Internal Granular Layer Research Articles

Neuropathologic features in the hippocampus and cerebellum of three older men with fragile X syndrome

BackgroundFragile X syndrome (FXS) is the most common inherited form of intellectual disability, and is the most common single-gene disorder known to be associated with autism. Despite recent advances in functional neuroimaging and our understanding of the molecular pathogenesis, only limited neuropathologic information on FXS is available.MethodsNeuropathologic examinations were performed on post-mortem brain tissue from three older men (aged 57, 64 and 78 years) who had received a clinical or genetic diagnosis of FXS. In each case, physical and cognitive features were typical of FXS, and one man was also diagnosed with autism. Guided by reports of clinical and neuroimaging abnormalities of the limbic system and cerebellum of individuals with FXS, the current analysis focused on neuropathologic features present in the hippocampus and the cerebellar vermis.ResultsHistologic and immunologic staining revealed abnormalities in both the hippocampus and cerebellar vermis. Focal thickening of hippocampal CA1 and irregularities in the appearance of the dentate gyrus were identified. All lobules of the cerebellar vermis and the lateral cortex of the posterior lobe of the cerebellum had decreased numbers of Purkinje cells, which were occasionally misplaced, and often lacked proper orientation. There were mild, albeit excessive, undulations of the internal granular cell layer, with patchy foliar white matter axonal and astrocytic abnormalities. Quantitative analysis documented panfoliar atrophy of both the anterior and posterior lobes of the vermis, with preferential atrophy of the posterior lobule (VI to VII) compared with age-matched normal controls.ConclusionsSignificant morphologic changes in the hippocampus and cerebellum in three adult men with FXS were identified. This pattern of pathologic features supports the idea that primary defects in neuronal migration, neurogenesis and aging may underlie the neuropathology reported in FXS.

Liver X receptor agonist treatment promotes the migration of granule neurons during cerebellar development

Liver X receptor α (LXRα) and β (LXRβ) are members of the nuclear receptor superfamily of ligand-activated transcription factors, and expressed in the CNS. We have previously demonstrated that LXRβ is essential for migration of later-born neurons during cerebral cortex development, although the underlying mechanism is not clear. The cerebellum is organized in an exquisitely foliated structure with a simple layered cytoarchitecture and considered to be a good model to study morphogenesis of lamination and neuronal migration. Here, we found that T0901317, a potent LXR receptor agonist, administration to neonatal C57/BL6 mice, increased dendritic growth of Purkinje cell, although the appearance of the cerebellar cortex was not affected. We further demonstrated T0901317 treatment promoted the migration of granule neurons from the external granular layer to the internal granular layer during cerebellum development. Bergmann glial fibers serve as scaffolds for granule cells inward migration during cerebellum postnatal development. T0901317 treatment also inhibited premature differentiation of Bergmann glia during cerebellum development, which is related to the decreased levels of TGF-β1 and Smad4 in the cerebellum. Taken together, our findings suggest that endogenous LXR affects differentiation process of Bergmann glia and subsequently leads to promote the migration of granule neurons.

Neuronal Apoptosis in the Developing Cerebellum

The following study analysed apoptosis in proliferative cells and migrating neurons of the developing cerebellum. The external granular layer, Purkinje cell layer and internal granular layer in the developing mouse cerebellar cortex were analysed by active caspase-3 immunohistochemistry, Hoechst 33258 staining and Western blot analysis. Immunocytochemistry results indicated that the peak of apoptosis appeared at postnatal days P8, P5 and P9 in the external granular layer, Purkinje cell layer and internal granular layer, respectively. Subsequently, in each region, the rate of apoptosis decreased with increasing age. In contrast, Western blot results demonstrated the highest expression of activated caspase-3 in the cerebellum at P5, followed by a subsequent decline and disappearance of expression by P14. Activated caspase-8 was expressed maximally at P10, and subsequently disappeared by P30. The results of this study suggest that the key period of neuronal apoptosis in the cerebellar cortex is between P0 and P14, indicating that this developmental period could be susceptible to treatment for congenital neurodegenerative diseases.

