Characterization of a human perinatal myosin heavy-chain transcript.

Using a monoclonal antibody specific to the neonatal myosin heavy chain, we have cloned the full-length heavy chain cDNA from an 18-week human fetal cDNA library. Ribonuclease protection assays were used to survey a human muscle collection ranging from 11 weeks gestation to 16 years. Expression of the RNA encoded by this cDNA was observed at 20 and 21 weeks gestation and at 2 days after birth. No expression was observed at 13.5 weeks, before 2 years, at 2 years, or after 2 years gestation. Due to the timing of its expression, this cDNA appears to represent of the human fetal myosin heavy chain. Sequencing of the entire 6010 bases showed high similarity to the rat perinatal myosin heavy chain [Periasamy, M., Wieczorek, D. F. & Nadal-Ginard, B. (1984) J. Biol. Chem. 21, 13,573-13,578]. However, moderate divergence was observed when compared to a previously described human perinatal myosin heavy chain [Karsch-Mizrachi, I., Feghali, R., Shows, T. B. & Leinwand, L. A. (1990) Gene 89, 289-294; Feghali, R. & Leinwand, L. A. (1989) J. Cell Biol. 108, 1791-1797]. Restriction fragment-length polymorphism analyses of sites in both the S1 and rod domains showed the presence of this fetal myosin heavy chain sequence in all 27 genomic samples examined. Restriction fragment-length polymorphism analysis failed to find the previously described perinatal isoform in any sample.

Expression of c-fos and c-myc oncogenes in the P388D1 murine macrophage line treated by immunomodulators: absence of direct correlation with DNA synthesis.

Complex patterns of metabolic and functional characteristics are induced in macrophages by biological response modifiers. The study of the early events resulting from the transduction of immunomodulatory signals could be an approach for a better understanding of this activation process. The transcription of c-fos and c-myc genes has been shown to be rapidly modified in many cells responding to various signals. Since murine peritoneal macrophages are a rather heterogeneous population we chose to investigate the c-fos and c-myc modulation in the P388D1 murine macrophage line. Owing to the frequent implication of the c-myc gene in the tumorigenicity of hematopoietic cells we first demonstrated the normal c-myc status in this cell line by Southern analysis. The modulation of the c-fos and c-myc expression has been studied by Northern analysis, 15, 30 and 60 minutes after treatment of the P388D1 cells by the phorbol ester (TPA), the Calcium ionophore A 23187 (Ca2+I), the N-acetyl muramyldipeptide (MDP) or the macrophage Colony Stimulating Factor (CSF-1). The mitogenic activity of these compounds, as evaluated by [3H] thymidine incorporation, has been measured either after a 30 minute or a 24 hour treatment. An early increase in c-fos expression always preceded a c-myc augmentation. The highest modulation of c-fos and c-myc was observed with TPA. Ca2+I and TPA presented a low mitogenic effect if compared to CSF-1. MDP did not change DNA synthesis even after 24 hours. Therefore, in the present study on the P388D1 macrophage cell line, no direct correlation could be evidenced between the mitogenic effect and the modulation of c-fos and c-myc induced by these immunomodifiers. Investigations are in progress in order to evaluate the role of these proto-oncogenes on terminal differentiation induced by immunomodulators in this cell line.

C-fos and c-myc modulation, mitogenic effect and Ia expression in the P388D1 murine macrophage line treated by immunomodifiers.

The aim of the present study was to investigate whether the early modulation of the c-fos and c-myc oncogenes could give some orientation to the impact of immunomodulators on the monocyte-macrophage lineage. In order to work in a homogeneous system we used the P388D1 mouse macrophage cell-line which is considered as an almost mature macrophage. When P388D1 cells were stimulated by LPS, interferon-gamma or the association of both compounds, no direct correlation could be found between the modulation of DNA synthesis and the early expression of the c-fos and c-myc oncogenes. The positive regulation of Ia antigen expression seemed to correlate with the absence of induction of c-fos oncogene.