Biomedical subjects

M Dierssen

Publications and source records attributed to M Dierssen.

At least 37 records · Page 2Linked to original sources

PubMed2001

Increased protein levels of heterogeneous nuclear ribonucleoprotein A2/B1 in fetal Down syndrome brains.

Heterogeneous nuclear ribonucleoproteins (hnRNPs) are predominantly nuclear RNA-binding proteins that form complexes with RNA polymerase II transcripts. These proteins play pivotal roles in transcription, pre-mRNA processing in the nucleus, cytoplasmic mRNA translation and its turnover. In addition, hnRNPs have been shown to be essential for embryonic development of Drosophila. Here we studied the protein levels of hnRNPs (A2/B1, H and H') in fetal brain with Down syndrome (DS; n = 5) compared to controls (n = 7). We used two-dimensional (2-D) gel electrophoresis, matrix-assisted laser desorption ionization mass spectroscopy (MALDI-MS) and specific software for quantification. hnRNP A2/B1 was significantly increased in fetal DS brain (13.52+/-4.50) compared to controls (9.16+/-1.35), but both hnRNP H and H' were unchanged. Increased hnRNP A2/B1 in fetal DS brain may represent high activity of RNA processing such as RNA trafficking and telomere protection, and/or it could contribute to abnormal development of DS brains. Furthermore, comparable expression of hnRNP H and H' suggest a specific upregulation of hnRNP A2/B.

Brain↗

PubMed2001

Decreased protein levels of stathmin in adult brains with Down syndrome and Alzheimer's disease.

Stathmin, distributed in neurons with high abundance, acts as an intracellular relay, integrating various transduction pathways triggered by extracellular signals and it is involved in physiological regulation of microtubule destabilization. Stathmin has been also shown to be a critical molecule in pathology of neurodegeneration such as Alzheimer's disease (AD), particularly, in neurofibrillary tangle (NFT) formation. Here we evaluated protein levels of stathmin in adult brain from patients with AD and Down syndrome (DS) showing AD-like pathology by applying proteomic technologies with two-dimensional (2-D) gel electrophoresis, matrix-assisted laser desorption ionization mass spectroscopy (MALDI-MS) identification and specific software for quantification of proteins. Significantly decreased protein levels of stathmin were observed in frontal (2.12+/-1.17, n = 6) and temporal (3.05+/-2.81, n = 10) cortices of AD compared to controls (frontal cortex: 4.41+/-1.70, n = 8; temporal cortex: 5.26+/-2.26, n = 13). Stathmin was also significantly decreased in frontal (2.47+/-1.11, n = 7) and temporal (2.02+/-1.18, n = 9) cortices of DS. We also investigated stathmin levels in fetal brain. Stathmin was not significantly changed between fetal DS brain and controls. We suggest that the decreased protein level of stathmin in brains is associated with tangle formation and microtubule instability in DS as well as AD, but stathmin is not involved in the abnormal development of fetal DS brain.

Adult↗

PubMed2001

Down syndrome patients start early prenatal life with normal cholinergic, monoaminergic and serotoninergic innervation.

Information on the fetal brain in Down syndrome (DS) is limited. In particular, there is no systematic study available on cholinergic, monoaminergic or serotoninergic innervation in the early second trimester. It was therefore the aim of the study to investigate whether deficits of any of these systems known to occur in adults with DS, was present at this early phase. For this purpose we determined markers for neuronal density (neuron-specific enolase, NSE), for cholinergic innervation (vesicular acetylcholine transporter, VAChT), for monoaminergic innervation (vesicular monoamine transporter 2, VMAT2; tyrosine hydroxylase, TH) and for the serotoninergic system (serotonine transporter, SERT) in brain of control and DS fetuses in the early second trimester using immunoblotting. Values for all neurotransmission systems were measurable at this time point of human development and comparable in control and DS fetuses. We conclude that during the second trimester DS patients do not differ in terms of immunoreactivity for all markers studied. This first study on that subject warrants further investigations for the determination of the time point when neurotransmitter deficits in DS brain are starting, a hallmark most important for pathogenesis and pharmacotherapy.

Biomarkers↗

PubMed2001

Expression profiles of proteins in fetal brain with Down syndrome.