The Thyroid Hormone Receptor α1 Protein Is Expressed in Embryonic Postmitotic Neurons and Persists in Most Adult Neurons

Thyroid hormone is essential for brain development where it acts mainly through the thyroid hormone receptor α1 (TRα1) isoform. However, the potential for the hormone to act in adult neurons has remained undefined due to difficulties in reliably determining the expression pattern of TR proteins in vivo. We therefore created a mouse strain that expresses TRα1 and green fluorescent protein as a chimeric protein from the Thra locus, allowing examination of TRα1 expression during fetal and postnatal development and in the adult. Furthermore, the use of antibodies against other markers enabled identification of TRα1 expression in subtypes of neurons and during specific stages of their maturation. TRα1 expression was first detected in postmitotic cells of the cortical plate in the embryonic telencephalon and preceded the expression of the mature neuronal protein NeuN. In the cerebellum, TRα1 expression was absent in proliferating cells of the external granular layer, but switched on as the cells migrated towards the internal granular layer. In addition, TRα1 was expressed transiently in developing Purkinje cells, but not in mature cells. Glial expression was found in tanycytes in the hypothalamus and in the cerebellum. In the adult brain, TRα1 expression was detected in essentially all neurons. Our data demonstrate that thyroid hormone, unexpectedly, has the capacity to play an important role in virtually all developing and adult neurons. Because the role of TRα1 in most neuronal cell types in vivo is largely unknown, our findings suggest that novel functions for thyroid hormone remain to be identified in the brain.

Differential expression of FABP 3, 5, 7 in infantile and adult monkey cerebellum

To clarify the involvement of fatty acid binding proteins (FABPs) in cerebellar development and function, we explored the distribution of three brain-expressed FABPs, FABP 3, 5 and 7, by comparing three animal groups – infantile, normal and postischemic adult monkeys. Immunoblotting analysis revealed intense expression of FABP 3 and 7, but not of FABP5, in the control and postischemic adult cerebellum. The protein levels of FABP7, but not of FABP 3 or 5, gradually increased until 2 weeks after the insult. Immunohistochemical analysis showed that cerebellar FABP3-positive cells were Purkinje cells and Bergmann glia. FABP5-positive cells were found only in the postischemic cerebellum, and were identified as activated microglia. Interestingly, in the infantile cerebellum, both the granule cell progenitors in the external granular layer (EGL) and the oligodendrocyte progenitors in the internal granular layer (IGL) expressed FABP5. In the adult cerebellum, FABP7 was expressed in Purkinje cells and basket interneurons, while in the infantile cerebellum it was also found in Bergmann glia. These results showed differential expression of FABPs in cerebellar neuronal and glial cell types; FABP 3 and 7 were predominantly expressed in normal cerebellum, FABP5 after ischemic injury, while FABP 3, 5 and 7 were expressed during cerebellar development.

Mechanism of ethanol-induced Purkinje cell death in developing rat cerebellum: Its implication in apoptosis and oxidative damage

Ethanol treatment during the brain growth spurt period has been known to induce the death of Purkinje cells. The underlying molecular mechanisms and the role of reactive oxygen species (ROS) in triggering ethano-induced Purkinje cell death are，however， largely unresolved. We underlook TUNEL staining，Eestern blotting assay and immunohistochemistry for the cleaved Forms of caspase-3 and -9 ，with calbindin D28K double immunostaining to identify apoptotic Purkinje cells. The possibility of ROS-induced Purkinje cell death was immunohistochemically determined by using anti-8-hydroxy-2'--deoxyguanosine (8-OHdG), a specific cellular marker for oxidative damage. The results show thal Purkinje cell death of PD 5 rat cerebellum following ethanol administration is mediated by the activation of caspase-3 and -9. However，unexpectedly，TUNEL staining did not reveal any positive Purkinje cells while there were some TUNEL-positive cells in the internal and external granular layer. 8-OHdG was detected in the Purkinje cell layers at 8 h，peaked al 12-24 h，but not at 30 h post-Ethanol treatment. No 8-0HdG immunoreactive cells were detected in the internal and external granular layer. The lobule-specific S-QHdG staining patterns following ethanol exposure are consistent with thal of ethanol-induced Purkinje cell loss. Thus. we suggest that ethanol-induced Purkinje cell death may not occur by the classical apoptotic pathway and oxidative damage is involved in ethanol-induced Purkinje cell death in the developing cerebellum.

