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C Babinet

Publications and source records attributed to C Babinet.

At least 91 records · Page 5Linked to original sources
PubMed1991

Synthesis and developmental regulation of an egg specific mouse protein translated from maternal mRNA.

Proteins synthesized by DDK mice embryos were analyzed by 2D electrophoresis and a new egg-specific polypeptide, D14, was identified. The protein is characterized by its high rate of synthesis and electrophoretic properties (MW 36,500, pl greater than 8). The synthesis of D14 is strictly developmentally regulated: starting in the maturing oocyte in the few hours following germinal vesicle breakdown (GVBD), it remains high over the first cell cycle and decreases abruptly during the two-cell stage. The arrest of D14 synthesis is triggered by egg activation and does not directly depend on transcription by the zygotic genome. Nevertheless, drugs that perturb the onset of zygotic transcription concomitantly inhibit D14 arrest of synthesis. D14 is present in both cytoplasmic and nuclear compartments at the two-cell stage; it is very stable and remains detectable at least until the eight-cell stage in the preimplantation embryo. Embryos of wild strains of mice synthesized either D14 or a D14 related polypeptide at a rate comparable to that of DDK embryos, which was at least ten times greater than that found in other laboratory strains. Both the developmental regulation and the genetic variability in its rate of synthesis make D14 an interesting polypeptide for the study of regulation of maternal information in the very early stages of mouse embryo development.

Animals↗
PubMed1991

Participation of the paternal genome is not required before the eight-cell stage for full-term development of mouse embryos.

Differential expression of the paternal and maternal genomes during mouse embryonic development is considered a reason for both genomes being required for development to term. Extending previous studies performed on two-cell embryos, we show here that diploid embryos reconstituted at the four-cell stage from uniparental haploid blastomeres can produce living offspring. This result shows that for normal development to occur, a paternal genome does not need to be associated with a maternal genome within the same nucleus before the eight-cell stage.

Animals↗
PubMed1990

c-myc, c-fos, and c-jun regulation in the regenerating livers of normal and H-2K/c-myc transgenic mice.

We investigated the mechanisms of regulation of c-myc, c-fos, and c-jun at the early stages of liver regeneration in mice. We show that the transient increase in steady-state levels of c-myc mRNA at the start of liver regeneration is most probably regulated by posttranscriptional mechanisms. Although there was a marked increase in c-myc transcriptional initiation shortly after partial hepatectomy, a block in elongation prevented the completion of most transcripts. To gain further information on the mechanism of regulation of c-myc expression during liver regeneration, we used transgenic mice harboring the human c-myc gene driven by the H-2K promoter. In these animals, the murine c-myc responded to the growth stimulus generated by partial hepatectomy, whereas the expression of the transgene was constitutive and did not change in the regenerating liver. However, the mRNA from both genes increased markedly after cycloheximide injection, suggesting that the regulation of c-myc mRNA abundance in the regenerating liver differs from that occurring after protein synthesis inhibition. Furthermore, we show that in normal mice c-fos and c-jun mRNA levels and transcriptional rates increase within 30 min after partial hepatectomy. c-fos transcriptional elongation was restricted in nongrowing liver, but the block was partially relieved in the regenerating liver. Nevertheless, for both c-fos and c-jun, changes in steady-state mRNA detected after partial hepatectomy were much greater than the transcriptional increase. In the regenerating liver of H-2K/c-myc mice, c-fos and c-jun expression was diminished, whereas mouse c-myc expression was enhanced in comparison with that in nontransgenic animals.

Animals↗
PubMed1990

The DDK inbred strain as a model for the study of interactions between parental genomes and egg cytoplasm in mouse preimplantation development.

The DDK strain of mice has unusual genetic properties. When females of this strain are crossed to males of other strains, they generally exhibit a very low fertility, whereas reciprocal crosses are fully fertile as are the intrastrain crosses. The observed low fertility results from early embryonic lethality, the F1 embryos dying around the late morula-early blastocyst stage. Nuclear transplantation experiments between hybrid eggs of BALB/c and DDK strains has shown that failure of F1 (DDK female x BALB/c male) embryos to develop is not due to the combination per se of maternal (DDK) and paternal (BALB/c) genomes but rather to an incompatibility between paternal (BALB/c) genomic contribution and DDK cytoplasm. This incompatibility does not occur between a female BALB/c pronucleus and the DDK cytoplasm, suggesting the involvement of a differential imprinting of parental genomes. Introduction of cytoplasts isolated from DDK 1- to 8-cell embryos into BALB/c female x BALB/c male or BALB/c female x DDK male embryos of the corresponding developmental stage demonstrate that the cytoplasm of DDK embryos prevents the formation of normal blastocysts through a specific interaction with the paternal component of the BALB/c diploid nucleus. Genetic and molecular studies are underway to try and isolate the gene(s) responsible for the failure of (DDK female x BALB/c male)F1 embryos. These experiments should help in our understanding of nucleocytoplasmic interactions and the respective roles of parental genomes in early embryonic development.

