Beta-amyloid controls altered Reelin expression and processing in Alzheimer's disease.

Reelin is a glycoprotein that modulates synaptic function and plasticity in the mature brain, thereby favouring memory formation. We recently reported altered cerebral Reelin expression in Alzheimer's disease (AD). Here we demonstrate pronounced Reelin changes at protein and mRNA levels in the frontal cortex in adult Down's syndrome (DS), where the extra copy of chromosome 21 leads to overexpression of beta-amyloid. In cortical extracts of fetal DS samples we detected increased levels of the full-length Reelin and the 310-kDa fragment. Overexpression of mutant human amyloid precursor protein also led to an increase in levels of Reelin fragments in Tg2576 transgenic mice for human beta-amyloid. Finally, in vitro Abeta42 treatment of SH-SY5Y neuroblastoma cells led to increased Reelin levels. An altered pattern of Reelin glycosylation was detected in extracts from the frontal cortex of AD patients and in Abeta42-treated SH-SY5Y cells, supporting the notion that beta-amyloid triggers altered Reelin processing. These results provide evidence that Reelin expression and processing is altered in several amyloid conditions.

Radial glia fibers translate Fgf8 morphogenetic signals to generate a thalamic nuclear complex protomap in the mantle layer.

Thalamic neurons are distributed between different nuclear groups of the thalamic multinuclear complex; they develop topologically ordered specific projections that convey information on voluntary motor programs and sensory modalities to functional areas in the cerebral cortex. Since thalamic neurons present a homogeneous morphology, their functional specificity is derived from their afferent and efferent connectivity. Adequate development of thalamic afferent and efferent connections depends on guide signals that bind receptors in nuclear neuropils and axonal growth cones, respectively. These are finally regulated by regionalization processes in the thalamic neurons, codifying topological information. In this work, we studied the role of Fgf8 morphogenetic signaling in establishing the molecular thalamic protomap, which was revealed by Igsf21, Pde10a and Btbd3 gene expression in the thalamic mantle layer. Fgf8 signaling activity was evidenced by pERK expression in radial glia cells and fibers, which may represent a scaffold that translates neuroepithelial positional information to the mantle layer. In this work, we describe the fact that Fgf8-hypomorphic mice did not express pERK in radial glia cells and fibers and presented disorganized thalamic regionalization, increasing neuronal death in the ventro-lateral thalamus and strong disruption of thalamocortical projections. In conclusion, Fgf8 encodes the positional information required for thalamic nuclear regionalization and the development of thalamocortical projections.

Reelin is overexpressed in the liver and plasma of bile duct ligated rats and its levels and glycosylation are altered in plasma of humans with cirrhosis.

Reelin is an extracellular matrix protein secreted by a variety of cell types in both embryonic and adult tissues, including the liver. However, the physiological significance of Reelin in normal and cirrhotic liver has thus far not been elucidated. We have investigated Reelin levels in the liver and plasma of bile duct ligated (BDL) rats. We observe a 115% increase in full-length Reelin and its 310- and 180-kDa fragments in liver extracts from BDL rats, compared to sham-operated controls (p = 0.005). The overall increase in protein levels was associated with a 30% increase of Reelin transcripts (p = 0.03). Immunohistochemical analysis demonstrated that hepatic stellate cells are the major source of Reelin in the injured liver. Increased liver Reelin in BDL rats leads to a pronounced 165% increase in the plasma levels (p < 0.001), particularly in the less abundant 180-kDa fragment (300% increase; p < 0.001). The data provides evidence that a fraction of plasma Reelin is synthesized in the liver. In human subjects suffering liver cirrhosis the level of the 180-kDa fragment was also increased by 140% in the plasma (p < 0.001). Analysis of Reelin glycosylation by lectin binding demonstrated that the 180- and predominant 310-kDa Reelin fragments in the plasma of cirrhotic patients are differentially glycosylated compared to non-diseased control subjects. The data show that Reelin is up-regulated in experimental liver cirrhosis and that its levels and glycosylation are altered in plasma from patients with cirrhosis, thereby supporting that Reelin is involved in the pathogenesis of liver disease.

Clinical Phenotypes Associated to Engrailed 2 Gene Alterations in a Series of Neuropediatric Patients.

