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J Mallet

Publications and source records attributed to J Mallet.

At least 19 recordsLinked to original sources
PubMed1999

Adenovirus-mediated over-expression of TGFbeta1 in the striatum decreases dopaminergic cell survival in embryonic nigral grafts.

Neurotrophic factors may be valuable for improving the survival and the functional efficacy of fetal nigral grafts to treat Parkinson's disease (PD). However, further characterization of their effects is required. New methods of protein delivery also need to be explored to supply sustained and regulated levels of these molecules. Gene transfer via adenoviral vectors is a promising strategy for this purpose. We show herein the effect of adenovirus-mediated transforming growth factor beta1 (TGFbeta1) gene transfer on fetal nigral grafts in a rat model of PD. Direct injection of AdTGFbeta1 into the dopamine-depleted striatum decreased the survival of the transplanted tyrosine hydroxylase-positive (TH+) neurons and impaired the functional efficacy of grafts. Viral toxicity to the graft was avoided by separating the site of viral infection from the transplant by a distance that allowed TGFbeta1 effect on the graft. This infection protocol may be useful for delivering secreted molecules with neurotrophic effects to dopaminergic grafts.

Adenoviridae↗
PubMed1999

A human tyrosine hydroxylase isoform associated with progressive supranuclear palsy shows altered enzymatic activity.

A novel human tyrosine hydroxylase (HTH) messenger RNA subgroup generated by alternative splicing and characterized by the absence of the third exon was recently identified. The corresponding putative protein lacks 74 amino acids including Ser31 and Ser40, two major phosphorylation sites implicated in the regulation of HTH activity. These mRNA species are detected in adrenal medulla and are overexpressed in patients suffering from progressive supranuclear palsy, a neurodegenerative disease mostly affecting catecholaminergic neurons of the basal ganglia. In the present work, an HTH protein isoform lacking exon 3 was identified in human adrenal medulla. For this purpose, an antibody was raised against the HTH exon 3. The effect of the removal of exon 3 on the enzymatic activity of HTH was studied in vitro by comparing a purified recombinant fusion protein without exon 3 (glutathione S-transferase (GST)-HTHDelta3) to the equivalent protein containing exon 3 (GST-HTH3). In initial velocity conditions, GST-HTHDelta3 has 30% of the maximal velocity of GST-HTH3. Moreover, the skipping of exon 3 results in the absence of activation of GST-HTH by heparin and increases by 10-fold the retroinhibition constant for dopamine, demonstrating the involvement of exon 3 in the regulation of HTH enzymatic activity. The identification of a variably expressed HTH isoform that lacks an exon implicated in activity regulation supports the view that HTH alternative splicing contributes to the functional diversity within the catecholaminergic system and may be implicated in some neurological diseases.

Adrenal Glands↗
PubMed1999

Adenovirus-mediated suicide gene therapy in an in vitro model of reactive gliosis.

Adenovirus-mediated herpes simplex thymidine kinase/ganciclovir (HSV-tk/GCV) system has been demonstrated to be efficient for the treatment of experimental brain tumors. However, no study has been directed to the elimination of proliferating cellular populations in other pathological conditions. In this study we used this suicide gene approach in a primary culture of astrocytes, as a model of reactive gliosis, in order to evaluate its efficiency as a therapeutic strategy for post-traumatic astrogliosis in vivo. First, we evaluated the peak of astrocytic proliferation to characterize our model. Second, the efficiency of adenovirus-mediated lacZ gene transfer is shown to be dependent on vector multiplicity of infection (MOI). As expected, the cells transfected with the HSV-tk gene showed an increase in sensibility to GCV compared with cells transfected with lacZ gene. Finally, an unexpected interaction between the adenoviral vector and bromodeoxyuridine (BrdU) or [3H]-Thymidine ([3H]-Thy) was evidenced in transfected cultures, whose interpretation is discussed. The present study demonstrates that a recombinant adenoviral vector carrying the tk gene confers to in vitro cultured astrocytes a cytotoxic sensibility to GCV, and that this system constitutes a potentially efficient tool to eliminate the hyperplasia of astrocytes following injury to the central nervous system in vivo.

Adenoviridae↗
PubMed1999

Toward autologous ex vivo gene therapy for the central nervous system with human adult astrocytes.

