Microglia, the principal neuroimmune sentinels of the brain, continuously sense changes in their environment and respond to invading pathogens, toxins and cellular debris. Microglia exhibit plasticity and can assume neurotoxic or neuroprotective priming states that determine their responses to danger. We used direct RNA sequencing, without amplification or cDNA synthesis, to determine the quantitative transcriptomes of microglia of healthy adult and aged mice. We validated our findings by fluorescent dual in-situ hybridization, unbiased proteomic analysis and quantitative PCR. We report here that microglia have a distinct transcriptomic signature and express a unique cluster of transcripts encoding proteins for sensing endogenous ligands and microbes that we term the “sensome”. With aging, sensome transcripts for endogenous ligand recognition are downregulated, whereas those involved in microbe recognition and host defense are upregulated. In addition, aging is associated with an overall increase in expression of microglial genes involved in neuroprotection.

SUMMARY Polycomb proteins play essential roles in stem cell renewal and human disease. Recent studies of HOX genes and X-inactivation have provided evidence for RNA cofactors in Polycomb repressive complex 2 (PRC2). Here, we develop a RIP-seq method to capture the PRC2 transcriptome and identify a genome-wide pool of >9,000 PRC2-interacting RNAs in embryonic stem cells. The transcriptome includes antisense, intergenic, and promoter-associated transcripts, as well as many unannotated RNAs. A large number of transcripts occur within imprinted regions, oncogene and tumor suppressor loci, and stem-cell-related bivalent domains. We provide evidence for direct RNA-protein interactions, most likely via the Ezh2 subunit. We also identify Gtl2 RNA as a PRC2 cofactor that directs PRC2 to the reciprocally imprinted Dlk1 coding gene. Thus, Polycomb proteins interact with a genome-wide family of RNAs, some of which may be used as biomarkers and therapeutic targets for human disease.

SUMMARY Balanced chromosomal abnormalities (BCAs) represent a reservoir of single gene disruptions in neurodevelopmental disorders (NDD). We sequenced BCAs in autism and related NDDs, revealing disruption of 33 loci in four general categories: 1) genes associated with abnormal neurodevelopment (e.g., AUTS2, FOXP1, CDKL5), 2) single gene contributors to microdeletion syndromes (MBD5, SATB2, EHMT1, SNURF-SNRPN), 3) novel risk loci (e.g., CHD8, KIRREL3, ZNF507), and 4) genes associated with later onset psychiatric disorders (e.g., TCF4, ZNF804A, PDE10A, GRIN2B, ANK3). We also discovered profoundly increased burden of copy number variants among 19,556 neurodevelopmental cases compared to 13,991 controls (p = 2.07×10−47) and enrichment of polygenic risk alleles from autism and schizophrenia genome-wide association studies (p = 0.0018 and 0.0009, respectively). Our findings suggest a polygenic risk model of autism incorporating loci of strong effect and indicate that some neurodevelopmental genes are sensitive to perturbation by multiple mutational mechanisms, leading to variable phenotypic outcomes that manifest at different life stages.