Biomedical subjects

M Schalling

Publications and source records attributed to M Schalling.

At least 37 records · Page 2Linked to original sources

PubMed2001

A cloning strategy for identification of genes containing trinucleotide repeat expansions.

Until today, nineteen trinucleotide repeat expansions larger than forty repeat copies have been found in the human genome. Of these, the CAG/CTG repeat is predominant motif with twelve loci identified, ten of which have been associated with the development of neurodegenerative diseases. We have developed a cloning approach which isolates disease genes containing trinucleotide repeat expansions. The method is based on size separation of genomic fragments, followed by subcloning and library hybridization with an oligonucleotide probe. Fractions and clones containing expanded repeats are identified by the repeat expansion detection (RED) method throughout the cloning procedure. Large family materials are not required and as little as 10 microg genomic DNA from a single individual is sufficient for this method. Using this strategy we have cloned two DNA fragments containing expanded repeats from two unrelated patients with a clinical diagnosis of cerebellar ataxia. Sequencing of the two fragments showed sequence identities with two disease genes, the Huntington gene and the ataxin 3 gene, respectively. The method should be adaptable to the cloning of any long repeat motif in any species. Furthermore the experimental steps can be performed in less than a month, making it very effective and time efficient to disease gene identification.

Ataxin-3↗

PubMed2001

Reboxetine modulates the firing pattern of dopamine cells in the ventral tegmental area and selectively increases dopamine availability in the prefrontal cortex.

Central dopaminergic neurons have been suggested to be involved in the pathophysiology of several psychiatric disorders, including depression, and appear to be modulated by noradrenergic activity both at the nerve terminal level and at the somatodendritic level. In recent years reboxetine, a selective noradrenaline reuptake inhibitor that differs from tricyclic antidepressants by its low affinity for muscarinic, cholinergic and alpha(1)-adrenergic receptors, has been introduced clinically. In the present study the effect of reboxetine on the function of the mesolimbocortical dopamine system was investigated by means of single cell recording and microdialysis in rats following administration of reboxetine in doses that appear to yield clinically relevant plasma concentrations. Reboxetine (0.625--20 mg/kg intravenously) induced an increase in burst firing, but not in average firing frequency of dopamine (DA) cells in the ventral tegmental area (VTA). Moreover, reboxetine (0.15--13.5 mg/kg intraperitoneally) caused a significantly enhanced DA output in the medial prefrontal cortex, whereas no effect was observed in the nucleus accumbens. Local administration of reboxetine (333 microM, 60 min), by means of reversed microdialysis into these brain regions, caused a significant increase in DA output in both brain regions. However, local administration of reboxetine into the VTA (333 microM, 60 min) did not affect DA availability in these terminal areas. Our results imply that clinical treatment with reboxetine may result in facilitation of both prefrontal DA output and the excitability of VTA DA neurons, effects that may contribute to its antidepressant action, especially on drive and motivation.

Adrenergic Uptake Inhibitors↗

PubMed2000

Hypothalamic CART and serum leptin levels are reduced in the anorectic (anx/anx) mouse.

Cocaine- and amphetamine-regulated transcript (CART) is expressed in the hypothalamus, and putative peptides encoded by CART potently inhibit feeding when administered centrally. CART is strongly down-regulated in the lateral hypothalamic area and the arcuate nucleus in animal models of obesity with disrupted leptin signaling. Here we have used in situ hybridization and immunohistochemistry to study CART expression in mice homozygous for the anorexia (anx) mutation which are characterized by a much reduced food intake and premature death. anx/anx mice had significantly decreased levels of CART mRNA label and peptide-immunoreactive cell bodies and fibers in the arcuate nucleus and a lower number of detectable CART-expressing cells in the dorsomedial hypothalamic nucleus/lateral hypothalamic area. Moreover, serum leptin levels were significantly lower in anx/anx mice compared to normal littermates, most likely due to the prominent depletion of body fat in these animals. The decrease in the anorexigenic agents leptin and CART, may reflect a compensatory down-regulation in response to the energy-deprived state of anx/anx mice. Alternatively, the reduced arcuate CART expression may be a consequence of a molecular defect in the arcuate nucleus of these animals.

