Approximately 5,600 people in the U.S. are diagnosed with ALS each year. The incidence of ALS is two per 100,000 people, and it is estimated that as many as 30,000 Americans may have the disease at any given time. There are no effective therapies of ALS to-date. Recent genetic discoveries have pinpointed mutations that lead to the aberrant function of two proteins that bind to RNA transcripts in neurons. Misregulation of these RNA binding proteins is responsible for the aberrant levels and processing of hundreds of RNA representing genes that are important for neuronal survival and function. In this proposal, we will use neurons generated from patient cells that harbor the mutations in these RNA binding proteins to (1) prioritize a RNA “signature” unique to neurons suffering from the toxic function of these proteins and (2) as an abundant source of raw material to enable high-throughput screens of drug-like compounds that will bypass the mutations in the proteins and “correct” the RNA signature to resemble that of a healthy neuron. If successful, our unconventional approach that uses hundreds of parallel measurements of specific RNA events, will identify drugs that will treat ALS patients.
Our research aims to develop drug-like compounds that are aimed to treat Amyotrophic Lateral Sclerosis (ALS), which may be applicable to other neurological diseases that heavily impact Californians, such as Frontotemporal Lobar Degeneration, Parkinson’s and Alzheimer’s. The cellular resources and genomic assays that we are developing in this research will have great potential for future research and can be applied to other disease areas. The cells, in particular will be beneficial to California health care patients, pharmaceutical and biotechnology industries in terms of improved human models for drug discovery and toxicology testing. Our improved knowledge base will support our efforts as well as other Californian researchers to study stem cell models of neurological disease and design new diagnostics and treatments, thereby maintaining California's position as a leader in clinical research.
Our research aims to develop drug-like compounds that are aimed to treat Amyotrophic Lateral Sclerosis (ALS), which may be applicable to other neurological diseases that heavily impact Californians, such as Frontotemporal Lobar Degeneration, Parkinson’s and Alzheimer’s. In the first year, we have succeeded in improving the efficiency of motor neuron differentiation to generate high-quality motor neurons from induced pluripotent stem cells. We have generated RNA signatures from motor neurons differentiated from induced pluripotent stem cells from normal, healthy individuals whereby key proteins implicated in ALS are depleted using RNAi technology. We have also generated motor neurons from induced pluripotent stem cells that contained mutations in these key proteins and are in the process of applying genomic technologies to compare these cells to ones where we have depleted the proteins themselves. In parallel, we have started to optimize conditions for a small molecule screen to identify previously FDA-approved compounds that may alter aberrant and ALS-associated phenotypes in human cell lines.
In this reporting period, we have successfully generated lines that we have used to identify small molecules that alter the formation of aggregates in human neural progenitors and non-neuronal cell lines. These molecules will be tested for the reversal of aberrant RNA signatures in motor neurons from patients with ALS-associated mutations.
5,910 small molecule compounds sourced from 4 libraries of small molecules with drug-like properties as well as 2 small molecule libraries with neuroprotective properties from unrelated screens were subject to screens to prevent formation of stress granules in neuronal cells. Stress granules are relevant to amyotrophic lateral sclerosis as mutations in RNA binding proteins lead to cytoplasmic aggregates precipitated by these stress granules. In this reporting period (since 6 months ago), ~10 compounds remain effective at inhibiting stress granule formation in counter screens and secondary assays. Successfully, we have shown that a subset of these compounds can reduce stress granules in mutant-containing IPSC-derived motor neuron models of ALS.