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Biomedical subjects

F Côté

Publications and source records attributed to F Côté.

At least 19 recordsLinked to original sources
PubMed2004

Effects of repetition, interval between treatments and season on the results from laparoscopic ovum pick-up in goats.

The present study was conducted to evaluate the follicular response and oocyte yield following repeated gonadotrophin stimulation and laparoscopic aspiration in goats and to assess the effects of the time interval between procedures and season. A total of 98 adult goats were subjected to laparoscopic ovum pick-up (LOPU) five consecutive times in a transgenic production programme. Oestrus was synchronised by means of intravaginal sponges inserted for 10 days coupled with 125 microg cloprostenol 36 h before sponge removal and LOPU, and follicular development was stimulated with 80 mg follicle stimulating hormone and 300 IU equine chorionic gonadotrophin administered 36 h before LOPU. No difference was detected in the response for LOPUs 1, 2, 3 and 4. Although a small decrease in response was detected at LOPU 5 (P < 0.05), the numbers of follicles aspirated and oocytes recovered were not different from those at LOPU 1 and LOPUs 1 and 4, respectively. With respect to time interval between LOPU and season, all intervals and seasons produced acceptable responses, with no difference in follicles aspirated and oocytes recovered between intervals and seasons. These results indicate that LOPU may be repeated up to five times in goats at different intervals and in different seasons with little or no important change in overall response.

Animals↗
PubMed2002

Involvement of NF-Y and Sp1 in basal and cAMP-stimulated transcriptional activation of the tryptophan hydroxylase (TPH ) gene in the pineal gland.

The expression of the tryptophan hydroxylase (TPH) gene, encoding the rate-limiting enzyme of serotonin biosynthesis, is tightly regulated both at the transcriptional and at the post-transcriptional levels. In the pineal gland, transcription of the gene is activated in response to an intracellular circadian increase of the cAMP concentration. We have previously shown that transcription of a 2.1-kb fragment of the human TPH promoter is induced by cAMP, although it lacks the canonical cAMP responsive element, CRE. The minimal promoter (-73/+29) has only weak transcriptional activity but is responsive to cAMP. It contains an inverted CCAAT box, which was demonstrated to be involved in this response. Here, we have extended our investigation to the functional features of the inverted CCAAT box in the -252/+29 TPH promoter, which has a higher basal activity. We show that an additional cis -acting sequence, the adjacent GC-rich region, cooperates with the inverted CCAAT box for the full activation of basal transcription, and that both elements are essential for the full cAMP response. We also show that in pinealocytes, NF-Y and Sp1 transactivators bind the inverted CCAAT box and GC-rich-region, respectively. These factors participate in a novel pathway for the cAMP-mediated response of the TPH promoter, which is independent of the canonical CRE-mediated response.

Animals↗
PubMed2001

Alternative promoter usage and splicing of ZNF74 multifinger gene produce protein isoforms with a different repressor activity and nuclear partitioning.

We have previously shown that ZNF74, a candidate gene for DiGeorge syndrome, encodes a developmentally expressed zinc finger gene of the Kruppel-associated box (KRAB) multifinger subfamily. Using RACE, RT-PCR, and primer extension on human fetal brain and heart mRNAs, we here demonstrate the existence of six mRNA variants resulting from alternative promoter usage and splicing. These transcripts encode four protein isoforms differing at their N terminus by the composition of their KRAB motif. One isoform, ZNF74-I, which corresponds to the originally cloned cDNA, was found to be encoded by two additional mRNA variants. This isoform, which contains a KRAB motif lacking the N terminus of the KRAB A box, was devoid of transcriptional activity. In contrast, ZNF74-II, a newly identified form of the protein that is encoded by a single transcript and contains an intact KRAB domain with full A and B boxes, showed strong repressor activity. Deconvolution immunofluorescence microscopy using transfected human neuroblastoma cells and nonimmortalized HS68 fibroblasts revealed a distinct subcellular distribution for ZNF74-I and ZNF74-II. In contrast to ZNF74-I, which largely colocalizes with SC-35 in nuclear speckles enriched in splicing factors, the transcriptionally active ZNF74-II had a more diffuse nuclear distribution that is more characteristic of transcriptional regulators. Taken with the previously described RNA-binding activity of ZNF74-I and direct interaction with a hyperphosphorylated form of the RNA polymerase II participating in pre-mRNA processing, our results suggest that the two ZNF74 isoforms exert different or complementary roles in RNA maturation and in transcriptional regulation.

Alternative Splicing↗
PubMed2001

Natural 2',5'-phosphodiester bonds found at the ligation sites of peach latent mosaic viroid.

