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M A Ripoche

Publications and source records attributed to M A Ripoche.

At least 19 recordsLinked to original sources
PubMed1998

Embryonic implantation in galectin 1/galectin 3 double mutant mice.

Galectin 1 and galectin 3 are first expressed in the trophectoderm cells of the implanting embryo and have been implicated in the process of implantation. However, we had previously shown that the lack of galectin 1 in galectin 1 null mutant mice is compatible with implantation. In this study, we describe the generation of galectin 3 null mutant mice and show that they are viable and have no overt abnormalities. The importance of galectin 1 and galectin 3 in implantation was assessed by obtaining double mutant mice [gal1 -/-; gal3 -/-]. We find that implantation can still occur in the absence of both galectin 1 and galectin 3. However, we show that galectin 5, a third member of this gene family, is also present in the blastocyst at the time of implantation.

Animals↗
PubMed1998

Maintenance of granulocyte numbers during acute peritonitis is defective in galectin-3-null mutant mice.

Galectin-3, also known as the macrophage marker Mac-2, is a member of a family of structurally related animal lectins that exhibit specificity for beta-galactosides. In order to investigate the role of galectin-3 in acute inflammation, we have compared the number of leucocytes present in the peritoneal cavity of wild type and galectin-3 null mutant mice after intraperitoneal (i.p.) injection of thioglycolate broth. At day 1 after injection, we found no difference in the recruitment of mononuclear phagocytes and granulocytes to the peritoneal cavity. However, 4 days after thioglycolate injection, galectin-3 mutant mice exhibited a significantly reduced number of recoverable granulocytes compared to wild-type animals. As mutant granulocytes did not exhibit an accelerated rate of apoptosis and their uptake by macrophages appeared to be unaffected by the mutation, the phenotype described here suggests that galectin-3 participates in an additional level of control during the resolution of acute inflammation.

Acute Disease↗
PubMed1997

Deletion of the H19 transcription unit reveals the existence of a putative imprinting control element.

The distal region of mouse chromosome 7 contains a cluster of imprinted genes that includes H19 and Igf2 (insulin-like growth factor 2). H19 is expressed as an untranslated RNA found at high levels in endodermal and mesodermal embryonic tissues. This gene is imprinted and exclusively expressed from the allele of maternal origin. The Igf2 gene shows a similar pattern of expression but is expressed from the paternal allele. We have generated a targeted deletion of the H19 transcription unit by insertion of a neo replacement cassette. The homozygous mutant animals are viable and fertile and display an overgrowth phenotype of 8% compared with wild-type littermates. This is associated with the disruption of Igf2 imprinting and the consequent biallelic expression of this gene. A striking feature of the recombinant H19 allele is the occurrence of a parental imprint set on the neo replacement cassette. Therefore imprinting of the H19 locus is independent of the H19 gene itself. Taken together with the results of a larger H19 mutation described previously, this indicates that an imprinting control element is located within the region 10 kb upstream of H19.

Animals↗
PubMed1995

Galectin-3 is expressed in the notochord, developing bones, and skin of the postimplantation mouse embryo.

The galectins are a family of low molecular weight, calcium-independent mammalian carbohydrate binding proteins that exhibit specificity for beta-galactoside derivatives. We have examined the expression pattern of galectin-3 in the developing mouse embryo by in situ hybridisation and immunohistochemistry. In the embryo proper, galectin-3 message and protein are first detected in notochord, starting from 8.5 days post coitum (dpc), and persist until this structure disappears. Galectin-3 is later found in cartilage primordia and in developing skin from 13.5 dpc. This very restricted and dynamic pattern suggests that galectin-3 may participate in the establishment and/or maintenance of notochord as well as the formation of cartilage and differentiation of skin. Finally, we find that galectin-3, which is identical to the macrophage marker Mac-2, is also expressed in embryonic macrophages.

Animals↗
PubMed1992

DNase-I hypersensitivity analysis of the L-type pyruvate kinase gene in rats and transgenic mice.

