The human leukocyte antigen-G (HLA-G), a protein highly expressed at the human maternal- fetal interface during pregnancy, is thought to be critical in survival of the semi-allogenic fetus. Our long-term goal is to elucidate the role of HLA-G in pregnancy as a prerequisite to assessing the therapeutic potential of recombinant HLA-G proteins in pregnancy-related pathologies and transplantation. Current evidence suggests HLA-G programs immune cells at the maternal-fetal interface into immunosuppressive phenotypes. It has been implicated in development of preeclampsia, implantation success in in vitro fertilization (IVF) programs, survival of heart transplants and survival of some tumors. However, definitive proof of HLA-G function remains elusive since in vivo experiments in humans are not possible due to ethical concerns. In the search for an appropriate animal model, we have identified the olive baboon (Papio anubis) as a potential candidate. This primate expresses an HLA-G-like protein termed Paan-AG in the placenta. Our hypothesis is that Paan-AG could be the functional homologue of HLA-G. Preliminary data shows that Paan-AG shares many characteristics with HLA-G, including limited polymorphism, alternative splicing of the mRNA, and restricted tissue of expression of the protein (mainly in the placenta). The restricted tissue expression of the proteins suggests the two genes might share tissue-specific regulatory elements. In order to confirm whether the baboon is a useful model, it is necessary to establish whether regulation of Paan-AG is similar to that of HLA-G as known to date.
The aim of this proposal is to identify tissue-specific regulatory elements in the 5' and 3' untranslated regions or introns of Paan-AG. We previously identified a number of putative regulatory elements in these regions using a transcription factor search system software. We will assess activity of these elements using electrophoretic mobility shift assays and luciferase reporter assays in different cell lines. The results will show whether the tissue-specific expression of Paan-AG is controlled by tissue- specific regulatory element, and the location of such element(s). A negative result will guide our future research to focus on post-translational mechanisms as candidates for tissue-specific expression of Paan-AG, and by inference, HLA-G. TO PUBLIC HEATH: Understanding the function of HLA-G is critical because of the potential therapeutic use of recombinant HLA-G proteins in the management of pregnancy complications or in transplantation. The baboon's reproductive system closely resembles that of human in terms of maturation sequence of fertilized eggs, implantation and placentation process, and in production of HLA-G- like proteins (Paan-AG) in the placenta. Thus the baboon is clearly an excellent model for HLA-G functional experiments, and testing the therapeutic applications of HLA-G in human pregnancy and transplantation. ? ? ? ?
