# Characterization and engineering of a compact genome editor for adeno-associated virus delivery to correct mutations causing cystic fibrosis > **NIH NIH F31** · UNIVERSITY OF CALIFORNIA BERKELEY · 2021 · $40,288 ## Abstract Project Summary/Abstract: Cystic fibrosis (CF) is a monogenic disease caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) gene, which encodes for an important ion channel protein. While some mutations result in the production of faulty CFTR protein, which can be modulated by small molecule therapies, rare nonsense mutations prevent the production of CFTR and are currently untreatable. With the recent explosion in genome editing technologies, such as CRISPR-Cas systems that can bind and cleave DNA with sequence specificity, there has been increasing interest in correcting mutations in CFTR to provide a single dose, permanent genetic cure for CF. However, current technologies for genome editing are larger than molecular delivery strategies can handle, hindering the possibility of translating into a genetic cure for CF. This study proposes the characterization and development of a compact genome editing tool that is compatible with proven delivery vehicles for genome editing of CFTR mutations. CasΦ is a recently discovered programmable endonuclease that is about half the size of other Cas nucleases and is functional in human genome editing. In order to better understand how CasΦ behaves in human genome editing, mainly how CasΦ recognizes intended DNA targets and discriminates from unintended DNA targets, high-throughput sequencing screens in human cell culture will be employed. CasΦ will additionally be molecularly engineered into an adenine base editor (CasΦ-ABE), a previously described set of tools that allows for sequence specific changes from A/T to C/G without the creation of a double-stranded DNA break. CasΦ-ABE could correct nonsense point mutations in CFTR, which are currently untreatable. Importantly, unlike current base editor technologies, CasΦ-ABE is compact enough to be compatible with delivery methods such as adeno-associated virus (AAV), which has been proven safe and effective in numerous clinical trials. At the conclusion of this study, CasΦ-ABE will be delivered by a single AAV to primary human bronchial epithelial cells with nonsense mutations in CFTR, an important first step toward developing a genetic therapy for CF. The findings of this study will better characterize how CasΦ, a unique genome editing tool, works in human cells. Additionally, this work includes the development of a CasΦ adenine base editor compatible with delivery via AAV to correct nonsense mutations in CFTR. This study paves the way for a potential in vivo gene editing therapy for CF. The University of California, Berkeley and the Innovative Genomics Institute offer a collaborative, interdisciplinary, and world-class scientific environment that when complemented by the expertise and resources of the Doudna Lab, will ensure the success of the proposed fellowship training plan. ## Key facts - **NIH application ID:** 10141099 - **Project number:** 1F31HL156468-01 - **Recipient organization:** UNIVERSITY OF CALIFORNIA BERKELEY - **Principal Investigator:** Connor Andrew Tsuchida - **Activity code:** F31 (R01, R21, SBIR, etc.) - **Funding institute:** NIH - **Fiscal year:** 2021 - **Award amount:** $40,288 - **Award type:** 1 - **Project period:** 2021-08-01 → 2024-07-31 ## Primary source NIH RePORTER: https://reporter.nih.gov/project-details/10141099 ## Citation > US National Institutes of Health, RePORTER application 10141099, Characterization and engineering of a compact genome editor for adeno-associated virus delivery to correct mutations causing cystic fibrosis (1F31HL156468-01). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10141099. Licensed CC0. --- *[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*