Dab1 Expression Research Articles

Connexin Expression Is Altered in the Eye Development of Yotari Mice: A Preliminary Study.

This study aimed to explore how Dab1 functional silencing influences the expression patterns of different connexins in the developing yotari (yot) mice eyes as potential determinants of retinogenesis. Using immunofluorescence staining, the protein expression of Dab1, Reelin, and connexin 37, 40, 43, and 45 (Cx37, Cx40, Cx43, and Cx45) in the wild-type (wt) and yot eyes at embryonic days 13.5 and 15.5 (E13.5 and E15.5) were analyzed. Different expression patterns of Cx37 were seen between the wt and yot groups. The highest fluorescence intensity of Cx37 was observed in the yot animals at E15.5. Cx40 had higher expression at the E13.5 when differentiation of retinal layers was still beginning, whereas it decreased at the E15.5 when differentiation was at the advanced stage. Higher expression of Cx43 was found in the yot group at both time points. Cx45 was predominantly expressed at E13.5 in both groups. Our results reveal the altered expression of connexins during retinogenesis in yot mice and their potential involvement in retinal pathology, where they might serve as prospective therapeutic targets.

Effect of the Reelin-Dab1 signaling pathway on the abnormal metabolism of Aβ protein induced by aluminum.

Aluminum (Al) is a common neurotoxic element that can exacerbate intracellular β-amyloid (Aβ) deposition. Reelin is a highly conserved extracellular glycoprotein that is involved in intracellular Aβ deposition. However, the action of Reelin on aluminum-induced Aβ deposition is not fully understood. Here, we investigated the effects of the Reelin-Dab1 signaling pathway on Aβ deposition in aluminum maltol (Al(mal)3) exposure in rat pheochromocytoma-derived cells (PC12). Our results showed that Al(mal)3 exposure decreased activity of PC12, increased expression of Aβ42, and decreased expression of Aβ40. Moreover, Al(mal)3 exposure in PC12 induced Reelin-Dab1 signaling pathway-associated proteins changed, decreased expression of Reelin and Dab1, and increased expression of pdab1. Moreover, the expression of Reelin, Dab1, and Aβ40 was found to be elevated in PC12 exposed to Al(mal)3 and corticosterone compared to those exposed to Al(mal)3. Also, the expression of Reelin, Dab1, and Aβ40 was found to be depressed in PC12 exposed to Al(mal)3 and streptozotocin compared with cells exposed to Al(mal)3 alone. These results suggested that Al(mal)3 inhibits the expression of the Reelin-Dab1 signaling pathway, promoting Aβ deposition. Thus, our findings provided important evidence to better understand how the Reelin-Dab1 signaling pathway may be a potential mechanism of Aβ deposition induced by aluminum.

The Significance of Expression Pattern of Dab1 and Reelin in the Postnatal Bladder of Dab1 -/- (Yotari) Mice

Background. The aim of our study is to provide an insight into the genetic expression landscape of Dab1 and Reelin, which are important in human genitourinary tract development and could help elucidate the critical stages of the onset of bladder anomalies.Methods. Yotari, heterozygote and wild type mice were sacrificed on the 4th, 11th and 14th postnatal day. Morphological parameters were analyzed using immunohistochemistry on mice bladder samples.Results. Significant expression of Dab1 was observed in the bladder epithelium during the 4th postnatal day and in the wt -wild type, but also in the yot -/- mouse. Reelin expression was significant in bladder epithelium during the 4th postnatal day in the wild-type and mutant mouse type. A significant expression of Dab1 positive cells in lamina propria was observed on the 4th postnatal day in yot -/- and in wt. The percentage of Reelin positive cells in lamina propria was significant on the 4th postnatal day in mutated and wild-type mice.Conclusions. An increase in the expression of Dab1 and Reelin proteins in the bladder of a yotari mouse may indicate bladder damage, due to congenital renal abnormalities and caused by a mutation in the Dab1 gene.Key words: Dab1; Reelin, CAKUT, bladder development, yotari mice

Ingestion of Bifidobacterium longum changes miRNA levels in the brains of mice.

