CRISPRi enables isoform-specific loss-of-function screens and identification of gastric cancer-specific isoform dependencies

Rebecca Davies, Ling Liu, Sheng Taotao, Natasha Tuano, Richa Chaturvedi, Kie Kyon Huang, Catherine Itman, Amit Mandoli, Aditi Qamra, Changyuan Hu, David Powell, Roger J. Daly, Patrick Tan, Joseph Rosenbluh

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Abstract

Introduction: Genes contain multiple promoters that can drive the expression of various transcript isoforms. Although transcript isoforms from the same gene could have diverse and non-overlapping functions, current loss-of-function methodologies are not able to differentiate between isoform-specific phenotypes. Results: Here, we show that CRISPR interference (CRISPRi) can be adopted for targeting specific promoters within a gene, enabling isoform-specific loss-of-function genetic screens. We use this strategy to test functional dependencies of 820 transcript isoforms that are gained in gastric cancer (GC). We identify a subset of GC-gained transcript isoform dependencies, and of these, we validate CIT kinase as a novel GC dependency. We further show that some genes express isoforms with opposite functions. Specifically, we find that the tumour suppressor ZFHX3 expresses an isoform that has a paradoxical oncogenic role that correlates with poor patient outcome. Conclusions: Our work finds isoform-specific phenotypes that would not be identified using current loss-of-function approaches that are not designed to target specific transcript isoforms.

Original languageEnglish
Article number47
Number of pages19
JournalGenome Biology
Volume22
Issue number1
DOIs
Publication statusPublished - 26 Jan 2021

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