Histone modifications are fundamental epigenetic regulators that control many crucial cellular processes. However, whether these marks can be passed on from mammalian gametes to the next generation is a long-standing question that remains unanswered. Here, by developing a highly sensitive approach, STAR ChIP-seq, we provide a panoramic view of the landscape of H3K4me3, a histone hallmark for transcription initiation, from developing gametes to post-implantation embryos. We find that upon fertilization, extensive reprogramming occurs on the paternal genome, as H3K4me3 peaks are depleted in zygotes but are readily observed after major zygotic genome activation at the late two-cell stage. On the maternal genome, we unexpectedly find a non-canonical form of H3K4me3 (ncH3K4me3) in full-grown and mature oocytes, which exists as broad peaks at promoters and a large number of distal loci. Such broad H3K4me3 peaks are in contrast to the typical sharp H3K4me3 peaks restricted to CpG-rich regions of promoters. Notably, ncH3K4me3 in oocytes overlaps almost exclusively with partially methylated DNA domains. It is then inherited in pre-implantation embryos, before being erased in the late two-cell embryos, when canonical H3K4me3 starts to be established. The removal of ncH3K4me3 requires zygotic transcription but is independent of DNA replication-mediated passive dilution. Finally, downregulation of H3K4me3 in full-grown oocytes by overexpression of the H3K4me3 demethylase KDM5B is associated with defects in genome silencing. Taken together, these data unveil inheritance and highly dynamic reprogramming of the epigenome in early mammalian development.

In mammals, extensive chromatin reorganization is essential for reprogramming terminally committed gametes to a totipotent state during preimplantation development. However, the global chromatin landscape and its dynamics in this period remain unexplored. Here we report a genome-wide map of accessible chromatin in mouse preimplantation embryos using an improved assay for transposase-accessible chromatin with high throughput sequencing (ATAC-seq) approach with CRISPR/Cas9-assisted mitochondrial DNA depletion. We show that despite extensive parental asymmetry in DNA methylomes, the chromatin accessibility between the parental genomes is globally comparable after major zygotic genome activation (ZGA). Accessible chromatin in early embryos is widely shaped by transposable elements and overlaps extensively with putative cis-regulatory sequences. Unexpectedly, accessible chromatin is also found near the transcription end sites of active genes. By integrating the maps of cis-regulatory elements and single-cell transcriptomes, we construct the regulatory network of early development, which helps to identify the key modulators for lineage specification. Finally, we find that the activities of cis-regulatory elements and their associated open chromatin diminished before major ZGA. Surprisingly, we observed many loci showing non-canonical, large open chromatin domains over the entire transcribed units in minor ZGA, supporting the presence of an unusually permissive chromatin state. Together, these data reveal a unique spatiotemporal chromatin configuration that accompanies early mammalian development.

Importance Germline pathogenic variants in BRCA1 and BRCA2 predispose to an increased lifetime risk of breast cancer. However, the relevance of germline variants in other genes from multigene hereditary cancer testing panels is not well defined. Objective To determine the risks of breast cancer associated with germline variants in cancer predisposition genes. Design, Setting, and Participants A study population of 65 057 patients with breast cancer receiving germline genetic testing of cancer predisposition genes with hereditary cancer multigene panels. Associations between pathogenic variants in non-BRCA1 and non-BRCA2 predisposition genes and breast cancer risk were estimated in a case-control analysis of patients with breast cancer and Exome Aggregation Consortium reference controls. The women underwent testing between March 15, 2012, and June 30, 2016. Main Outcomes and Measures Breast cancer risk conferred by pathogenic variants in non-BRCA1 and non-BRCA2 predisposition genes. Results The mean (SD) age at diagnosis for the 65 057 women included in the analysis was 48.5 (11.1) years. The frequency of pathogenic variants in 21 panel genes identified in 41 611 consecutively tested white women with breast cancer was estimated at 10.2%. After exclusion of BRCA1, BRCA2, and syndromic breast cancer genes (CDH1, PTEN, and TP53), observed pathogenic variants in 5 of 16 genes were associated with high or moderately increased risks ofbreast cancer: ATM (OR, 2.78; 95% CI, 2.22-3.62), BARD1 (OR, 2.16; 95% CI, 1.31-3.63), CHEK2 (OR, 1.48; 95% CI, 1.31-1.67), PALB2 (OR, 7.46; 95% CI, 5.12-11.19), and RAD51D (OR, 3.07; 95% CI, 1.21-7.88). Conversely, variants in the BRIP1 and RAD51C ovarian cancer risk genes; the MREHA, RAD50, and NBN MRN complex genes; the MLH1 and PMS2 mismatch repair genes; and NF1 were not associated with increased risks of breast cancer. Conclusions and Relevance This study establishes several panel genes as high- and moderate-risk breast cancer genes and provides estimates of breast cancer risk associated with pathogenic variants in these genes among individuals qualifying for clinical genetic testing.

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IMPORTANCE Individuals genetically predisposed to pancreatic cancer may benefit from early detection. Genes that predispose to pancreatic cancer and the risks of pancreatic cancer associated with mutations in these genes are not well defined. OBJECTIVE To determine whether inherited germline mutations in cancer predisposition genes are associated with increased risks of pancreatic cancer. DESIGN, SETTING, AND PARTICIPANTS Case-control analysis to identify pancreatic cancer predisposition genes; longitudinal analysis of patients with pancreatic cancer for prognosis. The study included 3030 adults diagnosed as having pancreatic cancer and enrolled in a Mayo Clinic registry between October 12, 2000, and March 31, 2016, with last follow-up on June 22, 2017. Reference controls were 123 136 individuals with exome sequence data in the public Genome Aggregation Database and 53 105 in the Exome Aggregation Consortium database. EXPOSURES Individuals were classified based on carrying a deleterious mutation in cancer predisposition genes and having a personal or family history of cancer. MAIN OUTCOMES AND MEASURES Germline mutations in coding regions of 21 cancer predisposition genes were identified by sequencing of products from a custom multiplex polymerase chain reaction–based panel; associations of genes with pancreatic cancer were assessed by comparing frequency of mutations in genes of pancreatic cancer patients with those of reference controls. RESULTS Comparing 3030 case patients with pancreatic cancer (43.2% female; 95.6% non-Hispanic white; mean age at diagnosis, 65.3 [SD, 10.7] years) with reference controls, significant associations were observed between pancreatic cancer and mutations in CDKN2A (0.3% of cases and 0.02% of controls; odds ratio [OR], 12.33; 95% CI, 5.43–25.61); TP53 (0.2% of cases and 0.02% of controls; OR, 6.70; 95% CI, 2.52–14.95); MLH1 (0.13% of cases and 0.02% of controls; OR, 6.66; 95% CI, 1.94–17.53); BRCA2 (1.9% of cases and 0.3% of controls; OR, 6.20; 95% CI, 4.62–8.17); ATM (2.3% of cases and 0.37% of controls; OR, 5.71; 95% CI, 4.38–7.33); and BRCA1 (0.6% of cases and 0.2% of controls; OR, 2.58; 95% CI, 1.54–4.05). CONCLUSIONS AND RELEVANCE In this case-control study, mutations in 6 genes associated with pancreatic cancer were found in 5.5% of all0 pancreatic cancer patients, including 7.9% of patients with a family history of pancreatic cancer and 5.2% of patients without a family history of pancreatic cancer. Further research is needed for replication in other populations.