Parvovirus-Associated Cerebellar Hypoplasia and Hydrocephalus in Day Old Broiler Chickens

Cerebellar hypoplasia and hydrocephalus were identified in day old broiler chickens showing nervous signs, impaired mobility, and diarrhea. At postmortem examination, brains of chickens were misshapen and cerebellums were smaller than normal. Microscopically, cerebellar folia were reduced in size and irregularly shaped, and the ventricles were widely distended. Affected cerebellums had focal areas along the base of folia where the internal granular cell layer had been lost, and Purkinje cells were disorganized and located within the molecular layer. Parvovirus DNA was detected by polymerase chain reaction in three of nine brains with oligonucleotide primers designed for amplification of chicken and turkey parvoviruses. On the basis of phylogenetic analyses, the detected virus was most closely related to chicken parvoviruses. These findings suggest that a chicken parvovirus might cause a neurologic disease of young chickens characterized by cerebellar hypoplasia and hydrocephalus; however, its role as the cause of the disease remains to be confirmed.

Postnatal development of layer IV in fronto-opercular region (Broca’s area)

Abstract In the adult human fronto-opercular cortex, the grade of granularity of cortical layer IV represents a major architectonic feature for distinguishing the opercular area BA44 (which is typically described as being magnopyramidal and intermedio-granular) from the triangular area BA45 (which is typically described as being magnopyramidal and granular). We analyzed postnatal cytoarchitectonic development of internal granular layer (layer IV) of the fronto-opercular region in 23 brains of newborns, infants and children (age range: 15 days to 15 years) and in one adult brain. We found that: (1) the grade of granularity of layer IV in the fronto-opercular cortex displays a great interindividual variability throughout development as well as in the adult brain; (2) this variability is much more pronounced in the opercular area BA44 than in the triangular area BA45. Our findings support the classical interpretation provided by Constantin von Economo (von Economo & Koskinas, 1925) according to which BA44/FCBm represents a specialized variant of the wide premotor cortical zone, while BA45/FDG represents a specialized variant of the typical (associative) frontal granular cortex.

Postnatal Development of the Central Nervous System: Anomalies in the Formation of Cerebellum Fissures

A natural defect in rat cerebellum postnatal development has been found in the fissura prima, consisting in various complex configurations of the cerebellar layers. We investigated the genesis of fissure malformations through immunoreactions for PCNA, GFAP, GABAA alpha6, and calbindin to label proliferating cells of the external granular layer (egl), radial glial fibers, mature granule cells, and Purkinje cells, respectively. Results on critical stages of rat postnatal development provided interesting evidences on how the malformation develops in fissures prima and secunda. Early (postnatal day 10) at the site of malformation, the Bergmann radial glia was often retracted and showed distortions and irregular running. The interruption of GFAP-positive radial glial fibers could fit in with the presence of clusters of PCNA-unlabeled cells in the sites of fusion of the egl; the clusters of cells are granule cells since their soma is labeled by GABAA alpha6. Moreover, an altered migration of granule cell precursors to the internal granular layer was evident which, in turn, affected Purkinje cell differentiation and the growth of their dendrites. In summary, the changed relationship among glial fiber morphology, granule cell migration, and Purkinje cell differentiation suggests how the Bergmann glial fibers have a basic role in the foliation process, being the driving physical force in directing migration of the granule cells at the base of fissure.