Aging↗

PubMed2000

Long repeat tracts at SCA8 in major psychosis.

Expansion at a recently identified unstable trinucleotide repeat on chromosome 13q21 has been reported as the molecular cause for spinocerebellar ataxia type 8 (SCA8). The trinucleotide repeat, which consists of a [CTA]n repeat and adjacent [CTG]n repeat, was reported to have a pathogenic range of 107-127 CTG repeats (or 110-130 combined CTA and CTG repeats) in a large ataxia kindred. This repeat region was also cloned by our group from a bipolar affective disorder (BPAD) patient, who has approximately 600 combined repeats, and large alleles (>100 repeats) were reported to be present in 0.7% of controls and 1.5% of major psychosis patients (n = 710 and n = 1,120, respectively). We have followed up these findings by screening three new samples of BPAD and schizophrenia (SCZ) patients and controls, including 272 individuals from 14 BPAD families from Sweden, 130 individuals from 32 SCZ and BPAD families/trios from the Azores Islands, and 206 SCZ individuals from the United Kingdom and Ireland, and 219 matched controls. We found large repeat alleles above the SCA8 pathogenic range in individuals from 3 of 32 Azorean pedigrees and in 1 of 206 SCZ individuals from the United Kingdom, and repeat alleles within the SCA8 pathogenic range in 1 of 14 Swedish families. Although the rarity of major psychosis patients carrying the SCA8 expansion mutation would require a much larger sample size to reach statistical significance, these results support the previously reported observation of increased occurrence of large repeats at SCA8 in major psychosis. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:873-876, 2000.

Alleles↗

PubMed2000

P0 protein peptide 180-199 together with pertussis toxin induces experimental autoimmune neuritis in resistant C57BL/6 mice.

The C57BL/6 mice strain is known to be reputedly resistant to induction of experimental autoimmune neuritis (EAN), an animal model of Guillain-Barré syndrome in human by bovine peripheral myelin (BPM), and P2 protein or the P2 protein peptide 57-81. The P0 peptide 180-199 is a stronger neuritogenic antigen than the P2 peptide 57-81. We found that this synthetic peptide induced both clinical and pathological characteristics of an acute monophasic EAN in C57BL/6 mice. Only male mice were more sensitive to EAN induction with the P0 peptide 180-199. Intravenously administrated pertussis toxin (PT) had an adjuvant effect that increased the incidence of P0 peptide 180-199-induced EAN as well as the inflammation and demyelination in the peripheral nerves. Spontaneous and P0 peptide 180-199 stimulated proliferation of peripheral T-cells were enhanced by PT-treatment as well. The enhancing effect was lower before onset of the disease (Day 6 post immunization) (p.i.) as compared to the early phase of the disease (Day 22 p.i.). Thus, P0 peptides together with PT are able to break tolerance to myelin in C57BL/6 mice.

Adjuvants, Immunologic↗

PubMed2000

Mapping of spinocerebellar ataxia 13 to chromosome 19q13.3-q13.4 in a family with autosomal dominant cerebellar ataxia and mental retardation.

We examined a large French family with autosomal dominant cerebellar ataxia (ADCA) that was excluded from all previously identified spinocerebellar ataxia genes and loci. The patients-seven women and a 4-year-old boy-exhibited slowly progressive childhood-onset cerebellar gait ataxia associated with cerebellar dysarthria, moderate mental retardation (IQ 62-76), and mild developmental delays in motor acquisition. Nystagmus and pyramidal signs were also observed in some cases. This unique association of clinical features clearly distinguishes this new entity from other previously described ADCA. Cerebral magnetic-resonance imaging showed moderate cerebellar and pontine atrophy in two patients. We performed a genomewide search and found significant evidence for linkage to chromosome 19q13.3-q13.4, in an approximately 8-cM interval between markers D19S219 and D19S553.

