Reelin与小脑发育——Notch1信号通路的调节作用

目的 探讨Reelin在小脑放射状胶质细胞、神经干细胞和普肯耶细胞迁移和分布中的作用,并探讨Notch信号通路在其中的作用。 方法 取WT小鼠和reeler小鼠胚胎9d至生后60d的脑部共148例,运用免疫荧光技术检测两组小鼠小脑发育中放射状胶质细胞、神经干细胞、普肯耶细胞及激活型Notch1受体的表达。 结果 Reeler小鼠小脑发育中放射状胶质细胞极性紊乱导致迁移阻滞于内颗粒层,过早分化,分子层中数量减少(P<0.01);Sox2阳性的干细胞启动迁移较慢,随后未得到适当的终止信号越过普肯耶细胞层进入外颗粒层,野生型小鼠该细胞并不迁移进入外颗粒层;普肯耶细胞多数不能迁移至分子层大量阻滞于内颗粒层中形成细胞团;激活型的Notch1受体在reeler小鼠小脑中表达减少。 结论 Reelin在小脑神经干细胞、胶质细胞、普肯耶细胞发育和片层化分布中有重要作用,并且Notch1信号通路参与Reelin介导的小脑发育。     

Oligodendrocyte positioning in cerebral cortex is independent of projection neuron layering

The factors affecting normal oligodendrocyte positioning in the cerebral cortex are unknown. Apart from the white matter, the highest numbers of oligodendrocytes in the rodent cortex are found in Layers V/VI, where the infragranular neurons normally reside. Few, if any, oligodendrocytes are normally found in the superficial cortical layers. To test whether or not this asymmetric positioning of oligodendrocytes is linked to the lamina positions of Layer V/VI projection neurons, mutant mice that cause neuronal layer inversion were examined. In three lines of mutant mice (Reeler, disabled‐1, and p35) examined, representing two different genetic signaling pathways, the oligodendrocyte distribution was altered from an asymmetric to a symmetric distribution pattern. Unlike cortical neurons that are inverted in these mutant mice, the lack of oligodendrocyte inversion suggests a decoupling of the genetic mechanisms governing neuronal versus oligodendrocyte patterning. We conclude that oligodendrocyte positioning is not linked to the layer positions of V/VI projection neurons. © 2008 Wiley‐Liss, Inc.     

Postnatal effect of embryonic neurogenesis disturbance on reelin level in organotypic cultures of rat hippocampus

Despite a delayed emergence of the symptoms, schizophrenia is thought to be a late consequence of early disturbances during development. Several reports have found decreased levels of reelin in the cortex and the hippocampus of postmortem brains of schizophrenic patients. In the rat, intraperitoneal injection of the anti-mitotic agent methylazoxymethanol (MAM) during intra-uterine development (embryonic day 17) induces cytoarchitectural abnormalities in the hippocampus and the cortex and behavioural changes reminiscent of positive, negative and cognitive symptoms of schizophrenia. We aimed to examine whether a transient prenatal disturbance of neurogenesis induces postnatal changes in the expression of reelin in the hippocampus. Cellular modifications were explored using hippocampal organotypic slice cultures, which allow for conservation of the in vivo cytoarchitecture. MAM effect on hippocampal neurogenesis was confirmed by birthdating experiments. After 3 weeks in vitro, reelin was expressed by calretinin-negative cells. The number of reelin-positive neurons was increased whereas the total neuron number was decreased in the stratum oriens in the E17 MAM-exposed animals as compared to the control group. Not only an increase in the number of cells expressing reelin was observed, but there was also a slight increase in reelin mRNA levels in hippocampal pyramidal cells of MAM-exposed animals. In contrast, there was no significant change in the dentate gyrus. These results show that transient prenatal disturbance of neurogenesis induces long-term modifications in specific areas of the hippocampus and in particular in the number of neurons expressing reelin. They also confirm the value of organotypic slices to study postnatal maturation in the hippocampus.     

Reelin在不同组织和器官中的研究

Reelin是一种分泌型细胞外基质蛋白,在不同的组织和器官中reelin的表达是不同的。Reelin在精神分裂症、双相情感障碍、孤独症和重型抑郁症患者的脑中是降低的,也有报道指出了reelin在某些无脑回的常染色体隐性遗传患者的血清中几乎消失。而最近的一些研究发现r,eelin在成人外周组织中也有表达。由于reelin在控制细胞迁移中有作用,它可能在某些癌症的侵袭和转移中作为一个重要的观察指标。     

C‐terminal region‐dependent change of antibody‐binding to the Eighth Reelin repeat reflects the signaling activity of Reelin

Reelin is a secreted glycoprotein that plays pivotal roles in the development and function of the brain, but how it activates downstream intracellular signaling is not fully understood. We have recently reported that the highly conserved C‐terminal region (CTR) of Reelin is required for its full signaling activity, although the underlying mechanism remains unknown. During biochemical study of Reelin, we serendipitously found that one commercially available anti‐Reelin antibody G20 can bind to CTR‐lacking mutant Reelin proteins, but not wild‐type Reelin, on Western blotting. The G20 epitope resides in the last 19 residues of Reelin‐repeat 8 (RR8), and neither posttranslational modification nor proteolysis can explain this effect. Furthermore, when an unrelated sequence, such as FLAG‐tag, is inserted between RR8 and CTR, the reactivity of the corresponding antibody greatly decreases. These results suggest that RR8 and CTR form a tight structure that makes the surrounding sequence inaccessible to an antibody. Taking advantage of this phenomenon, we show the existence of CTR‐lacking Reelin isoform in vivo for the first time and estimate its contribution to the total amount of secreted Reelin. Importantly, the extent to which Reelin mutants react with G20 is inversely correlated with their signaling activity, indicating that the CTR‐induced structural change of RR8 is a prerequisite for downstream signaling activation, presumably via binding to a certain neuronal membrane molecule(s). © 2009 Wiley‐Liss, Inc.     

