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D Arnaud

Publications and source records attributed to D Arnaud.

At least 19 recordsLinked to original sources
PubMed2005

[Transconjunctival inferior blepharoplasty].

The transconjunctival approach is the appropriate standard for lower eyelid blepharoplasty in patients presenting with lower eyelid herniated fat without excess skin. A transconjunctival incision is made approximately 2 mm below the tarsal border and extended inferiorly following a plane posterior to the orbital septum. No conjunctival suture is necessary. Although transconjunctival blepharoplasty diminishes the occurrence of postoperative complications when compared to the transcutaneous method and constitutes a more comfortable option for the patient, we always recommend a preoperative test of the eyes. Patients must be informed of the risk of amaurosis.

Adipose Tissue↗
PubMed2001

Methylation of histone H3 at Lys-9 is an early mark on the X chromosome during X inactivation.

Coating of the X chromosome by Xist RNA is an essential trigger for X inactivation. However, little is known about the early chromatin remodeling events that transform this signal into transcriptional silencing. Here we report that methylation of histone H3 lysine 9 on the inactive X chromosome occurs immediately after Xist RNA coating and before transcriptional inactivation of X-linked genes. X-chromosomal H3 Lys-9 methylation occurs during the same window of time as H3 Lys-9 hypoacetylation and H3 Lys-4 hypomethylation. Histone H3 modifications thus represent the earliest known chromatin changes during X inactivation. We also identify a unique "hotspot" of H3 Lys-9 methylation 5' to Xist, and we propose that this acts as a nucleation center for Xist RNA-dependent spread of inactivation along the X chromosome via H3 Lys-9 methylation.

A Kinase Anchor Proteins↗
PubMed2001

Tsix-mediated repression of Xist accumulation is not sufficient for normal random X inactivation.

During the X inactivation process, one X chromosome in each female embryonic cell is chosen at random to become coated by Xist RNA and silenced. Tsix, a transcript anti-sense to Xist, participates in the choice of the inactive X and in Xist regulation through as yet unknown mechanisms. Undifferentiated female ES cells, which have two active Xs, recapitulate random X inactivation when induced to differentiate. A 65 kb deletion targeted to one of the two Xs in a female ES cell line, and including both the end of the Xist gene and the site of initiation of Tsix, resulted in the exclusive inactivation of the deleted X in differentiated ES cells. We have re-examined the phenotype of the 65 kb deletion and targeted Tsix and the terminal exons of Xist back to the deleted locus using a cre/loxP site-specific re-insertion strategy. We show that prior to inactivation the deleted X is associated in undifferentiated ES cells with both increased Xist expression and diffusion of the Xist transcript away from its site of synthesis. Restoration of Tsix repressed the steady-state level of Xist expression and restricted Xist RNA to its transcription site. At the onset of inactivation in differentiated ES cells, restoration of Tsix failed to restore random X-inactivation, even though the levels of Xist RNA accumulation in cis were markedly reduced. These results identify for the first time a dual function for Tsix as both a repressor of the steady-state level of Xist expression and as a regulator of the distribution of Xist RNA within the nucleus. They also establish that random inactivation requires mechanisms additional to the in cis repression of XIST:

Alleles↗
PubMed2001

Methylation profiles of DXPas34 during the onset of X-inactivation.

X chromosome inactivation is controlled by the cis-acting X-inactivation centre (Xic). In addition to initiating inactivation, Xic, which includes the XIST: gene, is involved in both a counting process that senses the number of X chromosomes and the choice of X chromosome to inactivate. Controlling elements lying 3' to XIST: include the DXPas34 locus. Deletion of DXPas34 in undifferentiated embryonic stem (ES) cells eliminates expression of both XIST: and the antisense transcript TSIX:, thought to initiate from a CpG island lying close to, but telomeric to, the DXPas34 locus itself. Deletion of DXPas34 leads to non-random inactivation on ES cell differentiation and disrupts imprinted X-inactivation in vivo. In order to investigate the role of methylation at DXPas34 in the initial steps of X-inactivation, we studied its methylation status during pre- and post-implantation embryonic development and ES cell differentiation, using the bisulphite sequencing technique. Analysis of the methylation status of both the DXPas34 locus and the associated downstream CpG island shows that extensive hypermethylation of the DXPas34 locus is a relatively late event in differentiation and embryogenesis. We conclude that methylation of DXPas34 cannot be the X chromosome imprint, nor can it be involved in the parent-of-origin effects associated with deletion of the DXPas34 locus and the neighbouring CpG island.