Adult↗

PubMed2000

No evidence for long CAG/CTG repeats in families with spastic paraplegia linked to chromosome 2p21-24.

Autosomal dominant familial spastic paraplegia (AD-FSP) is a genetically heterogeneous, neurodegenerative disorder characterized by spasticity and progressive weakness in the lower limbs. Anticipation has been suggested to occur and an association between expanded CAG/CTG repeats and AD-FSP linked to the SPG4 locus (2p21-p24) has been described. In this study, 42 affected individuals from six SPG4 families were screened for expanded CAG/CTG repeats using the repeat expansion detection (RED) method. Large RED products (range 180-240 nucleotides) corresponding in size to repeats at the ERDA1 locus were detected in eight patients and at the CTG 18.1 locus in one patient. The large ERDA1 repeats did not segregate with the disorder within families. Mean age at onset and index of severity were not significantly different between patients with or without expanded RED products. Furthermore, no abnormal proteins were found by Western blot in 15 selected patient samples as compared with controls, using the 1C2 antibody, which detects long polyglutamine stretches. Thus, in contrast to previous reports, our study provides evidence against the hypothesis that a large translated CAG repeat expansion is the basis of SPG4. We propose that mechanisms other than large pathogenic CAG/CTG repeats may account for the disease in the SPG4 families tested here.

Adolescent↗

PubMed2000

Expression of cholecystokinin, enkephalin, galanin and neuropeptide Y is markedly changed in the brain of the megencephaly mouse.

Megencephaly, enlarged brain, is a major sign in several human neurological diseases. The mouse model for megencephaly (mceph/mceph) has an enlarged brain, presumably due to brain cell hypertrophy, and exhibits neurological and motor disturbances with seizure-like activity, as well as disturbances in the insulin-like growth factor system. Here, we report that expression of the neuropeptides cholecystokinin, enkephalin, galanin and neuropeptide Y is dramatically changed in mceph/mceph brains compared to wild type, as revealed by in situ hybridization and immunohistochemistry. The changes were confined to discrete brain regions and occurred in a parallel fashion for peptides and their transcripts. For cholecystokinin, mceph/mceph brains had region-specific up- and down-regulations in several layers of the hippocampal formation and increased levels in, especially ventral, cortical regions. Enkephalin messenger RNA expression was up-regulated in the dentate gyrus granular layer and in ventral cortices, but down-regulated in the CA1 pyramidal layer. Enkephalin-like immunoreactivity was elevated in mossy fibers of the hippocampus and the ventral cortices. Galanin expression was increased in several layers and interneurons of the hippocampal formation, as well as in ventral cortices. Galanin-like immunoreactivity was reduced in nerve terminals in the forebrain. Neuropeptide Y expression was increased in the hippocampal formation and ventral cortices. Whether the mainly increased peptide levels contribute to the excessive growth of the brain or represent a consequence of this growth and/or of the neurological and motor disturbances remains to be elucidated.

Animals↗

PubMed2000

ARSACS, a spastic ataxia common in northeastern Québec, is caused by mutations in a new gene encoding an 11.5-kb ORF.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS or SACS) is an early onset neurodegenerative disease with high prevalence (carrier frequency 1/22) in the Charlevoix-Saguenay-Lac-Saint-Jean (CSLSJ) region of Quebec. We previously mapped the gene responsible for ARSACS to chromosome 13q11 and identified two ancestral haplotypes. Here we report the cloning of this gene, SACS, which encodes the protein sacsin. The ORF of SACS is 11,487 bp and is encoded by a single gigantic exon spanning 12,794 bp. This exon is the largest to be identified in any vertebrate organism. The ORF is conserved in human and mouse. The putative protein contains three large segments with sequence similarity to each other and to the predicted protein of an Arabidopsis thaliana ORF. The presence of heat-shock domains suggests a function for sacsin in chaperone-mediated protein folding. SACS is expressed in a variety of tissues, including the central nervous system. We identified two SACSmutations in ARSACS families that lead to protein truncation, consistent with haplotype analysis.

