Histone Acetylome-wide Association Study of Autism Spectrum Disorder.

The association of histone modification changes with autism spectrum disorder (ASD) has not been systematically examined. We conducted a histone acetylome-wide association study (HAWAS) by performing H3K27ac chromatin immunoprecipitation sequencing (ChIP-seq) on 257 postmortem samples from ASD and matched control brains. Despite etiological heterogeneity, ≥68% of syndromic and idiopathic ASD cases shared a common acetylome signature at >5,000 cis-regulatory elements in prefrontal and temporal cortex. Similarly, multiple genes associated with rare genetic mutations in ASD showed common "epimutations." Acetylome aberrations in ASD were not attributable to genetic differentiation at cis-SNPs and highlighted genes involved in synaptic transmission, ion transport, epilepsy, behavioral abnormality, chemokinesis, histone deacetylation, and immunity. By correlating histone acetylation with genotype, we discovered >2,000 histone acetylation quantitative trait loci (haQTLs) in human brain regions, including four candidate causal variants for psychiatric diseases. Due to the relative stability of histone modifications postmortem, we anticipate that the HAWAS approach will be applicable to multiple diseases.

Cytoplasmic polyadenylation-mediated translational control of maternal mRNAs directs maternal-to-zygotic transition.

In the earliest stages of animal development following fertilization, maternally deposited mRNAs direct biological processes to the point of zygotic genome activation (ZGA). These maternal mRNAs undergo cytoplasmic polyadenylation (CPA), suggesting translational control of their activation. To elucidate the biological role of CPA during embryogenesis, we performed genome-wide polysome profiling at several stages of zebrafish development. Our analysis revealed a correlation between CPA and polysome-association dynamics, demonstrating a coupling of translation to the CPA of maternal mRNAs. Pan-embryonic CPA inhibition disrupted the maternal-to-zygotic transition (MZT), causing a failure of developmental progression beyond the mid-blastula transition and changes in global gene expression that indicated a failure of ZGA and maternal mRNA clearance. Among the genes that were differentially expressed were those encoding chromatin modifiers and key transcription factors involved in ZGA, including nanog, pou5f3 and sox19b, which have distinct CPA dynamics. Our results establish the necessity of CPA for ensuring progression of the MZT. The RNA-seq data generated in this study represent a valuable zebrafish resource for the discovery of novel elements of the early embryonic transcriptome.

Zebrafish mRNA sequencing deciphers novelties in transcriptome dynamics during maternal to zygotic transition.

Maternally deposited mRNAs direct early development before the initiation of zygotic transcription during mid-blastula transition (MBT). To study mechanisms regulating this developmental event in zebrafish, we applied mRNA deep sequencing technology and generated comprehensive information and valuable resources on transcriptome dynamics during early embryonic (egg to early gastrulation) stages. Genome-wide transcriptome analysis documented at least 8000 maternal genes and identified the earliest cohort of zygotic transcripts. We determined expression levels of maternal and zygotic transcripts with the highest resolution possible using mRNA-seq and clustered them based on their expression pattern. We unravel delayed polyadenylation in a large cohort of maternal transcripts prior to the MBT for the first time in zebrafish. Blocking polyadenylation of these transcripts confirms their role in regulating development from the MBT onward. Our study also identified a large number of novel transcribed regions in annotated and unannotated regions of the genome, which will facilitate reannotation of the zebrafish genome. We also identified splice variants with an estimated frequency of 50%-60%. Taken together, our data constitute a useful genomic information and valuable transcriptome resource for gene discovery and for understanding the mechanisms of early embryogenesis in zebrafish.

Histone acetylome-wide associations in immune cells from individuals with active Mycobacterium tuberculosis infection.

Host cell chromatin changes are thought to play an important role in the pathogenesis of infectious diseases. Here we describe a histone acetylome-wide association study (HAWAS) of an infectious disease, on the basis of genome-wide H3K27 acetylation profiling of peripheral blood granulocytes and monocytes from persons with active Mycobacterium tuberculosis (Mtb) infection and healthy controls. We detected >2,000 differentially acetylated loci in either cell type in a Singapore Chinese discovery cohort (n = 46), which were validated in a subsequent multi-ethnic Singapore cohort (n = 29), as well as a longitudinal cohort from South Africa (n = 26), thus demonstrating that HAWAS can be independently corroborated. Acetylation changes were correlated with differential gene expression. Differential acetylation was enriched near potassium channel genes, including KCNJ15, which modulates apoptosis and promotes Mtb clearance in vitro. We performed histone acetylation quantitative trait locus (haQTL) analysis on the dataset and identified 69 candidate causal variants for immune phenotypes among granulocyte haQTLs and 83 among monocyte haQTLs. Our study provides proof-of-principle for HAWAS to infer mechanisms of host response to pathogens.