Proteomics is a powerful tool for evaluating differential protein expression comparing hundreds of proteins simultaneously. In the current study we performed "gene hunting" at the protein level and identified and quantified 10 protein spots in control and Down syndrome (DS) fetal brains. Using two-dimensional (2-D) electrophoresis of fetal brain proteins with subsequent MALDI-identification and quantification with specific software, we identified a series of poorly known proteins, in part hypothetical and orphans or poorly documented proteins. Hypothetical protein DKFZp564D177.1-human (fragment), one of these proteins was identified in fetal brain and was significantly decreased in DS (0.61+/-0.44, n = 7) compared to controls (3.43+/-1.83, n = 7). Septin 6, previously shown to be associated with synaptic vesicles, was present in all of 7 controls, but only in 1 out of 6 DS brains. We suggest that decreased protein levels of hypothetical protein DKFZp564D177.1-human (fragment) and lower prevalence of septin 6 could be involved in the maldevelopment of fetal DS brains. The other 8 proteins (WD repeat protein 1, novel protein highly similar to septin 2 homolog, septin 5, septin 2, DJ37E16.5 (novel protein similar to nitrophenylphosphatases from various organism), hypothetical 30.2 kDa protein, neuronal protein NP25, and DC7 protein (vacuolar sorting protein 29)) were comparable between controls and DS but could be identified in fetal and DS cortex, thus proposing them as tentative brain proteins.

Brain↗

PubMed2001

Expression patterns of chaperone proteins in cerebral cortex of the fetus with Down syndrome: dysregulation of T-complex protein 1.

Chaperone proteins reduce stress-induced denaturation and aggregation of intracellular proteins and exert protective actions by interfering with the stress-induced apoptotic pathway in the neuronal cells. Although many studies have focused on the critical role of chaperones in protein folding and their relevance in protein conformational diseases such as Alzheimer's disease (AD) and prion disease, limited information is available on their expression pattern in AD-related disease, Down Syndrome (DS). In a previous study, we reported differentially expressed molecular chaperone proteins in the brains of adult DS patients. This report demonstrated the relevance of the aberrant expression patterns to biochemical and neuropathological abnormalities in adult DS brain. To investigate whether this aberrant expression patterns already exist in second trimester DS brain, we performed two-dimensional polyacrylamide gel electrophoresis (2-DE) and matrix-associated laser desorption ionization mass spectroscopy (MALDI-MS) using fetal DS brain. We unambiguously identified and quantified twelve heat shock proteins (HSPs), three glucose regulated proteins (GRPs) and eight T-complex 1 (TCP-1) subunits. Unlike in adult brain with DS, these studies provide evidence for the normal response of most molecular chaperone proteins at the given time point of DS brain development. However, chaperonin protein TCP-1 alpha and beta subunits showed a significant decrease (P < 0.05) in second trimester brain with DS. Comparable response of chaperone proteins in fetal DS brain suggests that not heat-shock induced proteins but rather chaperonin protein TCP-1 may contribute significantly to neuropathogenesis in the early second trimester DS brain. This study extends observations of distinct expression patterns of molecular chaperones in DS brain and we discuss the relevance of aberrant TCP-1 expression patterns to developmental DS brain at the early stage.

Cerebral Cortex↗

PubMed2001

Beta-amyloid precursor protein, ETS-2 and collagen alpha 1 (VI) chain precursor, encoded on chromosome 21, are not overexpressed in fetal Down syndrome: further evidence against gene dosage effect.

Down syndrome (DS) is the most common human chromosomal abnormality caused by an extra copy of chromosome 21 and characterized clinically by somatic anomalies, mental retardation and precocious dementia. The phenotype of DS is thought to result from overexpression of a gene or genes located on the triplicated chromosome or chromosome region. Reports that challenge this notion, however, have been published. To add to this body of evidence, the expression of beta-amyloid precursor protein (APP), ETS-2 and collagen alpha1 (VI) chain precursor, encoded on chromosome 21, was investigated in fetal brain by western blot and two-dimensional electrophoresis (2-DE). Western blot detected APP and ETS-2 that migrated at approximately 75 and 50kDa, respectively. Subsequent densitometric analysis of APP and ETS-2 immunoreactivity did not produce any significant change between controls and DS. Since the metabolic fate of APP determines the propensity of amyloid beta production, the expression of the secreted forms of APP (sAPP) had been examined. Neither the expression of sAPPalpha nor sAPPbeta showed any detectable changes among the two groups. Collagen alpha1 (VI) chain precursor, a protein resolved as a single spot on 2D gel was identified by matrix associated laser desorption ionization mass spectroscopy. Quantitative analysis of this spot using the 2D Image Master software revealed a significant decrease in fetal DS (P < 0.01) compared to controls. Linear regression analysis did not show any correlation between protein levels and age. The current data suggest that overexpression per se can not fully explain the DS phenotype.

