A YAC contig containing the reeler locus with preliminary characterization of candidate gene fragments

Reelin is an essential glycoprotein for the establishment of the highly organized six-layered structure of neurons of the mammalian neocortex. Although the role of Reelin in the control of neuronal migration has been extensively studied at the molecular level, the mechanisms underlying Reelin-dependent neuronal layer organization are not yet fully understood. In this study, we directly showed that Reelin promotes adhesion among dissociated neocortical neurons in culture. The Reelin-mediated neuronal aggregation occurs in an N-cadherin-dependent manner, both in vivo and in vitro. Unexpectedly, however, in a rotation culture of dissociated neocortical cells that gradually reaggregated over time, we found that it was the neural progenitor cells [radial glial cells (RGCs)], rather than the neurons, that tended to form clusters in the presence of Reelin. Mathematical modeling suggested that this clustering of RGCs could be recapitulated if the Reelin-dependent promotion of neuronal adhesion were to occur only transiently. Thus, we directly measured the adhesive force between neurons and N-cadherin by atomic force microscopy, and found that Reelin indeed enhanced the adhesiveness of neurons to N-cadherin; this enhanced adhesiveness began to be observed at 30 min after Reelin stimulation, but declined by 3 h. These results suggest that Reelin transiently (and not persistently) promotes N-cadherin-mediated neuronal aggregation. When N-cadherin and stabilized β-catenin were overexpressed in the migrating neurons, the transfected neurons were abnormally distributed in the superficial region of the neocortex, suggesting that appropriate regulation of N-cadherin-mediated adhesion is important for correct positioning of the neurons during neocortical development.T he mammalian neocortex is highly organized into six neuronal layers. This laminar structure is responsible for the complex motor, sensory, and cognitive functions of the mammalian brain (1). Neuronal migration plays an important role in the establishment of this layered structure. Cortical neurons are generated within the ventricular zone (VZ) or subventricular zone (SVZ), and migrate along radial fibers toward the pial surface. Newly born excitatory neurons migrate radially into the cortical plate (CP) past the neurons born earlier, resulting in a birth date-dependent "inside-out" alignment of the neurons in the CP (2-4).Reelin is a glycoprotein that is secreted by the Cajal-Retzius cells in the marginal zone (MZ) of the cortex during neocortical development (5-7). This glycoprotein is essential for establishment of the aforementioned birth date-dependent layered structure of the neocortex, because the CP neurons show an almost inverted alignment in the neocortex of the Reelindeficient, reeler mice. In addition, neurons born at the same time tend to be distributed broadly and not to form clear layers in the reeler cortex (8, 9). Although extensive studies, including at the molecular level, have been conducted to determine the role of Reelin in neuronal migration i...

mentioning

confidence: 99%

Reelin transiently promotes N-cadherin–dependent neuronal adhesion during mouse cortical development

Matsunaga

Noda

Murakawa

et al. 2017

“…Thus, occlusion of the CR-50 epitope was thought to be related to the reeler pattern of neocortex organization, at least in vitro (8). A cDNA of the candidate reeler gene recently was identified by insertional mutagenesis (12) or positional cloning (13,14) and designated reelin (12). The predicted Reelin protein resembles extracellular matrix proteins, and thus is likely to be responsible for the reeler phenotype.…”

mentioning

confidence: 99%

Disruption of hippocampal development in vivo by CR-50 mAb against Reelin

Nakajima

Mikoshiba

Miyata

et al. 1997

159

111

We previously generated a monoclonal alloantibody, CR-50, by immunizing reeler mutant mice with homogenates of normal embryonic brains. This antibody recently was shown to recognize a Reelin protein, which is coded by the recently identified candidate gene for the reeler mutation. However, it is still unclear whether Reelin, especially the CR-50 epitope region, is indeed responsible for the reeler phenotype in vivo. Here we show that Reelin is localized on Cajal-Retzius neurons in the hippocampus and that intraventricular injection of CR-50 at the embryonic stage disrupts the organized development of the hippocampus in vivo, converting it to a reeler pattern. Labeling experiments with 5-bromodeoxyuridine demonstrated that the labeled cells in the stratum pyramidale of the CR-50-treated mice were distributed in a pattern similar to that of reeler. Thus, Cajal-Retzius neurons play a crucial function in hippocampus development, and the CR-50 epitope on Reelin plays a central role in this function.

“…The intrinsic molecular mechanisms that are operative in evoking the neurological reeler phenotype may differentially affect Reelin function in each of the five different phenotypes. The complete gene deletions per se may be a factor operative in the expression of the neurological phenotype Reln rl-tg (2), but in other phenotypes, Reelin gene deletions, though modest in extension, prevent Reelin transcription or secretion (4,12,14). In the cortex and hippocampus of rat embryos, Reelin begins to be synthesized in Cajal-Retzius (CR) cells from embryonic day 13 to the second postnatal week, and in the cerebellum Reelin is expressed first in the external granule cell layer (EGL) before the granule cell migration to the internal granule cell layer (IGL) (2,(15)(16)(17).…”

mentioning

confidence: 99%

Reelin is preferentially expressed in neurons synthesizing γ-aminobutyric acid in cortex and hippocampus of adult rats

Pesold

Impagnatiello

Pisu

et al. 1998

366

323

During embryonic development of brain laminated structures, the protein Reelin, secreted into the extracellular matrix of the cortex and hippocampus by Cajal-Retzius (CR) cells located in the marginal zone, contributes to the regulation of migration and positioning of cortical and hippocampal neurons that do not synthesize Reelin. Soon after birth, the CR cells decrease, and they virtually disappear during the following 3 weeks. Despite their disappearance, we can quantify Reelin mRNA (approximately 200 amol͞g of total RNA) and visualize it by in situ hybridization, and we detect the translated product of this mRNA by immunocytochemistry preferentially in ␥-aminobutyric acid (GABA)ergic neurons of adult rat cortex and hippocampus. In adult rat cerebellum, Reelin is expressed in glutamatergic neurons (granule cells). The translated product of this mRNA is readily exported from the granule cell somata to the parallel fibers, where it has been detected by electron microscopy in axon terminals located presynaptically to Purkinje cell dendrites.