Development Biology:Stem Cells and Origins of Adult Disease

1. Stem Cells
Stem cells allow us to dissect the key steps taken in cell regeneration and diversity and to recreate the basic processes of development and cell fate determination. The field of embryonic stem cells, which now includes the new induced pluripotent stem cells (iPS), has catapulted this work to the next level — stem cell therapy for patient-specific disease treatment. Very recently, three groups have shown the ability to reprogram adult human cells into embryonic cells and back into different adult cells. These iPS cells have then been used to treat and successfully ameliorate a model of sickle cell anemia in mice. The initial promise of stem cells to revolutionize cell-based therapies, tissue regeneration and transplantation medicine without rejection is gaining data-based support from the latest research and personalized drug development and screening, as well as the creation of new models of human diseases. Because of their ability to self-renew or differentiate into more specialized cell types, stem cell research offers many exciting opportunities for the science of the future and supports all of the goals identified above from understanding basic biological processes to developing new therapeutic interventions. Stem cells will be a dominant vehicle for translational research in the future. The initial promise of stem cells to revolutionize cell-based therapies, tissue regeneration and transplantation medicine without rejection is gaining data-based support from the latest research. Personalized drug development and screening, as well as the creation of new models of human diseases, are only months –  not years – away. David I. Gottlieb, PhD, and Kelle H. Moley, MD, are co-chairs of the Regenerative and Developmental Medicine Subcommittee at Washington University School of Medicine and have proposed an interdepartmental center as part of the Biomed21 initiative. Tim B. Schedl, PhD, is also an active member of this committee. These three investigators are a core group of developmental biologists interested in stem cell biology.

David I. Gottlieb, PhD, is professor of anatomy and neurobiology at Washington University School of Medicine. His lab’s focus is embryonic stem (ES) and neural stem (NS) cells and how a network of transcription factors guides development from the totipotent ES cell to a committed NS cell. He uses a model of mammalian neural development in which ES cells efficiently differentiate into neural stem cells in cell culture. Induction protocols are straightforward and involve culture in the presence of retinoic acid. They result in an efficient conversion of undifferentiated ES cells to neural cells. Mature neurons produced have the key physiological, morphological and molecular properties of primary cultured neurons derived from the central nervous system. Most significantly, they form functional chemical synapses that use either glutamate, GABA or glycine as neurotransmitters. ES cell-derived glial cells also correspond well with their normal counterparts. During induction, ES cells undergo a series of developmental steps that resemble key stages in the early mouse embryo. This supports the hypothesis that the in vitro pathway is a valid model of the normal developmental pathway leading to neurons and glia. The in vitro system combines three experimental strengths. It is suitable for genetic manipulation, affords large numbers of cells and allows precise manipulation of the culture environment. It is thus suitable for a wide variety of mechanistic studies in the areas of neural development and cell biology.

Kelle H. Moley, MD, is the James P. Crane Professor of Obstetrics and Gynecology, professor of cell biology and physiology, and vice chair of basic science research in the Department of Obstetrics and Gynecology at Washington University School of Medicine.

The adverse effects of maternal diabetes on embryo development and pregnancy outcomes have recently been shown to occur as early as the one-cell zygote stage. From animal and human studies it is clear that mammalian gametes and embryos are vulnerable to injury during the period of oocyte maturation as well as during pre-implantation stages of development. Maternal diabetes, insulin resistance and obesity all have adverse effects on pregnancy outcome. Glucose transport and metabolism are critical for oocyte maturation, blastocyst formation and further development. These maternal metabolic conditions all perturb glucose utilization at all stages of development. The primary focus of the Moley laboratory is on how these perturbations in mouse models translate into developmental abnormalities at a molecular level.

Using mouse embryonic stem cells as well as trophoblast stem cells, Moley focuses on the themes of glucose transport, insulin signaling, maternal type 1 and type 2 diabetes and preimplantation embryos. The main areas of study include: 1. Maternal diabetes and oocyte quality; 2. Insulin and IGF-1 signaling in blastocyst stage embryos; 3. Fetal origins of adult diseases; 4. GLUTs expression and Akt/ERK signaling in endometrium and non-genomic effects of estrogen; 5. Aberrant embryo autophagy leads to abnormal embryo development.

Tim Schedl, PhD, is professor of genetics and a member of the steering committee of the Reproductive Sciences T32 training grant in the Department of Obstetrics and Gynecology at Washington University School of Medicine. His research focuses on stem cell and germ cell development. Germ cells are unique in animals as they are the means by which genetic material and cytoplasmic constituents are perpetuated within any species. Schedl’s lab is studying three processes that are critical for this: 1) the decision of stem cells to proliferate versus initiate meiotic development; 2) control of progression through meiotic prophase and its coordination with oogenesis; and 3) control of germline sex determination. Little is known about these processes in any animal. We utilize Caenorhabditis elegans for our studies because its genetic sequence is entirely known and due to its transparency, tractable genetics and functional genomics.

The three germline processes are each initially regulated by cell-cell signaling. GLP-1/Notch receptor signaling controls the decision to proliferate versus initiate meiosis, RAS-ERK MAP kinase signaling acts at multiple points to control meiotic prophase cell cycle transitions and oogenesis, while the somatic gonad sex determination signal is unknown. GLD-1 is a translational regulator that functions in all three processes. Schedl’s lab uses genetic analysis, including high-throughput RNAi screens in sensitized genetic backgrounds, to identify genes that are necessary for different steps in germline development and to define the regulatory pathways in which they function. He has identified a number of new genes that function downstream of GLP-1/Notch signaling in redundant pathways to repress germline stem cell proliferation and promote initiation of meiotic development; disruption of particular sets of these pathways causes germline tumor formation. Schedl has used a combined computational, RNAi and biochemical approach to identify novel, evolutionarily conserved, phosphorylation targets of ERK MAP kinase that execute steps in oogenesis.

SUMMARY
Gottleib, Moley and Schedl have collaborated on several papers, projects and committees. Although all current projects focus on traditional models of mouse embryonic stem cells and germ cells, they are actively pursuing establishment of a Regenerative and Developmental Medicine Institute for generation of inducible pluripotent stem cells, which all three groups have started working with. Junior faculty interested in this area of investigation would have access to advanced techniques and facilities in this field as well as the expertise of these outstanding mentors.