Amyloid beta-Protein Precursor↗

PubMed2001

Reduction of nucleoside diphosphate kinase B, Rab GDP-dissociation inhibitor beta and histidine triad nucleotide-binding protein in fetal Down syndrome brain.

Information on the various factors leading to impairments in the developing brain of fetal Down Syndrome patients is limited to few histological reports. We therefore attempted to describe expression levels of proteins in brain using the proteomic technique of two-dimensional electrophoresis with subsequent mass spectroscopical identification of protein spots and quantification with specific software. Cortical tissue was obtained from autopsy of human fetal abortus. Protein levels of GTP-binding nuclear protein ran, guanine nucleotide-binding protein g(o), alpha subunit 2, guanine nucleotide-binding protein g(i)/g(s)/g(t) beta subunit 1, -beta subunit 2, guanine nucleotide-binding protein beta subunit 5, nucleoside diphosphate kinase A, nucleoside diphosphate kinase B, Rab GDP-dissociation inhibitor beta, Rho GDP-dissociation inhibitor 1, biphosphate 3'-nucleotidase, small glutamine-rich tetra-tricopeptide repeat-containing protein and histidine triad nucleotide-binding protein were studied. Quantification revealed statistically significant reduced levels of nucleoside diphosphate kinase B, Rab GDP-dissociation inhibitor beta and histidine triad nucleotide-binding protein in fetal DS brain as compared to controls. We conclude that in early prenatal life proteins involved in neural differentiation, migration and synaptic transmission are impaired in DS cortex. These results may help to understand the abundant mechanisms leading to abnormalities in the wiring, structure and function of DS brain.

Brain↗

PubMed2001

Fetal life in Down syndrome starts with normal neuronal density but impaired dendritic spines and synaptosomal structure.

Information on fetal brain in Down Syndrome (DS) is limited and there are only few histological, mainly anecdotal reports and no systematic study on the wiring of the brain in early prenatal life exists. Histological methods are also hampered by inherent problems of morphometry of neuronal structures. It was therefore the aim of the study to evaluate neuronal loss, synaptic structures and dendritic spines in the fetus with Down Syndrome as compared to controls by biochemical measurements. 2 dimensional electrophoresis with subsequent mass spectroscopical identification of spots and their quantification with specific software was selected. This technique identifies proteins unambiguously and concomitantly on the same gel. Fetal cortex samples were taken at autopsy with low post-mortem time, homogenized and neuron specific enolase (NSE) determined as a marker for neuronal density, the synaptosomal associated proteins alpha SNAP [soluble N-ethylmaleimide-sensitive fusion (NSF) attachment protein], beta SNAP, SNAP 25 and the channel associated protein of synapse 110 (chapsyn 110) as markers for synaptosomal structures and drebrin (DRB) as marker for dendritic spines. NSE, chapsyn 110 and beta SNAP were comparable in the control fetus panel and in Down Syndrome fetuses. Drebrin was significantly and remarkably reduced and not even detectable in several Down Syndrome brain samples. Quantification of SNAP 25 revealed significantly reduced values in DS cortex and alpha SNAP was only present in half of the DS individuals. We conclude that at the time point of about 19 weeks of gestation (early second trimester) no neuronal loss can be detected but drebrin, a marker for dendritic spines and synaptosomal associated proteins alpha SNAP and SNAP 25 were significantly reduced indicating impaired synaptogenesis. Early dendritic deterioration maybe leading to the degeneration of the dendritic tree and arborization, which is a hallmark of Down Syndrome from infancy.

