What this entity is
Canonical name: CRISPRi-based transcriptional knockdown for testing essential dark genes. 1
Known aliases: CRISPRi; CRISPR interference; Mobile-CRISPRi. 1
Stable external identifier: None was specified in the source document. 1
CRISPRi, or CRISPR interference, is a method recommended for transcriptionally reducing expression of essential genes whose complete disruption prevents recovery of viable mutants. 1
Key facts
The Functional Dark Matter report identified 9,557 essential dark genes among 57,011 dark genes. 1
These genes require a separate experimental strategy because standard RB-TnSeq, randomly barcoded transposon sequencing, yields no viable knockout fitness profiles for essential genes. 1
Essential-gene candidates were prioritized using gene-neighbor context, cross-organism conservation, phylogenetic breadth, domain annotations, and CRISPRi tractability. 1
Among all 57,011 dark genes, 30,190 (52.9%) shared a predicted operon with an annotated gene, and 97.2% had at least one annotated neighbor within a five-gene window. 1
The report cautions that the 97.2% neighborhood rate is expected in part because the genome-wide annotation rate was 75%. 1
The highest-ranked essential candidates were Escherichia coli Keio 14796, with score 0.875 and a YbeY domain; MR-1 200382, with score 0.874 and RimP_N/DUF150_C domains; and Klebsiella oxytoca BWI76_RS08540, with score 0.865 and OmpA/TIGR02802 domains. 1
The recommended workflow is CRISPRi knockdown followed by growth measurements under standard and stress conditions. 1
The report specifically recommends Mobile-CRISPRi for organisms with less-established genetic tools. 1
The newer truly-dark-gene analysis supports this strategy by proposing Mobile-CRISPRi for rapid functional testing of its prioritized candidates, including genes selected from fitness, annotation, orthology, genomic-context, and tractability evidence. 2
It also refines the experimental design: proposed follow-up includes motility assays for PV4/5210953 and nitrogen-limitation growth assays for ANA3/7026383, rather than relying only on generic stress measurements. 2
CRISPRi therefore addresses a limitation of gene-essentiality analysis: essential dark genes lack direct transposon-derived fitness magnitudes, so controlled knockdown can provide condition-specific phenotypes for testing their inferred functions. 1
The truly-dark-gene report cautions that some strong fitness phenotypes may reflect polar effects on downstream genes, so CRISPRi results should be interpreted with operon structure and neighboring-gene measurements in mind. 2
Condition-specific growth measurements can connect essential-gene knockdown effects to condition-specific fitness, while neighborhood and co-fitness evidence can refine candidate interpretation through co-fitness network architecture. 1
The source reports are summarized at Functional Dark Matter — Experimentally Prioritized Novel Genetic Systems and Truly Dark Genes — What Remains Unknown After Modern Annotation?. 1, 2