Polycomb group proteins form two main complexes, PRC2 and PRC1, which generally coregulate their target genes. Here, we show that PRC1 components act as neoplastic tumor suppressors independently of PRC2 function. By mapping the distribution of PRC1 components and the histone H3K27me3 mark, we identify a large set of genes that acquire PRC1 in the absence of H3K27me3 in Drosophila larval tissues. These genes massively outnumber canonical targets and they are preeminently involved in the regulation of cell proliferation, signaling and polarity. Mutation in PRC1 components specifically deregulates this set of genes, whereas canonical targets are derepressed in both PRC1 and PRC2 mutants. In human ES cells, PRC1 components colocalize with H3K27me3 like in Drosophila embryos, whereas in differentiated cell types they are selectively recruited to a large set of proliferation and signaling-associated genes that are H3K27me3 negative, showing that the redeployment of PRC1 components during development is evolutionarily conserved.Polycomb group (PcG) proteins form two main classes of evolutionarily conserved complexes called PRC2 and PRC1. In Drosophila, PRC2 contains the enzymatic E(Z) subunit that deposits the H3K27me3 mark, along with SU(Z)12, ESC and p55 1-4. A second class of PcG complex, PRC1, was shown to contain PH, PC, PSC and the SCE subunits 5. These two complexes are recruited to their target sites by a set of DNA binding proteins, notably PHO 6. They colocalize almost perfectly in embryogenesis7, and their Correspondence to: Anne-Marie.Martinez@igh.cnrs.fr and Giacomo.Cavalli@igh.cnrs.fr. Accession codes Drosophila ChIP-Seq and RNA-Seq data are deposited to the Gene Expression Omnibus (GEO) repository under the accession number GSE74080.

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Chromatin Immunoprecipitation coupled either to qPCR (qChIP) or high-throughput sequencing (ChIP-Seq) has been extensively used in the last decades to identify the DNA binding sites of transcription factors or the localization of various histone marks along the genome. The ChIP experiment generally includes 7 steps: collection of biological samples (A), cross-linking proteins to DNA (B), chromatin isolation and fragmentation by sonication (C), sonication test (D), immunoprecipitation with antibodies against the protein or the histone mark of interest (E), DNA recovery (E), identification of factor-associated DNA sequences by PCR or sequencing (F). The protocol described here can readily be used for ChIP-seq and ChIP-qPCR experiments. The entire procedure, describing experimental setup conditions to optimize assays in intact Drosophila tissues, can be completed within four days.

The possibility of providing investigative leads when conventional DNA identification methods fail to solve a case can be of extreme relevance to law enforcement. Therefore, the forensic genetics community has focused research towards the broadened use of DNA, particularly for prediction of appearance traits, bio-geographical ancestry and age. The VISible Attributes through GEnomics (VISAGE) Consortium expanded the use of DNA phenotyping by developing new molecular and statistical tools for appearance, age and ancestry prediction. The VISAGE basic tool for appearance (EVC) and ancestry (BGA) prediction was initially developed using Ampliseq chemistry, but here is being evaluated using ForenSeq chemistry. The VISAGE basic tool offers a total of 41 EVC and 115 BGA SNPs and thus provides more predictions, i.e., skin color, than achieved with the ForenSeq DNA Signature Prep kit that is based on 24 EVC and 56 BGA SNPs. Five VISAGE laboratories participated in collaborative experiments to provide foreground for developmental validation of the assay. Assessment of assay performance and quality metrics, reproducibility, sensitivity, inhibitor tolerance and species specificity are described. Furthermore, the assay was tested using challenging samples such as mock casework samples and artificially degraded DNA. Two different analysis strategies were applied for this study and output on genotype calls and read depth was compared. Overall, interlaboratory, inter-method and concordance with publicly available data were analysed and compared. Finally, the results showed a reliable and robust tool, which can be easily applied for laboratories already using a MiSeq FGx with ForenSeq reagents.