The purpose of this research is to investigate the relationship between the microbiota of the gastrointestinal (GI) system and relative gene expression of miRNAs and mRNAs in the brain. C57BL/6 mice and Balb/c mice are fed Bifidobacterium longum, a well-characterized probiotic bacterial species shown to change behavior and improve sociability of Balb/c mice. After feeding, RNA was extracted from whole brains and PCR arrays were utilized to determine changes in the gene expression of brain-specific miRNAs. The results of these PCR arrays reveal that the relative gene expression of mmu-mir-652-3p is sensitive to B. longum probiotic treatment in C57BL/6 mice. qPCR was performed to measure expression of Dab1, an mRNA target of this miRNA. Dab1 expression is also dependent on B. longum. The goal of this study is to further understand the relationship between the gut microbiota and its impacts on neurological gene expression and brain function.

Analysis of Reelin signaling and neurodevelopmental trajectory in primary cultured cortical neurons with RELN deletion identified in schizophrenia

Reelin, an extracellular matrix protein, is secreted by Cajal-Retzius cells and plays crucial roles in the development of brain structures and neuronal functions. Reductions in Reelin cause the brain dysfunctions associated with mental disorders, such as schizophrenia. A recent genome-wide copy number variation analysis of Japanese schizophrenia patients identified a novel deletion in RELN encoding Reelin. To clarify the pathophysiological role of the RELN deletion, we developed transgenic mice carrying the RELN deletion (Reln-del) and found abnormalities in their brain structures and social behavior. In the present study, we performed an in vitro analysis of Reelin expression, intracellular Reelin signaling, and the morphology of primary cultured cortical neurons from wild-type (WT) and Reln-del mice. Reelin protein levels were lower in Reln-del neurons than in WT neurons. Dab1 expression levels were significantly higher in Reln-del neurons than in WT neurons, suggesting that Reelin signaling was decreased in Reln-del neurons. Reelin was mainly expressed in γ-aminobutyric acid (GABA)-ergic inhibitory neurons, but not in parvalbumin (PV)-positive neurons. A small proportion of Ca2+/calmodulin-dependent protein kinase II α subunit (CaMKIIα)-positive excitatory neurons also expressed Reelin. In comparisons with WT neurons, significant decreases were observed in neurite lengths and branch points as well as in the number of postsynaptic density protein 95 (PSD95) immunoreactive puncta in Reln-del neurons. A disintegrin and metalloproteinase with thrombospondin motifs-3 (ADAMTS-3) is a protease that inactivates Reelin by cleavage at the N-t site. The knockdown of ADAMTS-3 by short hairpin RNAs suppressed Reelin cleavage in conditioned medium and reduced Dab1 expression, indicating that Reelin signaling was enhanced in the primary cultured cortical neurons of WT and heterozygous Reln-del. Accordingly, the inhibition of ADAMTS-3 may be a potential candidate in the clinical treatment of schizophrenia by enhancing Reelin signaling in the brain.

Expression and localization of DAB1 and Reelin during normal human kidney development

AimTo explore the spatial and temporal expression patterns of DAB1 and Reelin in the developing and postnatal healthy human kidneys as potential determinants of kidney development.MethodsParaffin-embedded fetal kidney tissue between the 13/14th and 38th developmental weeks (dw) and postnatal tissue at 1.5 and 7 years were stained with DAB1 and Reelin antibodies by double immunofluorescence.ResultsDuring the fetal kidney development and postnatal period, DAB1 and Reelin showed specific spatial expression pattern and diverse fluorescence intensity. During the fetal period, DAB1 was strongly expressed in the distal convoluted tubules (DCT), with strong reactivity, and diversely in the proximal convoluted tubules (PCT) and glomeruli. In the postnatal period, DAB1 expression decreased. The strongest Reelin expression in early fetal stages was observed in the PCT. In the postnatal period, Reelin expression decreased dramatically in all observed structures. These two markers were colocalized during early developmental stages, mostly in PCT, DCT, and podocytes.ConclusionThe appearance of DAB1 and Reelin during fetal kidney development confirms their potential significant role in the formation of kidney structure or function. High DAB1 expression in the DCT implies its regulatory role in tubular formation or function maintenance during development. Reelin was highly expressed in human kidneys at early fetal stages, mostly in the PCT, while at later fetal stages and postnatal period its expression decreased.

