Papers by Demetrios Vassilatis
Human Molecular Genetics, 2021
Duplication/triplication mutations of the SNCA locus, encoding alpha-synuclein (ASYN), and loss o... more Duplication/triplication mutations of the SNCA locus, encoding alpha-synuclein (ASYN), and loss of function mutations in Nurr1, a nuclear receptor guiding midbrain dopaminergic neuron development, are associated with familial Parkinson’s disease (PD). As we age, the expression levels of these two genes in midbrain dopaminergic neurons follow opposite directions and ASYN expression increases while the expression of Nurr1 decreases. We investigated the effect of ASYN and Nurr1 age-related expression alterations in the pathogenesis of PD by coupling Nurr1 hemizygous with ASYN(s) (heterozygote) or ASYN(d) (homozygote) transgenic mice. ASYN(d)/Nurr1+/− (2-hit) mice, contrary to the individual genetic traits, developed phenotypes consistent with dopaminergic dysfunction. Aging ‘2-hit’ mice manifested kyphosis, severe rigid paralysis, L-DOPA responsive movement impairment and cachexia and died prematurely. Pathological abnormalities of phenotypic mice included SN neuron degeneration, exten...
Molecular Neurobiology, 2021
In Parkinson’s disease, the dysfunction of the dopaminergic nigrostriatal tract involves the loss... more In Parkinson’s disease, the dysfunction of the dopaminergic nigrostriatal tract involves the loss of function of dopaminergic neurons of the substantia nigra pars compacta followed by death of these neurons. The functional recovery of these neurons requires a deep knowledge of the molecules that maintain the dopaminergic phenotype during adulthood and the mechanisms that subvert their activity. Previous studies have shown that transcription factor NURR1, involved in differentiation and maintenance of the dopaminergic phenotype, is downregulated by α-synuclein (α-SYN). In this study, we provide a mechanistic explanation to this finding by connecting α-SYN-induced activation of glycogen synthase kinase-3 (GSK-3) with NURR1 phosphorylation followed by proteasomal degradation. The use of sequential deletion mutants and single point mutants of NURR1 allowed the identification of a domain comprising amino acids 123-PSSPPTPSTPS-134 that is targeted by GSK-3 and leads to subsequent ubiquiti...
The Journal of Neuroscience, 1997
We report the isolation and characterization of a cDNA encoding a novel member of the GABA recept... more We report the isolation and characterization of a cDNA encoding a novel member of the GABA receptor gene family, ε. This polypeptide is 506 amino acids in length and exhibits its greatest amino acid sequence identity with the GABAAreceptor γ3 subunit (47%), although this degree of homology is not sufficient for it to be classified as a fourth γ subunit. The ε subunit coassembles with GABAAreceptor α and β subunits inXenopus laevisoocytes and transfected mammalian cells to form functional GABA-gated channels. α1β1ε GABAAreceptors, like α1β1γ2s receptors, are modulated by pentobarbital and the steroid 5α-pregnan-3α-ol-20-one but, unlike α1β1γ2s receptors, are insensitive to flunitrazepam. Additionally, α1β1ε receptors exhibit rapid desensitization kinetics, as compared with α1β1 or α1β1γ2s. Northern analysis demonstrates widespread expression of a large ε subunit transcript in a variety of non-neuronal tissues and expression of a smaller transcript in brain and spinal cord. Sequence a...
Proceedings of the National Academy of Sciences of the United States of America, Jan 11, 2017
Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the los... more Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of dopaminergic (DAergic) neurons in the substantia nigra and the gradual depletion of dopamine (DA). Current treatments replenish the DA deficit and improve symptoms but induce dyskinesias over time, and neuroprotective therapies are nonexistent. Here we report that Nuclear receptor-related 1 (Nurr1):Retinoid X receptor α (RXRα) activation has a double therapeutic potential for PD, offering both neuroprotective and symptomatic improvement. We designed BRF110, a unique in vivo active Nurr1:RXRα-selective lead molecule, which prevents DAergic neuron demise and striatal DAergic denervation in vivo against PD-causing toxins in a Nurr1-dependent manner. BRF110 also protects against PD-related genetic mutations in patient induced pluripotent stem cell (iPSC)-derived DAergic neurons and a genetic mouse PD model. Remarkably, besides neuroprotection, BRF110 up-regulates tyrosine hydroxylase (T...