Animals↗
PubMed1990

Differential regulation and expression of jun, c-fos and c-myc proto-oncogenes during mouse liver regeneration and after inhibition of protein synthesis.

In order to obtain information in vivo about the possible relationships between early response gene products, we have analysed the expression of c-myc, c-fos and jun proto-oncogenes in regenerating mouse liver. We show that c-myc, c-fos, jun B, c-jun and jun D mRNA expression is transiently increased soon after partial hepatectomy, jun and fos expression being induced earlier (30 min) than that of c-myc (1-2 h). C-fos, jun B and c-jun mRNA expression is dramatically enhanced (50 fold) while that of jun D and c-myc is weaker (less than 10 fold), but lasts longer. Moreover, the relative contributions of transcriptional and post-transcriptional regulations are unique for each proto-oncogene analysed. These results suggest that following the growth signal delivered by partial hepatectomy, the five proto-oncogenes analysed are all involved in the progression of hepatocytes through G1; however, due to their differential regulation and kinetics, they might play different roles in the changes in gene expression that occur during the transition from quiescence to proliferation. When protein synthesis is inhibited by injection of cycloheximide, the expression of c-myc, c-fos, jun B, c-jun and jun D mRNA is also transiently increased. Although this increase is mainly due to post-transcriptional mechanisms, c-myc, c-jun, jun D and, to a lesser extent, jun B transcription is enhanced, suggesting that labile repressor-like molecules may inhibit transcription of these genes in the quiescent liver. Moreover, the kinetics of c-myc, c-fos and jun mRNA induction are not identical, showing that different components are involved in their turnover or stability.

Animals↗
PubMed1989

Immunoglobulin kappa light chain gene promoter and enhancer are not responsible for B-cell restricted gene rearrangement.

We have produced transgenic mice which synthesize chimeric mouse-rabbit immunoglobulin (Ig) kappa light chains following in vivo recombination of an injected unrearranged kappa gene. The exogenous gene construct contained a mouse germ-line kappa variable (V kappa) gene segment, the mouse germ-line joining (J kappa) locus including the enhancer, and the rabbit b9 constant (C kappa) region. A high level of V-J recombination of the kappa transgene was observed in spleen of the transgenic mice. Surprisingly, a particularly high degree of variability in the exact site of recombination and the presence of non germ-line encoded nucleotides (N-regions) were found at the V-J junction of the rearranged kappa transgene. Furthermore, unlike endogenous kappa genes, rearrangement of the exogenous gene occurred in T-cells of the transgenic mice. These results show that additional sequences, other than the heptamer-nonamer signal sequences and the promoter and enhancer elements, are required to obtain stage- and lineage- specific regulation of Ig kappa light chain gene rearrangement in vivo.

Animals↗
PubMed1989

Transgenic mice.

Stable integration into the mouse genome of exogenous genetic information has become, over the past few years, a very potent approach for different aspects of biology. It is a common feature that the integrated exogenous gene (the transgene) is expressed properly both spatially and temporally. Constructing different lines of transgenic mice carrying various versions of a gene, therefore, permits cis acting DNA sequences involved in the specificity of expression to be defined, in the context of the developing animal. This in turn opens the way to a variety of experiments in which a given gene product is targeted to one or another cell type, thus offering some insight into the physiological role of this product. Such a strategy has been used, for example, to address the questions of the role of oncogenes in malignant transformation. The insertion of foreign DNA per se may disrupt the function of endogenous genes, thus creating an insertional mutation. The corresponding affected genes may subsequently be cloned, using the transgene as a tag. Finally, the ability to perform homologous recombination, recently demonstrated with embryonic stem cells that can colonize the germ line of a foreign embryo, should constitute in the near future a unique way to analyse in detail the functioning of the mammalian genome.

Animals↗
PubMed1989

Renin-promoter SV40 large T-antigen transgenes induce tumors irrespective of normal cellular expression of renin genes.

