Genetically targeting adenosine deaminase to trophoblasts of the murine placenta rescues adenosine deaminase deficient fetuses from perinatal lethality

Abstract

s: R.T.C. and T.G.W.M.S. Canada 1996 Genetically Targeting Aakrwsine Deaminase to Trophoblasts of the Murine Placenta Rescues Adenosine Deaminase Deficient Fetuses from Perinatal Lethality. mlackburn, R.E. Kellems, Department of Biochemistry, Baylor College of Medicine, Houston, TX, USA. Adenosine deaminase (ADA) is an essential enzyme of purine metabolism that is expressed at very high levels in trophoblasts of the muring placenta where it accounts for over 95% of the ADA present at the fetal gestation site. ADA deficient fetuses, which also lack ADA in their adjoining placentas, die during late fetal development in association with profound purine metabolic disturbances and hepatocellular impairment. To investigate the potential importance of placental ADA we genetically restored the enzyme to placentas of ADA deficient fetuses. This was accomplished by using regulatory elements from the murine Ada gene to drive the murine ADA cDNA specitically to the placenta prenatally in transgenic mice. These mice were then bred to mice heterozveous for the null Ada allele, generating progeny heterozygous ?or both the placental snecific ADA miniaene and an Ada null allele. Intercrosses between these mice s 072” *The Babraham Institute, Cambrrdge, CB2 : . . A unique feature of equine placentation is the annulate chorionic girdle of specialised trophoblast cells that invade the maternal endometrium around day 36 of pregnancy (term=320-340 days). This chorionic girdle develops through hyperplasia of trophoblast cells on the region of chorion adjacent to its point of fusion with the aliantois, and we have proposed a model to explain its formation that involves local stimuli from the allantoic mesenchyme. The most important of these appear to be the growth factors, insulin-like growth factor II (IGF II) and hepatocyte growth factor-scatter factor (HGF-SF), the latter having morphogenic, motogenic and mitogenic actions. We have now examined the effects of these growth factors on equine uophoblast cells in vitro by means of a colourimetric mitogenic assay using pure populations of growth-arrested equine trophoblast cells in serum-free medium. The cells demonstrated significant dose-related mitogenic responses to both growth factors with the maximum response to HGF-SF being 63% of that obtained with fetal calf serum compared to only 20% for IGF II. Furthermore, HGFSF stimulated an increased secretion of equine chorionic gonadotrophin, a marker of trophoblast differentiation. These results support our hypothesis that the allantoic mesenchyme-derived growth factors, IGF II and HGFSF, are important for the growth and differentiation of equine trophoblast.