Mesial Temporal Lobe Epilepsy: Role of Reelin Signalling Pathway

Abstract INTRODUCTION Granule cell dispersion (GCD) is pathognomonic of hippocampal sclerosis seen in mesial temporal lobe epilepsy (MTLE). Current animal studies associate GCD to deficiency of Reelin, an extracellular matrix protein. The present study evaluated complete Reelin signalling pathway in MTLE in human tissue hippocampus and anterior temporal lobe (ATL). ATL was included, as ATL resection along with amygdalo-hippocampectomy results in better disease control. METHODS Hematoxylin and Eosin (H&E) staining was done to identify the MTLE. Gene expression profiles of Reelin and its receptors (very low density lipoprotein-VLDLR and Apolipoprotein E 2-ApoER2), its downstream molecule Disabled 1 (Dab1) and its upstream inhibitor tissue inhibitor of metalloproteinases-1 (TIMP-1) were compared in normal and epileptic human tissue. Quantitative real-time PCR was done to determine the gene expression in the hippocampus and ATL. Western blotting was done to quantify the protein expression. Ethical clearance was taken from the Institute Ethical committee. RESULTS Typical features of MTLE were seen histologically. Width of granule cell layer was found to be broadened than normal controls. The expression of Reelin was found to be in same order to that of control. But its expression has been reduced as compared to the other genes. Reactive increase in the expression of both receptors was found. In hippocampus increase was more for ApoER2 while in ATL VLDLR showed increased expression. Similarly increased expression of Dab1 was seen, more in the hippocampus. Significantly increased expression was found in TIMP-1. CONCLUSION Data suggests a causative role of Reelin deficiency in MTLE. The increase in TIMP-1 would inhibit the Reelin cleavage, leading to deficiency of active Reelin. Downstream components of the Reelin show reactive increase. Reelin deficiency in ATL validates the surgical significance of ATL resection. Establishing a causative role of Reelin in MTLE in human tissue might have significant therapeutic potential.

Disabled-1 is down-regulated in clinical breast cancer and regulates cell apoptosis through NF-κB/Bcl-2/caspase-9.

Disabled‐1 (Dab1) is best known as an adaptor protein regulating neuron migration and lamination during development. However, the exact function of Dab1 in breast cancer is unknown. In this study, we examined the expression of Dab1 in 38 breast cancer paraffin sections, as well as 60 paired frozen breast cancer and their adjacent tissues. Our results showed that Dab1 was reduced in breast cancer, and its compromised expression correlated with triple negative breast cancer phenotype, poor differentiation, as well as lymph node metastasis. Functional analysis in breast cancer cell lines demonstrated that Dab1 promoted cell apoptosis, which, at least partially, depended on its regulation of NF‐κB/Bcl‐2/caspase‐9 pathway. Our study strongly suggests that Dab1 may be a potential tumour suppressor gene in breast cancer.

A new BCR-ABL1 Drosophila model as a powerful tool to elucidate the pathogenesis and progression of chronic myeloid leukemia.

The oncoprotein BCR-ABL1 triggers chronic myeloid leukemia. It is clear that the disease relies on constitutive BCR-ABL1 kinase activity, but not all the interactors and regulators of the oncoprotein are known. We describe and validate a Drosophila leukemia model based on inducible human BCR-ABL1 expression controlled by tissue-specific promoters. The model was conceived to be a versatile tool for performing genetic screens. BCR-ABL1 expression in the developing eye interferes with ommatidia differentiation and expression in the hematopoietic precursors increases the number of circulating blood cells. We show that BCR-ABL1 interferes with the pathway of endogenous dAbl with which it shares the target protein Ena. Loss of function of ena or Dab, an upstream regulator of dAbl, respectively suppresses or enhances both the BCR-ABL1-dependent phenotypes. Importantly, in patients with leukemia decreased human Dab1 and Dab2 expression correlates with more severe disease and Dab1 expression reduces the proliferation of leukemia cells. Globally, these observations validate our Drosophila model, which promises to be an excellent system for performing unbiased genetic screens aimed at identifying new BCR-ABL1 interactors and regulators in order to better elucidate the mechanism of leukemia onset and progression.

Clinical, genetic and neuropathological characterization of spinocerebellar ataxia type 37.

