Pcl-PRC2 is needed to generate high levels of H3-K27 trimethylation at Polycomb target genes

PRC2 is thought to be the histone methyltransferase (HMTase) responsible for H3-K27 trimethylation at Polycomb target genes. Here we report the biochemical purification and characterization of a distinct form of Drosophila PRC2 that contains the Polycomb group protein polycomblike (Pcl). Like PRC2, Pcl-PRC2 is an H3-K27-specific HMTase that mono-, di- and trimethylates H3-K27 in nucleosomes in vitro. Analysis of Drosophila mutants that lack Pcl unexpectedly reveals that Pcl-PRC2 is required to generate high levels of H3-K27 trimethylation at Polycomb target genes but is dispensable for the genome-wide H3-K27 mono- and dimethylation that is generated by PRC2. In Pcl mutants, Polycomb target genes become derepressed even though H3-K27 trimethylation at these genes is only reduced and not abolished, and even though targeting of the Polycomb protein complexes PhoRC and PRC1 to Polycomb response elements is not affected. Pcl-PRC2 is thus the HMTase that generates the high levels of H3-K27 trimethylation in Polycomb target genes that are needed to maintain a Polycomb-repressed chromatin state

Polycomb Repressive Complex 2 (PRC2) Restricts Hematopoietic Stem Cell Activity

Polycomb group proteins are transcriptional repressors that play a central role in the establishment and maintenance of gene expression patterns during development. Using mice with an N-ethyl-N-nitrosourea (ENU)-induced mutation in Suppressor of Zeste 12 (Suz12), a core component of Polycomb Repressive Complex 2 (PRC2), we show here that loss of Suz12 function enhances hematopoietic stem cell (HSC) activity. In addition to these effects on a wild-type genetic background, mutations in Suz12 are sufficient to ameliorate the stem cell defect and thrombocytopenia present in mice that lack the thrombopoietin receptor (c-Mpl). To investigate the molecular targets of the PRC2 complex in the HSC compartment, we examined changes in global patterns of gene expression in cells deficient in Suz12. We identified a distinct set of genes that are regulated by Suz12 in hematopoietic cells, including eight genes that appear to be highly responsive to PRC2 function within this compartment. These data suggest that PRC2 is required to maintain a specific gene expression pattern in hematopoiesis that is indispensable to normal stem cell function

Efficacy and Safety of Ticagrelor and Aspirin in Patients With Moderate Ischemic Stroke : An Exploratory Analysis of the THALES Randomized Clinical Trial.

Importance: Prior trials of dual antiplatelet therapy excluded patients with moderate ischemic stroke. These patients were included in the Acute Stroke or Transient Ischaemic Attack Treated With Ticagrelor and ASA for Prevention of Stroke and Death (THALES) trial, but results have not been reported separately, raising concerns about safety and efficacy in this subgroup. Objective: To evaluate the efficacy and safety of ticagrelor plus aspirin in patients with moderate ischemic stroke (National Institutes of Health Stroke Scale [NIHSS] score of 4 to 5). Design, Setting, and Participants: The THALES trial was a randomized trial conducted at 414 hospitals in 28 countries in January 2018 and December 2019. This exploratory analysis compared patients with moderate stroke (baseline NIHSS score of 4 to 5) with patients with less severe stroke (NIHSS score of 0 to 3). A total of 9983 patients with stroke were included in the present analysis, after excluding 2 patients with NIHSS scores greater than 5 and 1031 patients with transient ischemic attack. Data were analyzed from March to April 2021. Interventions: Ticagrelor (180-mg loading dose on day 1 followed by 90 mg twice daily on days 2 to 30) or placebo within 24 hours after symptom onset. All patients received aspirin, 300 to 325 mg, on day 1 followed by aspirin, 75 to 100 mg, daily on days 2 to 30. Patients were observed for 30 additional days. Main Outcomes and Measures: The primary outcome was time to stroke or death within 30 days. The primary safety outcome was time to severe bleeding. Results: In total, 3312 patients presented with moderate stroke and 6671 presented with less severe stroke. Of those in the moderate stroke group, 1293 (39.0%) were female, and the mean (SD) age was 64.5 (10.8) years; of those in the less severe stroke group, 2518 (37.7%) were female, and the mean (SD) age was 64.8 (11.2) years. The observed primary outcome event rate in patients with moderate stroke was 7.6% (129 of 1671) for those in the ticagrelor group and 9.1% (150 of 1641) for those in the placebo group (hazard ratio, 0.84; 95% CI, 0.66-1.06); the primary outcome event rate in patients with less severe stroke was 4.7% (158 of 3359) for those in the ticagrelor group and 5.7% (190 of 3312) for those in the placebo group (hazard ratio, 0.82; 95% CI, 0.66-1.01) (P for interaction = .88). Severe bleeding occurred in 8 patients (0.5%) in the ticagrelor group and in 4 patients (0.2%) in the placebo group in those with moderate stroke compared with 16 patients (0.5%) and 3 patients (0.1%), respectively, with less severe stroke (P for interaction = .26). Conclusions and Relevance: In this study, patients with a moderate ischemic stroke had consistent benefit from ticagrelor plus aspirin vs aspirin alone compared with patients with less severe ischemic stroke, with no further increase in the risk of intracranial bleeding or other severe bleeding events. Trial Registration: ClinicalTrials.gov Identifier: NCT03354429