The combination of gene transfer techniques and cell transplantation is a promising approach to deliver therapeutic molecules into the CNS. To optimize gene transfer systems, several neural and nonneural cell types are currently under investigation. Among these cells, astrocytes are particularly well suited because of their CNS origin, their efficient secretory mechanisms, and their role as neuronal support. Most importantly, the use of human adult astrocytes as cellular vehicles for ex vivo gene transfer may open the way to autologous transplantation, thus obviating immunological rejection and the side effects of immunosuppressors. In the present study, we report the ability of these cells to be expanded and genetically modified in vitro. Astrocytes derived from human adult cerebral cortex were grown and maintained in vitro as pure primary cultures for at least 10 months. In addition, cells were efficiently transduced by an adenoviral vector encoding human tyrosine hydroxylase (hTH) under the negative control of the tetracycline-based regulatory system (tet-off). The infected cells synthesized large amounts of active hTH and released L-dopa. In addition, doxycycline, a potent analog of tetracycline, efficiently regulated transgene expression. This work is a first step toward the development of therapeutic strategies based on the use of genetically engineered human adult astrocytes for autologous transplantation in human neurodegenerative diseases and CNS trauma.

Adenoviridae↗
PubMed1999

A single adenovirus vector mediates doxycycline-controlled expression of tyrosine hydroxylase in brain grafts of human neural progenitors.

Ex vivo gene transfer is emerging as a promising therapeutic approach to human neurodegenerative diseases. By combining efficient methodologies for cell amplification and gene delivery, large numbers of cells can be generated with the capacity to synthesize therapeutic molecules. These cells can then be transplanted into the degenerating central nervous system (CNS). Applying this approach to human diseases will require the development of suitable cellular vehicles, as well as safe gene delivery systems capable of tightly controlled transgene expression. For such brain repair technologies, human neural progenitors may be extremely valuable, because of their human CNS origin and developmental potential. We have used these cells to develop a system for the regulated expression of a gene of therapeutic potential. We report the construction of a single adenovirus encoding human tyrosine hydroxylase 1 (hTH-1) under the negative control of the tetracycline-based gene regulatory system. Human neural progenitors infected with this vector produced large amounts of hTH-1. Most importantly, doxycycline allowed a reversible switch of transgene transcription both in vitro and in vivo. This system may be applied to the development of therapies for human neurodegenerative diseases.

Adenoviridae↗
PubMed1999

Genetic differentiation and natural hybridization between two morphological forms of the common woodlouse, oniscus asellus linnaeus 1758

The common woodlouse Oniscus asellus can be divided into two forms on the basis of morphology, particularly male accessory genitalia. Where these taxa meet, morphological intermediates are found, and the forms were therefore described as subspecies; O. a. asellus and O. a. occidentalis. In this study allozyme loci are used to test the hypothesis that intermediate forms result from hybridization, and to study the nature of hybridization. Thirteen enzyme loci were scored across five English sites representative of each subspecies and intermediates. Ten loci showed strong frequency differences between asellus and occidentalis populations, although no loci showed completely fixed differences. These data confirm that asellus and occidentalis represent genetically distinct taxa, and that intermediate populations are of hybrid origin. There is apparently substantial population substructuring in the contact zone, as indicated by deficits of heterozygotes (FIS) and sporadic gametic (i. e. linkage) disequilibria. Population structure in the Oniscus hybrid zone appears to be analogous to that seen in plant hybrid swarms rather than the narrow hybrid zones observed in many animal taxa. Values of Nei's genetic distance between the subspecies range from 0.65 to 0.70; these are much higher than between typical conspecific taxa and are indicative of ancient genetic divergence. However, because asellus and occidentalis do not remain distinct in areas of overlap, it is simplest to regard these taxa as members of the same species.

Journal Article↗
PubMed1998

No association between dopamine D1, D2, and D3 receptor genes and manic-depressive illness.

BACKGROUND: The dopaminergic receptor genes are candidate genes for manic-depressive illness (MDI). To test this putative involvement we used a case-control study on samples from the native population of the northwest part of France. METHODS: Fifty patients for D1 and D2, 61 patients for D3, and 86-223 controls were tested. RESULTS: No significant association was found between allelic frequencies or genotype counts and MDI, even when the data were pooled with those from published studies. CONCLUSIONS: Single mutations of either of the studied receptor genes are not major determinants of MDI.

Adult↗
PubMed1998

Anticipation in schizophrenia: no evidence of expanded CAG/CTG repeat sequences in French families and sporadic cases.

A decrease in age of onset of schizophrenia through consecutive family generations (anticipation) has been found in several studies. Anticipation is known to result from expansion of CAG repeats in genes that determine several neurodegenerative disorders. In a previous study we analysed 26 unilineal two-generation French pedigrees and found clinical evidence of anticipation. A 10-year mean reduction in age of onset of schizophrenia was found in the second generation compared with the parental generation. The repeat expansion detection method was used to screen for CAG expansion in 21 of the 26 families with evidence of anticipation for the disease and in 59 sporadic schizophrenics and 59 controls. Comparison of the frequency distributions of CAG/CTG repeat size observed in schizophrenics and controls showed no significant difference, even when we considered familial (P = 0.23) and sporadic (P = 0.25) affected individuals separately. These results do not support the association between long CAG repeats and schizophrenia. However, the possibility that expansions with fewer than 40 repeats are involved in schizophrenia cannot be excluded.