Peach latent mosaic viroid (PLMVd) is a circular RNA pathogen that replicates in a DNA-independent fashion via a rolling circle mechanism. PLMVd has been shown to self-ligate in vitro primarily via the formation of 2',5'-phosphodiester bonds; however, in vivo the occurrence and necessity of this nonenzymatic mechanism are not evident. Here, we unequivocally report the presence of 2', 5'-phosphodiester bonds at the ligation site of circular PLMVd strands isolated from infected peach leaves. These bonds serve to close the linear conformers (i.e., intermediates), yielding circular ones. Furthermore, these bonds are shown to stabilize the replicational circular templates, resulting in a significant advantage in terms of viroid viability. Although the mechanism responsible for the formation of these 2',5'-phosphodiester bonds remains to be elucidated, a hypothesis describing in vivo nonenzymatic self-ligation is proposed. Most significantly, our results clearly show that 2',5'-phosphodiester bonds are still present in nature and that they are of biological importance.

Mosaic Viruses↗
PubMed2000

Identification of high-affinity binding sites for the hepta-beta-glucoside elicitor in membranes of the model legumes Medicago truncatula and Lotus japonicus.

Previous studies have led to the identification and characterization of specific, high-affinity binding sites for a hepta-beta-glucoside elicitor in soybean. A survey of plant species for elicitor-binding activity reveals that among the plants tested, the hepta-beta-glucoside elicitor is only recognized by plants belonging to the legume family. We have characterized in detail the glucan elicitor-binding site in the model legume Medicago truncatula Gaertn., and partially characterized the site in Lotus japonicus. These sites have characteristics that are very similar to the one in soybean, with dissociation constants of 4.7 and 8.9 nM respectively. The elicitor-binding sites from both plants are stable during solubilization with non-ionic alkylglycoside detergents. However, differences are observed in the abundance of the binding sites and their selectivity towards structurally related analogues of the hepta-beta-glucoside elicitor. Our results suggest that similar, but perhaps not identical, binding sites for the hepta-beta-glucoside elicitor exist in diverse legumes, but not in plants outside of the legume family.

Binding Sites↗
PubMed2000

Mapping in solution shows the peach latent mosaic viroid to possess a new pseudoknot in a complex, branched secondary structure.

We have investigated the secondary structure of peach latent mosaic viroid (PLMVd) in solution, and we present here the first description of the structure of a branched viroid in solution. Different PLMVd transcripts of plus polarity were produced by using the circularly permuted RNA method and the exploitation of RNA internal secondary structure to position the 5' and 3' termini and studied by nuclease mapping and binding shift assays using DNA and RNA oligonucleotides. We show that PLMVd folds into a complex, branched secondary structure. In general, this structure is similar to that reported previously, which was based on sequence comparison and computer modelling. The structural microheterogeneity is apparently limited to only some small domains. More importantly, this structure includes a novel pseudoknot that is conserved in all PLMVd isolates and seems to allow folding into a very compact form. This pseudoknot is also found in chrysanthemum chlorotic mottle viroid, suggesting that it is a unique feature of the viroid members of the PLMVd subgroup.

Base Sequence↗
PubMed1999

ZNF74, a gene deleted in DiGeorge syndrome, is expressed in human neural crest-derived tissues and foregut endoderm epithelia.

DiGeorge syndrome (DGS) is a developmental disorder associated with large hemizygous deletions on chromosome 22q11.2. ZNF74 zinc finger gene is a candidate from the commonly deleted region. To address the potential involvement of ZNF74 in DGS, its human developmental expression pattern has been assessed. In situ hybridization on Carnegie Stage 18 embryos revealed that ZNF74 expression is limited to specific neural crest-derived tissues and neuroepithelium of the spinal cord as well as to foregut endoderm epithelia (esophagus and respiratory tract). Interestingly, ZNF74 expression was detected in the wall of the pulmonary artery and aorta and in the aortic valve, which are populated by neural crest-derived cells. This finding is significant, considering that DGS is believed to result from defective neural crest contributions and that outflow tract and aorticopulmonary septation defects are typical features of the DGS phenotype. Thus, the restricted expression of ZNF74 in structures affected in DGS suggests a role for this putative regulator of gene expression in aspects of the DGS phenotype.

Aorta↗
PubMed1999

Activation of the AT(2) receptor of angiotensin II induces neurite outgrowth and cell migration in microexplant cultures of the cerebellum.

