363 A CRISPR/dCas9 Epigenetic Therapuetic Approach for CASK-Related MICPCH

Abstract

OBJECTIVES/GOALS: CASK-related microcephaly with pontine and cerebellar hypoplasia (MICPCH) is a rare X-linked neurodevelopmental disorder caused by mutations in calcium/calmodulin-dependent serine protein kinase (CASK). We aim to rescue CASK expression via an CRISPR/dCas9 epigenetic therapeutic and create iPSC-based CASK relevant in vitro model systems. METHODS/STUDY POPULATION: As females have two X-chromosomes, disease causing mutations present with a 50/50 expression of mutant and wildtype, due to the mosaicism caused by random X-chromosome inactivation (XCI). This project will adapt an established CRISPR/dCas9 epigenetic approach to rescue expression from the silenced, wild-type CASK allele. We aim to accomplish this through testing different dCas9 orthologues and a guide RNA screen targeting the CASK promoter. Constructs will be tested for optimal targeting efficacy in vitro and assessed via RT-qPCR. Additionally, epigenetic modifications from our approach will be analyzed through bisulfite sequencing. We also aim to apply this epigenetic rescue technology in disease relevant cell lines and eventually in engineered patient mutation iPSC-derived neurons. RESULTS/ANTICIPATED RESULTS: Our results show the ability to target CASK and assess gene expression changes with CRISPR/dCas9 paired with an epigenetic modifier and transcriptional activator. Additionally, our fibroblast model with nonpathogenic single nucleotide polymorphisms within CASKallow for allele specific analysis of our targeted reactivation. We anticipate that following an increase of CASK expression, there would be a decrease in region specific promoter methylation. Further, with the identification of clinically described disease-causing point mutations that result in a loss of function of CASK protein, induction of the mutant sequence onto a healthy cell background will result in a similar reduction of CASK protein in our cell model. DISCUSSION/SIGNIFICANCE: This project will demonstrate the first therapeutic avenue for CASK-related MICPCH, and the potential to utilize targeted X-reactivation as a platform approach for X-linked disorders. Further, investigation of smaller dCas9 orthologues prepares our approach for future translational applications such as packaging into AAV for delivery.