Its is generally accepted that development and differentiation are mediated by growth factors. Imbalance in embryonic tissue growth may result in development abnormalities as manifested by malformations in organs of progeny from diabetic pregnancies in humans and in mice, which are considered to occur during organogenesis. Insulin-like growth factor I (IGF-I) and IGF-11 are polypeptide growth factors which are mitogenic and bring about differentiation in cultured cells of embryonic origin. They are considered to be important growth factors in fetal and post-natal development and are thought to act through a paracrine and/or autocrine mechanism in concert with platelet derived growth factor (PDGF). The expression of the genes for IGFs have been studied in human and rodent fetal organs after organogenesis. We propose to study by in situ hybridization the timing and pattern of the expression of the above genes during early mouse embryogenesis from day 5 to day 10 post coitum (p.c.), during organogenesis, when the genes controlling differentiation and morphogenesis of organs are gradually brought into play. The expression of the IGFs and PDGF B chain will also be followed by in situ hybridization in early mouse embryos from experimentally induced diabetic mothers. Early embryos of both human and rodent diabetic mothers are known to be growth retarded. The involvement of these genes in the development of the decidua as well as extra embryonic structures in normal and diabetic pregnancies will be analyzed. The possibility of development and tissue specific expression utilizing different processing or different promoters of IGF-II will be followed by in situ hybridization as well as RNA blot analysis using unique probes for the 5' untranslated region specific to placenta or to adult liver cDNA. We will determine the pattern and timing of production of IGFs during early development by immunocytochemistry in sections of embryos from normal pregnant mice as well as from mice rendered diabetic prior to pregnancy. The mechanism by which diabetes brings about elevated expression of IGFs in human placenta will be investigated by incubating human placental explants in different concentrations of glucose, hPL and HCG. The alteration in the rate of transcription will be followed by """"""""run-on"""""""" nuclear assays and the role of specific mRNA degradation will be followed by pulse- experiments.
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