Tigroid pattern of the white matter: a previously unrecognized MR finding in lissencephaly with cerebellar hypoplasia

Brain MR images of a 14-month-old boy with lissencephaly and cerebellar hypoplasia showed numerous radiating linear structures in the white matter. This finding was identical to the tigroid or leopard-skin pattern that is seen in Pelizaeus-Merzbacher disease or metachromatic leukodystrophy and represents the perivascular white matter spared from demyelination. We speculate that mutations of the reelin gene, expressed both in the cortex and in the white matter, may play an important role in its development.     

Migratory pathway of sympathetic preganglionic neurons in normal and reeler mutant mice

Our previous study showed that the migration of sympathetic preganglionic neurons (SPN) in the spinal cord is affected in the reeler mutant. The present study, using morphometric analysis to describe and compare the location of SPN at progressive developmental stages, provides detailed information on how SPN migrate in the presence or absence of the reelin gene. We found that the initial migration (prior to E11.5) of SPN from the neuroepithelium to the ventrolateral spinal cord is similar in both control (wild-type and heterozygous) and reeler mice. However, as development progressed (E12.5-E15.5), SPN in control mice migrated dorsally toward the intermediate lateral spinal cord region, where 80% settled to form the intermediolateral column (IML); the rest migrated medially to locations between the IML and the central canal. In reeler, 80% of SPN migrated dorsomedially to cluster around the central canal, with the rest distributed between the central canal and the intermediate lateral spinal cord region. The present study also examined the relationship among SPN, Reelin, and radial glial fibers in control and reeler mice. Confocal microscopic studies showed that during their initial migration, SPN in both control and reeler mice were closely apposed to radial glial fibers in the ventrolateral spinal cord. The majority of SPN in control mice then migrated dorsolaterally, in a direction perpendicular to radial glial fibers, to form the IML. In contrast, the majority of SPN in reeler migrated in the same orientation as radial glial fibers back toward the central canal, instead of migrating dorsolaterally to form the IML. A possible explanation for these results is that Reelin acts to prevent SPN from back-migration on radial glial fibers toward the central canal.     

The effects of prenatal H1N1 infection at E16 on FMRP,glutamate, GABA,and reelin signaling systems in developing murine cerebellum

Prenatal viral infection has been identified as a potential risk factor for the development of neurodevelopmental disorders such as schizophrenia and autism. Additionally, dysfunction in gamma‐aminobutyric acid, Reelin, and fragile X mental retardation protein (FMRP)–metabotropic glutamate receptor 5 signaling systems has also been demonstrated in these two disorders. In the current report, we have characterized the developmental profiles of selected markers for these systems in cerebella of mice born to pregnant mice infected with human influenza (H1N1) virus on embryonic day 16 or sham‐infected controls using SDS‐PAGE and Western blotting techniques and evaluated the presence of abnormalities in the above‐mentioned markers during brain development. The cerebellum was selected in light of emerging evidence that it plays roles in learning, memory, and emotional processing—all of which are disrupted in autism and schizophrenia. We identified unique patterns of gene and protein expression at birth (postnatal day 0 [P0]), childhood (P14), adolescence (P35), and young adulthood (P56) in both exposed and control mouse progeny. We also identified significant differences in protein expression for FMRP, very‐low‐density lipoprotein receptor, and glutamic acid decarboxylase 65 and 67 kDa proteins at specific postnatal time points in cerebella of the offspring of exposed mice. Our results provide evidence of disrupted FMRP, glutamatergic, and Reelin signaling in the exposed mouse offspring that explains the multiple brain abnormalities observed in this animal model. © 2016 Wiley Periodicals, Inc.     

Assessment of cognitive function in the heterozygous reeler mouse

Rationale The heterozygous reeler mouse has been proposed as a genetic mouse model of schizophrenia based on several neuroanatomical and behavioral similarities between these mice and patients with schizophrenia. However, the effect of reelin haploinsufficiency on one of the cardinal symptoms of schizophrenia, the impairment of prefrontal-cortex-dependent cognitive function, has yet to be determined.Objective Here, we investigated multiple aspects of cognitive function in heterozygous reeler mice that are known to be impaired in schizophrenic patients.Methods Heterozygous reeler mice were assessed for (1) cognitive flexibility in an instrumental reversal learning task, (2) impulsivity in an inhibitory control task, (3) attentional function in a three-choice serial reaction time task, and (4) working memory in a delayed matching-to-position task.Results No differences were found between heterozygous reeler mice and wild-type littermate controls in any prefrontal-related cognitive measures. However, heterozygous reeler mice showed deficits in the acquisition of two operant tasks, consistent with a role for reelin in certain forms of learning.Conclusions These findings suggest that heterozygous reeler mice may not be an appropriate model for the core prefrontal-dependent cognitive deficits observed in schizophrenia, but may model more general learning deficits that are associated with many psychiatric disorders.