Chimeric genes containing the 5'-flanking regions of the mouse renin genes, Ren1 and Ren2, associated with the early region of the simian virus 40 (SV40) were constructed. The two recombinant genes which contain, respectively, 0.45- and 2.5-kb the Ren1 and Ren2 5'-flanking sequences, named Ren1Tag and Ren2Tag, were microinjected into fertilized eggs. Tumors arose after a latency of 5-9 months in mouse lines harboring these hybrid genes except for one, in which a different and earlier pathology was observed (peripheral neuropathies). Most of the pathologies developed by these transgenic mice reflect the tumorigenic spectrum of the SV40 early region gene (choroid plexus, kidney, intestinal tumors, and peripheral neuropathies). None of these tumors arose from renin-producing cells nor produced renin. As suggested by the tumor pathology, the expression of the SV40 large T-antigen did not follow the normal expression of the Ren1 and the Ren2 genes since SV40 large T-antigen mRNA was found in tissues which normally do not express renin.

Animals↗
PubMed1989

Lymphoproliferative syndrome associated with c-myc expression driven by a class I gene promoter in transgenic mice.

We have produced transgenic mice carrying an H-2K/human c-myc fusion gene. In this construct, the human c-myc proto-oncogene expression is driven by the 5' flanking sequences (including promoter) of the class I H-2Kb gene, which have previously been shown to direct the expression of a marker gene, the human growth hormone (hGH), in most tissues of H-2K/hGH transgenic mice. Comparative analysis, by S1 nuclease mapping, of the H-2K and human c-myc gene expression in different organs of the H-2K/myc mice shows that exogenous c-myc and endogenous H-2K expression is found in most organs examined. However, the liver is a notable exception, for here c-myc expression is very weak. The exogenous c-myc expression is maximal in lymphoid organs of all H-2K/myc transgenic strains. One strain, H-2K/myc 27, hereditarily develops a lymphoproliferative syndrome which eventually leads to death. The H-2K/myc 27 lymphoid tissues are profoundly abnormal: pre-B cells as well as mature B cells are underrepresented in the bone marrow but the thymus as well as lymph nodes are largely infiltrated by B cells. Moreover, in the thymus, the proportions of the different thymic cell populations are altered. However, in the other H-2K/myc transgenic strains, even in those expressing a comparable or even higher level of myc, no pathology has been observed over a period of 20 months. Our results, therefore, demonstrate that constitutive enforced c-myc expression might disturb lymphocyte development, but does not directly lead to malignancy.

Animals↗
PubMed1989

Tissue-specific post-transcriptional regulation of c-myc expression in normal and H-2K/human c-myc transgenic mice.

We show that the steady-state levels of c-myc mRNAs vary considerably in different organs of normal adult mice, maximal expression being observed in lymphoid organs and minimal expression in liver and brain. Nuclear run-on analysis of c-myc gene transcription in adult liver and spleen reveals that the difference in c-myc gene expression in these two organs is due to differential post-transcriptional control. Moreover, these nuclear run-on assays indicate that no premature termination of c-myc gene transcription takes place in the nuclei of the three adult tissues analysed. In fetal liver development, we observe a decrease in c-myc mRNA, but this is not due to changes in transcriptional activity implicating post-transcriptional regulatory mechanisms. Our studies of c-myc gene expression in organs of H-2K/myc transgenic mice, harboring an H-2K promoter driven human c-myc gene, confirm that the in vivo c-myc regulation is mainly post-transcriptional and shows that sequences shared by the murine and human c-myc proto-oncogenes are involved in this control.

Animals↗
PubMed1989

Exogenous c-myc gene overexpression interferes with early events in F9 cell differentiation.

The effect of c-myc gene expression on F9 teratocarcinoma stem cell differentiation was studied by transfecting mouse metallothionein I promoter-driven human c-myc genes into F9 cells. Human c-myc gene expression was triggered by cadmium treatment at different stages of differentiation. When this expression was induced before or just after addition of retinoic acid plus cyclic AMP (RA +cAMP), the death of 70-80% of the cells was observed. This cell mortality was not observed either when the parental F9 cells were induced to differentiate in the presence of cadmium or when the undifferentiated transfected clone was permanently grown in the presence of this inducer. The 30% surviving cells underwent terminal differentiation despite high c-myc mRNA levels and expressed differentiation-specific genes normally like their parental F9 cells. When cadmium was added 24 or 48 hr after RA +cAMP, no cell mortality or any other detectable effect on differentiation were observed, even though c-myc gene transcripts were induced. We therefore conclude that c-myc gene expression only inhibits F9 differentiation at an early stage in 70-80% of cells. The significance of these results will be discussed.

Actins↗
PubMed1988

Replication and gene expression of hepatitis B virus in a transgenic mouse that contains the complete viral genome.