Adult↗
PubMed1998

CAG repeat sequences in bipolar affective disorder: no evidence for association in a French population.

Anticipation has been described in bipolar affective disorder (BPAD). However, there are conflicting results from association studies screening for a link between BPAD and CAG/CTG repeat expansions, the molecular basis of anticipation in several hereditary neurodegenerative disorders. Here, the repeat expansion detection (RED) method was used to screen for CAG repeat expansion in 119 French BPAD patients. Western blotting was also used to search for polyglutamine stretches, encoded by CAG expansion, among proteins, extracted from lymphoblastoid cell lines, from six selected familial cases. Maximum CAG/CTG repeat length did not differ significantly (P = 0.38) between the 119 BPAD patients and the 88 controls included in the study. Several categories of subgroups were used, none of which showed significant association with a long repeat. Nor was a specific protein with an unusually long polyglutamine stretch (lower detection limit, approximately 33 polyglutamines) detected in cell lysates from the familial cases studied. In conclusion, an association between a long CAG/CTG repeat and BPAD in the French population sample studied was not found. Nonetheless, a short repeat (<40 repeats) might still be implicated, and this possibility warrants further study.

Adult↗
PubMed1998

Cotranscription and intergenic splicing of human galactose-1-phosphate uridylyltransferase and interleukin-11 receptor alpha-chain genes generate a fusion mRNA in normal cells. Implication for the production of multidomain proteins during evolution.

In the past 10 years, much attention has been focused on transcription preinitiation complex formation as a target for regulating gene expression, and other targets such as transcription termination complex assemblage have been less intensively investigated. We established the existence of poly(A) site choice and fusion splicing of two adjacent genes, galactose-1-phosphate uridylyltransferase (GALT) and interleukin-11 receptor alpha-chain (IL-11Ralpha), in normal human cells. This 16-kilobase (kb) transcription unit contains two promoters (the first one is constitutive, and the second one, 8 kb downstream, is highly regulated) and two cleavage/polyadenylation signals separated by 12 kb. The promoter from the GALT gene yields two mRNAs, a 1.4-kb mRNA encoding GALT and a 3-kb fusion mRNA when the first poly(A) site is spliced out and the second poly(A) is used. The 3-kb mRNA codes for a fusion protein of unknown function, containing part of the GALT protein and the entire IL-11Ralpha protein. The GALT promoter/IL-11Ralpha poly(A) transcript results from leaky termination and alternative splicing. This feature of RNA polymerase (pol) II transcription, which contrasts with efficient RNA pol I and pol III termination, may be involved, together with chromosome rearrangements, in the generation of fusion proteins with multiple domains and would have major evolutionary implications in terms of natural processes to generate novel proteins with common motifs. Our results, together with accumulation of genomic informations, will stimulate new considerations and experiments in gene expression studies.

Animals↗
PubMed1998

Cells of the neuronal lineage play a major role in the generation of amyloid precursor fragments in gelsolin-related amyloidosis.

Gelsolin-related amyloidosis or familial amyloidosis, Finnish type (FAF) (OMIM No105120) is a hereditary amyloid disease caused by a mutation in a precursor protein for amyloid (gelsolin) and characterized by corneal dystrophy and polyneuropathy. In vitro expression of the FAF-mutant (Asp187 --> Asn/Tyr) secretory gelsolin in COS cells leads to generation of an aberrant polypeptide presumably representing the precursor for tissue amyloid. Here, we provide evidence that this abnormal processing results from defective initial folding of the secreted FAF gelsolin due to the lack of the Cys188-Cys201 disulfide bond, normally formed next to the FAF mutation site. We compared cells of different tissue origin and discovered a dramatic difference between the amount of cleavage of FAF gelsolin to the amyloid precursor in neuronal and non-neuronal cells. More than half of the mutant gelsolin was cleaved in PC12 and in vitro differentiated human neuronal progenitor cells. In contrast, human fibroblasts and Schwannoma cell cultures showed only a limited capacity to cleave FAF gelsolin, although the cleavage mechanism per se seems to be similar in the various cell types. The present findings of processing and distribution of secreted FAF gelsolin in the neuronal cells emphasize the role of neurons in the tissue pathogenesis of this amyloid polyneuropathy.

Amyloid Neuropathies↗
PubMed1998

Human tyrosine hydroxylase isoforms. Inhibition by excess tetrahydropterin and unusual behavior of isoform 3 after camp-dependent protein kinase phosphorylation.

