in part by regulating the expression level of Ctip2 by CThPN, via combinatorial interactions with other molecular controls. Loss of Fog2 specifically disrupts differentiation of subsets of CThPN specialized in motor function, indicating that Fog2 coordinates subtype and functional-area differentiation. These results confirm that we identified key controls over CThPN development and identify Fog2 as a critical control over CThPN diversity.
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Proteínas de Unión al ADN/genética , Regulación del Desarrollo de la Expresión Génica , Neocórtex/metabolismo , Vías Nerviosas/metabolismo , Neurogénesis/genética , Neuronas/citología , Factores de Transcripción/genética , Animales , Ratones , Neurogénesis/fisiología , Factores de Transcripción/metabolismoRESUMEN
Neuronal subtype-specific transcription factors (TFs) instruct key features of neuronal function and connectivity. Activity-dependent mechanisms also contribute to wiring and circuit assembly, but whether and how they relate to TF-directed neuronal differentiation is poorly investigated. Here we demonstrate that the TF Cux1 controls the formation of the layer II/III corpus callosum (CC) projections through the developmental transcriptional regulation of Kv1 voltage-dependent potassium channels and the resulting postnatal switch to a Kv1-dependent firing mode. Loss of Cux1 function led to a decrease in the expression of Kv1 transcripts, aberrant firing responses, and selective loss of CC contralateral innervation. Firing and innervation were rescued by re-expression of Kv1 or postnatal reactivation of Cux1. Knocking down Kv1 mimicked Cux1-mediated CC axonal loss. These findings reveal that activity-dependent processes are central bona fide components of neuronal TF-differentiation programs and establish the importance of intrinsic firing modes in circuit assembly within the neocortex.
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Potenciales de Acción/fisiología , Regulación del Desarrollo de la Expresión Génica , Proteínas de Homeodominio/metabolismo , Neuronas/fisiología , Proteínas Nucleares/metabolismo , Proteínas Represoras/metabolismo , Canales de Potasio de la Superfamilia Shaker/fisiología , Animales , Cuerpo Calloso/citología , Cuerpo Calloso/crecimiento & desarrollo , Cuerpo Calloso/fisiología , Técnicas de Silenciamiento del Gen , Ratones , Ratones Transgénicos , Cultivo Primario de Células , Canales de Potasio de la Superfamilia Shaker/biosíntesis , Canales de Potasio de la Superfamilia Shaker/genéticaRESUMEN
Neurons in layer IV of the rodent whisker somatosensory cortex are tangentially organized in periodic clusters called barrels, each of which is innervated by thalamocortical axons transmitting sensory information from a single principal whisker, together forming a somatotopic map of the whisker pad. Proper thalamocortical innervation is critical for barrel formation during development, but the molecular mechanisms controlling layer IV neuron clustering are unknown. Here, we investigate the role in this mapping of the nuclear orphan receptor RORß, which is expressed in neurons in layer IV during corticogenesis. We find that RORß protein expression specifically increases in the whisker barrel cortex during barrel formation and that in vivo overexpression of RORß is sufficient to induce periodic barrel-like clustering of cortical neurons. Remarkably, this clustering can be induced as early as E18, prior to innervation by thalamocortical afferents and whisker derived-input. At later developmental stages, these ectopic neuronal clusters are specifically innervated by thalamocortical axons, demonstrated by anterograde labeling from the thalamus and by expression of thalamocortical-specific synaptic markers. Together, these data indicate that RORß expression levels control cytoarchitectural patterning of neocortical neurons during development, a critical process for the topographical mapping of whisker input onto the cortical surface.
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Tipificación del Cuerpo/fisiología , Neocórtex/citología , Neurogénesis/fisiología , Neuronas/citología , Miembro 2 del Grupo F de la Subfamilia 1 de Receptores Nucleares/metabolismo , Corteza Somatosensorial/citología , Animales , Técnica del Anticuerpo Fluorescente , Ratones , Ratones Transgénicos , Microscopía Confocal , Neocórtex/embriología , Neocórtex/metabolismo , Neuronas/metabolismo , Corteza Somatosensorial/embriología , Corteza Somatosensorial/metabolismo , Vibrisas/inervaciónRESUMEN
Input to apical dendritic tufts is now deemed crucial for associative learning, attention, and similar "feedback" interactions in the cerebral cortex. Excitatory input to apical tufts in neocortical layer 1 has been traditionally assumed to be predominantly cortical, as thalamic pathways directed to this layer were regarded relatively scant and diffuse. However, the sensitive tracing methods used in the present study show that, throughout the rat neocortex, large numbers (mean approximately 4500/mm(2)) of thalamocortical neurons converge in layer 1 and that this convergence gives rise to a very high local density of thalamic terminals. Moreover, we show that the layer 1-projecting neurons are present in large numbers in most, but not all, motor, association, limbic, and sensory nuclei of the rodent thalamus. Some layer 1-projecting axons branch to innervate large swaths of the cerebral hemisphere, whereas others arborize within only a single cortical area. Present data imply that realistic modeling of cortical circuitry should factor in a dense axonal canopy carrying highly convergent thalamocortical input to pyramidal cell apical tufts. In addition, they are consistent with the notion that layer 1-projecting axons may be a robust anatomical substrate for extensive "feedback" interactions between cortical areas via the thalamus.