Mutant NURR1 gene in Parkinson's disease
DNA encoding glutamate gated chloride channels
Proceedings of the National Academy of Sciences of the United States of America, Jan 15, 2003
Diverse members of the G protein-coupled receptor (GPCR) superfamily participate in a variety of ... more Diverse members of the G protein-coupled receptor (GPCR) superfamily participate in a variety of physiological functions and are major targets of pharmaceutical drugs. Here we report that the repertoire of GPCRs for endogenous ligands consists of 367 receptors in humans and 392 in mice. Included here are 26 human and 83 mouse GPCRs not previously identified. A direct comparison of GPCRs in the two species reveals an unexpected level of orthology. The evolutionary preservation of these molecules argues against functional redundancy among highly related receptors. Phylogenetic analyses cluster 60% of GPCRs according to ligand preference, allowing prediction of ligand types for dozens of orphan receptors. Expression profiling of 100 GPCRs demonstrates that most are expressed in multiple tissues and that individual tissues express multiple GPCRs. Over 90% of GPCRs are expressed in the brain. Strikingly, however, the profiles of most GPCRs are unique, yielding thousands of tissue- and ce...
Neurobiology of Aging, 2014
JOA, MJF, and ZKW report holding a patent on LRRK2 genetic variability and MJF has received royal... more JOA, MJF, and ZKW report holding a patent on LRRK2 genetic variability and MJF has received royalties for licensing of genetically modified LRRK2 mouse models. DMM declares a patent pending entitled Methods to treat PD. CK and RK declare receiving payment in their role as consultants for Centogene and Takeda Pharmaceutical, respectively. All other authors declare that they have no conflicts of interest.
The Journal of Neuroscience, 2007
TheKiss1gene codes for kisspeptin, which binds to GPR54, a G-protein-coupled receptor. Kisspeptin... more TheKiss1gene codes for kisspeptin, which binds to GPR54, a G-protein-coupled receptor. Kisspeptin and GPR54 are expressed in discrete regions of the forebrain, and they have been implicated in the neuroendocrine regulation of reproduction.Kiss1-expressing neurons are thought to regulate the secretion of gonadotropin-releasing hormone (GnRH) and thus coordinate the estrous cycle in rodents; however, the precise role of kisspeptin–GPR54 signaling in the regulation of gonadotropin secretion is unknown. In this study, we used female mice with deletions in theGPR54gene [GPR54knock-outs (KOs)] to test the hypothesis that kisspeptin–GPR54 signaling provides the drive necessary for tonic GnRH/luteinizing hormone (LH) release. We predicted that tonic GnRH/LH secretion would be disrupted inGPR54KOs and that such animals would be incapable of showing a compensatory rise in LH secretion after ovariectomy. As predicted, we found thatGPR54KO mice do not exhibit a postovariectomy rise in LH, sugge...
Proceedings of the National Academy of Sciences, 2000
The ability of organisms to evolve resistance threatens the effectiveness of every antibiotic dru... more The ability of organisms to evolve resistance threatens the effectiveness of every antibiotic drug. We show that in the nematode Caenorhabditis elegans, simultaneous mutation of three genes, avr-14, avr-15 , and glc-1 , encoding glutamate-gated chloride channel (GluCl) α-type subunits confers high-level resistance to the antiparasitic drug ivermectin. In contrast, mutating any two channel genes confers modest or no resistance. We propose a model in which ivermectin sensitivity in C. elegans is mediated by genes affecting parallel genetic pathways defined by the family of GluCl genes. The sensitivity of these pathways is further modulated by unc-7 , unc-9 , and the Dyf (dye filling defective) genes, which alter the structure of the nervous system. Our results suggest that the evolution of drug resistance can be slowed by targeting antibiotic drugs to several members of a multigene family.
Proceedings of the National Academy of Sciences, 2007
We describe the construction of a large-scale, orderly assembly of mutant ES cells, generated wit... more We describe the construction of a large-scale, orderly assembly of mutant ES cells, generated with retroviral insertions and having mutational coverage in >90% of mouse genes. We also describe a method for isolating ES cell clones with mutations in specific genes of interest from this library. This approach, which combines saturating random mutagenesis with targeted selection of mutations in the genes of interest, was successfully applied to the gene families of G protein-coupled receptors (GPCRs) and nuclear receptors. Mutant mouse strains in 60 different GPCRs were generated. Applicability of the technique for the GPCR genes, which on average represent fairly small targets for insertional mutagenesis, indicates the general utility of our approach for the rest of the genome. The method also allows for increased scale and automation for the large-scale production of mutant mice, which could substantially expedite the functional characterization of the mouse genome.