Biomarkers↗

PubMed2001

Decreased protein levels of complex I 30-kDa subunit in fetal Down syndrome brains.

Defects of mitochondrial electron transport enzymes have been implicated in the pathogenesis of several neurodegenerative diseases. In previous work, we reported decreased protein levels of mitochondrial electron transport enzyme subunits in adult brain with Down syndrome (DS). However it is not clear whether cellular damage due to mitochondrial defects in brain of DS fetus begins in utero. Here we investigated the protein levels of mitochondrial electron transport enzymes in fetal DS brain using the proteomic technologies. Two-dimensional (2-D) gel electrophoresis, matrix-assisted laser desorption ionization mass spectroscopy (MALDI-MS) and specific software for quantification were used. The protein levels of complex I 30-kDa subunit were significantly decreased in cerebral cortex of fetal DS brain. We conclude that decreased mitochondrial electron transport enzyme subunits in fetal DS brains could contribute to the impaired energy and free radical metabolism affecting brain development in DS fetus. Furthermore, the defects of mitochondrial electron enzymes shown in adult DS brains could begin in utero and continue during the life span of the individual with DS.

Adenosine Triphosphatases↗

PubMed2001

Murine models for Down syndrome.

The availability of the recently published DNA sequence of human chromosome 21 (HSA21) is a landmark contribution that will have an immediate impact on the study of the role of specific genes to Down syndrome (DS). Trisomy 21 or DS is the only autosomal aneuploidy that is not lethal in the fetal or early postnatal period. DS phenotypes show variable penetrance, affecting many different organs, including brain (mental retardation, early onset of Alzheimer's disease, AD), muscle (hypotonia), skeleton, and blood. DS phenotypes may stem directly from the cumulative effect of overexpression of specific HSA21 gene products or indirectly through the interaction of these gene products with the whole genome, transcriptome, or proteome. Mouse genetic models have played an important role in the elucidation of the contribution of specific genes to the DS phenotype. To date, the strategies used for modeling DS in mice have been three: (1) to assess single-gene contributions to DS phenotype, using transgenic techniques to create models overexpressing single or combinations of genes, (2) to assess the effects of overexpressing large foreign DNA pieces, introduced on yeast artificial chromosomes (YACs) or bacterial artificial chromosomes (BACs) into transgenic mice, and (3) mouse trisomies that carry all or part of MMU16, which has regions of conserved homology with HSA21. Here we review the existing murine models and the relevance of their contribution to DS research.

Animals↗

PubMed2000

Synaptic deficit in the temporal cortex of partial trisomy 16 (Ts65Dn) mice.

Down syndrome results from triplication of human chromosome 21. The distal end of mouse chromosome 16 shares a large region of genetic homology with the Down syndrome 'critical region' of human chromosome 21. Therefore, a partially trisomic mouse (Ts65Dn) that possesses a triplication of the distal region of chromosome 16 has been developed as a putative model for Down syndrome. Ts65Dn mice display learning and memory deficits. However, despite the importance of preserved synaptic integrity for learning and memory, the ultrastructure of neural connectivity has not yet been studied in Ts65Dn mice. Therefore, the density and apposition zone length of synapses in the temporal cortex of aged Ts65Dn mice (n=4) were compared with those in diploid controls (n=4), using quantitative electron microscopy. There were significantly less (30%) asymmetric synapses in the temporal cortex of Ts65Dn mice than in controls (t=-5.067; p=0.023). However, there was no significant difference between the mean density of symmetric synapses in Ts65Dn mice and control mice. In addition, the mean synaptic apposition lengths of both asymmetric (15%; t=9.812, p<0.0001) and symmetric (11%; t=5. 582; p<0.0001) synapses were significantly larger in Ts65Dn mice than in controls. These results suggest that excitatory synapses are preferentially affected in Ts65Dn mice and that there is an attempt to compensate for the deficit of asymmetric synapses by increasing the contact zone area of existing synapses. The results may also reveal the morphological basis for the learning and memory deficits observed in Ts65Dn mice and have a bearing on the cognitive deficits in Down syndrome in old age.

Animals↗

PubMed2000

The mouse brain transcriptome by SAGE: differences in gene expression between P30 brains of the partial trisomy 16 mouse model of Down syndrome (Ts65Dn) and normals.