Animals↗
PubMed1999

Human XIST yeast artificial chromosome transgenes show partial X inactivation center function in mouse embryonic stem cells.

Initiation of X chromosome inactivation requires the presence, in cis, of the X inactivation center (XIC). The Xist gene, which lies within the XIC region in both human and mouse and has the unique property of being expressed only from the inactive X chromosome in female somatic cells, is known to be essential for X inactivation based on targeted deletions in the mouse. Although our understanding of the developmental regulation and function of the mouse Xist gene has progressed rapidly, less is known about its human homolog. To address this and to assess the cross-species conservation of X inactivation, a 480-kb yeast artificial chromosome containing the human XIST gene was introduced into mouse embryonic stem (ES) cells. The human XIST transcript was expressed and could coat the mouse autosome from which it was transcribed, indicating that the factors required for cis association are conserved in mouse ES cells. Cis inactivation as a result of human XIST expression was found in only a proportion of differentiated cells, suggesting that the events downstream of XIST RNA coating that culminate in stable inactivation may require species-specific factors. Human XIST RNA appears to coat mouse autosomes in ES cells before in vitro differentiation, in contrast to the behavior of the mouse Xist gene in undifferentiated ES cells, where an unstable transcript and no chromosome coating are found. This may not only reflect important species differences in Xist regulation but also provides evidence that factors implicated in Xist RNA chromosome coating may already be present in undifferentiated ES cells.

Animals↗
PubMed1999

A new family of mouse genes homologous to the human MAGE genes.

The human MAGE genes are expressed in a wide variety of tumors but not in normal cells, with the exception of the male germ cells, placenta, and, possibly, cells of the developing embryo. These genes encode tumor-specific antigens recognized by cytolytic T lymphocytes. The MAGE genes are located on the X chromosome, in three clusters denoted MAGE-A, B, and C, mapping at q28, p21.3, and q26, respectively. The function of these genes remains unknown. Because mice offer many advantages for the study of genes that may be involved in embryonic development, we looked for the murine equivalents of the 12 human MAGE-A genes. Using a MAGE-A probe, we isolated 8 new murine genes that are homologous to the MAGE genes. On average, the open reading frames (ORFs) of these 8 closely related genes display a slightly higher degree of nucleotide identity with the MAGE-A ORFs than with the MAGE-B or MAGE-C ORFs. Furthermore, like MAGE-A genes, they encode acidic proteins, whereas the MAGE-B genes encode basic proteins. Accordingly, these 8 murine genes were named Mage-a1 to 8 (approved symbols Magea1 to 8). Mage-a genes were mapped in two different loci on the mouse X chromosome. Mage-a4 and Mage-a7 are located in a region that is syntenic to either Xp21 or Xq28. The 6 other genes are arranged in a cluster located in a region syntenic to Xp22. Like their human counterparts, Mage-a genes were found to be transcribed in adult testis, but not in other tissues. Expression of some Mage-a genes was also detected in tumor cell lines. Two Mage-a genes were found to be expressed in blastocysts.

Animals↗
PubMed1999

Functional analysis of the DXPas34 locus, a 3' regulator of Xist expression.

