One of the main objectives of stem cell biology is to create physiologically relevant cell types that can be used to either facilitate the study of or directly treat human disease. Tremendous progress towards these goals has been made in the area of motor neuron disease and spinal cord injury through the findings that motor neurons can be generated from human embryonic stem cells and induced pluripotent stem cells. These advances have made possible the creation of motor neurons from patients afflicted with neurodegenerative diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy that can be studied in the laboratory to determine the root causes of these diseases. In addition, stem cell-derived motor neurons could potentially serve as replacement cells that could be introduced into the spinal cord to recover motor functions in these patients, as well as those suffering from spinal cord injuries. A major assumption, however, is that human embryonic and induced pluripotent cell-derived motor neurons are identical to their normal counterparts. Despite its relevance, few studies of human motor neuron development have been carried out, and little information on the genetic and functional similarities between stem cell- and embryo-derived motor neurons has been obtained. The proposed research will provide important new insights into the profile of human motor neurons that must be recapitulated by stem cell studies. This approach is critical given that most of our knowledge on human motor neuron development is based on animal models. In addition, work with mouse embryonic stem cell-derived motor neurons has revealed limitations in the motor neuron subtypes that can be generated in culture, something others and we have also observed in human embryonic and induced pluripotent stem cell-derived motor neurons. The differences between embryo and stem cell-derived motor neurons are currently unknown, though our preliminary studies suggest that this deficiency may result from the inability of stem cell-derived motor neurons to express key regulators of motor neuron development. We will directly test this hypothesis by examining whether artificially expressing some of these important motor neuron fate determinants can alter the classes of motor neurons formed in culture and thereby broaden their innervation potential. Since most motor neuron diseases tend to affect certain motor neuron populations more than others, and that the pattern of motor innervation is highly specific to the type of cells formed, these studies will significantly advance our understanding of how the full repertoire of motor neuron subtypes may be created from stem cells to build disease models and generate therapeutically beneficial cells.
Neurological diseases are among the most debilitating medical conditions that affect millions of Californians each year, and many more worldwide. Few effective treatments for these diseases currently exist, in part because we know very little about the mechanisms underlying these conditions. Through the use of human embryonic stem cell and induced pluripotent stem cell technologies, it is now possible to create neurons from patients suffering from a variety of neurological disorders that can serve as the basis for cell culture-based models to study disease pathologies in an experimentally accessible setting. Our proposed research seeks to develop the means to form different classes of neurons, confirm their physiological identities, and establish a system for studying their neurological activity in a cell culture setting. The generation of these models will constitute an important step towards understanding the basis of neurological illnesses and developing a platform for the discovery of drugs that can alter disease progression and improve the productivity and quality of life for many Californians. Moreover, progress in this field will help solidify the leadership role of California in bringing stem cell research to the clinic, and stimulate the future growth of the biotechnology and pharmaceutical industries within the state.
The goal of this proposal is to profile motor neurons (MNs) derived from human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) and to compare the molecular, genetic, and physiological similarity and differences of derived MNs to primary embryonic human MNs. This proposal will additionally address challenges in generating MNs in culture. MNs generated from human pluripotent cells in vitro, thus far, represent only a subset of the motor neuron cell types found in vivo. The applicant hypothesizes that the regulated expression of key transcription factors will direct hESCs and iPSCs to become specific MN classes, broadening their therapeutic and disease modeling potential. The applicant will also investigate the innervation capacity of hESC- and iPSC-derived MNs using both in vitro MN and muscle co-culture system and in vivo transplantation experiments.
Reviewers agreed that this proposal addresses a major unsolved problem and could have a profound impact. The significance of the project is one of its major strengths, as successful accomplishment of the aims will both improve our understanding of basic biological mechanisms of motor neuron development and impact transplantation strategies for the treatment of motor neuron disease and spinal cord injury. One reviewer’s concern regarding the appropriateness of transplantation for treatment of diseases like amyotrophic lateral sclerosis did not dampen that reviewer’s enthusiasm for the contribution the proposal would have in understanding motor neuron development. Reviewers described the proposal as highly innovative with a true focus on human stem cell biology and a sound scientific rationale.
Reviewers praised the research plan as well-written and logical with ambitious and technically challenging achievable and creative aims. Reviewers appreciated the extremely strong preliminary data, which demonstrates clearly that the basic methods to derive MNs from hESCs and iPSCs are well-established in this group. They noted that one of the most attractive aspects of the proposal is the comparison of in vitro differentiated MNs to the in vivo correlates obtained from human tissue. The reviewers considered the experimental approach appropriate and sophisticated with clever touches throughout the proposal.
Reviewers agreed that the applicant, although at an early stage of career development, has already contributed to the field and is well known and respected in the neurobiology field. They praised the applicant’s impressive publication record and described the applicant’s qualifications to carry out the proposed research as outstanding. Reviewers appreciated the contributions of two key collaborators who will lend essential support for electrophysiology, stem cell biology and expression profiling. They described the institution as one of the best for these studies, and the assembled research team as perfectly qualified.
Overall, reviewers were extremely enthusiastic about this proposal. They appreciated its logical design and impressive preliminary data as well as the significance of the scientific problem it addresses.