Efficient manipulation of gene expression using Natronobacterium gregoryi Argonaute in zebrafish

Background: Natronobacterium gregoryi Argonaute (NgAgo) was found to reduce mRNA without generating detectable DNA double-strand breaks in a couple of endogenous genes in zebrafish, suggesting its potential as a tool for gene knockdown. However, little is known about how it interacts with nucleic acid molecules to interfere with gene expression. Results: In this study, we first confirmed that coinjection of NgAgo and gDNA downregulated target genes, generated gene-specific phenotypes and verified some factors (including 5' phosphorylation, GC ratio, and target positions) of gDNAs affecting gene downregulation. Therein, the sense and antisense gDNAs were equally effective, suggesting that NgAgo possibly binds to DNA. NgAgo-VP64 with gDNAs targeting promoters upregulated the target genes, further providing evidence that NgAgo interacts with genomic DNA and controls gene transcription. Finally, we explain the downregulation of NgAgo/gDNA target genes by interference with the process of gene transcription, which differs from that of morpholino oligonucleotides. Conclusions: The present study provides conclusions that NgAgo may target genomic DNA and that target positions and the gDNA GC ratio influence its regulation efficiency.