X inactivation in female mammals is controlled by a key locus on the X chromosome, the X-inactivation center (Xic). The Xic controls the initiation and propagation of inactivation in cis. It also ensures that the correct number of X chromosomes undergo inactivation (counting) and determines which X chromosome becomes inactivated (choice). The Xist gene maps to the Xic region and is essential for the initiation of X inactivation in cis. Regulatory elements of X inactivation have been proposed to lie 3' to Xist. One such element, lying 15 kb downstream of Xist, is the DXPas34 locus, which was first identified as a result of its hypermethylation on the active X chromosome and the correlation of its methylation level with allelism at the X-controlling element (Xce), a locus known to affect choice. In this study, we have tested the potential function of the DXPas34 locus in Xist regulation and X-inactivation initiation by deleting it in the context of large Xist-containing yeast artificial chromosome transgenes. Deletion of DXPas34 eliminates both Xist expression and antisense transcription present in this region in undifferentiated ES cells. It also leads to nonrandom inactivation of the deleted transgene upon differentiation. DXPas34 thus appears to be a critical regulator of Xist activity and X inactivation. The expression pattern of DXPas34 during early embryonic development, which we report here, further suggests that it could be implicated in the regulation of imprinted Xist expression.

Animals↗
PubMed1999

Xist yeast artificial chromosome transgenes function as X-inactivation centers only in multicopy arrays and not as single copies.

X-chromosome inactivation in female mammals is controlled by the X-inactivation center (Xic). This locus is required for inactivation in cis and is thought to be involved in the counting process which ensures that only a single X chromosome remains active per diploid cell. The Xist gene maps to the Xic region and has been shown to be essential for inactivation in cis. Transgenesis represents a stringent test for defining the minimal region that can carry out the functions attributed to the Xic. Although YAC and cosmid Xist-containing transgenes have previously been reported to be capable of cis inactivation and counting, the transgenes were all present as multicopy arrays and it was unclear to what extent individual copies are functional. Using two different yeast artificial chromosomes (YACs), we have found that single-copy transgenes, unlike multicopy arrays, can induce neither inactivation in cis nor counting. These results demonstrate that despite their large size and the presence of Xist, the YACs that we have tested lack sequences critical for autonomous function with respect to X inactivation.

Animals↗
PubMed1998

The mouse Tsx gene is expressed in Sertoli cells of the adult testis and transiently in premeiotic germ cells during puberty.

Tsx is a gene of unknown function that was previously shown to be expressed specifically in the testis. In order to gain insight into the function of Tsx its pattern of expression was characterized with regard to both timing and cell type in the testis. Northern blot analysis of early postnatal testes showed not only that Tsx message was detectable shortly after birth, but that it increased substantially between 7 and 12 days postpartum (dpp), roughly coincident with the onset of meiosis in the mouse. Alternative Tsx transcripts, detected by RT-PCR, included a spliced form that first appeared at around 12 dpp. In situ hybridization revealed Tsx signal in the somatic Sertoli cells of the adult testis. Consistent with the data from Northern blots, in situ hybridization signal was first detectable in normal pubertal testes at 12 dpp. An anti-Tsx polyclonal antiserum specifically stained premeiotic germ cells in addition to Sertoli cells of pubertal testes at 16, 19, and 27 dpp. Tsx immunostaining in germ cells was nuclear, while Sertoli cells displayed signal throughout the cytoplasm and nucleus. In the adult, Tsx was detected exclusively in Sertoli cells. In contrast, in the adult testis of the oligotriche (olt) mutant, where spermatogenesis is blocked after meiosis, Tsx protein was still present in the spermatogonial nuclei of a subset of tubules. Taken together, these results demonstrate that Tsx expression is induced in both premeiotic germ cells and Sertoli cells during the first wave of spermatogenesis, but that expression is maintained at a detectable level only in Sertoli cells of the normal adult. The persistence of Tsx expression seen in spermatogonia of the adult olt mutant supports the hypothesis that during the first wave of normal spermatogenesis, the advent of a late-stage cell type, either elongating spermatid or spermatozoan, is responsible for extinguishing expression in spermatogonia in normal adult testis. To our knowledge, Tsx is the first gene to show a pattern of germ cell expression that is apparently specific to the pubertal testis.

