Loss of age-associated increase in m6A-modified RNA contributes to GABAergic dysregulation in Alzheimer's disease
Dysregulated RNA metabolism is a significant feature of Alzheimers disease (AD), yet how post-transcriptional RNA modifications like N6-methyladenosine (m6A) are altered in AD is unknown. Here, we performed deamination adjacent to RNA modification targets (DART-seq) on human dorsolateral prefrontal cortices to assess changes in m6A with nucleotide resolution. In non-AD brains, m6A sites increased with age, predominantly within the 3'UTR of transcripts encoding tripartite synapse proteins. In contrast, AD brains lost the age-associated m6A site increase and exhibited global hypomethylation of transcripts, including MAPT and APP. Hypomethylated genes involved with GABAergic signaling, glutamate transport, and ubiquitin-mediated proteolysis exhibited reduced expression, connecting m6A to synaptic excitotoxicity and disrupted proteostasis in AD. Site-specific m6A levels were linked with GABRA1 expression and protein levels, but this relationship was abolished in AD. Our findings provide insight into post-transcriptional mechanisms of dysregulated RNA metabolism in AD that are related to aging and GABAergic regulation. HIGHLIGHTSO_LIWith age, the number of m6A sites increases among Control cases (lacking AD pathology) but remains unchanged in AD cases. C_LIO_LITranscripts are globally hypomethylated in AD cases. C_LIO_LIHypomethylation is linked to decreased mRNA expression of transcripts related to synaptic and proteostatic function in AD. C_LIO_LI3UTR-localized m6A sites lack typical association with transcript metabolism of GABRA1 in AD. C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=196 SRC="FIGDIR/small/651974v3_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@995c55org.highwire.dtl.DTLVardef@7d0619org.highwire.dtl.DTLVardef@1b6a20org.highwire.dtl.DTLVardef@1d47dce_HPS_FORMAT_FIGEXP M_FIG C_FIG