The engrailed homeobox protein (EN) plays an important role in the regionalization of the neural tube. EN distribution regulates the cerebellum and midbrain morphogenesis, as well as retinotectal synaptogenesis. In humans, the EN1 and EN2 genes code for the EN family of transcription factors. Genetic alterations in the expression of EN2 have been related to different neurologic conditions and more particularly to autism spectrum disorders (ASD). We aimed to study and compare the phenotypes of three series of patients: (1) patients with encephalic structural anomalies (ESA) and abnormalities in the genomic (DNA) and/or transcriptomic (RNAm) of EN2 (EN2-g), (2) ESA patients having other gene mutations (OG-g), and (3) ESA patients free of these mutations (NM-g). Subjects and Methods: We have performed a descriptive study on 109 patients who suffer from mental retardation (MR), cerebral palsy (CP), epilepsy (EP), and behavioral disorders (BD), showing also ESA in their encephalic MRI. We studied genomic DNA and transcriptional analysis (cDNA) on EN2 gene (EN2), and in other genes (OG): LIS1, PTAFR, PAFAH1B2, PAFAH1B3, FGF8, PAX2, D17S379, D17S1866, and SMG6 (D17S5), as a routine genetic diagnosis in ESA patients. Results: From 109 patients, fifteen meet the exclusion criteria. From the remaining 94 patients, 12 (12.8%) showed mutations in EN2 (EN2-g), 20 showed mutations in other studied genes (OG-g), and 62 did not showed any mutation (NM-g). All EN2-g patients, suffered from MR, nine EP, seven BD and four CP. The proportions of these phenotypes in EN2-g did not differ from those in the OG-g, but it was significantly higher when comparing EN2-g with NM-g (MR: p = 0.013; EP: p = 0.001; BD: p = 0.0001; CP: p = 0.07, ns). Groups EN2-g and OG-g showed a 100 and a 70% of comorbidity, respectively, being significantly (p = 0.04) greater than NM-group (62.9%). Conclusion: Our series reflects a significant effect of EN2 gene alterations in neurodevelopmental abnormalities associated to ESA. Conversely, although these EN2 related anomalies might represent a predisposition to develop brain diseases, our results did not support direct relationship between EN2 mutations and specific clinical phenotypes.

HNK-1 Carrier Glycoproteins Are Decreased in the Alzheimer's Disease Brain.

The human natural killer-1 (HNK-1), 3-sulfonated glucuronic acid, is a glycoepitope marker of cell adhesion that participates in cell-cell and cell-extracellular matrix interactions and in neurite growth. Very little is known about the regulation of the HNK-1 glycan in neurodegenerative disease, particularly in Alzheimer's disease (AD). In this study, we investigate changes in the levels of HNK-1 carrier glycoproteins in AD. We demonstrate an overall decrease in HNK-1 immunoreactivity in glycoproteins extracted from the frontal cortex of AD subjects, compared with levels from non-demented controls (NDC). Immunoblotting of ventricular post-mortem and lumbar ante-mortem cerebrospinal fluid with HNK-1 antibodies indicate similar levels of carrier glycoproteins in AD and NDC samples. Decrease in HNK-1 carrier glycoproteins were not paralleled by changes in messenger RNA (mRNA) levels of the enzymes involved in the synthesis of the glycoepitope, ß-1,4-galactosyltransferase (ß4GalT), glucuronyltransferases GlcAT-P and GlcAT-S, or sulfotransferase HNK-1ST. Over-expression of amyloid precursor protein in Tg2576 transgenic mice and in vitro treatment of SH-SY5Y neuroblastoma cells with the amyloidogenic Aß42 peptide resulted in a decrease in HNK-1 immunoreactivity levels in brain and cellular extracts, whereas the levels of soluble HNK-1 glycoproteins detected in culture media were not affected by Aß treatment. HNK-1 levels remain unaffected in the brain extracts of Tg-VLW mice, a model of mutant hyperphosphorylated tau, and in SH-SY5Y cells over-expressing hyperphosphorylated wild-type tau. These results provide evidence that cellular levels of HNK-1 carrier glycoforms are decreased in the brain of AD subjects, probably influenced by the ß-amyloid protein.

FoxP2 protein levels regulate cell morphology changes and migration patterns in the vertebrate developing telencephalon.

In the mammalian telencephalon, part of the progenitor cells transition from multipolar to bipolar morphology as they invade the mantle zone. This associates with changing patterns of radial migration. However, the molecules implicated in these morphology transitions are not well known. In the present work, we analyzed the function of FoxP2 protein in this process during telencephalic development in vertebrates. We analyzed the expression of FoxP2 protein and its relation with cell morphology and migratory patterns in mouse and chicken developing striatum. We observed FoxP2 protein expressed in a gradient from the subventricular zone to the mantle layer in mice embryos. In the FoxP2 low domain cells showed multipolar migration. In the striatal mantle layer where FoxP2 protein expression is higher, cells showed locomoting migration and bipolar morphology. In contrast, FoxP2 showed a high and homogenous expression pattern in chicken striatum, thus bipolar morphology predominated. Elevation of FoxP2 in the striatal subventricular zone by in utero electroporation promoted bipolar morphology and impaired multipolar radial migration. In mouse cerebral cortex we obtained similar results. FoxP2 promotes transition from multipolar to bipolar morphology by means of gradiental expression in mouse striatum and cortex. Together these results indicate a role of FoxP2 differential expression in cell morphology control of the vertebrate telencephalon.