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Dendritas/fisiología , Neocórtex/anatomía & histología , Tálamo/anatomía & histología , Vías Aferentes/anatomía & histología , Animales , Axones/fisiología , Femenino , Colorantes Fluorescentes , Procesamiento de Imagen Asistido por Computador , Inmunohistoquímica , Ratas , Ratas Sprague-DawleyRESUMEN
Thalamocortical (TC) pathways are still mainly understood as the gateway for ascending sensory-motor information into the cortex. However, it is now clear that a great many TC cells are involved in interactions between cortical areas via the thalamus. We review recent data, including our own, which demonstrate the generalized presence in rodent thalamus of two major TC cell types characterized, among other features, by their axon development, arborization and laminar targeting in the cortex. Such duality may allow inputs from thalamus to access cortical circuits via "bottom-up"-wired axon arbors or via "top-down"-wired axon arbors.
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Corteza Cerebral/fisiología , Tálamo/fisiología , Animales , Corteza Cerebral/anatomía & histología , Vías Nerviosas , Neuronas/fisiología , Ratas , Ratas Sprague-Dawley , Tálamo/anatomía & histologíaRESUMEN
Inputs to the layer I apical dendritic tufts of pyramidal cells are crucial in "top-down" interactions in the cerebral cortex. A large population of thalamocortical cells, the "matrix" (M-type) cells, provides a direct robust input to layer I that is anatomically and functionally different from the thalamocortical input to layer VI. The developmental timecourse of M-type axons is examined here in rats aged E (embryonic day) 16 to P (postnatal day) 30. Anterograde techniques were used to label axons arising from 2 thalamic nuclei mainly made up of M-type cells, the Posterior and the Ventromedial. The primary growth cones of M-type axons rapidly reached the subplate of dorsally situated cortical areas. After this, interstitial branches would sprout from these axons under more lateral cortical regions to invade the overlying cortical plate forming secondary arbors. Moreover, retrograde labeling of M-type cell somata in the thalamus after tracer deposits confined to layer I revealed that large numbers of axons from multiple thalamic nuclei had already converged in a given spot of layer I by P3. Because of early ingrowth in such large numbers, interactions of M-type axons may significantly influence the early development of cortical circuits.
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Corteza Motora/citología , Corteza Motora/crecimiento & desarrollo , Neuronas/citología , Neuronas/fisiología , Tálamo/citología , Tálamo/crecimiento & desarrollo , Animales , Animales Recién Nacidos , Corteza Motora/embriología , Red Nerviosa/citología , Red Nerviosa/embriología , Red Nerviosa/crecimiento & desarrollo , Vías Nerviosas/citología , Vías Nerviosas/embriología , Vías Nerviosas/crecimiento & desarrollo , Ratas , Ratas Wistar , Tálamo/embriologíaRESUMEN
Reelin, a large extracellular matrix glycoprotein, is secreted by several neuron populations in the developing and adult rodent brain. Secreted Reelin triggers a complex signaling pathway by binding lipoprotein and integrin membrane receptors in target cells. Reelin signaling regulates migration and dendritic growth in developing neurons, while it can modulate synaptic plasticity in adult neurons. To identify which adult neural circuits can be modulated by Reelin-mediated signaling, we systematically mapped the distribution of Reelin in adult rat brain using sensitive immunolabeling techniques. Results show that the distribution of intracellular and secreted Reelin is both very widespread and specific. Some interneuron and projection neuron populations in the cerebral cortex contain Reelin. Numerous striatal neurons are weakly immunoreactive for Reelin and these cells are preferentially located in striosomes. Some thalamic nuclei contain Reelin-immunoreactive cells. Double-immunolabeling for GABA and Reelin reveals that the Reelin-immunoreactive cells in the visual thalamus are the intrinsic thalamic interneurons. High local concentrations of extracellular Reelin selectively outline several dendrite spine-rich neuropils. Together with previous mRNA data, our observations suggest abundant axoplasmic transport and secretion in pathways such as the retino-collicular tract, the entorhino-hippocampal ('perforant') path, the lateral olfactory tract or the parallel fiber system of the cerebellum. A preferential secretion of Reelin in these neuropils is consistent with reports of rapid, activity-induced structural changes in adult brain circuits.
