CMTR1-catalyzed 2'-O-methylation promotes NMDA receptor signaling, long-term potentiation and memory

Eukaryotic mRNA includes a 5'-end m7G cap to prevent degradation and enable cap-dependent translation. The first transcribed ribonucleotide undergoes additional 2'-O-ribose methylation by Cap Methyltransferase 1 (CMTR1). Although this modification impacts gene expression, its physiological role remains largely unclear. High CMTR1 expression in the adult hippocampus prompted us to examine its role in learning and memory. In CMTR1-deficient hippocampi, numerous downregulated genes from transcriptome and proteome analyses were linked to glutamatergic synapses, including N-methyl-D-aspartate receptor (NMDAR) subunits. We generated CMTR1 conditional knockout mice targeting forebrain excitatory neurons and observed deficits in long-term potentiation (LTP) and spatial memory consolidation. D-cycloserine, an NMDAR allosteric agonist, restored memory consolidation and NMDAR hypofunction in these mice. Additionally, re-expression of wild-type, but not catalytically inactive, CMTR1 in hippocampal CA1 neurons rescued LTP and memory deficits. Our findings highlight the role of CMTR1 in regulating NMDAR signaling, which is critical for synaptic plasticity and memory consolidation.