How Long a Fragment to Delete for an lncRNA Knockout?

Three standard designs, in increasing size:

The trade-off is consistent: larger deletions remove more transcript, and also more DNA that might have independent function.

If your claim is about the RNA: delete the minimum needed to abolish detectable transcript — usually the TSS and first exon — and verify absence of the transcript by qPCR across multiple amplicons, including the 3′ end.

If your claim is about the locus: delete the whole transcribed region, and state the claim at locus level.

If the locus overlaps a protein-coding gene or another non-coding gene: delete the smallest interval that abolishes your transcript while leaving the neighbour's promoter and exons intact; consider an exon-skipping or polyA-insertion design instead of a deletion.

• • Alternative TSSs. Many lncRNAs have multiple start sites; deleting one leaves the others active. Check CAGE or 5′-end data.
• • Overlapping features. miRNAs hosted in introns, enhancers in the gene body, CTCF sites at boundaries — map them first.
• • Neighbouring gene promoters. A deletion that removes a bidirectional promoter will produce a phenotype unrelated to your RNA.
• • Repeat content. Breakpoints in repeats make junction verification unreliable.
• • Transcript orientation and splicing. A single-exon lncRNA and a multi-exon lncRNA need different strategies.

1. Junction PCR and sequencing — both breakpoints.
2. Zygosity by digital PCR; heterozygous clones behave like hypomorphs.
3. Transcript absence using amplicons spanning the whole transcript, not only the deleted region — an alternative promoter can produce a truncated species.
4. Neighbour expression — the gene on each side, to detect collateral effects.
5. Two independent clones with different breakpoints where feasible.

Step 3 is where most knockouts fail quietly: the deleted region is gone, but a shorter transcript is still made.

• • Try CRISPRi at the TSS — repression without deletion.
• • Insert a polyA signal to terminate transcription at a chosen point.
• • Use an ASO to deplete the transcript and see whether the phenotype appears at all before investing in more clones.

EDITGENE designs lncRNA knockouts with mapped alternative TSSs, annotated overlapping features, sequenced breakpoints, ddPCR zygosity, whole-transcript absence confirmation, and neighbour-gene expression panels.

Tell us the locus. Contact EDITGENE to request a project consultation or quote.

Recommended sizes are indicative; the appropriate interval depends on transcript architecture, alternative start sites, and overlapping features at the locus.

Deletions larger than the transcript test a genomic region, not an RNA, and should be described accordingly.

• • Liu SJ, et al. CRISPRi-based genome-scale identification of functional long noncoding RNA loci in human cells. Science. 2017;355:eaah7111.
• • Engreitz JM, et al. Local regulation of gene expression by lncRNA promoters, transcription and splicing. Nature. 2016;539:452–455.
• • Statello L, et al. Gene regulation by long non-coding RNAs and its biological functions. Nature Reviews Molecular Cell Biology. 2021;22:96–118.