PTU-induced hypothyroidism modulates antioxidant defence status in the developing cerebellum

The objective of the present study was to evaluate the effect of 6-n-propylthiouracil (PTU)-induced hypothyroidism on oxidative stress parameters, expression of antioxidant defence enzymes, cell proliferation and apoptosis in the developing cerebellum. PTU challenged neonates showed significant decrease in serum T3 and T4 levels and marked increase in TSH levels. Significantly elevated levels of cerebellar H2O2 and lipid peroxidation were observed in 7 days old hypothyroid rats, along with increased activities of superoxide dismutase and glutathione peroxidase and decline in catalase activity. In 30 days old hypothyroid rats, a significant decline in cerebellar lipid peroxidation, superoxide dismutase and glutathione peroxidase activity and expression was observed along with an up-regulation in catalase activity and expression. Expression of antioxidant enzymes was studied by Western blot and semi-quantitative rt-PCR. A distinct increase in cell proliferation as indicated by proliferating cell nuclear antigen (PCNA) immunoreactivity was observed in the internal granular layer of cerebellum of 7 days old hypothyroid rats and significant drop in PCNA positive cells in the cerebellar molecular layer and internal granular layer of 30 days old PTU treated rats as compared to controls. In situ end labeling by TUNEL assay showed increased apoptosis in cerebellum of hypothyroid rats in comparison to controls. These results suggest that the antioxidant defence system of the developing cerebellum is sensitive to thyroid hormone deficiency and consequent alterations in oxidative stress status may play a role in regulation of cell proliferation of the cerebellum during neonatal brain development.

Vav3-deficient Mice Exhibit a Transient Delay in Cerebellar Development

Vav3 is a guanosine diphosphate/guanosine triphosphate exchange factor for Rho/Rac GTPases that has been involved in functions related to the hematopoietic system, bone formation, cardiovascular regulation, angiogenesis, and axon guidance. We report here that Vav3 is expressed at high levels in Purkinje and granule cells, suggesting additional roles for this protein in the cerebellum. Consistent with this hypothesis, we demonstrate using Vav3-deficient mice that this protein contributes to Purkinje cell dendritogenesis, the survival of granule cells of the internal granular layer, the timely migration of granule cells of the external granular layer, and to the formation of the cerebellar intercrural fissure. With the exception of the latter defect, the dysfunctions found in Vav3(-/-) mice only occur at well-defined postnatal developmental stages and disappear, or become ameliorated, in older animals. Vav2-deficient mice do not show any of those defects. Using primary neuronal cultures, we show that Vav3 is important for dendrite branching, but not for primary dendritogenesis, in Purkinje and granule cells. Vav3 function in the cerebellum is functionally relevant, because Vav3(-/-) mice show marked motor coordination and gaiting deficiencies in the postnatal period. These results indicate that Vav3 function contributes to the timely developmental progression of the cerebellum.

Histomorphometric study on the effect of low dose deltamethrin on the developing cerebellar cortex

Deltamethrin is a widely used type II pyrethroid-based insecticide. Studies have indicated that neonatal exposure to deltamethrin, even at relatively low doses, results in behavioral and neurological changes. In the present study, the effect of early neonatal exposure to low doses of deltamethrin on the histogenesis of the cerebellar cortex was investigated. Materials and methods: Sprague Dawley male pups were exposed to deltamethrin daily at a dose of 1 mg/kg via intraperitoneal injection from the 2nd to the 5th postnatal day and sacrificed on postnatal days 6, 14, and 21. Following intracardiac perfusion, the cerebellum was removed, embedded with paraffin wax, and serially sectioned. The thickness of the different layers of the vermal cerebellar cortex was measured using Image-Pro Plus software. Results: There were no significant differences in the measured thickness of the external granular, molecular, and internal granular layers between the deltamethrin-treated and the control animals in all age groups studied. Conclusion: In contrast to a previous study, the present study showed that neonatal administration of low dose deltamethrin did not significantly affect the morphogenesis of the cerebellar cortex.

The expression of simiRP58 preceded that of RP58 in the development of cerebellum

Cerebellar slices of 9-day-old rats were cultured for a week at the interface between air and a culture medium containing horse serum and hormone cocktail, and the development of granule cells was characterized morphologically. The typical layered structure of the cerebellar cortex was well preserved during the cultivation. Many granule cells in the external granular layer (EGL) proliferated actively within the early culture period. They were migrating downward at 3 days in vitro (DIV) and almost completed the migration to the internal granular layer (IGL) after 6 DIV. In the middle and upper molecular layer (ML), parallel fibers were elongated horizontally, which is the orientation 90° rotated compared to that in vivo. They formed synapses with Purkinje cell dendrites. Regional differences in synapse density and maturity existed which might reflect a gradient in progressive synapse formation comparable to that in vivo. Thus, a serial process of highly organized development of granule cells was realized for the first time in vitro, although some spatial or temporal modifications existed. Such a culture system could be a useful experimental model for the study of cellular and molecular mechanisms of spatiotemporally organized neuronal development.

