CRISPR/Cas9-mediated generation of GATA3 knockout in Bovine Fibroblast and MDBK cell lines to assess sgRNAs targeting...

GATA3 is expressed in the outer cells of the morula stage during embryonic development and is considered a key driver of the regulation of early lineage development in bovines. This research presents an optimised somatic cell validation resource, successfully generating GATA3 knockout (KO) Bovine Fetal Fibroblasts and MDBK cells using CRISPR/Cas9-mediated genome editing for their future implications in vivo studies designed to definitively understand the role of GATA3 in cell lineage specification and bovine embryo development. This involved designing single-guide RNAs (sgRNAs) targeting different regions of the GATA3 gene, cloning them into the px459 plasmid, delivering the CRISPR clone into bovine fibroblast cells and the MDBK cell line, screening for successful targeting and knockouts, and MiSeq analysis to verify successful disruption of the GATA3 gene. A total of eleven guides were designed targeting the functional domains in Exons 4 and 5 and the transcription initiation site in Exon 2. Designed guides were first optimized and screened using an in vitro cleavage assay. The guides with the best cutting efficiencies were then tested in vivo by targeting bovine fetal fibroblast (BFFs) and MDBK cell line followed by MiSeq analysis to verify the successful knockouts. A total of two effective guides were identified targeting the zinc-finger (ZnF) functional domains of the GATA3 gene (sgRNA#5 and sgRNA#8 in Exon 4 and Exon 5, respectively) and one in Exon 2 (sgRNA#1) targeting the transcription initiation site of the GATA3 gene. MiSeq data from targeted bovine cells showed indel frequency of 47.40%, 55.5%, and 42.4% in bovine fetal fibroblasts, 11.03%, 28.9% and 7.3% for MDBK cells for top three sgRNAs. Overall, MiSeq data for 3 selected sgRNAs showed successful disruption of the GATA3 gene, inserting a base pair 2-3 bp upstream of the PAM site, ultimately resulting in a premature stop codon TAA in the downstream region. This study established and validated highly efficient sgRNAs targeting the GATA3 gene, forming a molecular basis for forthcoming functional investigations in bovine embryos to explore gene function and protein-level effects.