The rat L-type pyruvate kinase gene possesses two promoters located 500 bp apart. The L' promoter is specific to erythroid cells. The L promoter is specific to liver and is regulated by diet and hormones; positively by glucose and insulin and negatively by glucagon via cAMP. The DNA elements involved in this tissue-specific and hormone-regulated gene expression are located within 3.2 kbp of 5' flanking region as previously demonstrated by transgenic mice analysis [Tremp, G. L., Boquet, D., Ripoche, M. A., Cognet, M., Yu-Chun, L., Jami, J., Kahn, A. and Daegelen, D. (1989) J. Biol. Chem. 264, 19,904-19,910]. Moreover, we have observed in these mice that gene expression was dependent on the transgene copy number and independent of the integration site. We present here DNase-I-hypersensitivity analysis of the endogenous rat L-type pyruvate kinase gene and of two transgene constructs in relation to development, tissue differentiation, nutritional and hormonal status. In rats, two groups of proximal sites were detected on the endogenous gene; hypersensitive site (HSS) HSS-1 in adult liver and HSS-A in fetal liver (a major erythropoietic tissue). Both groups are probably related to the transcriptional initiation complexes at either the L or L' promoter. Two other distal groups were detected; HSS-2 at -3 kbp (with respect to the liver-specific cap site) in adult liver and HSS-B around -4 kbp in fetal liver. These sites are thought to correspond to activating sequences; in adult liver, deletion of a fragment encompassing HSS-2 provokes a dramatic reduction of transcription starting at the L promoter of the transgene. In adult liver, HSS-1 appears to be a transcription-associated site, being greatly weakened in fasted rats, while HSS-2 is transcription independent. The pattern of DNase-I hypersensitivity is similar for the rat endogenous gene and for the complete rat transgene; the liver-specific HSS-1 and HSS-2 are present and the intensity of the sites is correlated to the number of integrated copies. Interestingly, HSS-1 is still detectable and its intensity remains proportional to the number of integrated copies in a truncated transgene with HSS-2 deletion, while this transgene is very weakly (but nevertheless tissue-specifically) expressed. These results strongly suggest that each transgene copy possesses a complete set of specific nucleoprotein complexes and that, with or without HSS-2, the DNA is in a potentially active configuration.

Animals↗
PubMed1991

Polyclonal origin of pancreatic islets in aggregation mouse chimaeras.

In the present study, we have examined the origin and growth pattern of the beta cells in pancreatic islets, to determine whether a single progenitor cell gave rise to all the precursors of the islets, or if each of a few progenitor cells is the founder of a different islet, or if each islet is a mixture of cells originating from a pool of progenitor cells. Aggregation mouse chimaeras where the pancreatic beta cells derived from each embryo can be identified in the islets on histological sections were analyzed. In two chimaeras, all the islets contained cells from both the aggregated embryo. This clearly demonstrates that each islet resulted from several independent cells. In addition, the beta cells derived from either embryo component were in very small clusters in the islets, suggesting that in situ cell division did not account significantly for islet growth.

Animals↗
PubMed1990

Effect of 5'-flanking sequence deletions on expression of the human insulin gene in transgenic mice.

Expression of the human insulin gene was examined in transgenic mouse lines carrying the gene with various lengths of DNA sequences 5' to the transcription start site (+1). Expression of the transgene was demonstrated by 1) the presence of human C-peptide in urine, 2) the presence of specific transcripts in pancreas, but not in other tissues, 3) the specific immunofluorescence staining of pancreatic islets for human C-peptide, and 4) the synthesis and accumulation of human (pro)insulin in isolated islets. Deletions in the injected DNA fragment of sequences upstream from positions -353, -258, and -168 allowed correct initiation of the transcripts and cell specificity of expression, while quantitative expression gradually decreased. Deletion to -58 completely abolished the expression of the gene. The amount of human product that in mice harboring the longest fragment contributes up to 50% of the total insulin does not alter the normal proportion of mice insulins I and II. These results suggest that expression of the human insulin gene in vivo results from the cooperation of several cis-regulatory elements present in the various deleted fragments. With none of the deletions used, expression of the transgene was observed in cell types other than beta-islet cells.

Animals↗
PubMed1989

Expression of the rat L-type pyruvate kinase gene from its dual erythroid- and liver-specific promoter in transgenic mice.

The gene for the L-type pyruvate kinase possesses two promoters which are located 500 base pairs apart. The L promoter is specific to liver and regulated by hormones and diet; the L' promoter is specific to erythroid cells. We produced two series of transgenic mice carrying either the entire rat L-pyruvate kinase gene or a minigene devoid of exons two to nine, with 2.7 kilobases of flanking sequences 5' to the cap site of the L' promoter and 1.4 kilobases 3' to the downstream polyadenylation site. In both series the patterns of expression from the two promoters were similar to those of the endogenous rat gene. The rat L promoter was expressed strongly in liver and weakly in kidney and gut of adult transgenic mice. Moreover, it was regulated like the endogenous rat L-pyruvate kinase gene upon hormonal and nutritional adaptation: the level of L-pyruvate kinase mRNA was decreased dramatically by 24 h of starvation, while refeeding a carbohydrate-rich diet strongly stimulated expression of the transgenes. This stimulation was prevented by glucagon. Use of alternative polyadenylation sites in the last exon of the rat L-type pyruvate kinase gene was similar for both types of transgenes and similar to that in rat and not control mice, suggesting that the transgenes contain the sequences that control the choice of polyadenylation site. Transcription of the minigene was higher than that of the entire transgene, probably due to the high copy number of the minigene. At the protein level, rat L subunits encoded by the entire transgene were more abundant than mouse subunits in the liver of adult transgenic mice. In contrast, expression of the rat L' promoter in fetal liver was only 5% of that in fetal rat liver, and we were unable to detect rat L' subunits of pyruvate kinase enzyme in the red blood cells from transgenic mice. Our results suggest that the integrated DNA contains all elements necessary for tissue specificity (L' and L) as well as hormonal and nutritional control (L) of expression of the rat transgene. Nevertheless, a L'-specific activating element may be missing.

