Model Of Cortical Dysplasia Research Articles

Comparative proteomics of rat brain in the BCNU-induced model of cortical dysplasia

Objective To screen the differential proteins in the brain (neocortex and hippocampus) between the rats with cortical dysplasia (CD) and control ones,and investigate the role of their alteration in the development of epilepsy in CD.Methods Cortical dysplasia was induced in rat pups via in utero delivery of BCNU.A two-dimensional electrophoresis (2-DE)-based approach was used to construct the expression profiles of proteins in both the neocortex and hippocampus at different age groups (postnatal day 7 and 60) and to detect proteome changes between CD rats and control ones.Following gel image analysis,protein spots that differed in abundance between CD and control rats were identified by using Matrx-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) and MS/MS.Results A total of 57 kinds of protein were screened out (P ＜ 0.05),in which 35 were found up-regulated and 22 were down-regulated compared with the control,35 from neonatal stage (postnatal day 7) and others from adult stage.Finally,12 among them were identified,including tubulin,alpha-lB,Beta-actin,tubulin beta-2A,GAP-43,UbCKmit,GAPDH and TMBr-3,etc.Conclusions Changed expression of specific proteins which were found in our study are involved in construction of brain 's cytoskeleton,synaptic function,mitochondrial function and so forth.Thus,they may be related to the pathogenic mechanisms of epileptogenicity of CD. Key words: Cortical dysplasia; BCNU; Neocortex; Hippocampus; 2-DE; Mass spectrometry; Comparative Proteomics ; Epilepsy

Development of cortical malformations in BCNU-treated rat, model of cortical dysplasia

Cortical dysplasia (CD) comprises a wide range of cerebral cortex alterations ranging from severe brain malformations to local disruption of the cortical structure. Most hypotheses focused on the role of embryonic/perinatal development insults as the main cause for the majority of CD. Rats with prenatal exposure to BCNU (1-3-bis-chloroethyl-nitrosurea) represent an injury-based model and reproduce many anatomical features seen in human patients with CD, such as altered cortical layering and the presence of heterotopia and dysmorphic/heterotopic neurons. With the aim to investigate the formation and evolution of CD during development, we analysed the expression of a panel of layer-specific genes (Nurr1, Er81, Ror-β and Cux2, markers of layers VI, V, IV and superficial layers, respectively) in BCNU-treated cortices from E17 to postnatal day 14. By means of appropriate immunohistochemical markers, we also analysed the structural organization of embryonic ventricular zone and of glial and axonal fibres, substrates supporting radial and tangential migration, respectively. The main results of the present study are: (i) the ventricular zone appeared disorganized and the neuroependyma was partially disrupted; (ii) radial glia scaffold and tangential fibres were deeply disarranged, thus explaining the neuronal migration defects; (iii) cortical heterotopia were detectable by E19, whereas periventricular heterotopia were detectable after birth; (iv) both cortical and periventricular heterotopia showed a pseudo-laminar structure, with cells of the upper cortical layers in the core of the nodules and cells of layer IV and V at their border; (v) the distribution of GABAergic cells was altered since the embryonic stages, as a consequence of the derangement of tangential fibres. Our analysis sheds light on how a malformed cortex develops after a temporally discrete environmental insult and adds additional knowledge on specific aspects of the etiopathogenesis of CD.

Populations of Radial Glial Cells Respond Differently to Reelin and Neuregulin1 in a Ferret Model of Cortical Dysplasia

Radial glial cells play an essential role during corticogenesis through their function as neural precursors and guides of neuronal migration. Both reelin and neuregulin1 (NRG1) maintain the radial glial scaffold; they also induce expression of Brain Lipid Binding Protein (BLBP), a well known marker of radial glia. Although radial glia in normal ferrets express both vimentin and BLBP, this coexpression diverges at P3; vimentin is expressed in the radial glial processes, while BLBP appears in cells detached from the ventricular zone. Our lab developed a model of cortical dysplasia in the ferret, resulting in impaired migration of neurons into the cortical plate and disordered radial glia. This occurs after exposure to the antimitotic methylazoxymethanol (MAM) on the 24th day of development (E24). Ferrets treated with MAM on E24 result in an overall decrease of BLBP expression; radial glia that continue to express BLBP, however, show only mild disruption compared with the strongly disrupted vimentin expressing radial glia. When E24 MAM-treated organotypic slices are exposed to reelin or NRG1, the severely disrupted vimentin+ radial glial processes are repaired but the slightly disordered BLBP+ processes are not. The realignment of vimentin+ processes was linked with an increase of their BLBP expression. BLBP expressing radial glia are distinguished by being both less affected by MAM treatment and by attempts at repair. We further investigated the effects induced by reelin and found that signaling was mediated via VLDLR/Dab1/Pi3K activation while NRG1 signaling was mediated via erbB3/erbB4/Pi3K. We then tested whether radial glial repair correlated with improved neuronal migration. Repairing the radial glial scaffold is not sufficient to restore neuronal migration; although reelin improves migration of neurons toward the cortical plate signaling through ApoER2/Dab1/PI3K activation, NRG1 does not.

