Terminal nucleotidyltransferase Tent2 microRNA tailing regulates excitatory/inhibitory balance in the hippocampus
One of the post-transcriptional mechanisms regulating the stability of RNA molecules involves the addition of non-templated nucleotides to their 3' ends, a process known as RNA tailing. To systematically investigate the physiological consequences of terminal nucleotidyltransferase TENT2 absence on RNA 3' end modifications in the mouse hippocampus we developed a new Tent2 knockout mouse. Electrophysiological measurements revealed increased excitability in Tent2 KO hippocampal neurons, and behavioral analyses showed decreased anxiety and improved fear extinction in these mice. At the molecular level, we observed a significant contribution of TENT2 to the monoadenylation of various classes of miRNAs, but found no effect of the enzyme's loss on the total poly(A) tail length of mRNAs, as measured by Direct Nanopore RNA sequencing. Alterations in the monoadenylation of a large population of microRNAs affected the overall mRNA abundance, particularly transcripts related synaptic transmission, which were downregulated in the hippocampus of Tent2 knockout mice. These changes explain the observed behavioral and electrophysiological alterations. Our data thus establish a link between TENT2-dependent microRNA tailing and the balance of inhibitory and excitatory neurotransmission.