Animals↗
PubMed1998

Molecular correlates of the murine Xce locus.

The murine Xce locus, first identified by Bruce Cattanach, influences the primary choice of the X chromosome to be inactivated. Methylation of a GC-rich region (DXPas34) that includes multiple 34 bp repeats and lies some 15 kb 3' to Xist has been shown to vary with Xce haplotype. The degree of methylation on the active X chromosome at this locus represents one of the few molecular correlates of Xce action currently available. Data relating to the specificity and other characteristics of this association are presented.

Animals↗
PubMed1993

A panel of deleted mouse X chromosome somatic cell hybrids derived from the embryonic stem cell line HD3 shows preferential breakage in the Hprt-DXHX254E region.

A panel of 91 somatic cell hybrids containing deleted mouse X chromosomes and falling into seven nested intervals has been isolated and characterized from fusions involving the murine embryonic stem cell HD3. Many of the X chromosome breakpoints present in these hybrids fall within regions in which few or no other hybrids were previously available. The apparent enrichment for breakpoints lying within the Hprt-DXHX254E region is discussed in relation to both the nature of the embryonic stem cell fusions and the presence of the Fmr1 gene associated with FRAXA in man within this span.

Animals↗
PubMed1992

Characterization of the central region containing the X-inactivation center and terminal region of the mouse X chromosome using irradiation and fusion gene transfer hybrids.

The irradiation and fusion gene transfer (IFGT) procedure provides a means of isolating subchromosomal fragments for use in the mapping of loci and for cloning probes from a particular area of a chromosome. Using this procedure, two large panels of somatic cell hybrids that contain mouse X Chromosome (Chr) fragments have been generated. These hybrid panels were generated by irradiating the monochromosomal mouse-hamster hybrid HYBX, which retains the mouse X Chr, with either 10 K or 50 K rads of X-irradiation followed by fusion with a recipient Chinese hamster cell line. IFGT hybrids retaining mouse material were generated at high frequency. These hybrids were used to orient loci in the X-inactivation center region that had not been resolvable in our interspecies backcross panel and also to map, within the terminal region of the X Chr, repeat elements detected by the probe p15-4. These hybrids not only complement existing interspecies meiotic mapping panels for the detailed analysis of specific regions of particular chromosomes, but also provide a potential source of material for chromosome-specific probe isolation.

Animals↗
PubMed1991

Characterization of a murine gene expressed from the inactive X chromosome.

In mammals, equal dosage of gene products encoded by the X chromosome in male and female cells is achieved by X inactivation. Although X-chromosome inactivation represents the most extensive example known of long range cis gene regulation, the mechanism by which thousands of genes on only one of a pair of identical chromosomes are turned off is poorly understood. We have recently identified a human gene (XIST) exclusively expressed from the inactive X chromosome. Here we report the isolation and characterization of its murine homologue (Xist) which localizes to the mouse X inactivation centre region and is the first murine gene found to be expressed from the inactive X chromosome. Nucleotide sequence analysis indicates that Xist may be associated with a protein product. The similar map positions and expression patterns for Xist in mouse and man suggest that this gene may have a role in X inactivation.

Amino Acid Sequence↗
PubMed1988

Relationship between cellular adhesiveness and metastatic activity in polyomavirus-transformed FR3T3 rat cell lines.

