Search PubMed⌕ Search

Biomedical subjects

J Rossant

Publications and source records attributed to J Rossant.

At least 127 records · Page 7Linked to original sources
PubMed1989

Expression of the c-fms proto-oncogene and of the cytokine, CSF-1, during mouse embryogenesis.

The c-fms gene encodes the cell surface receptor of the colony-stimulating factor, CSF-1. CSF-1 has recently been shown to be expressed in the maternal uterine endometrium of pregnant mice. The ontogenetic and spatial patterns of expression of the murine proto-oncogene c-fms were analyzed in the developing mouse placenta by the technique of in situ hybridization. c-fms expression was not detected in fetally derived tissues until 9.5 days postcoitum (pc) when expression first appeared in the mural trophoblast giant cells. Expression persisted at high levels in trophoblast cells throughout gestation. In the mature placenta from 13.5 days pc on, c-fms was expressed chiefly in the spongiotrophoblast layer and, to a lesser extent, in the labyrinthine trophoblast. CSF-1 expression was first detectable in the uterine epithelium at 8.5 days pc which loosely correlated with the appearance at 7.5 days of c-fms in the decidual cells around the developing egg cylinder. The time course and spatial pattern of expression of these two genes suggest a functional role for the c-fms receptor and its ligand, CSF-1, in trophoblast development and differentiation.

Animals↗
PubMed1989

Towards a molecular-genetic analysis of mammalian development.

The mouse has been a slower starter than many other organisms in the race to unravel the genetic control of embryonic development. Recent cloning of putative developmental genes combined with new approaches to manipulating the mouse genome seem set, however, to allow the mammalian embryo to move towards the front of the field.

Animals↗
PubMed1989

Cardiac and neurological abnormalities in v-fps transgenic mice.

Transgenic mice that widely express the v-fps protein-tyrosine kinase develop several independent pathological conditions, in addition to a high tumor incidence. v-fps expression and protein-tyrosine kinase activity in the heart were directly correlated with cardiac enlargement. This cardiomegaly was accompanied by severe myocardial and endocardial damage, which was concentrated in the left ventricular wall, and characterized by a progressive atrophy and necrosis of cardiac muscle fibers with concomitant fibrosis. This pathology was associated with congestive heart failure. Mice from five lines developed a marked trembling, correlated with expression of the v-fps transgene in the brain, and two lines showed a striking bilateral enlargement of the trigeminal nerves. Unlike tumor formation, these cardiac and neurological phenotypes were evident shortly after birth and showed 100% penetrance. The pleiotropic effects of the v-fps transgene suggest the involvement of protein-tyrosine kinases in mammalian neural development and cardiac function.

Animals↗
PubMed1989

Lymphoid and mesenchymal tumors in transgenic mice expressing the v-fps protein-tyrosine kinase.

src, abl, and fps/fes are prototypes for a family of genes encoding nonreceptor protein-tyrosine kinases. The oncogenic potential of the v-fps protein-tyrosine kinase was investigated by introduction of the gag-fps coding sequence of Fujinami sarcoma virus into the mouse germ line. Transgenic mice with v-fps under the transcriptional control of a 5' human beta-globin promoter (GF) or with both 5' and 3' beta-globin regulatory sequences (GEF) were viable. Unexpectedly, both GF and GEF transgenes were expressed in a wide variety of tissues and induced a spectrum of benign and malignant tumors. These tumors, which included lymphomas, thymomas, fibrosarcomas, angiosarcomas, hemangiomas, and neurofibrosarcomas, developed with various frequencies after latent periods of 2 to 12 months. The majority of lymphoid neoplasms appeared to be of T-cell origin and were monoclonal, as judged by rearrangements of the T-cell receptor beta or immunoglobulin genes. Some tissues that expressed the v-fps oncogene, such as heart, brain, lung, and testes, developed no malignant tumors. The v-fps protein-tyrosine kinase therefore has a broad but not unrestricted range of oncogenic activity in cells of lymphoid and mesenchymal origin. The incomplete penetrance of the neoplastic phenotype and the monoclonality of lymphoid tumors suggest that tumor formation in v-fps mice requires genetic or epigenetic events in addition to expression of the P130gag-fps protein-tyrosine kinase.

Animals↗
PubMed1989

High incidence of lung, bone, and lymphoid tumors in transgenic mice overexpressing mutant alleles of the p53 oncogene.