Animals↗
PubMed1988

Chromosome localization of the human insulin gene in transgenic mouse lines.

Three transgenic mouse lines, Tg 74, Tg 174, and Tg 171, were obtained by microinjection of an 11-kb human DNA fragment carrying the insulin gene into pronuclei of fertilized mouse eggs. The human insulin gene was expressed in all three transgenic mouse lines as shown by the presence of human C peptide in serum and urine and of human insulin transcripts in RNA prepared from pancreas. Several copies of the human DNA fragment arranged in head-to-tail arrays were present in each line. The human DNA insert was transmitted to the progeny as a single genetic locus. The chromosomal integration of the human insulin transgene was directly demonstrated by in situ hybridization to metaphase chromosomes of mitotic cells prepared from spleen and bone marrow. The insert appeared unique and located on a different chromosome in each line, namely 7 for Tg 74, 13 for Tg 174, and 18 for TG 171. Separation of DNA fragments larger than 20 kb by pulse-field electrophoresis showed that several insertion sites were present in each chromosome locus. This is the first direct evidence in transgenic mice that a gene located at various chromosome loci can be correctly expressed.

Animals↗
PubMed1986

Pancreatic expression of human insulin gene in transgenic mice.

We have investigated the possibility of obtaining integration and expression of a native human gene in transgenic mice. An 11-kilobase (kb) human chromosomal DNA fragment including the insulin gene (1430 base pairs) was microinjected into fertilized mouse eggs. This fragment was present in the genomic DNA of several developing animals. One transgenic mouse and its progeny were analyzed for expression of the foreign gene. Synthesis and release of human insulin was revealed by detection of the human C-peptide in the plasma and urine. Human insulin mRNA was found in pancreas but not in other tissues. These findings indicate that the 11-kb human DNA fragment carries the sequences necessary for tissue-specific expression of the insulin gene and the human regulatory sequences react to homologous signals in the mouse.

Animals↗
PubMed1985

Presence of immunoreactive vitamin D-binding protein in rat yolk sac endodermal cells.

The visceral yolk sac is, in the rat, an organ which possesses true placental functions. We recently showed that yolk sac is involved in the control of metabolism and action of vitamin D in the fetoplacental unit, since its endodermal cells contain a 24-hydroxylase for vitamin D metabolites and the 1,25-dihydroxyvitamin D receptor. In the present work, by using indirect immunoperoxidase staining, we demonstrate that an immunoreactive vitamin D-binding protein (DBP) is present in this yolk sac throughout embryonic and fetal development. It is mainly located at the apex of the endodermal cells. Immunoprecipitation studies of radioactive proteins synthesized in vitro by yolk sac explants showed that yolk sac DBP, in contrast to alpha-fetoprotein, is not synthesized in situ by yolk sac. This result, combined with the location of DBP at the apex of the endodermal cells which face the uterus, strongly suggests that yolk sac DBP is of maternal origin. The concomitant presence in the endodermal cells of this DBP, of the 1,25-dihydroxyvitamin D receptor, and of the system hydroxylating vitamin D metabolites in position 24, certainly has considerable physiological significance.

Animals↗
PubMed1983

Adult hemoglobins are synthesized in yolk sac microenvironment obtained from murine cultured blastocysts.

The capability of yolk sac (YS) hematopoietic stem cells to produce in vitro either primitive or definite erythrocytes under the influence of stimulating agents was analyzed. Two systems were used: either 9-day-old yolk sacs were explanted and cultured or 3-day-old blastocysts were cultured under conditions in which they give rise only to YS tissue. In both systems, YS tissue produced only primitive erythrocytes. When the stimulating agents (spleen cell-conditioned medium or erythropoietin) were added to the medium, YS cultures gave rise to definitive erythrocytes. These data confirm the intrinsic ability of the YS stem cells to undergo primitive erythropoiesis; furthermore, they provide evidence that YS hemopoietic progenitor cells do not require any direct interaction with cells of the embryo to undergo definitive erythropoiesis but only stimulation by agents, such as pokeweed mitogen spleen conditioned medium or erythropoietin; the YS microenvironment does not counteract this capacity.