Cystic degeneration of the cerebellar tonsils in pediatric patients with Chiari Type I malformation

The operative indications and treatment algorithms for pediatric patients with Chiari Type I malformation (CM-I) vary widely. When an intradural approach and duraplasty are thought necessary at the time of surgery, neurosurgeons may elect to fulgurate or resect a portion of the cerebellar tonsils. Histological analyses of cerebellar tonsils resected during decompression in pediatric patients with CM-I have revealed multiple abnormal findings including extensive ischemic and degenerative changes. The authors describe an interesting phenomenon of cystic degeneration in the distal ends of the cerebellar tonsils in children undergoing operative treatment of CM-I. The authors reviewed the clinical database of 440 pediatric patients who underwent surgical decompression for CM-I performed by a single surgeon. The clinical course, preoperative MR imaging and intraoperative ultrasound characteristics, and histological findings in 3 children found to have tonsillar cystic degeneration were analyzed and detailed. Cystic changes were subtle but uniformly evident on preoperative MR imaging and were more readily apparent on intraoperative ultrasonography. In each patient, the tonsillar cyst was resected. Histological examination revealed areas of cystic degenerative change characterized by distortion of the normal cerebellar architecture with absent Purkinje and internal granular cell layers. All children experienced improvement in their symptoms, without complication, postoperatively. Cystic degeneration of the tonsils in pediatric patients with CM-I is an uncommon pathological process most likely resulting from long-standing and excessive compression. Based on their experience, the authors advocate expeditious surgical treatment, including intradural exploration and capacious duraplasty, for patients in whom there is evidence of this phenomenon on preoperative imaging.

Mutation of the Variant α-Tubulin TUBA8 Results in Polymicrogyria with Optic Nerve Hypoplasia

The critical importance of cytoskeletal function for correct neuronal migration during development of the cerebral cortex has been underscored by the identities of germline mutations underlying a number of human neurodevelopmental disorders. The proteins affected include TUBA1A, a major alpha-tubulin isoform, and microtubule-associated components such as doublecortin, and LIS1. Mutations in these genes are associated with the anatomical abnormality lissencephaly, which is believed to reflect failure of neuronal migration. An important recent observation has been the dependence of cortical neuronal migration upon acetylation of alpha-tubulin at lysine 40 by the histone acetyltransferase Elongator complex. Here, we describe a recognizable autosomal recessive syndrome, characterized by generalized polymicrogyria in association with optic nerve hypoplasia (PMGOH). By autozygosity mapping, we show that the molecular basis for this condition is mutation of the TUBA8 gene, encoding a variant alpha-tubulin of unknown function that is not susceptible to the lysine 40 acetylation that regulates microtubule function during cortical neuron migration. Together with the unique expression pattern of TUBA8 within the developing cerebral cortex, these observations suggest a role for this atypical microtubule component in regulating mammalian brain development.

Adult Ceramide Synthase 2 (CERS2)-deficient Mice Exhibit Myelin Sheath Defects, Cerebellar Degeneration, and Hepatocarcinomas

