Basic Biology V
$1 139 310
Krabbe disease (KD) is a devastating disease that affects neural development and causes early death. The most common form of KD occurs within the first six months of life and infants usually die by the age of two. Symptoms include being easily irritable, having difficulty in swallowing, muscle stiffness, seizures, cognitive and sensory deterioration. There is no cure and the treatments available only relieve the symptoms temporarily. Recently, deficits in several types of nervous system cells have been reported for KD, including the accumulation of a toxic compound and early cell death. This is due to a defect in a special cell compartment called the lysosome, which degrades unwanted biomolecules by serving as the waste disposal system of the cells. We have generated special cells, called induced pluripotent stem cells (iPSCs), from the skin cells of KD patients, and coaxed them to differentiate into nervous system cells. We propose to study these cells to find out what causes the degeneration and death of KD nervous system cells. Furthermore, these cells will provide a novel, unprecedented platform to screen for new drugs and to test novel treatments developed for KD. We expect our results will not only benefit KD patients, but also be beneficial to patients suffering from other neurological diseases that involve lysosomal defects and neuronal degeneration, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis.
Statement of Benefit to California:
Stem cells provide great hope for the treatment of a variety of human diseases, including neurological disorders, which are usually devastating. KD is one such disorder, whose most common form is infantile and KD children usually die by the age of two. This disease is found in all ethnic groups. It is estimated that California has approximately 12% of all US cases of KD, and at present, there is no cure; treatment is primarily supportive and symptomatic. Therefore, there is a real need to understand the underlying mechanisms of this disease in order to develop an effective treatment strategy. At present, the primary defect of this disease is thought to be the deficiency of an enzyme that functions in the lysosomes of cells. Our proposal to establish stem cell-based cellular models for KD could lead to a better understanding of the underlying pathological mechanisms for KD, and to the development of new KD therapies that will have great benefits for Californian health care patients, and also for the Californian pharmaceutical and biotechnology industries. In addition to benefiting KD patients, we expect that our approach and results will also be relevant and translatable to other neurological diseases that have been reported to involve lysosomal defects, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis. Therefore, our research could meet the need of a broad range of Californians.
This proposal aims to establish the mechanistic basis for Krabbe’s Disease (KD), a lysosomal disorder associated with diminished levels of the GalC enzyme. The most common form of KD appears in the first 6 months of life, and affected children usually die of the disease by age 2. The proposed research will utilize pre-established induced pluripotent stem cells (iPSCs) derived from KD skin cells and control cells that have been corrected for the gene defect. The PI will differentiate these cells to neuronal stem cells (NSCs) in order to determine the molecular basis for deficiencies in self-renewal of KD NSCs and investigate causes of degeneration and death KD nervous system cells. The PI also plans to identify the key signaling pathways that contribute to these defects in KD patients. This is a Fundamental Mechanisms application that could lead to identification of novel treatments for KD, a devastating neuronal disease with no current cure. Significance and Innovation - The project addresses an unsolved problem, the molecular etiology of KD. - The hypothesized signaling pathway to be examined may provide a novel therapeutic target for KD, which provides an innovative element to the proposal. However, the candidate target molecules to be investigated are narrowly selected and obvious ones, rather than those found by unbiased approaches. - The overall significance of the proposal is limited, based on its narrow focus, some of which is not well founded in preliminary data. - Reviewers felt that the proposal lacked rigorous characterization of cellular defects in KD specimens. There was concern that even though proposed experiments could be interpreted, the knowledge gained was likely to be only incremental. Feasibility and Experimental Design - The proposed studies are supported by relevant preliminary work including the generation of a large panel of appropriate iPSC lines together with control lines that have been corrected for appropriate GalC expression. This in vitro system is a key strength of the proposal. - Reviewers found many of the proposed experiments too narrowly focused on several specific hypotheses that are not convincing supported by preliminary data. - Generally, experimental details appear well thought-out and use established techniques. - The project lacks an unbiased appraisal of cellular and molecular phenotypes that could provide novel insights into KD disease mechanisms. Principal Investigator (PI) and Research Team - The applicant is an established PI with proven experience in investigating molecular mechanisms controlling NSC identity, self-renewal and differentiation. - The PI has assembled a team of researchers with appropriate expertise for the proposed experiments. Appropriate collaborations have been established. - The PI has an excellent record of productivity and publication. Responsiveness to the RFA - The application was deemed responsive to the RFA in that it uses an iPSC-based model to investigate basic disease mechanisms. No concerns about responsiveness were noted by the reviewers.