We have investigated the role of the p53 gene in oncogenesis in vivo by generating transgenic mice carrying murine p53 genomic fragments isolated from a mouse Friend erythroleukemia cell line or BALB/c mouse liver DNA. Elevated levels of p53 mRNA were detected in several tissues of two transgenic lines tested. Increased levels of p53 protein were also detected in most of the tissues analyzed by Western blotting (immunoblotting). Because both transgenes encoded p53 proteins that were antigenically distinct from wild-type p53, it was possible to demonstrate that overexpression of the p53 protein was mostly, if not entirely, due to the expression of the transgenes. Neoplasms developed in 20% of the transgenic mice, with a high incidence of lung adenocarcinomas, osteosarcomas, and lymphomas. Tissues such as ovaries that expressed the transgene at high levels were not at higher risk of malignant transformation than tissues expressing p53 protein at much lower levels. The long latent period and low penetrance suggest that overexpression of p53 alone is not sufficient to induce malignancies and that additional events are required. These observations provide direct evidence that mutant alleles of the p53 oncogene have oncogenic potential in vivo and that different cell types show intrinsic differences in susceptibility to malignant transformation by p53. Since recent data suggest that p53 may be a recessive oncogene, it is possible that the elevated tumor incidence results from functional inactivation of endogenous p53 by overexpression of the mutant transgene. The high incidence of lung and bone tumors suggests that p53 transgenic mice may provide a useful model to investigate the molecular events that underlie these malignancies in humans.

Alleles↗
PubMed1989

Inducible expression of an hsp68-lacZ hybrid gene in transgenic mice.

Transgenic mice have been generated that express the E. coli beta-galactosidase gene under the control of the promoter from the mouse heat-shock gene, hsp68. Sequences from -664 to +113 relative to the start of transcription of the hsp68 gene were sufficient to direct stress-induced expression of the beta-galactosidase gene in adult tail tissue and various tissues of fetal stages of development. Expression was detected in situ by staining with the chromogenic substrate, X-gal. The hybrid gene was refractory to induction in preimplantation embryos until the blastocyst stage of development, as reported for the endogenous hsp68 gene. No constitutive expression was observed by in situ staining or Northern analysis at any stage of development, even in tissues that constitutively express the endogenous hsp68 gene. We conclude that the hsp68 promoter region included in the construct contains sufficient sequence information for heat and arsenite inducibility, but it does not contain sequences controlling tissue-specific expression during development. This tightly regulated inducible promoter may provide a useful tool for short-term inducible gene expression in transgenic mice.

Animals↗
PubMed1988

A transgene containing lacZ inserted into the dystonia locus is expressed in neural tube.

The site of integration of transgenes in the host genome can affect levels of expression and occasionally confer ectopic patterns of expression on otherwise tissue-specific genes. We describe here a line of mice in which an hsp68-lacZ transgene is expressed in unstressed developing neural tissue and where the transgene insertion has caused a mutation of a neural tissue-specific gene, dystonia musculorum (dt). This coincidence suggests that expression of the hsp68-lacZ construct may be controlled directly by cis-acting regulatory sequences that normally control the developmental expression of the dt gene. Such constructs may serve as useful tools for identifying new tissue-specific enhancers and their associated genes.

Animals↗
PubMed1988

Isolation and characterization of a novel trophoblast-specific cDNA in the mouse.

A novel trophoblast-specific cDNA has been isolated by differential screening of a 13.5-day mouse placental cDNA library. The 755-bp cDNA, which is almost full length, encodes a polypeptide of 124 amino acids with an 18-amino-acid hydrophobic leader sequence. No significant homology with any known gene or protein has been detected. Northern blot analysis has shown that the gene is expressed abundantly in the placenta and is not detected in any other tissues. In situ hybridization revealed that the gene is expressed first in a subgroup of ectoplacental cone cells at 7.5 days of development and its later expression is confined to the spongiotrophoblast cells of the mature placenta. The role of the gene is not currently known, but the presence of a signal peptide suggests that it may be a secreted protein.

Amino Acid Sequence↗
PubMed1988

Expression of the homeo box-containing gene En-2 delineates a specific region of the developing mouse brain.

