Effective knockdown of Drosophila long non-coding RNAs by CRISPR interference

Area of Science:

• Molecular Biology
• Genetics
• Epigenetics

Background:

• Long non-coding RNAs (lncRNAs) regulate gene expression in metazoa.
• Some lncRNAs function independently of their transcripts, with transcription of the locus impacting target genes.
• Current loss-of-function methods are inadequate for studying lncRNA transcriptional roles.

Purpose of the Study:

• To develop and validate a novel method for analyzing lncRNA function based on transcriptional repression.
• To assess the efficacy of a minimal CRISPR interference (CRISPRi) system for targeting lncRNA loci.
• To demonstrate the utility of CRISPRi for in vivo loss-of-function studies of lncRNAs in a multicellular organism.

Main Methods:

• Utilized a minimal CRISPR interference (CRISPRi) system with catalytically inactive Cas9 (dCas9) and guide RNAs.
• Targeted the endogenous roX locus in Drosophila cells for robust and specific knockdown of roX1 and roX2 RNAs.
• Tested functional human and Drosophila codon-optimized dCas9 genes.
• Validated the CRISPRi system's ability to suppress transcription in vivo, leading to loss-of-function phenotypes.

Main Results:

• The minimal CRISPRi system achieved robust and specific knockdown of roX1 and roX2 RNAs without recruiting chromatin modifiers.
• Both human and Drosophila codon-optimized dCas9 genes demonstrated functional transcription repressive activity.
• The CRISPRi system successfully suppressed roX transcription in vivo, inducing loss-of-function phenotypes.
• The method was validated for the first time in a multicellular organism.

Conclusions:

• The minimal CRISPRi system provides an effective tool for gene silencing by targeting lncRNA transcription.
• This approach overcomes limitations of previous methods for studying lncRNA transcriptional function.
• The validated CRISPRi system expands the genetic toolkit for in situ lncRNA functional analysis across model organisms.