Dana Thyra Byrd - US grants

Project Summary PACS1 Syndrome is a de novo neurogenetic disorder affecting young children, characterized by distinct dysmorphic facial features, intellectual disability and developmental delays. In all cases identified throughout the world, individuals have the same exact amino acid substitution, p.R203W, in a highly conserved position of the PACS1 protein. PACS1 (Phosphofurin Acidic Cluster Sorting Protein 1) was first identified by its interaction with the proprotein convertase furin, and subsequent studies have revealed its role in secretary pathway, particularly the trans-Golgi network. PACS1 is conserved in all animals, and humans express an additional ortholog, PACS2. All PACS proteins contain multiple functional domains including the furin-binding region, in which the PACS1 syndrome variant resides. Currently, most understanding of PACS1 function is from cultured cells. A key question that must be addressed is how R203W changes PACS1 function and results in syndrome symptoms. The nematode C. elegans is a tractable model for studying human disease genes. A single C. elegans pacs-1 gene encodes a protein that shares all conserved domains, and the furin-binding region is especially well conserved between C. elegans and humans (45% identical/70% similar) with the disease variant site, R203, denoted as R116 in C. elegans. Here, we have generated a cePACS-1(R116W) model, using genome-editing. Additionally, using drugs to probe neuronal function, we found that pacs-1(R116W) animals are resistant to the paralyzing effect of the choline esterase inhibitor aldicarb. Consistent with its neuronal function, we also found that endogenous PACS-1 is expressed in the nervous system. Our C. elegans pacs-1(R116W) provides the first germline-expressed model of PACS1 syndrome. In this R03 application, we propose to complete a chemical compound screen, using the LOPAC chemical library, for behavioral effects on our cePACS1 model. We will then test top candidate hits using additional cell biology and functional assays. The project goal is within the feasibility and guideline of R03 application. The outcome will be informative for the development of designer-strategies in treatment of PACS1 syndrome, and also aid further characterization of physiological mechanisms underlying PACS1 syndrome.