Microexplant cultures from three-day-old rats were used to investigate whether angiotensin II (Ang II), through its AT(1) and AT(2) receptors, could be involved in the morphological differentiation of cerebellar cells. Specific activation of the AT(2) receptor during 4-day treatment induced two major morphological changes. The first was characterized by increased elongation of neurites. The second change was cell migration from the edge of the microexplant toward the periphery. Western blot analyses and indirect immunofluorescence studies revealed an increase in the expression of neuron-specific betaIII-tubulin, as well as an increase in expression of the microtubule-associated proteins tau and MAP2. These effects were demonstrated by co-incubation of Ang II with 1 microM DUP 753 (AT(1) receptor antagonist) or with 10 nM CGP 42112 (AT(2) receptor agonist) but abolished when Ang II was co-incubated with 1 microM PD 123319 (AT(2) receptor antagonist), indicating that differentiation occurs through AT(2) receptor activation and that the AT(1) receptor inhibits the AT(2) effect. Taken together, these results demonstrate that Ang II is involved in cerebellum development for both neurite outgrowth and cell migration, two important processes in the organization of the various layers of the cerebellum.

Angiotensin II↗
PubMed1997

Peach latent mosaic viroid is locked by a 2',5'-phosphodiester bond produced by in vitro self-ligation.

Although some viroid-like satellite RNAs possess self-cleavage and self-ligation activities, we show that the peach latent mosaic viroid (PLMVd) is unique among all known viroids since it also has such activities. These catalytic activities should have important roles in the rolling circle replication of PLMVd. According to this proposed mechanism, self-cleavage of the multimeric strands occurs via hammerhead structures producing monomers possessing 2',3'-cyclic phosphate and 5'-hydroxyl termini. In the most stable predicted secondary structure for PLMVd these two extremities are juxtaposed, in order for self-ligation to occur. To establish the nature of the phosphodiester bond produced by self-ligation, we followed the classical procedure of complete enzymatic RNA hydrolysis coupled with thin layer chromatography fractionation. Using this procedure, we report that the self-ligation of PLMVd transcripts produces almost exclusively the 2',5' isomer (>96%). Primer extension assays also revealed that reverse transcriptase can read througth this 2', 5' linkage, suggesting that it does not prevent further replication of the viroid. Moreover, we have observed that this 2',5' linkage is resistant to the debranching activity contained in nuclear extracts, as well as being capable of preventing further viroid self-cleavage. Thus, if viroids do indeed self-ligate in vivo, the resulting 2', 5'-phosphodiester bond could contribute to the stability of these RNA species. Finally, an analysis of both the sequence and the structural requirements for hammerhead self-cleavage and self-ligation suggests that these two RNA processes may be interrelated. We hypothesize that the intramolecular self-ligation which produces circular conformers may contribute to the circularization step of the rolling circle replication, while the intermolecular non-enzymatic ligation is a potential mechanism for the sequence reassortment of viroids and viroid-like species.

Endoribonucleases↗
PubMed1997

Direct interaction of the KRAB/Cys2-His2 zinc finger protein ZNF74 with a hyperphosphorylated form of the RNA polymerase II largest subunit.

We previously identified ZNF74 as a developmentally expressed gene commonly deleted in DiGeorge syndrome. ZNF74 encodes an RNA-binding protein tightly associated with the nuclear matrix and belongs to a large subfamily of Cys2-His2 zinc finger proteins containing a KRAB (Kruppel-associated box) repressor motif. We now report on the multifunctionality of the zinc finger domain of ZNF74. This nucleic acid binding domain is shown here to function as a nuclear matrix targeting sequence and to be involved in protein-protein interaction. By far-Western analysis and coimmunoprecipitation studies, we demonstrate that ZNF74 interacts, via its zinc finger domain, with the hyperphosphorylated largest subunit of RNA polymerase II (pol IIo) but not with the hypophosphorylated form. The importance of the phosphorylation in this interaction is supported by the observation that phosphatase treatment inhibits ZNF74 binding. Double immunofluorescence experiments indicate that ZNF74 colocalizes with the pol IIo and the SC35 splicing factor in irregularly shaped subnuclear domains. Thus, ZNF74 sublocalization in nuclear domains enriched in pre-mRNA maturating factors, its RNA binding activity, and its direct phosphodependent interaction with the pol IIo, a form of the RNA polymerase functionally associated with pre- mRNA processing, suggest a role for this member of the KRAB multifinger protein family in RNA processing.

Animals↗
PubMed1995

Defective axonal transport in a transgenic mouse model of amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a degenerative disease of motor neurons, characterized by depositions of neurofilaments in the perikarya and proximal axons. The pathogenesis of ALS remains poorly understood, but two lines of evidence suggest that neurofilament accumulation may play a causal role. First, transgenic mice that overexpress neurofilament proteins show motor neuron degeneration and, second, variant alleles of the neurofilament heavy-subunit gene (NF-H) have been found in some human ALS patients. To investigate how disorganized neurofilaments might cause neurodegeneration, we examined axonal transport of newly synthesized proteins in mice that overexpress the human NF-H gene. We observed dramatic defects of axonal transport, not only of neurofilament proteins but also of other proteins, including tubulin and actin. Ultrastructural analysis revealed a paucity of cytoskeletal elements, smooth endoplasmic reticulum and especially mitochondria in the degenerating axons. We therefore propose that the neurofilament accumulations observed in these mice cause axonal degeneration by impeding the transport of components required for axonal maintenance, and that a similar mechanism may account for the pathogenesis of ALS in human patients.

