Project Summary Autosomal dominant TPM3-related myopathy is primarily caused by missense mutations in the TPM3 gene that lead to muscle atrophy and weakness, and substantially affect patient’s quality of life. So far, there is no treatment for TPM3-related myopathy. K99 mentored phase: Currently, the absence of representative animal model systems limits the emergence of new pathophysiological findings in TPM3-related myopathy as well as potential therapeutics. To overcome this gap, we have recently generated CRISPR-based Tpm3 mice that carry one of the most prevalent mutations seen in patients. Our objectives are (1) to study the muscle pathology in the humanized mouse model of TPM3-related myopathy, and (2) to dissect the transcriptional changes in slow and fast myonuclear populations. Furthermore, we have characterized a tpm3-deficient zebrafish that show similar pathophysiological features of myopathy and holds promise for the development of complementary approaches that would be inconceivable with mammalian model systems. We also aim (3) to generate CRISPR-based tpm3 zebrafish that carry the same most prevalent mutation seen in patients. R00 independent phase: Zebrafish have become a powerful model to accelerate the discovery of potential therapeutics. Our objective is (4) to develop a drug screening assay in tpm3 zebrafish. Allele-specific RNA interference has also emerged as a powerful strategy for dominant inherited diseases such as TPM3-related myopathy. Based on our preliminary data, TPM3 haploinsufficiency is not the likely underlying mechanism of the myopathy. To complement our study in zebrafish, we aim (5) to screen for siRNAs that suppress the mutant allele expression without reducing the wild-type allele in in vitro experiments and to test their efficacy in vivo in our Tpm3 mouse. My long-term goal is to become an independent investigator with a lab that combines the genetic and molecular tools to study the neuromuscular diseases and develop therapeutic approaches. During the K99 mentored phase, I will gain additional skills in conceptual, technical and career development aspects which will enable me to make a successful transition to an independent position with my own research group. My short-term goals are (1) to acquire further skills in experimental procedures to study the muscle pathology in mouse and zebrafish, (2) to gain expertise in large-scale data analysis, (3) to improve my knowledge in the design of therapeutic strategies for neuromuscular disorders, (4) to obtain an independent tenure-track assistant professor position, and (5) to successfully obtain R01 funding within 5 years of this proposal.