Trisomy 21, or Down syndrome (DS), is the most common genetic cause of mental retardation. Changes in the neuropathology, neurochemistry, neurophysiology, and neuropharmacology of DS patients' brains indicate that there is probably abnormal development and maintenance of central nervous system structure and function. The segmental trisomy mouse (Ts65Dn) is a model of DS that shows analogous neurobehavioral defects. We have studied the global gene expression profiles of normal and Ts65Dn male and normal female mice brains (P30) using the serial analysis of gene expression (SAGE) technique. From the combined sample we collected a total of 152,791 RNA tags and observed 45,856 unique tags in the mouse brain transcriptome. There are 14 ribosomal protein genes (nine under expressed) among the 330 statistically significant differences between normal male and Ts65Dn male brains, which possibly implies abnormal ribosomal biogenesis in the development and maintenance of DS phenotypes. This study contributes to the establishment of a mouse brain transcriptome and provides the first overall analysis of the differences in gene expression in aneuploid versus normal mammalian brain cells.

Animals↗

PubMed1999

A murine model for Down syndrome shows reduced responsiveness to pain.

Ts65Dn mice have an extra chromosome that contains a segment of chromosome 16 homologous to the Down syndrome 'critical region' of human chromosome 21. Since pain transmission and expression may be limited in people with mental disabilities, including Down syndrome, responsiveness to nociception in Ts65Dn mice was compared with that in their control litter-mates. In the formalin test, a model of tonic pain, Ts65Dn mice showed depressed sensitivity to nociception during the early and late phases. In the tail-flick test, they showed longer latencies than controls, but no differences among groups were observed in morphine responses. In the hot-plate test, no changes were observed in escape latencies during the first exposure, but Ts65Dn mice showed smaller tendency to lick. The results indicate that trisomic mice present an overall depressed responsiveness to nociceptive stimulation.

Animals↗

PubMed1999

Application of Alu-splice PCR on chromosome 21: DSCR1 and Intersectin.

Down syndrome (DS) is a major cause of mental retardation and congenital heart defects, with an overall incidence of one in 700 live births. DS is caused by increases in the amounts of a number of normal gene products, the exact number and identity of which are presently unknown. Elucidating the molecular basis of DS relies on the identification of the gene products whose augmentation by 50% or more causes symptoms of the disease. With the aim of contributing to the transcriptional map of human chromosome 21 and to identify new genes with potential involvement in DS, we developed a technique to isolate expressed sequences called Alu-splice PCR, which is very simple to perform and is independent of gene expression patterns. Putative exons are PCR amplified in genomic DNA by virtue of their proximity to Alu repeats using primers designed from splice-site consensus sequences in combination with specific Alu repeat primers. The Alu repeats, which are repetitive DNA elements found exclusively and at high frequency in the genomes of primates, impart the human specificity to the method. The splice-site consensus sequences were used to direct primers to exon boundaries. Using the Alu-splice technique, we have identified at least three new genes. We trapped an exon of DSCR1 (Down Syndrome Candidate Region 1) and two different exons of a gene called human Intersectin (ITSN). Presently, we are working with another novel trapped exon to identify the corresponding gene. The major advantage of Alu-splice PCR is that the technique can be readily established in any laboratory which has the basic facilities for molecular biology because no specialised materials or expertise is required.

Adaptor Proteins, Vesicular Transport↗

PubMed1999

Short-term effects of postnatal manipulation on central beta-adrenoceptor transmission.

Neonatal handling is known to induce long-lasting changes in behavioral and neuroendocrine responses to stress. Since the central noradrenergic system participates in the adaptive responses to stressful conditions we have analyzed the effects of postnatal handling on beta-adrenoceptor binding sites and isoprenaline- and forskolin-stimulated cyclic AMP accumulation in cerebral cortex, hippocampus and cerebellum of rats at 1 and 3 months of age. Handled animals showed reduced emotional reactivity and lower ACTH and corticosterone secretion after stress. Binding studies using [(3) H]CGP12-177 revealed increased beta-adrenoceptor binding sites in handled rats in cerebellum and cerebral cortex with no changes in hippocampus, and decreased affinity in all cerebral regions. Handling reduced basal levels of cyclic AMP in hippocampus and cerebellum but not in cerebral cortex. The concentration-response curves of cyclic AMP to isoprenaline were displaced to the right in cerebellum of handled rats without differences in Emax; however, Emax was significantly reduced in cerebral cortex and hippocampus. Direct stimulation of the catalytic subunit of adenylyl cyclase by forskolin reduced the efficiency in hippocampus and cerebellum, but not in cerebral cortex of handled animals. It is concluded that neonatal handling reduces the binding properties of beta-adrenoceptor and its primary biochemical responses in the young rat brain, which may account for the reduced responsiveness to stress attained in the handled rats, and may explain the persistence of the effect. The present study emphasizes the role of the central noradrenergic system in modulating the behavioral and neurendocrine responses to neonatal handling.