Amyotrophic Lateral Sclerosis↗
PubMed1995

A heterogeneous set of FMR1 proteins is widely distributed in mouse tissues and is modulated in cell culture.

The fragile X syndrome is an X-linked inherited disease and is the result of transcriptional inactivation of the FMR1 gene and the absence of its encoded FMR protein (FMRP). Using a specific monoclonal antibody directed against human FMRP, we have studied the steady-state levels of its murine homolog in several tissues and organs of adult and young mice. In immunoblot analyses, the antibody recognizes a heterogeneous subset of proteins with apparent molecular weights ranging from 80 to 70 kDa. These proteins are detected in all the 27 tissues tested; however, the relative proportion of each polypeptide recognized varies between tissues, and a significantly higher expression is observed in young animals. Northern blot analysis of RNA extracted from selected tissues from adult mouse shows that these tissues express the major 4.8 kb mRNA, although at different levels, and contain several additional shorter transcripts, particularly in muscular tissues. We also report that expression of the FMR1 gene is modulated in proliferating and quiescent primary mouse kidney cell cultures with an inverse relationship between levels of FMR1 mRNA and of its encoded proteins. This suggests that FMRPs are highly stable in quiescent cells and that FMR1 expression is likely post-transcriptionally controlled. Our results document the widespread expression of the FMR1 gene, and suggest that it is controlled by different mechanisms implicated in cell growth and differentiation.

Animals↗
PubMed1995

Suppression of the Fix- phenotype of Rhizobium meliloti exoB mutants by lpsZ is correlated to a modified expression of the K polysaccharide.

The rhizobial production of extracellular polysaccharide (EPS) is generally required for the symbiotic infection of host plants that form nodules with an apical meristem (indeterminate nodules). One exception is Rhizobium meliloti AK631, an exoB mutant of Rm41, which is deficient in EPS production yet infects and fixes nitrogen (i.e., is Fix+) on alfalfa, an indeterminate nodule-forming plant. A mutation of lpsZ in AK631 results in a Fix- strain with altered phage sensitivity, suggesting that a cell surface factor may substitute for EPS in the alfalfa-AK631 symbiosis. Biochemical analyses of the cell-associated polysaccharides of AK631 and Rm5830 (AK631 lpsZ) demonstrated that the lpsZ mutation affected the expression of a surface polysaccharide that is analogous to the group II K polysaccharides of Escherichia coli; the polysaccharide contains 3-deoxy-D-manno-2-octulosonic acid or a derivative thereof in each repeating unit. Rm5830 produced a polysaccharide with altered chromatographic and electrophoretic properties, indicating a difference in the molecular weight range. Similar results were obtained in a study of Rm1021, a wild-type isolate that lacks the lpsZ gene: the introduction of lpsZ into Rm1021 exoB (Rm6903) both suppresses the Fix- phenotype and results in a modified expression of the K polysaccharide. Chromatography and electrophoresis analysis showed that the polysaccharide extracted from Rm6903 lpsZ+ differed from that of Rm6903 in molecular weight range. Importantly, the effect of LpsZ is not structurally specific, as the introduction lpsZ+ into Rhizobium fredii USDA257 also resulted in a molecular weight range change in the structurally distinct K polysaccharide produced by that strain. This evidence suggests that LpsZ has a general effect on the size-specific expression of rhizobial K polysaccharides.

Chromatography, Gel↗
PubMed1995

Evidence for a model ancestral viroid.

The generation of a phylogenetic tree of viroids and viroid-like plant satellite RNAs via computer analysis, coupled with several conspicuous biochemical characteristics of the rolling circle replication of these RNAs -including both self-cleavage and self-ligation- leads us to propose the peach latent mosaic viroid (PLMVd) as a current "living fossil" dating from a precellular world. Incorporated within this proposal is a revised mechanism of PLMVd rolling circle replication which requires a minimal protein involvement.

Evolution, Molecular↗
PubMed1994

Copy-dependent and correct developmental expression of the human neurofilament heavy gene in transgenic mice.

We recently produced four lines of transgenic mice bearing a 34 kb DNA fragment that includes the human gene coding for the neurofilament heavy (NF-H) chain. Analysis of the NF-H transgenics revealed an increase in human NF-H mRNA and protein that parallels the increase in gene copy number, providing the first example of a transgene with copy-dependent expression in neurons. In addition, expression of the human NF-H transgene is induced post-natally following a developmental pattern similar to the endogenous mouse NF-H gene.

Aging↗