(Dihydro)ceramide synthase 2 (cers2, formerly called lass2) is the most abundantly expressed member of the ceramide synthase gene family, which includes six isoforms in mice. CERS2 activity has been reported to be specific toward very long fatty acid residues (C22-C24). In order to study the biological role of CERS2, we have inactivated its coding region in transgenic mice using gene-trapped embryonic stem cells that express lacZ reporter DNA under control of the cers2 promoter. The resulting mice lack ceramide synthase activity toward C24:1 in the brain as well as the liver and show only very low activity toward C18:0-C22:0 in liver and reduced activity toward C22:0 residues in the brain. In addition, these mice exhibit strongly reduced levels of ceramide species with very long fatty acid residues (>or=C22) in the liver, kidney, and brain. From early adulthood on, myelin stainability is progressively lost, biochemically accompanied by about 50% loss of compacted myelin and 80% loss of myelin basic protein. Starting around 9 months, both the medullary tree and the internal granular layer of the cerebellum show significant signs of degeneration associated with the formation of microcysts. Predominantly in the peripheral nervous system, we observed vesiculation and multifocal detachment of the inner myelin lamellae in about 20% of the axons. Beyond 7 months, the CERS2-deficient mice developed hepatocarcinomas with local destruction of tissue architecture and discrete gaps in renal parenchyma. Our results indicate that CERS2 activity supports different biological functions: maintenance of myelin, stabilization of the cerebellar as well as renal histological architecture, and protection against hepatocarcinomas.

Fluoride-induced brain damages in suckling mice

In order to reveal mechanisms of brain damages resulted from fluoride toxicity, we treated adult female mice of Swiss Albinos strain by 500 ppm NaF (226 ppm F −) in their drinking water from the 15th day of pregnancy until the day 14 after delivery. All mice were sacrificed on day 14 after parturition. During treatment, levels of thiobarbituric acid reactive substances (TBARS), the marker of lipid peroxidation extend, increased, while the activities of the antioxidant enzymes such as glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT), and the level of glutathione (tGSH) decreased significantly in both cerebellum and cerebrum compared with those of the control group. These results suggested that fluoride enhanced oxidative stress in the brain, thereby disturbing the antioxidant defense of nursing pups. In addition, acetylcholinesterase (AChE) activity in both cerebellum and cerebrum was inhibited after treatment with fluoride. In our previous studies we have found, a decrease in plasma thyroid hormone levels of nursing pups whose mothers were treated by NaF. In cerebellum of mice, migration of neurons from the external granular layer to the internal granular layer occurred postnatally and was dependent upon the presence of thyroid hormone. In hypothyroidism, several neurons failed to complete their migration and died. Key guidance signals to these migrating neurons were provided by laminin, an extracellular matrix protein fixed to the surface of astrocytes. In the present study we examined the expression and distribution of laminin in cerebellum of 14-day-old mice. Immunoreactive laminin was disappeared by postnatal day 14 in cerebellum parenchyma of control pups and was restricted to vasculature despite the continued presence of granular cells in the external granular layer. In contrast, in cerebellum of NaF treated pups, laminin was deposited in organised punctuate clusters in the molecular layer. These data indicated that the disruption of laminin distribution might play a major role in the profound derangement of neuronal migration observed in cerebellum of NaF treated pups.

Relocalization of a microtubule-anchoring protein, ninein, from the centrosome to dendrites during differentiation of mouse neurons

Microtubules in typical cells form radial arrays with their plus-ends pointing toward the cell periphery. In contrast, microtubules in dendrites of neurons are free from centrosomes and have a unique arrangement in which about half have a polarity with a minus-end distal orientation. Mechanisms for generation and maintenance of the microtubule arrangement in dendrites are not well understood. Here, we examined dendritic localization of a centrosomal protein, ninein, which has microtubule-anchoring and stabilizing functions. Immunohistochemical analysis of developing mouse cerebral and cerebellar cortices showed that ninein is localized at the centrosome in undifferentiated neural precursors. In contrast, ninein was barely detected in migrating neurons, such as those in the intermediate layer of the cerebral cortex and the internal granular layer of the cerebellar cortex. High expression was observed in thick dendrite-bearing neurons such as pyramidal neurons of the cerebral cortex and Purkinje neurons in the cerebellar cortex. Ninein was not detected at the centrosome of these cells, but was diffusely present in cell soma and dendrites. In cultured cortical neurons, ninein formed granular structures in soma and dendrites, being not associated with gamma-tubulin. About 60% of these structures showed resistance to detergent and association with microtubules. Our observations suggest that the minus-ends of microtubules may be anchored and stabilized by centrosomal proteins localized in dendrites.