Amino Acid Sequence↗

PubMed2000

Fat tissue accumulation during peritoneal dialysis is associated with a polymorphism in uncoupling protein 2.

BACKGROUND: Chronic treatment with peritoneal dialysis (PD) is a unique long-term metabolic procedure entailing a continuous 24-hour supply of glucose absorbed from the dialysis fluid. One common and important side effect of this treatment is weight gain and accumulation of body fat stores. However, not all patients accumulate body fat mass during PD, and the reason for this is not clear. Recently, two new mitochondrial uncoupling proteins (UCP2 and UCP3) have been found to have thermogenic properties that suggest involvement in the control of metabolic efficiency in humans. Moreover, recent results suggest that a polymorphism in the UCP2 gene may contribute to adipose tissue accumulation through its effects on energy metabolism. It could therefore be speculated that genetic differences in the metabolic rate might contribute to the differences in the accumulation of fat tissue during PD. METHODS: Genotyping of a polymorphism in the 3' untranslated region of exon 8 of UCP2 was performed in 41 patients (53 +/- 2 years) with chronic renal failure for whom we had prospective data on body composition (as estimated by dual-energy x-ray absorptiometry) following PD. In addition, indices of dialysis adequacy, peritoneal glucose absorption, and urea kinetics were followed (3 to 6 times per year in each patient) during treatment with PD. The degree of physical activity was assessed before the start of PD. RESULTS: Twenty patients with the deletion/deletion UCP2 genotype had a significant increase in body weight (3.0 +/- 0.8 vs. -1.0 +/- 1.1 kg, P < 0.01) and body fat mass (3.8 +/- 0.9 vs. 0.8 +/- 1.0 kg, P < 0.05) during PD, compared with 19 patients with an insertion/deletion UCP2 genotype. On the other hand, no significant differences in indices of dialysis adequacy, peritoneal glucose absorption, urea kinetic parameters, or degree of physical activity were observed when comparing patients who accumulated or lost fat tissue during PD. CONCLUSIONS: As most patients with the deletion/deletion UCP2 genotype acquired fat tissue during PD, the present results suggest that the UCP2 polymorphism contributes to variations in body composition. Thus, variations in UCP2 production or activity may be factors contributing to adipose tissue accumulation in a subgroup of patients treated with PD. It is possible that the polymorphism has a similar effect in the general population.

Adipose Tissue↗

PubMed1999

Primary megalencephaly at birth and low intelligence level.

OBJECTIVES: To evaluate the association between primary megalencephaly (PMG) at birth and psychosensory conditions and to determine mother-child similarity for PMG at birth. BACKGROUND: PMG is defined as a head circumference (HC) above the 98th percentile that most likely is due to brain enlargement and is not secondary to disease. Previously, PMG in children was reported to be associated with learning disabilities. Contradictory results regarding an association between PMG and intelligence in children exist. Many believe PMG expressed in childhood and adulthood may be inherited. METHODS: Birth records on HC from 144,273 boys, of whom 732 had PMG, were linked to data concerning intelligence level, mental retardation, and impairment of vision and hearing. A potential association between PMG at birth and mental retardation was also examined in 3,204 mentally retarded boys and girls. Parent-offspring similarity for PMG at birth was determined in 13,585 mother-child pairs. RESULTS: PMG was significantly associated with low intelligence level (odds ratio, 1.32; 95% confidence interval [CI], 1.11 to 1.38). The estimated odds ratio for mental retardation in PMG cases versus controls was 1.31 (95% CI, 0.80 to 2.02). There were no differences in frequencies of vision and hearing impairments between PMG cases and controls. Associations between mother's and child's birth weight-normalized HC (r = 0.14; p<0.0001) and PMG (odds ratio, 2.55; CI, 2.00 to 3.25) were found, supporting a multifactorial inheritance of PMG. CONCLUSIONS: PMG at birth is a risk factor for low intelligence level but not for vision and hearing impairments. The heritability of HC and PMG is moderate.

