Biomedical subjects

T Jaffredo

Publications and source records attributed to T Jaffredo.

25 records · Page 2Linked to original sources

PubMed1991

MC29-immortalized clonal avian heart cell lines can partially differentiate in vitro.

We established quail clonal heart muscle cell lines from cardiac rhabdomyosarcomas developed in embryos injected in ovo with the MC29 virus containing the v-myc oncogene. These clones were characterized by means of antibodies detecting markers of striated muscle cells. Two clones were selected for further characterization on the basis of a distribution of myogenic markers similar to that in normal early embryonic cardiac muscle cells. However, these muscle markers progressively disappeared with time in culture. Cardiomyocytic differentiation could be reinduced in culture, by associating the avain cardiac cells with 3T3 cells in a defined synthetic medium. Muscle markers were then reexpressed in all cardiac cells as soon as Day 1 after coculture. Multiplication of cardiac cells continued at the same time. This is characteristic of cardiac clones since MC29-infected quail myoblasts and MC29-infected quail fibroblasts exhibited a split response to 3T3 association, i.e., decreased growth and enhanced differentiation. The cardiac clones were maintained in vitro for more than 60 generations (6 months) without morphological changes. To our knowledge, this is the first description of clonal embryonic avian heart cell lines.

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PubMed1991

The relationship between cell proliferation and the transcription of the nuclear oncogenes c-myc, c-myb and c-ets-1 during feather morphogenesis in the chick embryo.

We have described the expression of three nuclear protooncogenes, c-myc, c-myb and c-ets-1 during feather morphogenesis in the chick embryo. In parallel with the expression patterns obtained by in situ hybridization, we have mapped the spatial distribution of S-phase cells by monitoring the incorporation of 5-bromodeoxyuridine. We do not detect c-myc or c-myb transcripts during the early stages when S-phase cells are scattered in the dermis and in the epidermis. Rather c-ets-1 transcripts are abundant in the dermal cells which divide and accumulate under the uniform epidermis. At the onset of the formation of the feather bud, cells within each rudiment cease DNA replicative activities and c-myc transcripts are detected both in the epidermis and in the underlying dermis. This expression precedes the reentry into the S phase. The transcription of c-myb, which has been previously tightly linked to hemopoietic cells is also detected in the developing skin. This expression is essentially located in proliferating epidermal cells on and after the beginning of feather outgrowth. As feather outgrowth proceeds, the distribution of c-myc and c-myb transcripts is restricted to the highly proliferating epidermis. In contrast c-ets-1 transcripts are never detected in the epidermis. During the later stages of skin morphogenesis, the transcription of c-ets-1 is restricted to the endothelial cells of blood vessels, as previously described. We suggest that the differential expression of these nuclear oncogenes reflects the activation of different mitotic controlling pathways during the development of the skin.

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PubMed1991

Cooperative effect of v-myc and v-erbA in the chick embryo.

We show that a construct designated as MAHEVA, which encodes oncogenes v-myc from MH2 virus and v-erbA from AEV under the control of the LTR of MH2, induces rapidly growing heart rhabdomyosarcomas, when it is injected in E3 but not E5 chick embryos. A similar pathology has previously been observed with MC29, within the same limited time frame. The tumors, which expressed P61-63myc, P75gag-erbA and Pr76gag proteins were detectable from E14 onwards. Compared with MC29, MAHEVA induced a secondary anomaly, not detectable prior to E17. This is the appearance of cartilage nodules within the heart rhabdomyosarcomas. The constant location of these nodules inside the rhabdomyosarcomas and their delayed appearance suggests that the chondrocytes originate from myoblasts prevented from differentiating by the expression of the v-myc product. This interpretation is supported by the appearance of chondrocytes in E3 heart muscle cells infected in vitro with MAHEVA.

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PubMed1990

Oncogenes and avian development.

In order to detect signs of oncogene activity and elucidate their possible role in avian ontogeny we implemented two different strategies. One was to detect either the protein product or messenger RNA in situ at various stages of development. The other was to try and disturb development with retroviruses carrying one or several oncogenes in their activated forms. Time- and tissue-specific expression of c-myc was apparently not related to particular phases of cell evolution, such as population amplification. Rather the presence of c-myc immunoreactive product at particular stages appeared to depend on cell types. c-myb and c-ets messenger RNAs were found expressed preferentially in the blood system, respectively in hemopoietic and differentiating endothelial cells. The developing embryo heart was found to be uniquely sensitive to the effect of retroviruses provided that two conditions were respected. The first was the injection of the virus or construct prior to E3.5. The second was the presence of the v-myc gene, whether alone or associated with one or several other v-onc. In such cases a large proportion (70%) of chick and all quail embryos developed multiple heart rhabdomyosarcomas within 10 days. In chickens the association of a second v-onc or of two others induced the formation of secondary tumors, whose type was determined by the nature of the other oncogene(s).(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1989

In situ study of c-myc protein expression during avian development.