Adenylyl Cyclases↗

PubMed1998

Hippocampal volume and neuronal number in Ts65Dn mice: a murine model of Down syndrome.

Ts65Dn mouse displays a partial triplication of chromosome 16 and is adopted as a model for Down syndrome (DS). It is known that Ts65Dn mice present memory deficiencies. In order to gain insight into the cause of these deficiencies, we studied the possibility of changes in volumes and neuronal numbers in different regions of the hippocampus (dentate gyrus, CA3, CA2 and CA1) in trisomic mice as compared to control littermates using stereological methods. The mean hippocampal volumes of Ts65Dn mice did not show significant differences as compared to controls, except in CA2 where there was a barely significant decrease. However, mean neuron number was significantly lower in Ts65Dn mice than in controls in dentate gyrus (43.7 x 10(4), CV 21%, n = 5, vs. 30.4 x 10(4), CV 18.1%, n = 4) and higher in CA3 (23.1 x 10(4), CV 18.9% vs. 33.3 x 10(4), CV 14.9%). These quantitative changes may account for the memory deficiencies observed in Ts65Dn mice.

Animals↗

PubMed1998

Impaired short- and long-term memory in Ts65Dn mice, a model for Down syndrome.

Ts65Dn (TS), control littermates (CO) and Swiss (SW) male mice were tested in the elevated plus-maze and in the Morris water maze (MWM) for memory evaluation. In the plus-maze, each mouse was placed at the end of an open arm and initial freezing and the time to enter into an enclosed arm (transfer latency) were measured. SW mice decreased both measures over repeated trials, whereas no decrease of freezing was observed in CO mice, thus suggesting increased emotionality in this group. Compared to CO mice, TS mice showed less initial freezing, shorter transfer latencies, and spent less time in enclosed arms, suggesting a reduced ability to habituate or to inhibit behaviour. Animals were also submitted to a learning-set paradigm consisting of reaching a new platform position each day in the MWM. Two training phases (separated by a resting period of 6 weeks), each including eight acquisition and four cued sessions, were performed (each session consisting of four pairs of trials). CO and SW mice already reached an asymptotic performance by the second day of the first phase whereas TS mice did not achieve that level until the second training phase. The progression over trials indicated that CO and SW animals learned the new platform position between trials 1 and 2 of each session, whereas TS animals failed to do it and had more difficulties to find the platform when it was placed in the centre of the pool as compared to the other positions (SW, NE, E). The results suggest that TS mice show working memory impairments in addition to long-term memory deficits, although extensive training appeared to facilitate TS mice to achieve a level of performance similar to their control littermates. This represents another aspect of the cognitive deficits shown by TS mice: a mouse model of the human Down syndrome.

Animals↗

PubMed1997

Cholinergic, serotonergic and catecholaminergic neurons are not affected in Ts65Dn mice.

Ts65DN mice were developed as a model of Down syndrome (DS); they are trisomic for the distal segment of chromosome 16 (MMU16), which contains genes syntenic with some of the genes located on the critical region of human chromosome 21 (HSA21). Since behavioral and neurochemical disturbances have been observed in this animal model, it seemed interesting to perform an immunohistochemical characterization of the main cholinergic, catecholaminergic and serotonergic nuclei. However, when the brains of Ts65Dn mice were compared with those of control littermates, no differences were found either in the morphology of the neurons of the three systems or in the number of immunoreactive cells. The results indicate that these systems are not affected by the triplication of some of the genes present on chromosome 16.

Animals↗