Adult↗

PubMed1999

Exclusion of dominant mutations within the FTDP-17 locus on chromosome 17 for Parkinson's disease.

Parkinson's disease (PD) is a prevalent movement disorder, and 10-30% of PD is familial. Several neurodegenerative disorders which are collectively called frontotemporal dementia and parkinsonism have been mapped to chromosome 17q and mutations in tau have been identified. The clinical and pathological overlap suggests that these related conditions may be due to mutations in tau. We examined linkage to the candidate region on chromosome 17 including and surrounding tau in eight familial PD kindreds. We found no evidence for linkage and excluded the 6cM candidate region which suggest that in our families, PD is not caused by dominant mutations within tau.

Adolescent↗

PubMed1999

The megencephaly mouse has disturbances in the insulin-like growth factor (IGF) system.

Megencephaly, enlarged brain, is a major sign in several human neurological diseases. The mouse model for megencephaly, mceph/mceph, has an enlarged brain and a lowered body weight. In addition, it displays several neurological and motoric disturbances. Previous studies suggest that the brain enlargement results from hypertrophy of the brain cells, rather than hyperplasia. No structural abnormalities, edema or increased myelination have been found. In this study, a major imbalance in the mRNA expression of molecules in the insulin-like growth factor (IGF) system was found in brains of 9-10 weeks old mceph/mceph mice compared to +/+ wild-type mice. In mceph/mceph brains, we found upregulation of IGF binding proteins (BP)-2, -4, -5, and -6 mRNA, the regulating hormone transforming growth factor (TGF)beta1 mRNA and also a local downregulation of IGFBP-5 mRNA compared to wild-type brains by in situ hybridization. The altered expression of these mRNA species is colocalized in cerebral cortex, hippocampus, amygdala and piriform/entorhinal cortex. The mceph/mceph mice express less of the myelin component proteolipid protein (PLP) mRNA in corpus callosum. No expression difference of the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in brain or IGF system components in liver was found between mceph/mceph and wild-type mice. These data suggest that the IGF system has an important role in the excessive growth of the mceph/mceph brains.

Amygdala↗

PubMed1999

Changes in neuropeptide Y receptors and pro-opiomelanocortin in the anorexia (anx/anx) mouse hypothalamus.

The pro-opiomelanocortinergic (POMCergic) system originating in the hypothalamic arcuate nucleus extends projections widely over the brain and has been shown to be intricately linked and parallel to the arcuate neuropeptide Y (NPY) system. Both NPY and POMC-derived peptides (melanocortins) have been strongly implicated in the control of feeding behavior, with the former exerting orexigenic effects and the latter having anorexigenic properties. Mice homozygous for the lethal anorexia (anx) mutation are hypophagic, emaciated, and exhibit anomalous processing of NPY exclusively in the arcuate nucleus, providing an interesting model to study NPY-POMC interactions. In the present study, several morphological markers were used to investigate the histochemistry and morphology of the POMC system in anx/anx mice. In situ hybridization demonstrated decreased numbers of POMC mRNA-expressing neurons in the anx/anx arcuate nucleus. In parallel, mRNA levels for both the NPY Y1 and Y5 receptors, which are expressed in POMC neurons, were decreased. Also, expression of the NPY Y2 autoreceptor was attenuated. Immunohistochemistry using antibodies against adrenocorticotropic hormone to demonstrate POMC cell bodies, against alpha-melanocyte-stimulating hormone to demonstrate axonal projections and against the NPY Y1 receptor to demonstrate dendritic arborizations, showed strikingly decreased immunoreactivities for all these markers. The present data suggest that degeneration of the arcuate POMC system is a feature characteristic of the anx/anx mouse. The possible relationship to the NPYergic phenotype of this animal is discussed.

