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N 6 -methyladenosine (m 6 A) is an abundant RNA modification that plays critical roles in RNA regulation and cellular function. Global m 6 A profiling has revealed important aspects of m 6 A distribution and function, but to date such studies have been restricted to large populations of cells. Here, we develop a method to identify m 6 A sites transcriptome-wide in single cells. We uncover surprising heterogeneity in the presence and abundance of m 6 A sites across individual cells and identify differentially methylated mRNAs across the cell cycle. Additionally, we show that cellular subpopulations can be distinguished based on their RNA methylation signatures, independent from gene expression. These studies reveal fundamental features of m 6 A that have been missed by m 6 A profiling of bulk cells and suggest the presence of cell-intrinsic mechanisms for m 6 A deposition., Competing Interests: Declaration of interests K.D.M. has filed a patent application for the DART-seq technology through Duke University., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Nuclear RNA interference (RNAi) pathways work together with histone modifications to regulate gene expression and enact an adaptive response to transposable RNA elements. In the germline, nuclear RNAi can lead to trans-generational epigenetic inheritance (TEI) of gene silencing. We identified and characterized a family of nuclear Argonaute-interacting proteins (ENRIs) that control the strength and target specificity of nuclear RNAi in C. elegans, ensuring faithful inheritance of epigenetic memories. ENRI-1/2 prevent misloading of the nuclear Argonaute NRDE-3 with small RNAs that normally effect maternal piRNAs, which prevents precocious nuclear translocation of NRDE-3 in the early embryo. Additionally, they are negative regulators of nuclear RNAi triggered from exogenous sources. Loss of ENRI-3, an unstable protein expressed mostly in the male germline, misdirects the RNAi response to transposable elements and impairs TEI. The ENRIs determine the potency and specificity of nuclear RNAi responses by gating small RNAs into specific nuclear Argonautes., Competing Interests: Declaration of Interests E.A.M. is a founder and director of STORM Therapeutics. This company has not contributed to this research in any way. The authors declare no competing interests., (Copyright © 2020. Published by Elsevier Inc.)