The autosomal dominant spinocerebellar ataxias (SCAs) consist of a highly heterogeneous group of rare movement disorders characterized by progressive cerebellar ataxia variably associated with ophthalmoplegia, pyramidal and extrapyramidal signs, dementia, pigmentary retinopathy, seizures, lower motor neuron signs, or peripheral neuropathy. Over 41 different SCA subtypes have been described evidencing the high clinical and genetic heterogeneity. We previously reported a novel spinocerebellar ataxia type subtype, SCA37, linked to an 11-Mb genomic region on 1p32, in a large Spanish ataxia pedigree characterized by ataxia and a pure cerebellar syndrome distinctively presenting with early-altered vertical eye movements. Here we demonstrate the segregation of an unstable intronic ATTTC pentanucleotide repeat mutation within the 1p32 5' non-coding regulatory region of the gene encoding the reelin adaptor protein DAB1, implicated in neuronal migration, as the causative genetic defect of the disease in four Spanish SCA37 families. We describe the clinical-genetic correlation and the first SCA37 neuropathological findings caused by dysregulation of cerebellar DAB1 expression. Post-mortem neuropathology of two patients with SCA37 revealed severe loss of Purkinje cells with abundant astrogliosis, empty baskets, occasional axonal spheroids, and hypertrophic fibres by phosphorylated neurofilament immunostaining in the cerebellar cortex. The remaining cerebellar Purkinje neurons showed loss of calbindin immunoreactivity, aberrant dendrite arborization, nuclear pathology including lobulation, irregularity, and hyperchromatism, and multiple ubiquitinated perisomatic granules immunostained for DAB1. A subpopulation of Purkinje cells was found ectopically mispositioned within the cerebellar cortex. No significant neuropathological alterations were identified in other brain regions in agreement with a pure cerebellar syndrome. Importantly, we found that the ATTTC repeat mutation dysregulated DAB1 expression and induced an RNA switch resulting in the upregulation of reelin-DAB1 and PI3K/AKT signalling in the SCA37 cerebellum. This study reveals the unstable ATTTC repeat mutation within the DAB1 gene as the underlying genetic cause and provides evidence of reelin-DAB1 signalling dysregulation in the spinocerebellar ataxia type 37.

Neuroprotective effect of melatonin on soluble Aβ1–42-induced cortical neurodegeneration via Reelin–Dab1 signaling pathway

Objective: Soluble Aβ1–42 oligomers play a vital role in the development and pathogenesis of Alzheimer’s disease (AD). Melatonin could delay the progress of AD through multiple mechanisms. Reelin–Dab1 signaling plays an important role in AD, including neuronal function and synaptic plasticity. However, whether melatonin could exert its neuroprotective function against soluble Aβ1–42-induced neurotoxicity during AD development through regulating Reelin–Dab1 signaling remains poorly understood.Methods: AD rat model was established by soluble Aβ1–42 repeated intracerebroventricular injection. Using immunohistochemistry and Western blot analyses, the effect of melatonin on synaptic plasticity, neuritic degeneration, and astrocyte activation was investigated in cerebral cortex. Meanwhile, the expression of Reelin and Dab1 was also examined in cerebral cortex. In our in vitro study, Reelin–Dab1 signaling was inhibited by Reelin antibody, and neuroprotective effect of melatonin against Aβ1–42 was further determined.Results: Melatonin ameliorated the neurotoxiciy and astrocyte activation induced by Aβ1–42 in the cerebral cortex. Melatonin also blocked the reduction in Reelin and Dab1 expression induced by Aβ1–42. Using in vitro study, Reelin inactivation completely abolished the protective effect of melatonin against Aβ1–42-induced neurotoxicity.Discussion: Melatonin might play its neuroprotective role against Aβ1–42 through mediating Reelin–Dab1 signaling pathway. Melatonin could be a safe and remarkable therapeutic candidate for AD and other aged-associated neurodegenerative diseases.

Mice with Dab1 or Vldlr insufficiency exhibit abnormal neonatal vocalization patterns.