Parasitology, 1996
SUMMARYIn this chapter we summarize the available data on a novel class of ligand-gated anion cha... more SUMMARYIn this chapter we summarize the available data on a novel class of ligand-gated anion channels that are gated by the neurotransmitter glutamate. Glutamate is classically thought to be a stimulatory neurotransmitter, however, studies in invertebrates have proven that glutamate also functions as an inhibitory ligand. The bulk of studies conductedin vivohave been on insects and crustaceans, where glutamate was first postulated to act on H-receptors resulting in a hyperpolarizing response to glutamate. Recently, glutamate-gated chloride channels have been cloned from several nematodes andDrosophila. The pharmacology and electrophysiological properties of these channels have been studied by expression inXenopusoocytes. Studies on the cloned channels demonstrate that the invertebrate glutamate-gated chloride channels are the H-receptors and represent important targets for the antiparasitic avermectins.
Neurobiology of Aging, 2010
Classical pathological signs of Parkinson's disease (PD) include loss of dopaminergic neurons in ... more Classical pathological signs of Parkinson's disease (PD) include loss of dopaminergic neurons in substantia nigra (SN) and noradrenergic neurons in locus coeruleus (LC), and deposition of Lewy bodies rich in the presynaptic protein alpha-synuclein (ASYN). Mammalian genetic models based on ASYN overexpression, however, have generally not reproduced the profound dopaminergic deficit of PD and do not display classical PD phenotypes. In the current study we examined these catecholaminergic systems in transgenic (Tg) mice expressing the A53T mutant of human ASYN under the Prion promoter. Surprisingly we detected a substantial reduction in norepinephine (NE), but not dopamine (DA), levels in spinal cord, olfactory bulb and striatum of aged (15-month-old), but not young (4-month-old) transgenic compared to control mice. In spinal cord and olfactory bulb of 15-month-old Tg mice there was an age-dependent decrease in tyrosine hydroxylase (TH) protein levels, which in spinal cord was accompanied by a decrease in TH-positive terminals detected by immunohistochemistry. There was no difference in the number of TH-positive neuron cell bodies in SN or LC between Tg and control mice. We conclude that aberrant ASYN, expressed in both SN and LC, induces preferential degeneration of noradrenergic terminals. These observations suggest that in mice the NE may be more vulnerable than the DA system to the toxic effects of aberrant alpha-synuclein, and are in line with the major damage to the NE system that occurs in patients with PD.
Nature Genetics, 2002
NR4A2, encoding a member of nuclear receptor superfamily 1 , is essential for the differentiation... more NR4A2, encoding a member of nuclear receptor superfamily 1 , is essential for the differentiation of the nigral dopaminergic neurons 2-4 . To determine whether NR4A2 is a susceptibility gene for Parkinson disease, we carried out genetic analyses in 201 individuals affected with Parkinson disease and 221 agematched unaffected controls. We identified two mutations in NR4A2 associated with Parkinson disease (-291Tdel and -245T→G), which map to the first exon of NR4A2 and affect one allele in 10 of 107 individuals with familial Parkinson disease but not in any individuals with sporadic Parkinson disease (n = 94) or in unaffected controls (n = 221). The age at onset of disease and clinical features of these ten individuals were not different from those of individuals with typical Parkinson disease. The mutations resulted in a marked decrease in NR4A2 mRNA levels in transfected cell lines and in lymphocytes of affected individuals. Additionally, mutations in NR4A2 affect transcription of the gene encoding tyrosine hydroxylase. These data suggest that mutations in NR4A2 can cause dopaminergic dysfunction, associated with Parkinson disease.
