The purpose of this project is to ascertain the possible source of insulin or insulin-like substances which may be synthesized and secreted by human placenta in gestation. We plan to investigate the characteristics of the gene(s) expressed for insulin and/or insulin-like molecules human placenta during placental development from both normal and diabetic pregnancies. Maternal insulin does not cross the blood-placenta barrier. The human fetus is known to utilize glucose as the major source of energy. It has been established that every mammalian fast growing tissue requires insulin as a growth factor. The most rapid rate of growth in human embryonic development occurs during the first ten weeks of embryonic development. However, the fetal pancreatic islets of Langerhans start to be capable of synthesis of insulin only at the 14th week of gestation. Therefore, it is most likely that during this critical period of growth and probably later as well, the placenta is responsible for the synthesis and secretion of insulin or insulin-like substances required for rapid fetal growth and fetal metabolism. Placenta is known as a source of other peptide hormones as well as steroid hormones. The long term goal of this project is to elucidate the involvement of the placenta in the synthesis and secretion of insulin and/or insulin-like growth factors needed for early fetal development. In particular we would like to know whether the same pancreatic gene is expressed in placenta or a tissue specific gene belonging to the same family is expressed as is known for other genes coding for tissue specific proteins such as actins, collagens and globin. We plan to investigate the levels of insulin-like genes expressed in both, placentas from normal pregnancies and compare them with the levels in diabetics. Moreover, we plan to quantify the mRNA for insulin-like sequences expressed during placental development and to investigate whether the same as well as other members of the insulin-like family are expressed in diabetic placenta or if the relative proportion of the different sequences is changed in diabetic pregnancies. We have been using recombinant DNA technology to investigate this problem. Cloned cDNA libraries encoded by polyadenylated mRNA extracted from various stages of placental development are being prepared. Insulin-like mRNA identified by Northern hybridization will be further studied by sequence analysis of the corresponding cDNA clones. Hybrid selected mRNA will be translated and the amino acid sequence of the specific product will be determined and compared to the sequence predicted from the nucleotide sequence of the respective cDNA.
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