Genetic and epigenetic changes in components of the Reelin-signaling pathway (RELN, DAB1) are associated with autism spectrum disorder (ASD) risk. Social communication deficits are a key component of the ASD diagnostic criteria, but the underlying neurogenetic mechanisms remain unknown. Reln insufficient mice exhibit ASD-like behavioral phenotypes including altered neonatal vocalization patterns. Reelin affects multiple pathways including through the receptors, Very low-density lipoprotein receptor (Vldlr), Apolipoprotein receptor 2 (Apoer2), and intracellular signaling molecule Disabled-1 (Dab1). As Vldlr was previously implicated in avian vocalization, here we investigate vocalizations of neonatal mice with a reduction or absence of these components of the Reelin-signaling pathway. Mice with low or no Dab1 expression exhibited reduced calling rates, altered call-type usage, and differential vocal development trajectories. Mice lacking Vldlr expression also had altered call repertoires, and this effect was exacerbated by deficiency in Apoer2. Together with previous findings, these observations 1) solidify a role for Reelin in vocal communication of multiple species, 2) point to the canonical Reelin-signaling pathway as critical for development of normal neonatal calling patterns in mice, and 3) suggest that mutants in this pathway could be used as murine models for Reelin-associated vocal deficits in humans.

Reelin expression in liver and pancreas and its correlation with liver fibrosis

Reelin is an extracellular glycoprotein secreted by a variety of cell types in both embryonic and adult tissue and plays a critical role during brain development (1,2). Reelin is up-regulated in experimental liver cirrhosis of rats in hepatic stellate cell(HSC)s, the cell type mainly implicated in liver fibrogenesis, supporting that reelin is involved in the pathogenesis of liver fibrosis (3). Pancreatic stellate cell(PSC)s share similar morphology and function to HSCs, in pancreatic fibrosis setting (4). Currently, the role of reelin in human liver and pancreas is still unclear. We investigated reelin expression in different stages of chronic liver disease in 81 liver biopsies of HCV affected patients and in pancreatic tissue near to tumoral lesions. The expression of Reelin, HSC markers (CRBP1, alpha-SMA) and Dab1, a Reelin adaptor protein, was investigated by immunohistochemistry and immunofluorescence. Reelin protein was expressed by HSCs and a strong correlation was found between Reelin expression and liver fibrosis stage (p<0.05). Reelin expression correlated with CRBP1 positive HSCs (p<0.05) but not with alpha-SMA positive ones, suggesting that Reelin should not be regarded as a marker of HSC differentiation but a functional protein expressed by HSCs in some phases of liver fibrosis. Dab1 was found expressed in ductular reaction (DR) cells and the number of Reelin positive HSCs correlated with DR (p<0.05), suggesting a paracrine role of Reelin during liver fibrosis. Furthermore we identified in the pancreas PSCs showing a variable degree of Reelin expression. A role of Reelin expression in liver fibrosis and in the remodelling pancreatic tissue surrounding tumoral lesions can be postulated on the basis of the present findings.

Notch1 Regulates Hippocampal Plasticity Through Interaction with the Reelin Pathway, Glutamatergic Transmission and CREB Signaling.

Notch signaling plays a crucial role in adult brain function such as synaptic plasticity, memory and olfaction. Several reports suggest an involvement of this pathway in neurodegenerative dementia. Yet, to date, the mechanism underlying Notch activity in mature neurons remains unresolved. In this work, we investigate how Notch regulates synaptic potentiation and contributes to the establishment of memory in mice. We observe that Notch1 is a postsynaptic receptor with functional interactions with the Reelin receptor, apolipoprotein E receptor 2 (ApoER2) and the ionotropic receptor, N-methyl-D-aspartate receptor (NMDAR). Targeted loss of Notch1 in the hippocampal CA fields affects Reelin signaling by influencing Dab1 expression and impairs the synaptic potentiation achieved through Reelin stimulation. Further analysis indicates that loss of Notch1 affects the expression and composition of the NMDAR but not AMPAR. Glutamatergic signaling is further compromised through downregulation of CamKII and its secondary and tertiary messengers resulting in reduced cAMP response element-binding (CREB) signaling. Our results identify Notch1 as an important regulator of mechanisms involved in synaptic plasticity and memory formation. These findings emphasize the possible involvement of this signaling receptor in dementia.HighlightsIn this paper, we propose a mechanism for Notch1-dependent plasticity that likely underlies the function of Notch1 in memory formation:Notch1 interacts with another important developmental pathway, the Reelin cascade.Notch1 regulates both NMDAR expression and composition.Notch1 influences a cascade of cellular events culminating in CREB activation.

Expression and regulation of reelin and its receptors in the enteric nervous system.

