Genetics and imaging to assess oocyte and preimplantation embryo health

Abstract

Two major criteria are currently used in human assisted reproductive technologies (ART) to evaluate oocyte and preimplantation embryo health: (1) rate of preimplantation embryonic development; and (2) overall morphology. A major gene that regulates the rate of preimplantation development is the preimplantation embryo development (Ped) gene, discovered in our laboratory. In mice, presence of the Ped gene product, Qa-2 protein, results in a fast rate of preimplantation embryonic development, compared with a slow rate of preimplantation embryonic development for embryos that are lacking Qa-2 protein. Moreover, mice that express Qa-2 protein have an overall reproductive advantage that extends beyond the preimplantation period, including higher survival to birth, higher birthweight, and higher survival to weaning. Data are presented that suggest that Qa-2 increases the rate of development of early embryos by acting as a cell-signalling molecule and that phosphatidylinositol-32 kinase is involved in the cell-signalling pathway. The most likely human homologue of Qa-2 has recently been identified as human leukocyte antigen (HLA)-G. Data are presented which show that HLA-G, like Qa-2, is located in lipid rafts, implying that HLA-G also acts as a signalling molecule. In order to better evaluate the second criterion used in ART (i.e. overall morphology), a unique and innovative imaging microscope has been constructed, the Keck 3-D fusion microscope (Keck 3DFM). The Keck 3DFM combines five different microscopic modes into a single platform, allowing multi-modal imaging of the specimen. One of the modes, the quadrature tomographic microscope (QTM), creates digital images of non-stained transparent cells by measuring changes in the index of refraction. Quadrature tomographic microscope images of oocytes and preimplantation mouse embryos are presented for the first time. The digital information from the QTM images should allow the number of cells in a preimplantation embryo to be counted non-invasively. The Keck 3DFM is also being used to assess mitochondrial distribution in mouse oocytes and embryos by using the k-means clustering algorithm. Both the number of cells in preimplantation embryos and mitochondrial distribution are related to oocyte and embryo health. New imaging data obtained from the Keck 3DFM, combined with genetic and biochemical approaches, have the promise of being able to distinguish healthy from unhealthy oocytes and embryos in a non-invasive manner. The goal is to apply the information from our mouse model system to the clinic in order to identify one and only one healthy embryo for transfer back to the mother undergoing an ART procedure. This approach has the potential to increase the success rate of ART and to decrease the high, and undesirable, multiple birth rate presently associated with ART.

Analysis of HLA-G in Maternal Plasma, Follicular Fluid, and Preimplantation Embryos Reveal an Asymmetric Pattern of Expression

“…In previous studies, HLA-G has been found colocalized in lipid rafts in JEG-3 cells (32). To facilitate focus on the cell membrane of the embryo and locate any HLA-G that may be present in low copy number, we double surface stained some embryos with cholera toxin B conjugated with Alexa Fluor-488 and MEM-G/9-PhyE.…”

Dynamic Expression of Qa-2 during Acute Graft Rejection

“…Qa-2 has structural and immunological characteristics similar to those of HLA-G. Reportedly, Qa-2 can increase the rate of development of early embryos and assist in their survival (23), as well as protect tumor cells from NK cell-and lymphokine-activated killer cell-mediated cytolysis (24). However, the relationship of Qa-2 expression with immunosuppressive agents and graft rejection remains unexplored.…”

Multimodal imaging of mouse development: Tools for the postgenomic era

“…Last, several research groups have focused on building new tools for image rendering and analysis for biological data mining. Although this is a vast area of research, I have included references for a small sampling of papers and reviews to provide examples of ongoing research (Lansford et al, 2001;AlKofahi et al, 2002AlKofahi et al, , 2003Jacobs et al, 2003;Megason and Fraser, 2003;Herskovits et al, 2004;Huang and Murphy, 2004;Warner et al, 2004;Ledesma-Carbayo et al, 2005;Liebling et al, 2005;Lin et al, 2005;Peng et al, 2005;Suhling et al, 2005;Toga, 2005;Tyszka et al, 2005a;Forouhar et al, 2006;Luders et al, 2006).…”