Ih modulation of neocortical network activity is altered in a model of cortical dysplasia

Ih modulation of neocortical network activity is altered in a model of cortical dysplasia

Glycine transporter-1 expression in the rat model of cortical dysplasia

Objective: Glycine transporter-1 (GLYT1) is an early marker of neural development and involved in the excitatory transmission in cortex. The study was designed to investigate the expression of GLYT1 in different parts of the brain by immunohistochemistry in the rat cortical dysplasia model.Methods: On postnatal day 0, one freeze lesion was carried out on ten rats between bregma and lambda on the skull in the right hemisphere for 5 seconds. Six weeks later, rats were transcardially perfused with fixative and then their brains were removed for both hamotoxylin–eosine (H&E) staining for histopathology and immunohistochemistry staining for glial fibrillary acidic protein (GFAP) for astrocytic activity and GLYT1 in the cortical dysplastic region and other rostral brain regions involving epileptogenesis such as hippocampus, pyriform cortex, amygdala, thalamus and substantia nigra.Results: GFAP immunoreactivity showed clusters of glial cells in the area of the microgyrus. Dense GLYT1 expression was localized to superficial layer of microgyric cortex and around the microgyrus. GLYT1 immunoreactivity was not detected in the other rostral regions.Discussion: GLYT1 stained superficial structures might correspond to immature neuron and higher concentrations of GLYT1 around microgyrus might be correlated with increased excitatory mechanisms in these regions.

Modest Thyroid Hormone Insufficiency during Development Induces a Cellular Malformation in the Corpus Callosum: A Model of Cortical Dysplasia

There is a growing body of evidence that subtle decreases in maternal thyroid hormone during gestation can impact fetal brain development. The present study examined the impact of graded levels of thyroid hormone insufficiency on brain development in rodents. Maternal thyroid hormone insufficiency was induced by exposing timed-pregnant dams to propylthiouracil (PTU) at doses of 0, 1, 2, 3, and 10 ppm in the drinking water from gestational d 6 through weaning on postnatal d 30. An examination of Nissl-stained sections of the brains from developmentally hypothyroid offspring killed on postnatal d 23 revealed the presence of a heretofore unreported bilateral cellular malformation, a heterotopia, positioned within the white matter of the corpus callosum of both hemispheres. Immunohistochemical techniques were used to determine that this heterotopia primarily consists of neurons born between gestational d 17-19 and exhibits a dose-dependent increase in size with decreases in thyroid hormone levels. Importantly, this structural abnormality is evident at modest levels of maternal thyroid hormone insufficiency ( approximately 45% reductions in T(4) with no change in T(3)), persists in adult offspring despite a return to normal hormonal status, and is dramatically reduced in size with prenatal thyroid hormone replacement. Developmental exposure to methimazole, another goitrogen, also induced formation of this heterotopia. Whereas the long-term consequence of this cortical malformation on brain function remains to be determined, the presence of the heterotopia underscores the critical role thyroid hormone plays in brain development during the prenatal period and provides a new model in which to study mechanisms of cortical development and cortical dysplasia.

A radialization factor in normal cortical plate restores disorganized radial glia and disrupted migration in a model of cortical dysplasia.

Treatment of pregnant ferrets on embryonic day 24 (E24) with the antimitotic methylazoxy methanol (MAM) leads to a specific constellation of effects in newborn kits, which include a very thin and poorly laminated neocortex, disruption of radial glial cell morphology with early differentiation into astrocytes, and abnormal positioning of Cajal-Retzius cells. We suggest that MAM treatment on E24 results in this model of cortical dysplasia by eliminating a population of cells that produce a factor capable of maintaining radial glia in their normal morphology. The abnormal radial glia, either alone or in combination with other abnormal features, are likely to prevent proper migration into the cortical plate. To test the possibility that normal cortex can provide the missing substance that influences radial glia, slices of E24 MAM-treated cortex were removed at postnatal day 0 (P0) and cultured adjacent to explants of P0 normal cortical plate. By labelling a small number of cells with injections of fluorescent dextrans into the cultured slices, we found that abnormal radial glia in MAM treated slices cocultured adjacent to normal cortical plate were restored toward normal, in comparison to E24 MAM treated slices cultured alone and in other control conditions. We also found that abnormally positioned Cajal-Retzius cells move into the marginal zone and that neurons are able to migrate into the cortical plate more effectively in the coculture condition. These data indicate that normal cortical plate of ferrets contains a factor causing radial glia to maintain their elongated morphology; the improved position of radial glia encourages repositioning of Cajal-Retzius cells and improved neuronal migration into the cortical plate.