Movement Disorders, 2013
Background: Variants within the leucine-rich repeat kinase 2 gene are recognized as the most freq... more Background: Variants within the leucine-rich repeat kinase 2 gene are recognized as the most frequent genetic cause of Parkinson's disease. Leucine-rich repeat kinase 2 variation related to disease susceptibility displays many features that reflect the nature of complex, late-onset sporadic disorders like Parkinson's disease. Methods: The Genetic Epidemiology of Parkinson's Disease Consortium recently performed the largest genetic association study for variants in the leucine-rich repeat kinase 2 gene across 23 different sites in 15 countries. Results: Herein, we detail the allele frequencies for the novel risk factors (p.A419V and p.M1646T) and the protective haplotype (p.N551K-R1398H-K1423K) nominated in the original publication. Simple population allele frequencies not only can provide insight into the clinical relevance of specific variants but also can help genetically define patient groups. Conclusions: Establishing individual patient-based genomic susceptibility profiles that incorporate both risk factors and protective factors will determine future diagnostic and treatment strategies. V
Movement Disorders, 2011
The disorders of voice and speech in Parkinson's disease (PD) result from involvements in several... more The disorders of voice and speech in Parkinson's disease (PD) result from involvements in several subsystems including respiration, phonation, articulation, and prosody. [1][2][3] We investigated the feasibility of acoustic measures for the identification of voice and speech disorders in PD, using a quick vocal test consisting of sustained phonation, diadochokinetic task, and running speech. Various traditional and novel acoustic measurements have been designed in order to be gender independent, represent all speech subsystems, reduce the time required for voice investigation, and provide a reliable automated assessment in practice. 4
Trichinella pseudospiralis secretes a protein related to the Trichinella spiralis 43-kDa glycoprotein
Molecular and Biochemical Parasitology, 1996
A 43-kDa secreted glycoprotein from the intracellular parasitic nematode Trichinella spiralis has... more A 43-kDa secreted glycoprotein from the intracellular parasitic nematode Trichinella spiralis has been considered as a factor involved in the formation of the Nurse cell in infected muscle. The closely related intracellular parasitic nematode Trichinella pseudospiralis that also infects muscle cells, does not form Nurse cells and was thought not to secrete the 43-kDa glycoprotein. This implied a unique role for the 43-kDa glycoprotein in T. spiralis infection and supported the hypothesis of involvement of the 43-kDa glycoprotein in Nurse cell formation. Following cloning of a full length cDNA encoding the 43-kDa protein, antibodies were raised against several domains of the 43-kDa glycoprotein. Here we show that a protein related to the 43-kDa glycoprotein exists in T. pseudospiralis. Immunohistochemical studies reveal important similarities in the distribution of the 43-kDa glycoprotein and the related protein from T. pseudospiralis in muscle infections with either of the two parasites. The 43-kDa glycoprotein may therefore play a common role in the life cycles of these two parasites and probably is not involved in Nurse cell formation.
Developmental expression of a 43-kDa secreted glycoprotein from Trichinella spiralis
Molecular and Biochemical Parasitology, 1996
Trichinella spiralis is an intracellular parasitic nematode that infects skeletal muscle cells. I... more Trichinella spiralis is an intracellular parasitic nematode that infects skeletal muscle cells. Infection results in loss of tissue specific characteristics and conversion of the muscle cell to a Nurse cell. The characteristic changes leading to the formation of the Nurse cell appear complete by day 12 after intramuscular infection. Proteins synthesized in the stichocytes (secretory cells) of T. spiralis and secreted in the host cell are believed to be involved in the process of Nurse cell formation. One secreted glycoprotein of 43 kDa has been considered as a candidate factor involved in Nurse cell formation. We determined the timing of synthesis and secretion of the 43-kDa glycoprotein and its temporal correlation to the changes of the infected host cell, to gain an understanding of the role of the 43-kDa glycoprotein in T. spiralis infection. We show that the 43-kDa glycoprotein is first expressed on day 11 following intramuscular infection, several days after the changes in the infected muscle cell have been initiated. Protein(s) immunologically related to the 43-kDa glycoprotein but not the 43-kDa glycoprotein itself are detected in the nuclei of mature Nurse cells. During the intramuscular stage the 43-kDa glycoprotein appears to be stored in the alpha-stichocytes of T. spiralis and appears to be secreted immediately following invasion of the intestinal columnar epithelial cells by the L1 larva. The role of the 43-kDa glycoprotein remains unknown, however, these findings argue against involvement of the 43-kDa glycoprotein in Nurse cell formation.
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Papers by Demetrios Vassilatis