Cooperation of long noncoding RNA LOC100909675 and transcriptional regulator CTCF modulates Cdk1 transcript to control astrocyte proliferation

Astrocyte activation and proliferation contribute to glial scar formation during spinal cord injury (SCI), which limits nerve regeneration. LncRNAs are involved in astrocyte proliferation and act as novel epigenetic regulators. Here, we found that lncRNA-LOC100909675 (LOC9675) expression promptly increased after SCI and that reducing its expression decreased the proliferation and migration of the cultured spinal astrocytes. Depletion of LOC9675 reduced astrocyte proliferation and facilitated axonal regrowth after SCI. FISH detection and RT‒qPCR assays using nuclear/cytoplasmic RNAs revealed LOC9675 mainly localized in astrocytic nuclei. We next used RNA-seq to analyze gene expression profile alterations in LOC9675-depleted astrocytes and identified the CDK1 gene as a hub candidate. Our RNA pull-down and RNA immunoprecipitation assays showed that LOC9675 directly interacted with the transcriptional regulator CTCF. Luciferase reporter and ChIP assays, together with down/upregulated expression investigation, revealed that CTCF is a novel regulator of the CDK1 gene. Interestingly, we found that with the simultaneous overexpression of CTCF and LOC9675 in astrocytes, the CDK1 transcript was restored to the normal level. We then designed the deletion construct of LOC9675 by removing its interacting region with CTCF, and found this effect disappeared. A transcription inhibition assay using actinomycin D revealed that LOC9675 could stabilize Cdk1 mRNA, while LOC9675 depletion or binding with CTCF reduced Cdk1 mRNA stability. These data suggest that the cooperation between CTCF and LOC9675 regulates CDK1 transcription at a steady level, thereby strictly controlling astrocyte proliferation. This study provides a novel perspective on the regulation of the CDK1 gene transcript by lncRNA LOC9675.

CTCF (CCCTC-binding factor); Cdk1 (Cyclin dependent kinase 1); LncRNA LOC100909675; astrocyte; spinal cord injury.