Animals↗
PubMed1983

In rat uterus 17 beta-estradiol stimulates a calcium-binding protein similar to the duodenal vitamin D-dependent calcium-binding protein.

A calcium-binding protein (CaBP) similar to rat duodenal vitamin D-dependent CaBP was identified in rat uterus. Uterine CaBP and duodenal CaBP had the same mol wt (9,000-10,000), exhibited the same calcium-dependent electrophoretic mobility, and were immunologically identical. The localization of CaBP in the rat uterus was explored using indirect immunoperoxidase methods, and by CaBP RIA in the endometrium and myometrium after enzyme separation. In the endometrium CaBP was found in the cytoplasm of the stroma cells but not in the epithelium or in the glandular cells. In the myometrium, it was located inside the smooth myometrial fibers. Hormonal regulation of CaBP was shown to differ in the uterus and duodenum. Duodenal CaBP concentrations increased in response to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), and were not influenced by ovariectomy or sex steroids administration. By contrast, CaBP synthesis fell drastically in the uterus of ovariectomized rats, but was greatly enhanced by low physiological doses of 17 beta-estradiol. This effect of 17 beta-estradiol on uterine CaBP was dose dependent. Medroxyprogesterone and more especially 1,25(OH)2D3 exerted no such stimulating effect on uterine CaBP. In vitamin D-deficient ovariectomized rats, administration of 17 beta-estradiol alone restored the uterine CaBP concentrations to normal and this potency contrasted with the apparent inability of 1,25(OH)2D3 to affect the uterine CaBP concentrations. Our data suggest that, unlike duodenal CaBP regulation, the expression of the CaBP gene in rat uterus is predominantly controlled by 17 beta-estradiol.

Animals↗
PubMed1982

Biochemical characterization of mouse vitamin D-dependent calcium-binding protein. Evidence for its presence in embryonic life.

We compared immunochemical and biochemical properties of the vitamin D-dependent Ca2+-binding protein (CaBP) from rat and mouse intestine. The two intestinal CaBP species were extensively purified by gel filtration and successive anion-exchange chromatographies. Both had a similar mol.wt. of 9000. Their pI values differed markedly, being 8.0 and 4.9 in rat and mouse CaBP respectively. Accordingly, mouse CaBP displayed more anodal migration in electrophoresis under non-denaturing conditions. Both mouse and rat CaBP only exhibited partial immunochemical similarities, but their amino acid compositions were very similar. Chromatofocusing was also found to be a good method of detecting calcium-dependent changes in their pI. We developed a sensitive radioimmunoassay for mouse CaBP enabling us to detect substantial amounts of CaBP in uterus, yolk sac and chorio-allantoic placenta. During normal mouse gestation, CaBP appeared on day 12 in the chorio-allantoic placenta but was already present on day 9 in the yolk sac, where its level rose sharply between days 9.5 and 10. CaBP may therefore be considered as a new marker for mouse yolk-sac differentiation.

Amino Acids↗
PubMed1979

Nuclear labeling in immunoperoxidase studies of mouse tissue as detected by staining at acid pH.

Several peroxidase-Ig conjugates were applied to sections of fixed mouse tissue. When the peroxidase staining reaction was done at pH 4.5 instead of pH 7.4, a striking reaction on nuclear membrane, chromatin, or chromosomes was observed. This staining was prevented by pretreatment of sections with DNase but not with RNase or after acid elution of histones. It is suggested that at acid pH a redistribution and binding DNA of oxidized chromogen or of a chromogen-conjugate complex to DNA may account for the results observed.

Animals↗
PubMed1978

Immunological studies of mouse decidual cells. I. Membrane markers of decidual cells in the days after implantation.

Mouse decidual cell suspensions from day 6 to day 8 of gestation were prepared by enzymatic treatment with collagenase and trypsin and tested for various membrane markers. (a) Besides H-2 antigens, Thy-1 antigens are present on about 50% of the cells; this may reflect the fibroblastic origin of decidual cells or be a marker expressed on some decidual cells possibly under hormonal control. (b) T or B lymphocytes, as defined by four Lyt antigens or surface immunoglobulins, are not present in significant amounts. (c) A substantial number of cells bearing receptors for the Fc portion of IgG (FcR) is detectable in the decidua, probably closely connected with trophoblast cells; these FcR-bearing cells may act in preventing excessive invasion of uterine tissue by trophoblast or could contribute to the protection of the embryo by interacting with maternal blocking antibodies and trophoblast. No receptors for for complement were detected, even after 16-20 h in culture after trypsin treatment.

Animals↗