In the central nervous system (CNS), reelin coordinates migration and lamination of neurons and regulates synaptic plasticity, whereas its role in the enteric nervous system (ENS) remains enigmatic. Thus we determined the expression pattern and localization of reelin in the human ENS and monitored the time course of mRNA expression of the reelin signaling system in the rat intestine as well as in GDNF treated ENS cultures. Reelin, its receptors and Dab1 were expressed in all intestinal layers as well as in isolated myenteric ganglia. Enteric ganglia and nerve fibers were immunoreactive for reelin which co-localized with PGP 9.5 and synaptophysin. In the rat small intestine, highest expression levels of reelin were detected at early postnatal stages. Enteric nerve cell cultures treated with GDNF showed marked up-regulation of reelin and its receptors. Reelin and its receptors are strongly expressed in the human ENS. Reelin is specifically localized in enteric neurons with highest expression levels during early postnatal life as well as in neuronal network forming enteric nerve cell cultures pointing to putative functions in the differentiation and maintenance of the ENS. Gene expression of reelin, its receptors and Dab1 were analyzed in the human colon and isolated enteric ganglia. Co-localization of reelin with the pan-neuronal marker PGP 9.5 and the synaptic vesicle marker synaptophysin was studied by dual-label-immunocytochemistry. The time course of reelin expression was monitored in an ontogenetic study of rat intestines as well as in GDNF-treated cultures of enteric neurons.

Effects of electromagnetic fields on Reelin and Dab1 expression in the developing cerebral cortex

Many studies describe the biological effects of electromagnetic fields (EMF) including brain damages, neuronal migration and neurogenesis within the central nervous system. Neuronal cell produced in the neuroepithelium migrates along radial glial fibers into the cortical plate. Reelin, which is produced by Cajal-Retzius cells directs neuronal migration. It was shown that Disabled 1 (Dab1) functions downstream of reelin signal transduction pathway that directs the correct cytoarchitecture of the developing cortex. In this study, the EMF effects on total protein concentration (TPC), reelin and Dab1 expression in the developing cortex was studied. 30 pregnant Balb/c mice were separated into three groups: control (n = 10), EMF (n = 10) and SHAM groups (n = 10). The 15-day pregnant mice were placed inside the solenoid for a daily EMF exposure of 5 h for 3 consecutive days (15-17). The SHAM group was also located in the same coil with no exposure. Mice were sacrificed 24 h after the final exposure session. TPC, reelin and Dab1 expression were studied by Bio-Rad protein assay and western blot. No significant change in the TPC was seen in the EMF-treated cerebral cortex samples compared with those from the SHAM and control groups. It was also shown that the reelin and Dab1 expression increases in the EMF-treated cerebral cortex extracts as compared to controls and SHAM group. It is concluded that EMF may play important role in the neural cell migration by increasing reelin and Dab1 expression in the developing cortex.

Dab1 and reelin participate in a common signal pathway that controls intestinal crypt/villus unit dynamics

The myofibroblasts placed underneath the epithelium of the rodent small intestine express reelin, and the reelin absence modifies both the morphology and the cell renewal processes of the crypt-villus unit. In the developing central nervous system, the reelin effects are mediated by the disabled-1 (Dab1) protein. The present work explores whether Dab1 mediates the reelin control of the crypt-villus unit dynamics by examining in the mouse small intestine the consequences of the absence of (i) Dab1 (scrambler mutation) on crypt-villus unit cell renewal processes and morphology and (ii) reelin (reeler mutation) on the intestinal expression of Dab1. The effects of the scrambler mutation on the crypt-villus unit renewal processes are remarkably similar to those caused by the lack of reelin. Thus, both mutations significantly reduce epithelial cell proliferation, migration and apoptosis, and the number of Paneth cells; affect the morphology of the villus, and expand the intercellular space of the adherens junctions and desmosomes. The Western blot assays reveal that the Dab1 isoform present in the enterocytes has a molecular weight of ∼63 kDa and that in the brain of ∼82 kDa. They also reveal that the absence of reelin increases Dab1 abundance in both brain and enterocytes. All together, the current findings link reelin with Dab1 and suggest that Dab1 functions downstream of reelin action on the homeostasis of the crypt-villus unit.

Novel Disabled-1-expressing neurons identified in adult brain and spinal cord.

