Interest Areas of Dr. Roberts' Research Group
Although a recent past interest of my laboratory has been to study the transcriptional control of expression and the evolution of the interferon-tau genes (IFNT), whose protein products play a crucial role in establishing communication between the conceptus and mother during early pregnancy of cattle, this work has largely been superseded by work on pluripotent and multipotent stem cells from both ungulate species and humans.
A major emphasis in the laboratory is the utilization of human embryonic stem cells (hESC) as models for trophoblast differentiation. These cells can be directed to form colonies with many features of trophoblast when they are exposed to the growth factor BMP4. We are using this model system to explore the initial events that specify trophoblast, the progressive conversion of these cells to more differentiated lineages (especially one with the invasive phenotype of extravillous trophoblast), and the role of oxygen in the differentiation process. A related area of interest involves induced pluripotent stem cells (iPSC) derived from umbilical cords of babies born to mothers who suffered from pre-eclampsia (PE). The goal here is to reprogram outgrowths of mesenchyme from the cord tissue, reprogram these cells to form iPSC, and convert the reprogrammed cells to the trophoblast lineage with BMP4 treatment. This step will enable us to essentially re-create a copy of the extravillous trophoblast (EVT) from the infants. The properties of these cells can then be compared with EVT generated from cord cells from pregnancies not complicated by PE. The hypothesis underpinning this aim is that some forms of PE are initiated by genetically-based placental pathology, and that these abnormalities will be manifested in the phenotype of EVT generated from umbilical cord-derived iPSC.
In a second area with Toshihiko Ezashi, a Research Assistant Professor, the laboratory has created induced pluripotent stem cells (iPSC) from porcine embryonic fibroblasts by re-programming. We are attempting to improve the efficiency of this process and exploring the possible use of such cells for tissue grafts of pigs. Reprogramming has also led to the production of cell lines with the properties of trophoblast, thereby providing a potential source of trophoblast stem cells and a means for studying trophoblast specification.
A related third area is to utilize iPSC derived from the inner cell mass (ICM) of porcine blastocysts to clone genetically modified pigs by nuclear transfer (NT) procedures. In our laboratory, the ICM-derived iPSC so far generated are LIF-dependent, have short cell cycle intervals and resemble mouse embryonic stem cells (ESC). They can survive multiple passages without senescing and are, therefore, suitable for introduction of multiple genetic changes under extended pharmacological selection. As the cells are pluripotent and “undifferentiated”, and possibly carry the epigenetic “memory” of the ICM from which they originated, they may be more easily reprogrammed during cloning than other somatic cell types and provide fewer abnormalities in offspring born. Accordingly, these cells are likely to have considerable potential for manipulating porcine genetics, and hence be of value to the livestock industry and to the biomedical research in general.
The laboratory is supported by numerous grants from the National Institutes of Health (NIH) and the United States Department of Agriculture (USDA), and has recently received support from the University of Missouri Research Board and the Agricultural Experiment Station.