A series of polyomavirus-transformed rat cells with varying tumorigenic potential were tested for biophysical parameters possibly related to metastatic properties: adhesive capacity and strength of adhesion to different substrates (laminin, fibronectin and albumin), cell deformability and spreading. Two groups of cell lines were defined according to their higher or lower adhesive capacity. Adhesivity did not appear to be related to cell deformability and spreading. A weak correlation was suggested between low adhesivity and high metastatic potential. A selection method was devised to separate cell samples into 3 subpopulations with different adhesive strength. Two cell lines, originally different, were chosen for this study: Py-tsa A25 cells were less adherent and highly metastatic, and Py-WTA2 cells were more adherent and less metastatic. After s.c. inoculation into syngeneic Fisher rats, the 3 selected subpopulations of the 2 cell lines induced pulmonary nodules to varying degrees, but only the less adherent ones were able to induce visceral metastasis located in stomach and intestine. In this case, animal survival time was 30% lower than for the highly adherent selected cells. After 10 culture passages, the same subpopulations were able to metastasize only in the lungs. However, when the selection procedure was repeated, the less adherent cells were again able to yield visceral nodules. Tumorigenicity remained unchanged in all cases. Study of cell dissemination and arrest in vivo showed a rapid targeting of labelled tumor cells toward lungs and stomach 5 hr after intradermal injection, where they remained up to 72 hr. More adherent cells displayed delayed localization after injection (24 hr) and radioactivity decreased more rapidly.

Animals↗
PubMed1988

Conservation and reorganization of loci on the mammalian X chromosome: a molecular framework for the identification of homologous subchromosomal regions in man and mouse.

By means of cross-reacting molecular probes, some 18 loci specific for the X chromosome of both man and mouse have been localized on the mouse X chromosome using an interspecific mouse cross involving the inbred SPE/Pas strain derived from Mus spretus. Comparison of the localizations of these loci on the mouse X with their positions on the human X chromosome suggests that intrachromosomal rearrangements involving at least five X chromosome breakage events must have occurred during the period of evolutionary divergence separating primates from rodents. Within the five blocks of chromosomal material so defined, there is for the moment little or no evidence that either chromosomal inversion events or extensive rearrangements have occurred. These data confirm the remarkable evolutionary conservation of the X chromosome apparent in mammalian species, compared to autosomal synteny groups in which both inter- and intrachromosomal rearrangement events appear to have occurred frequently. The breakage events described here for the X chromosome should therefore provide a minimal estimate for the frequency of chromosomal rearrangement events, such as breakage and inversion, which have affected autosomal synteny groups during the evolutionary period separating man from mouse. The definition of the number of chromosome breakage events by which the X chromosomes of these species differ, together with their localization, provides a framework for the use of interspecies mouse crosses for further detailed mapping of particular subchromosomal regions of the human X chromosome and for defining loci in the mouse homologous to those implicated in human congenital diseases.

Animals↗
PubMed1988

[Continuous monitoring, in the adult, of arterial oxygen saturation during apnea following intubation].

Twenty ASA I or II patients were studied to assess the safety of oxygenation for 4 min prior to intubing, so as to prevent the hypoxaemia related to tracheal intubation. The arterialized capillary blood saturation (Spo2) was continuously monitored with a pulse oximeter Nellcor 100 equipped with a finger probe. Patients spontaneously breathed oxygen (FIO2 = 1) while anaesthesia was induced with pancuronium bromide, thiopentone and fentanyl. Following apnoea, ventilation was manually controlled during 4 min (FIO2 = 1). The values of Spo2 were recorded before induction, at the end of the 4 min oxygenation period and after 5 min of apnoea. An arterial blood sample was withdrawn at the end of apnoea and analysed immediately using an OSM 2b hemoximeter. Apnoea was interrupted in case of desaturation below 95%, new arrhythmia or haemodynamic instability (blood pressure +/- 20% of control value). Mean saturation (+/- SD) before oxygenation was 98.6 +/- 1.35%. After oxygenating for 4 min, all the Spo2 reached 100%. After the 5 min apnoea period, no saturation was below 95% (mean +/- SD = 98.89 +/- 1.66); at this time, Sao2 and Spo2 did not significantly differ (p less than 0.001). In one case, apnoea had to be interrupted, because of the occurrence of arrhythmias, unrelated to a blood gas disorder (PaO2 = 225 mmHg; Paco2 = 34 mmHg; SaO2 = 100%; pH = 7.44). This study confirmed the efficacy and safety of oxygenating for 4 min before intubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