Adrenocorticotropic Hormone↗

PubMed1999

Molecular interpretation of expanded RED products in bipolar disorder by CAG/CTG repeats located at chromosomes 17q and 18q.

Previously we provided evidence that the anticipation observed in bipolar (BP) disorder may be explained by expanded CAG/CTG triplet repeats. Data were generated with the repeat expansion detection (RED) method in a BP case-control sample showing a significant association of BP disorder with expanded CAG/CTG repeats (RED products of 120 bp). In this study we demonstrated that 86% of the RED expansions could be accounted for by the ERDA1 and CTG18.1 CAG/CTG repeats located respectively on chromosomes 17 and 18. Further, significantly different allele distributions were observed for ERDA1, with a larger proportion of BP patients (34.7%) carrying one or two expanded ERDA1 alleles (CAG/CTG repeats >40) than controls (19.2%) (P = 0.032). Also, a negative correlation was observed for ERDA1 between CAG/CTG length and age at onset in affected offspring of eight BP families. Although interesting, these data should be interpreted with caution since the ERDA1 association did not remain significant after correcting for multiple testing. Also, no linkage was observed between BP disorder and expanded ERDA1 alleles in the families.

Base Sequence↗

PubMed1999

An integrated map of chromosome 18 CAG trinucleotide repeat loci.

Expansions of trinucleotide CAG repeats have been demonstrated in at least eight neurodegenerative disorders, and suggested to occur in several others, including bipolar disorder and schizophrenia. Chromosome 18 loci have been implicated in bipolar disorder pedigrees by linkage analysis. To address this putative link between chromosome 18 CAG trinucleotide repeats and neuropsychiatric illness, we have screened a chromosome 18 cosmid library (LL18NCO2" AD") and identified 14 novel candidate loci. Characterisation of these loci involved repeat flank sequencing, estimation of polymorphism frequency and mapping using FISH as well as radiation hybrid panels. These mapped trinucleotide loci will be useful in the investigation of chromosome 18 in neurodegenerative or psychiatric conditions, and will serve to integrate physical and radiation hybrid maps of chromosome 18.

Base Sequence↗

PubMed1999

Genes involved in animal models of obesity and anorexia.

Pathological deviations in bodyweight is a major increasing health problem in industrialized societies. It is currently unclear what genetic mechanisms are involved in the long-term control of human body-weight and to what extent these genes are involved in pathological deviations of bodyweight control such as anorexia and obesity. Major support for the concept of genetic control of bodyweight has recently emerged from different animal models. A number of new genes have been found during recent years that, when mutated, have a negative effect on bodyweight in animals and sometimes also in man. Although available evidence points toward a multifactorial nature of weight disorders in most human subjects, the single genes isolated in animal models may become powerful tools to elucidate the genetics also in man. In addition, these genes may serve to promote the development of targeted small-drug pharmaceuticals aimed at novel biochemical pathways. Finally, the uncovering of several quantitative trait loci (QTL) influencing body mass, body fat or fat topography in the mouse and rat has now also made it possible to perform studies of polygenically caused obesity in rodents. The role of the Genome Project in developing a complete gene map will greatly facilitate transforming these OTLs to actual molecules involved in the biology of bodyweight.

Adipose Tissue↗

PubMed1999

Leptin and its potential role in human obesity.

Genetic studies in inbred obese mice have revealed the ob gene, its product leptin and the leptin receptor as important factors in the regulation of both appetite and energy expenditure. Treatment with recombinant leptin has resulted in a marked weight reduction in obese animals with ob gene mutations as well as in normal mice. Also mutations in the Ob receptor gene result in marked obesity in rodents. These data have given hope of new treatment options in obesity. Further support of leptin being involved in regulation of obesity in man comes from the observation that inactivating mutations in the human ob gene lead to profound early onset obesity. However, the role of leptin and its feedback system in man is still only partly revealed. This review focuses on our present knowledge and hypotheses about the leptin pathway in humans and its potential importance in the clinic of obesity.

Adipose Tissue↗