Components of the Reelin-signaling pathway are highly expressed in embryos and regulate neuronal positioning, whereas these molecules are expressed at low levels in adults and modulate synaptic plasticity. Reelin binds to Apolipoprotein E receptor 2 and Very-low-density lipoprotein receptors, triggers the phosphorylation of Disabled-1 (Dab1), and initiates downstream signaling. The expression of Dab1 marks neurons that potentially respond to Reelin, yet phosphorylated Dab1 is difficult to detect due to its rapid ubiquitination and degradation. Here we used adult mice with a lacZ gene inserted into the dab1 locus to first verify the coexpression of β-galactosidase (β-gal) in established Dab1-immunoreactive neurons and then identify novel Dab1-expressing neurons. Both cerebellar Purkinje cells and spinal sympathetic preganglionic neurons have coincident Dab1 protein and β-gal expression in dab1(lacZ/+) mice. Adult pyramidal neurons in cortical layers II-III and V are labeled with Dab1 and/or β-gal and are inverted in the dab1(lacZ/lacZ) neocortex, but not in the somatosensory barrel fields. Novel Dab1 expression was identified in GABAergic medial septum/diagonal band projection neurons, cerebellar Golgi interneurons, and small neurons in the deep cerebellar nuclei. Adult somatic motor neurons also express Dab1 and show ventromedial positioning errors in dab1-null mice. These findings suggest that: (i) Reelin regulates the somatosensory barrel cortex differently than other neocortical areas, (ii) most Dab1 medial septum/diagonal band neurons are probably GABAergic projection neurons, and (iii) positioning errors in adult mutant Dab1-labeled neurons vary from subtle to extensive.

Reelin signalling in neuroblastoma: Migratory switch in metastatic stages

The essential functions of Reelin for the migratory behaviour of neuroblasts in the central nervous system are well documented. Its role in the dissemination of neuronal tumours of the peripheral nervous system has not been studied in detail. Here, we examined neuroblastoma (NB), a tumour derived from sympathoadrenal cells of neural crest origin. We studied the expression of Reelin, its receptors VLDLR and LRP8 and the adapter protein DAB1 in primary tumour samples and cell lines. We used real-time RT-PCR, immunohistology and western blot analysis. In NB cell lines we studied effects of all-trans retinoic acid and the in vitro effects of Reelin. In primary tumour samples of untreated patients, a significant downregulation of Reelin and DAB1 mRNA was found in the metastatic stages 3, 4 and 4s. Immunohistochemical studies revealed expression of Reelin, LRP8 and DAB1 in differentiating-type low-grade NB. In vitro, western blot analysis of selected NB cell lines showed variable expression patterns. Differentiation induction with all-trans retinoic acid induced the upregulation of Reelin and DAB1. Reelin acted as a chemoattractant for various NB cell lines but inhibited migration when applied together with the NB cells. In normal tissue, we found Reelin in lymphatic endothelial cells (LECs) but not in blood vessel endothelium (BECs). In primary NB, both BECs and LECs were positive. Our data strongly suggest that Reelin has a dual role in NB. Autocrine expression marks low-grade differentiating tumour cells, whereas paracrine Reelin presented by LECs and BECs may act as a chemoattractant and promote hematogenic and lymphogenic dissemination in progressed stages.

Dab1 (Disable Homolog-1) Reelin Adaptor Protein Is Overexpressed in the Olfactory Bulb at Early Postnatal Stages

Dab1 mediates reelin signalling and plays critical roles in early brain development such as the stereotypical positioning of neurons in the brain. The olfactory bulb undergoes a prominent layering reorganization, but shows not apparent differences between wild type and reeler in the layer organization. Therefore, an accurate regional and cellular simultaneous analysis of these molecules becomes essential to clarify the role played by Dab1 upon Reelin effect. The present study reveals a strong and consistent Dab1 mRNA and protein expressions, throughout the olfactory bulb layers in both wild type and reeler mice. In addition, noteworthy is the pattern of Dab1 location within cell nuclei in both strains. Furthermore, a temporal increment of Dab1 expression levels is detected from P0 to P15 in both strains, being the protein quantity higher in reeler than in wild type mice. Altogether, our results revealed that Reln acts directly from projection neurons via the production of different Reln fragments. Changes in the pattern of Dab1 expression could reflect an alternative Reln function in postnatal and adult stages, besides a possible regulation of Dab1 by other molecules distinct to Reln.