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Mapeo Encefálico , Moléculas de Adhesión Celular Neuronal/metabolismo , Proteínas de la Matriz Extracelular/metabolismo , Espacio Intracelular/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Neuronas/metabolismo , Serina Endopeptidasas/metabolismo , Animales , Western Blotting/métodos , Encéfalo/citología , Encéfalo/metabolismo , Diagnóstico por Imagen/métodos , Femenino , Masculino , Plasticidad Neuronal , Ratas , Ratas Sprague-Dawley , Proteína Reelina , Ácido gamma-Aminobutírico/metabolismoRESUMEN
Reelin is a large secretable protein which, when developmentally defective, causes the reeler brain malformation in mice and a recessive form of lissencephaly with cerebellar hypoplasia in humans. In addition, Reelin is heavily expressed throughout the adult brain, although its function/s there are still poorly understood. To gain insight into which adult neuronal circuits may be under the influence of Reelin, we systematically mapped Reelin-immunoreactive neuronal somata, axons, and neuropil in the brain and brainstem of ferrets. Results show that Reelin immunoreactivity is found in widespread but specific sets of neuronal bodies, axonal tracts, and gray matter neuropil regions. Depending on the region, the immunoreactive neuronal somata correspond to interneurons, projection neurons, or both. Some well-defined axonal projection systems are immunoreactive, whereas most other white matter tracts are unlabeled. The labeled pathways include, among others, the lateral olfactory tract, the entorhinohippocampal (perforant) pathway, the retroflex bundle, and the stria terminalis. Labeled axons in these tracts contain large numbers of discrete, very small, immunoreactive particles, suggestive of secretory vesicles under the light microscope. The neuropil in the terminal arborization fields of these axons is also heavily immunoreactive. Taken together, our observations are consistent with the notion that some neurons may anterogradely transport Reelin along their axons in large membrane-bound secretory vesicles (Derer et al. [2001] J. Comp. Neurol. 440:136-143) and secrete it into their terminal arborization fields, which may be quite distant from the somata synthesizing the protein. These findings have implications for identifying where Reelin acts in adult brain circuits.
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Química Encefálica , Moléculas de Adhesión Celular Neuronal/análisis , Proteínas de la Matriz Extracelular/análisis , Hurones , Proteínas del Tejido Nervioso/análisis , Neuronas/química , Animales , Axones/química , Tronco Encefálico/química , Moléculas de Adhesión Celular Neuronal/inmunología , Moléculas de Adhesión Celular Neuronal/metabolismo , Proteínas de la Matriz Extracelular/inmunología , Proteínas de la Matriz Extracelular/metabolismo , Femenino , Inmunohistoquímica , Proteínas del Tejido Nervioso/inmunología , Proteínas del Tejido Nervioso/metabolismo , Vías Nerviosas/química , Neurópilo/química , Proteína Reelina , Serina EndopeptidasasRESUMEN
Reelin is a large secretable protein which is widely expressed by specific neuronal populations. In the embryonic brain, Reelin plays a signaling role critical for the correct positioning of migrating neuroblasts. Reelin is also expressed in the adult mammalian brain, including humans; however, its function/s there remain poorly understood. To gain insight into which neuronal populations and specific circuits may be influenced by Reelin in the adult, we have conducted a light and electron microscope analysis of Reelin-immunoreactive neuron types in the cerebral cortex and subcortical regions of adult macaque monkeys. Results show that the great majority of brain neurons, including interneurons and projection neurons, are immunoreactive for Reelin although some neuronal populations do not contain Reelin. The immunoreactive protein is located intracellularly, mainly in neuronal somata. Reelin is also present in gray matter neuropil as well as in some long axonal pathways and their terminal arborizations, suggesting that it can be axonally transported over long distances. The staining patterns in the labeled neurons are remarkably diverse. Our observations reveal a wider distribution of Reelin in the adult macaque brain than in any other species investigated to date. The data show that Reelin is in a position to influence most brain circuits in the adult primate brain.