Polioencefalomalacia em bovinos: epidemiologia, sinais clínicos e distribuição das lesões no encéfalo

Trinta e um casos de polioencefalomalacia (PEM) diagnosticados de 1999-2008 em bovinos do Sul (13 casos) e Centro-Oeste (18 casos) brasileiros foram estudados. As taxas de morbidade (0,04%-6,66 %), mortalidade (0,04%-6,66 %) e letalidade (50%-100%) foram semelhantes em ambas as regiões estudadas. Não houve uma associação clara entre os casos de PEM e a idade, sexo dos bovinos e sazonalidade. Os casos ocorreram principalmente em bovinos criados de forma extensiva em pastagem. Na Região Sul a doença afetou principalmente bovinos jovens (um ano de idade ou menos), enquanto que principalmente bovinos mais velhos (3 anos de idade ou mais) foram afetados no Centro-Oeste. Os sinais clínicos mais frequentemente observados incluíram cegueira, incoordenação, andar em círculos, opistótono, decúbito e movimentos de pedalagem. A evolução do quadro clínico variou de 12 horas a 8 dias (media 3 dias e meio). Em 11 encéfalos não foram observadas alterações macroscópicas; as principais alterações macroscópicas nos outros casos incluíam congestão com tumefação e achatamento das circunvoluções, amolecimento e amarelamento do córtex telencefálico, focos de hemorragia no tronco encefálico, cerebelo e telencéfalo e herniação cerebelar. As principais alterações histológicas ocorreram no córtex dos lobos telencefálicos occipital, parietal e frontal; no entanto, lesões menos acentuadas e menos frequentemente observadas ocorreram no hipocampo, núcleos da base, tálamo, mesencéfalo e cerebelo. O tipo de lesão microscópica cortical era consistente em todos os casos e incluía necrose neuronal (neurônio vermelho) laminar segmentar, espongiose, tumefação do núcleo das células endoteliais, astrócitos Alzheimer tipo II e infiltração por células gitter. Em 20% dos casos havia um leve infiltrado celular linfo-histiocitário e em 13% dos casos havia leve infiltrado de neutrófilos e eosinófilos. Adicionalmente, lesões necro-hemorrágicas leves ou moderadas foram observadas em 49% dos casos nos núcleos da base, em 39% dos casos no tronco encefálico e em 26% dos casos no tálamo. Lesões telencefálicas foram consistentemente observadas nas lâminas dos córtices dos lobos occipital, parietal e frontal. Nessas regiões as camadas granular externa e interna foram as mais afetadas tanto por neurônios necróticos quanto por edema em todas as regiões avaliadas. Tanto os giros quanto os sulcos foram afetados igualmente.

The Gs-Linked Receptor GPR3 Inhibits the Proliferation of Cerebellar Granule Cells during Postnatal Development

BackgroundDuring postnatal murine and rodent cerebellar development, cerebellar granule precursors (CGP) gradually stop proliferating as they differentiate after migration to the internal granule layer (IGL). Molecular events that govern this program remain to be fully elucidated. GPR3 belongs to a family of Gs-linked receptors that activate cyclic AMP and are abundantly expressed in the adult brain.Methodology/Principal FindingsTo investigate the role of this orphan receptor in CGP differentiation, we determined that exogenous GPR3 expression in rat cerebellar granule neurons partially antagonized the proliferative effect of Sonic hedgehog (Shh), while endogenous GPR3 inhibition by siRNA stimulated Shh-induced CGP proliferation. In addition, exogenous GPR3 expression in CGPs correlated with increased p27/kip expression, while GPR3 knock-down led to a decrease in p27/kip expression. In wild-type mice, GPR3 expression increased postnatally and its expression was concentrated in the internal granular layer (IGL). In GPR3 −/− mice, the IGL was widened with increased proliferation of CGPs, as measured by bromodeoxyuridine incorporation. Cell cycle kinetics of GPR3-transfected medulloblastoma cells revealed a G0/G1 block, consistent with cell cycle exit.Conclusions/SignificanceThese results thus indicate that GPR3 is a novel antiproliferative mediator of CGPs in the postnatal development of murine cerebellum.