Human tyrosine hydroxylase exists as four isoforms (hTH1-4), generated by alternative splicing of pre-mRNA, with tissue-specific distribution. Unphosphorylated hTH3 and hTH1 were produced in large amounts in Escherichia coli and purified to homogeneity. The phosphorylation sites were determined after labeling with [32P]phosphate in the presence of cAMP-dependent protein kinase (PKA) and calmodulin-dependent protein kinase II (CaM-PKII). Ser40 was phosphorylated by PKA, and both Ser19 and Ser40 were phosphorylated by CaM-PKII. The enzyme kinetics of hTH3 were determined in the presence of various concentrations of the natural co-substrate (6R)-tetrahydrobiopterin and compared with those of recombinant hTH1 (similar to rat TH). We show that, under initial velocity conditions, excess (6R)-tetrahydrobiopterin inhibits hTH3 and hTH1. The TH catalytic constants (kcat) were determined for each of the two isoenzymes: hTH3 is about five times more active than hTH1. Phosphorylation by CaM-PKII did not affect the kinetic parameters of hTH3. The classical activation of TH by PKA phosphorylation, demonstrated for hTH1, was not observed with hTH3. Furthermore, hTH3 escapes activity regulation by phosphorylation and is always more active than phosphorylated hTH1. The properties of the hTH3 enzyme may be relevant to diseases affecting dopaminergic cells.

Cyclic AMP-Dependent Protein Kinases↗
PubMed1998

European Multicentre Association Study of Schizophrenia: a study of the DRD2 Ser311Cys and DRD3 Ser9Gly polymorphisms.

As part of the European Multicentre Association Study of Schizophrenia (EMASS), we studied polymorphisms in the dopamine DRD2 and DRD3 receptor genes. The EMASS collaboration was established to create a large, statistically powerful sample of schizophrenic patients and controls from different European centres. Previous studies have suggested associations between schizophrenia and the Ser311Cys polymorphism in exon 7 of the dopamine DRD2 receptor gene [Arinami et al., (1994): Lancet 343:703-704] and a polymorphism Ser9gly in exon 1 of the dopamine DRD3 receptor gene [Crocq et al. (1992): J Med Genet 29:858-860]. We tested for these associations in samples of 373 and 413, and 311 and 306 patients and controls, respectively. We found no evidence for allelic association between schizophrenia and the Cys311 variant of the DRD2 receptor gene and no homozygotes for this variant were observed by any group. However, an excess of homozygotes for both alleles of the DRD3 polymorphism was observed in schizophrenic patients (chi2 = 8.54, P = 0.003, odds ratio = 1.64, 95% CI = 1.18-2.29). We also observed a significant excess of the 1-1 (Ser9Ser) genotype (chi2 = 8.13, P = 0.004, odds ratio = 1.7, 95% CI = 1.18-2.4). No evidence of heterogeneity between samples was detected and there was no evidence of an allelic association. These findings suggest that the rare Cys311 variant in exon 7 of the DRD2 receptor gene does not play a role in the pathogenesis of schizophrenia in European populations. Currently, our results do support the previous findings of an association between increased homozygosity of the Ser/Gly variant of the Dopamine D3 receptor gene and schizophrenia.

Alleles↗
PubMed1998

Association between the tryptophan hydroxylase gene and manic-depressive illness.

BACKGROUND: Genes encoding proteins involved in serotonergic metabolism are major candidates in association studies of mood disorders and suicidal behavior. This association study explores whether the tryptophan hydroxylase (TPH) gene, which codes for the rate-limiting enzyme of serotonin biosynthesis, is a susceptibility factor for manic-depressive illness, with or without a history of suicide attempts. METHODS: The TPH intron 7 A218C polymorphism was determined using a polymerase chain reaction-based method in DNA samples from 152 patients with bipolar disorder and 94 healthy control subjects. RESULTS: There was a significant association between TPH genotypes and manic-depressive illness. Among patients with bipolar disorder, no association was found between TPH alleles and suicidal behavior. CONCLUSIONS: This result suggests the involvement of the TPH gene in susceptibility to manic-depressive illness. This preliminary result requires confirmation in further groups of patients and controls.

Adult↗
PubMed1998

Psychiatric genetics: search for phenotypes.

Failure to obtain convincing results in psychiatric genetics can partly be attributed to the fact that progress in molecular biology and genetic epidemiology has not been followed by an equivalent development in phenotypic description. Instead of relying entirely on classical nosological approaches, we argue that identifying more homogeneous forms of diseases through a'candidate symptom approach' among affected subjects and an endophenotype approach that identifies sub-clinical traits among non-affected relatives might yield better results. Examples where these strategies have already been fruitful when applied to complex diseases are presented in this review. Focusing on vulnerability traits might stimulate the redefinition of traditional psychiatric syndromes and help to bridge the gap between clinical and experimental approaches.

Animals↗