The distribution of the c-myc protein was studied in the developing embryo from the two-somite stage to embryonic day 17 (E17). A triple labelling method was used, with a polyclonal serum recognizing the human and avian c-myc proteins as the first marker followed by Hoechst 33258 for nuclear staining and the monoclonal antibody 13F4 which reveals the avian myogenic lineage. In situ hybridization was carried out at three selected stages (E3, E6 and E8), in order to compare the distribution of myc mRNA and myc protein. The c-myc protein signal was barely detectable in blastodisc nuclei during the period of somite formation, after which it became ubiquitous in the embryonic body until E4. Myotomal cell nuclei displayed a strong signal until their organization into premuscular masses. On day 4, the level of c-myc protein decreased in all embryonic tissues. By doubling the antibody titre and amplifying the signal by means of the streptavidin-biotin method, c-myc could still be detected in nuclei of defined groups of cells. Such was the case in some mesenchyme-derived tissues at critical periods of organogenesis, for instance in prechondrogenic condensations or hemopoietic cell foci at E6, the latter becoming negative at E9. The heart ventricle displayed a patch-work of positive and negative nuclei from E6 to E10. A myc signal restricted to the quail species was found in the wall of the carotid arteries. Cell nuclei in the nervous system displayed a detectable signal which became restricted to postmitotic neurones. In the ectoderm, the c-myc protein was generally not present after E4, except in presumptive feather buds at the time of epitheliomesenchymal interactions. Endodermal cells (such as hepatocytes, oesophageal and tracheal epithelia) did not express detectable levels of c-myc at any time. Our results reveal a time- and tissue-specific expression of c-myc during avian development. It is noteworthy that the expression of the c-myc protein often appears dissociated from cell proliferation as shown by the absence of the signal in endodermal cells at E3-E13 as well as its presence in postmitotic neurones. Finally, although RNA and protein are simultaneously detected in some structures such as presumptive feather buds, their expression is dissociated in endodermal tissues, notably hepatocytes, where in situ hybridization detects a large number of RNA copies with no detectable protein signal.

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PubMed1989

Complementary patterns of expression of c-ets 1, c-myb and c-myc in the blood-forming system of the chick embryo.

We have used in situ hybridization to study the spatial and temporal distribution of the transcription of three cellular oncogenes encoding DNA-binding proteins, c-ets 1, c-myb and c-myc during the development of the chick embryo. c-ets 1 mRNA expression appears linked to the mesodermal lineage and is strongly expressed in early endothelia; it subsequently becomes restricted to small vessel endothelia. Hemopoietic cells in extraembryonic blood islands at E2 express c-ets 1, while intraembryonic hemopoietic cells in aortic clusters (E3) and paraaortic foci (E6) express c-myb. c-myc transcripts are detected in cells undergoing hemopoiesis in both these extraembryonic and intraembryonic sites. Outside the blood-forming system, c-myc is transcribed in a large variety of cells; c-ets 1 displays tissue-specific expression in groups of mesodermal cells engaged in morphogenetic processes and appears excluded from all epithelia; finally the expression of c-myb is the most tightly linked to hemopoietic cells. In any case, it is clear that these three oncogenes display complementary expression in endothelial and hemopoietic cells where their patterns are modulated in relationship to multiplication and differentiation.

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PubMed1988

Myoblast migration specifically inhibited in the chick embryo by grafted CSAT hybridoma cells secreting an anti-integrin antibody.

We report a teratological method in which mouse hybridoma cells are grafted into a chick host. CSAT (Cell Substratum ATtachment) hybridoma was used. It produces an antibody directed against the avian integrin complex. The grafts were performed during the second and third days of incubation either at the level of the somites or in the coelom of the chick embryo. The anomalies were revealed by means of a monoclonal antibody that recognizes myogenic cells as soon as they become committed in the myotome. When embryos were grafted at the level of the somites, body wall muscles failed to develop on the side of the graft only. After coelomic grafting, total agenesis of abdominal muscles was induced. The anomalies were specific since the engraftment of three control hybridoma clones induced no change in muscle formation. These control hybridomas produce antibodies directed against the same molecular complex but not against the same epitope as CSAT. The injection of hybridoma cells in an embryo appears as a method of general interest to determine the long-term consequences of perturbing a specific developmental process.

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