We have examined the pattern of expression of the homeo box-containing gene En-2 during mouse embryogenesis using in situ hybridization. Transcripts were first detected in the neural folds of 8.0-day, 5-somite embryos, and expression continued throughout development into adulthood. Hybridization occurred only in the central nervous system (CNS) and was limited to one band of the neural tube and to parts of those structures that later developed from it; the cerebellum, pons, periaqueductal gray, and colliculi. Expression in the germinal zone of the CNS was uniform within the hybridizing band. However, later in development, once cells had migrated out of the germinal zone, there was a reduction in the extent of hybridization and an increase in its spatial complexity. In the adult, expression of En-2 appeared to be limited to specific groups of neurons. The early, localized expression of En-2 within an apparently homogeneous tissue is consistent with the hypothesis that En-2 plays a role in defining a spatial domain within the developing brain.

Animals↗
PubMed1988

Polytene chromosomes in mouse trophoblast giant cells.

Mouse trophoblast giant cells undergo successive rounds of DNA replication resulting in amplification of the genome. It has been difficult to determine whether giant cell chromosomes are polyploid as in liver cells or polytene as in Dipteran salivary glands because the chromosomes do not condense. We have examined the pattern of hybridization of mouse giant cells with a variety of in situ chromosome markers to address this question. Hemizygous markers displayed one hybridization signal per nucleus in both diploid and giant cells, while homozygous markers displayed two signals per nucleus in both cell types. These patterns are consistent with cytological evidence indicating that giant cell chromosomes are polytene rather than polyploid. However, in contrast to the situation in Dipteran salivary glands, the two homologues do not appear to be closely associated. We conclude that the mechanism of giant cell DNA amplification involves multiple rounds of DNA replication in the absence of both karyokinesis and cytokinesis, and that sister chromatids, but not homologous chromosomes, remain closely associated during this process.

Animals↗
PubMed1988

Cell-autonomous action of the testis-determining gene: Sertoli cells are exclusively XY in XX----XY chimaeric mouse testes.

The distribution of XX and XY cells in XX----XY chimaeric mouse testes was analysed by enzyme marker analysis of separated testicular tissues and by in situ DNA marker analysis of air-dried testicular cells and testis sections. XX cells contributed to the Leydig cells, the peritubular cells and the vascularized connective tissue of the tunica albuginea. The Sertoli cells, on the other hand, appeared to be exclusively XY. These results indicate that during the development of the testis, Sertoli cell differentiation is triggered by cell-autonomous activity of the Y chromosomal testis-determining gene Tdy. Subsequent steps in testis differentiation may be a consequence of Sertoli cell activity.

Animals↗
PubMed1988

The development potential of parthenogenetically derived cells in chimeric mouse embryos: implications for action of imprinted genes.

Parthenogenetic embryos of mice die shortly after implantation and characteristically contain poorly developed extraembryonic tissue. To investigate the basis of the abnormal development of parthenotes, we combined them with normal embryos to produce chimeras and examined the distribution of the parthenogenetically derived cells during preimplantation and early postimplantation development. The parthenogenetic embryos were derived from a transgenic mouse line bearing a large insert, which allowed these cells to be identified in histological sections using in situ hybridization. At the blastocyst stage, the parthenogenetic embryos contributed cells to the trophectoderm (TE) and inner cell mass (ICM) of chimeras. By 6.5 days, however, in almost every embryo, parthenogenetically derived cells were not detected in the extraembryonic trophoblast tissue descended from the TE. In contrast, parthenogenetically derived cells could contribute to all descendants of the ICM of 6.5-and 7.5-day chimeras, including the extraembryonic visceral and parietal endoderm. Quantitative analysis of the degree of chimerism in the embryonic ectoderm at 6.5-7.5 days indicated that parthenogenetically derived cells could contribute as extensively as normal cells. These results indicate that normal trophoblast development requires gene expression from the paternally inherited genome before 6.5 days of embryogenesis. Tissues of the ICM lineage, however, apparently can develop independently of the paternal genome at least to 7.5 days of embryogenesis. Comparison of these results with those of others suggests that the influence of imprinted genes is manifested at different times and in a variety of tissues during development.

Animals↗
PubMed1988

Suppression of chromosome condensation during meiotic maturation induces parthenogenetic development of mouse oocytes.

