Discovery and engineering of CRISPR/Cas systems

点击翻译按钮获取中文摘要

PROJECT SUMMARY/ABSTRACT: The long-term objectives of the proposed program are to (i) discover type V CRISPR/Cas systems in exotic microorganisms with unique features, (ii) elucidate a deeper understanding of the rules and mechanisms of CRISPR/Cas and apply it for engineering and improving its activity, and (iii) apply them for gene editing and diagnostic applications for a range of diseases. Although the type II CRISPR/Cas9 is the most studied genome editing tool, the type V CRISPR/Cas12 systems are the most diverse with a wide range of functionally distinct single-effector Cas12a-k nucleases that are emerging as next-generation tools for both genome editing and nucleic acid detection. The central hypothesis is that (i) since the type V systems are most diverse and relatively newer, only a handful (<5%) of these systems have been properly studied, while a vast majority of these systems are understudied and poorly characterized and therefore, a systematic study of these systems will enable novel tools for genome engineering, chromatin imaging, base editing, and diagnostics. (ii) A deeper understanding of the sequence-structure-activity relationship by engineering crRNA and Cas will enable the development of improved tools for metagenomic analysis, combinatorial enzymology, and multiplexing strategies for genome editing and diagnostic applications. While the type V CRISPR/Cas share challenges of poor delivery, low gene correction efficiency, and high off-target cleavage associated with other CRISPR-based genome editing tools, they possess both orthogonal and overlapping challenges for diagnostic applications, including a) low catalytic efficiency or poor sensitivity, b) high tolerance of mismatches or low specificity, c) poor stability for deployment, and d) lack of control, desirable for multiplexing. In the first program, novel orthologs of type V CRISPR/Cas systems will be discovered by metagenomic mining of exotic microorganisms that can thrive at extreme conditions followed by expression and purification of Cas enzymes and crRNAs, identification of protospacer adjacent motif requirement, and testing of enzymatic activity in a high-throughput fashion. In the second program, crRNAs and Cas proteins will be modified with various strategies to improve target specificity and activity. Modified crRNAs and Cas would allow elucidation of mechanisms of CRISPR/Cas systems that could further allow improved detection of target DNA or RNA. Finally, integrating novel and engineered CRISPR/Cas with model systems would enable the development of multiplexed technologies that will have broader impacts in the detection and treatment of a wide range of diseases. The PI's lab has already made significant contributions in all three proposed programs with several key collaborations and publications and is poised to run a successful research and training program. The expected outcomes of the support from the Maximizing Investigators' Research Award (MIRA) for Early Stage Investigators include the establishment of an integrative research program to discover, understand, and engineer unique CRISPR/Cas systems and addressing of major problems in their applications for diagnosing and treating infectious diseases, cancers, and genetic disorders.