We have sought to address the problem of the host and tissue specificity of the hepatitis B virus (HBV) by using transgenic mice obtained after injection of head-to-tail dimers of the HBV genome. Viral DNA replication and protein synthesis were obtained in one of nine transgenic mice containing integrated HBV DNA. The RNAs encoding the HBV surface antigen and the core antigen were synthesized in the liver, the kidney, and the heart. In these organs, DNA replicative intermediates similar to those found during normal infection were associated with corelike structures. Large amounts of core polypeptides and capsids were detected in the nuclei in the absence of any pathological effect. These results show that the different steps of HBV multiplication can take place in nonliver nonhuman cells once the problem of entry into the host cell is overcome. In the absence of a small laboratory animal infectable by HBV, such transgenic mice should be helpful for the study of many aspects of viral multiplication.

Animals↗
PubMed1988

[Action of the paternal genome at the beginning of embryonic development].

Recent experiments using nuclear transfer between mouse embryos shows that the parental genomes are not equivalent: both of them must be present at least in a part of the blastomeres to allow full term development of the embryo. The paternal genome is preferentially involved in the development of trophoectodermic cells and appears to be eliminated from the primitive ectoderm when kept alone in androgenetic cells aggregated with normal ones. Differences of expression between parental genomes affect not only the X chromosome, but also several autosomes as evidenced by genetic analysis using meiotic non-disjunction. The nature of the imprinting mechanism that leads to the modification of parental homologous chromosomes is unknown. From experiments involving a particular strain of mice called DDK it appears that the egg cytoplasm may exert a specific action not only on the male pronucleus at the one-cell stage, but also on the paternal contribution of the diploid nucleus of the embryo at the 2-cell stage; a paternal developmental effect on the cytoplasm of one-cell stage embryo can also be demonstrated. These results show that nucleocytoplasmic interactions regulate early paternal gene expression differently from the maternal one.

Animals↗
PubMed1987

Regulated expression of the Ren-2 gene in transgenic mice derived from parental strains carrying only the Ren-1 gene.

The Ren-2 gene encoding the mouse submaxillary gland (SMG) renin was microinjected into the pronuclei of fertilized eggs from mice carrying only the Ren-1 gene. In addition to the whole transcription unit, the injected DNA contained 2.5 and 3 kb of upstream and downstream flanking sequences, respectively. Three independent transgenic mice lines were obtained; two of them had integrated one copy of the Ren-2 gene, the last one had integrated five and eleven copies at two independent sites. Independently of the number of Ren-2 copies integrated, the pattern of Ren-2 gene expression in all the transgenic mice was identical to that observed in wild-type animals in which Ren-1 and Ren-2 are closely linked on chromosome 1. In particular, the exogenous Ren-2 gene was only transcribed in the kidney and in the SMG. In the kidney, Ren-1 and Ren-2 mRNAs were present at a comparable level, whereas in the SMG Ren-2 mRNA was at least 100-fold more abundant than Ren-1 mRNA. Moreover, Ren-2 expression in the SMG was positively regulated by androgens. Only one difference between transgenic mice and wild-type mice carrying the Ren-2 gene has been observed: the basal level of Ren-2 transcription in the SMG of transgenic females was lower than in two-gene strain females. Androgen treatment of transgenic females induced SMG renin mRNA to a level identical to that of transgenic males. This suggests that the basal level of SMG renin mRNA is dependent upon cis-acting elements which are not present in the microinjected fragment.

Animals↗
PubMed1987

Mouse 89 kD heat shock protein. Two polypeptides with distinct developmental regulation.

Unstressed early mouse embryos have been previously shown [1] to synthesize at very high rates 70 and 89 kD proteins belonging to the heat shock protein (HSP) family. But it was not clear whether expression of heat shock-inducible or non-inducible (cognate) genes accounted for this spontaneous synthesis. In this report we show that the 89 kD mouse HSP can be separated into two proteins by high resolution PAGE. These two components show distinct but related peptide pattern after limited proteolysis. They are synthesized from distinct mRNAs. One of these proteins--HSP89f--is synthesized at a high rate by unstressed cells and its synthesis is rather insensitive to stress, whereas synthesis of the other protein--HSP89s--is strongly stimulated by heat shock in fibroblasts. Both HSP89f and HSP89s are major proteins synthesized in unstressed mouse preimplantation embryos and embryonal carcinoma (EC) cells. After in vitro differentiation of the EC cells the spontaneous synthesis of HSP89s decreases. Thus spontaneous expression of a mammalian inducible HSP is developmentally regulated.

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