Mouse oocytes at metaphase I were treated with puromycin, which caused the chromosomes to become decondensed within an interphase nucleus. When the oocytes were allowed to resume protein synthesis, they returned to metaphase within 8-10 h and neither synthesized DNA nor cleaved, indicating that they had not been parthenogenetically activated by the puromycin treatment. However, when dibutyryl cyclic AMP was added to the medium after protein synthesis resumed, the oocytes remained in interphase. These oocytes maintained in interphase began DNA synthesis beginning 20 h after puromycin withdrawal, even though no activation stimulus had been given to them. After transfer to the oviducts of foster mothers, the oocytes could develop to the blastocyst stage. These results indicate that oocytes whose chromosomes were decondensed by puromycin treatment at metaphase I could begin parthenogenetic development in the absence of an activating stimulus, provided that they were prevented from returning to metaphase. In contrast, when the puromycin-treated oocytes were allowed to return to metaphase, they became developmentally arrested at the end of maturation. This suggests that the mechanism responsible for the developmental arrest of mature oocytes at metaphase II depends on cytoplasmic conditions that cause chromosome condensation to the metaphase state.

Animals↗
PubMed1987

Genetic ablation: targeted expression of a toxin gene causes microphthalmia in transgenic mice.

Lineage-specific regulatory elements can be used to direct expression of a variety of genes to specific tissues in transgenic mice. If the hybrid constructs contain a gene encoding a cytotoxic gene product, then genetic ablation of a specific cell lineage can be achieved. We have generated six transgenic mice by introducing into fertilized eggs the mouse gamma 2-crystallin promoter fused to the coding region of the diphtheria toxin A-chain gene. Three of these mice and all the transgenic offspring analyzed were microphthalmic. The lenses of these mice displayed considerable heterogeneity: some were almost normal morphologically but reduced in size, whereas others were grossly aberrant and deficient in nuclear fiber cells. These studies indicate that programmed ablation of specific cell types can be stably transmitted through the germ line.

Animals↗
PubMed1987

In situ detection of beta-galactosidase in lenses of transgenic mice with a gamma-crystallin/lacZ gene.

Transgenic mice carrying the gamma 2-crystallin promoter fused to the coding region of the bacterial lacZ gene were generated. The offspring of three founder mice expressed high levels of the enzyme solely in the central nuclear fiber cells of the lens as measured by an in situ assay for the detection of beta-galactosidase activity. These results suggest that gamma 2-crystallin sequences between -759 to +45 contain essential information required for appropriate tissue-specific and temporal regulation of the mouse gamma 2-crystallin gene. In a broader context, this study also demonstrates the utility of beta-galactosidase hybrid gene constructs for monitoring the activity of gene regulatory elements in transgenic mice.

Animals↗
PubMed1987

Mouse embryonic cells become susceptible to CTL lysis after midgestation.

The susceptibility of murine embryonic cells to CTL lysis has been assessed. Zona-free blastocysts were not lysed during 6 hr incubation with CTL sensitized against the embryonic genotype and remained capable of implantation and normal development in vivo as well as outgrowth in vitro. Freshly dissociated cells from postimplantation embryos before the 13th day of gestation were not lysed in a 51Cr-release assay, but cells from 13- to 16-day embryos were susceptible to lysis. Cells from Day 12 embryos cultured for 40 hr in the presence or absence of interferon became susceptible to CTL lysis. Cultured cells from Day 10 embryos were only lysed following culture in medium containing interferon. Cell populations lysed in the CTL assay remained resistant to lysis by NK effector cells. These experiments indicate that the murine fetus is protected from the maternal immune system at least during the first half of pregnancy by an intrinsic ability of early embryonic cells to resist cell mediated lysis. Suppression of maternal CTL responses may not be essential for fetal survival until later stages of gestation.

Animals↗
PubMed1987

Cell-lineage-specific expression of the mouse hsp68 gene during embryogenesis.

Transcription of the mouse hsp68 and hsc70 genes in embryonal carcinoma cells, various embryonic and extraembryonic tissues, and some adult tissues has been assessed using cloned probes to the mouse hsp68 gene. The results from Northern blots showed that both F9 and P19 cells respond in the expected manner to a heat shock. Hsp68 expression was only detected in heat-induced F9 and P19 cells. Hsc70 transcripts were present in uninduced cells and their levels increased after induction. In adult tissues, the hsp68 gene was expressed constitutively in the kidney. A different hsp68-like transcript was detected at significant levels in adult testes. Constitutive expression of hsp68 was observed in both the placenta (beginning at Day 8.5) and yolk sac (beginning at Day 11.5). No hsp68 expression was detected in embryonic tissues until Day 15.5. Expression of the mouse hsp68 gene during embryogenesis suggests that it may play some role in development.

Animals↗