Life-long persistence of nuclear RNAs in the mouse brain [Hippocampus]

Genomic DNA residing in the nuclei of mammalian neurons can be as old as the organism itself. The life span of non-coding nuclear RNAs, which are critical for proper chromatin architecture and transcription regulation, has not been determined in adult tissues. Here, we report the identification and characterization of nuclear RNAs that do not turn over for at least two years in the adult mouse brain. These long-lived RNAs (LL-RNA) are stably retained in nuclei in a neural cell type-specific manner and are required for the maintenance of heterochromatin. Thus, the remarkable life span of neural cells may depend on both the molecular longevity of DNA for the storage of genetic information but also the extreme stability of RNA for the functional organization of chromatin. To identify long-retained RNAs in the hippocampus, mice were injected with Ethynyluridine (EU) on postnatal days 3-5 and hippocampus tissue was harvested at postnatal day P36. Controls were injected with PBS (vehicle) instead of EU. EU-labelled RNA was purified using Biotin-Click reaction and Streptavidin beads (Life Technologies). To determine background binding, RNA from PBS-treated samples underwent the same pulldown procedure. Total RNA sequencing was performed using Universal Plus Total RNA-Sequencing kit (TECAN).