Beta-amyloid impairs reelin signaling.

Reelin is a signaling protein increasingly associated with the pathogenesis of Alzheimer's disease that relevantly modulates tau phosphorylation. We have previously demonstrated that ß-amyloid peptide (Aß) alters reelin expression. We have now attempted to determine whether abnormal reelin triggered by Aß will result in signaling malfunction, contributing to the pathogenic process. Here, we show that reelin forms induced by ß-amyloid are less capable of down-regulating tau phosphorylation via disabled-1 and GSK3ß kinase. We also demonstrate that the scaffold protein 14-3-3 that increases tau phosphorylation by modulating GSK3ß activity, is up-regulated during defective reelin signaling. Binding of reelin to its receptor, mainly ApoER2 in the brain, relays the signal into the cell. We associate the impaired reelin signaling with inefficiency of reelin in forming active homodimers and decreased ability to bind efficiently to its receptor, ApoER2. More remarkably, reelin from Alzheimer cortex shows a tendency to form large complexes instead of homodimers, the active form for signaling. Our results suggest that reelin expression is altered by Aß leading to impaired reelin signaling.

Bone marrow transplantation in hindlimb muscles of motoneuron degenerative mice reduces neuronal death and improves motor function.

Bone marrow has proved to be an adequate source of stem cells for the treatment of numerous disorders, including neurodegenerative diseases. Bone marrow can be easily and relatively painlessly extracted from a patient or allogenic donor and then transplanted into the degenerative area. Here, the grafted cells will activate a number of mechanisms in order to protect, repair, and/or regenerate the damaged tissue. These properties make the bone marrow a feasible source for cell therapy. In this work, we transplanted bone marrow cells into a mouse model of motoneuron degeneration, with the particularity of placing the cells in the hindlimb muscles rather than in the spinal cord where neuronal degeneration occurs. To this end, we analyze the possibility for the transplanted cells to increase the survival rate of the spinal cord motoneurons by axonal-guided retrograde neurotrophism. As a result, the mice significantly improved their motor functions. This coincided with an increased number of motoneurons innervating the treated muscle compared with the neurons innervating the non-treated contralateral symmetric muscle. In addition, we detected an increase in glial-derived neurotrophic factor in the spinal cord, a neurotrophic factor known to be involved in the rescue of degenerating motoneurons, exerting a neuroprotective effect. Thus, we have proved that bone marrow injected into the muscles is capable of rescuing these motoneurons from death, which may be a possible therapeutic approach for spinal cord motoneuron degenerative diseases, such as amyotrophic lateral sclerosis.

Reelin expression and glycosylation patterns are altered in Alzheimer's disease.

Reelin is a glycoprotein that is essential for the correct cytoarchitectonic organization of the developing CNS. Its function in the adult brain is less understood, although it has been proposed that Reelin is involved in signaling pathways linked to neurodegeneration. Here we analyzed Reelin expression in brains and cerebrospinal fluid (CSF) from Alzheimer's disease (AD) patients and nondemented controls. We found a 40% increase in the Reelin protein levels in the cortex of AD patients compared with controls. Similar increases were detected at the Reelin mRNA transcriptional level. This expression correlates with parallel increases in CSF but not in plasma samples. Next, we examined whether CSF Reelin levels were also altered in neurological diseases, including frontotemporal dementia, progressive supranuclear palsy, and Parkinson's disease. The Reelin 180-kDa band increased in all of the neurodegenerative disorders analyzed. Moreover, the 180-kDa Reelin levels correlated positively with Tau protein in CSF. Finally, we studied the pattern of Reelin glycosylation by using several lectins and the anti-HNK-1 antibody. Glycosylation differed in plasma and CSF. Furthermore, the pattern of Reelin lectin binding differed between the CSF of controls and in AD. Our results show that Reelin is up-regulated in the brain and CSF in several neurodegenerative diseases and that CSF and plasma Reelin have distinct cellular origins, thereby supporting that Reelin is involved in the pathogenesis of a number of neurodegenerative diseases.