Analysis of FGGY as a risk factor for sporadic amyotrophic lateral sclerosis.

A genome-wide association study (GWAS) using pooled DNA samples from 386 sporadic ALS patients and 542 controls from the USA, identified genetic variation in FGGY (FLJ10986) as a risk factor, as well as 66 additional candidate SNPs. Considering the large number of hypotheses that are tested in GWAS, independent replication of associations is crucial for identifying true-positive genetic risk factors for disease. The primary aim of this study was to study the association between FGGY and sporadic ALS in large, homogeneous populations from northern Europe. Genotyping experiments were performed using Illumina Beadchips, Sequenom iPLEX assays and Taqman technology on large case-control series from The Netherlands, Belgium, Sweden and Ireland (total: 1883 sporadic ALS patients and 2063 controls). No significant association between sporadic ALS and the six previously reported associated SNPs in FGGY was observed: rs6700125 (p=0.56), rs6690993 (p=0.30), rs10493256 (p=0.68), rs6587852 (p=0.64), rs1470407 (p=0.28) and rs333662 (p=0.44). Screening of the additional candidate loci did not yield significant associations either, with the lowest p-value in joint analysis for rs7772593 (p=0.14). We concluded that common genetic variation in FGGY is not associated with susceptibility to sporadic ALS in genetically homogeneous populations from northern Europe

Analysis of FGGY as a risk factor for sporadic amyotrophic lateral sclerosis.

Contains fulltext : 80041.pdf (publisher's version ) (Closed access)A genome-wide association study (GWAS) using pooled DNA samples from 386 sporadic ALS patients and 542 controls from the USA, identified genetic variation in FGGY (FLJ10986) as a risk factor, as well as 66 additional candidate SNPs. Considering the large number of hypotheses that are tested in GWAS, independent replication of associations is crucial for identifying true-positive genetic risk factors for disease. The primary aim of this study was to study the association between FGGY and sporadic ALS in large, homogeneous populations from northern Europe. Genotyping experiments were performed using Illumina Beadchips, Sequenom iPLEX assays and Taqman technology on large case-control series from The Netherlands, Belgium, Sweden and Ireland (total: 1883 sporadic ALS patients and 2063 controls). No significant association between sporadic ALS and the six previously reported associated SNPs in FGGY was observed: rs6700125 (p =0.56), rs6690993 (p =0.30), rs10493256 (p =0.68), rs6587852 (p =0.64), rs1470407 (p =0.28) and rs333662 (p =0.44). Screening of the additional candidate loci did not yield significant associations either, with the lowest p-value in joint analysis for rs7772593 (p =0.14). We concluded that common genetic variation in FGGY is not associated with susceptibility to sporadic ALS in genetically homogeneous populations from northern Europe