Highlights d Profiled spatiotemporal gene expression patterns in human cardiogenesis d Mapped cell-type distribution and spatial organization in the human embryonic heart d Thoroughly analyzed roles of diverse cell types in cardiac development d A publicly available web resource of the human embryonic heart

Precisely measuring the location and frequency of DNA double-strand breaks (DSBs) along the genome is instrumental to understanding genomic fragility, but current methods are limited in versatility, sensitivity or practicality. Here we present Breaks Labeling In Situ and Sequencing (BLISS), featuring the following: (1) direct labelling of DSBs in fixed cells or tissue sections on a solid surface; (2) low-input requirement by linear amplification of tagged DSBs by in vitro transcription; (3) quantification of DSBs through unique molecular identifiers; and (4) easy scalability and multiplexing. We apply BLISS to profile endogenous and exogenous DSBs in low-input samples of cancer cells, embryonic stem cells and liver tissue. We demonstrate the sensitivity of BLISS by assessing the genome-wide off-target activity of two CRISPR-associated RNA-guided endonucleases, Cas9 and Cpf1, observing that Cpf1 has higher specificity than Cas9. Our results establish BLISS as a versatile, sensitive and efficient method for genome-wide DSB mapping in many applications.

DNA fluorescence in situ hybridization (DNA FISH) is a powerful method to study chromosomal organization in single cells. At present, there is a lack of free resources of DNA FISH probes and probe design tools which can be readily applied. Here, we describe iFISH, an open-source repository currently comprising 380 DNA FISH probes targeting multiple loci on the human autosomes and chromosome X, as well as a genome-wide database of optimally designed oligonucleotides and a freely accessible web interface ( http://ifish4u.org ) that can be used to design DNA FISH probes. We individually validate 153 probes and take advantage of our probe repository to quantify the extent of intermingling between multiple heterologous chromosome pairs, showing a much higher extent of intermingling in human embryonic stem cells compared to fibroblasts. In conclusion, iFISH is a versatile and expandable resource, which can greatly facilitate the use of DNA FISH in research and diagnostics.

With the exception of lamina-associated domains, the radial organization of chromatin in mammalian cells remains largely unexplored. Here, we describe genomic loci positioning by sequencing (GPSeq), a genome-wide method for inferring distances to the nuclear lamina all along the nuclear radius that works by gradual enzymatic restriction of chromatin from the nuclear lamina towards the nucleus center, followed by sequencing of the generated cut sites. Using GPSeq, we mapped the radial organization of the human genome at 100 kb resolution, which revealed radial patterns of genomic and epigenomic features, gene expression, as well as A/B subcompartments. By combining radial information with chromosome contact frequencies measured by Hi-C, we substantially improved the accuracy of wholegenome structure modeling. Finally, we charted the radial topography of DNA double-strand breaks, germline variants and cancer mutations, and found that they have distinctive radial arrangements in A/B subcompartments. We conclude that GPSeq can reveal fundamental aspects of genome architecture.

Single-cell transcriptome analysis overcomes problems inherently associated with averaging gene expression measurements in bulk analysis. However, single-cell analysis is currently challenging in terms of cost, throughput and robustness. Here, we present a method enabling massive microarray-based barcoding of expression patterns in single cells, termed MASC-seq. This technology enables both imaging and high-throughput single-cell analysis, characterizing thousands of single-cell transcriptomes per day at a low cost (0.13 USD/cell), which is two orders of magnitude less than commercially available systems. Our novel approach provides data in a rapid and simple way. Therefore, MASC-seq has the potential to accelerate the study of subtle clonal dynamics and help provide critical insights into disease development and other biological processes.

BackgroundMisregulation of the PTGS (prostaglandin endoperoxide synthase, also known as cyclooxygenase or COX) pathway may lead to the accumulation of pro-inflammatory signals, which constitutes a hallmark of cancer. To get insight into the role of this signaling pathway in colorectal cancer (CRC), we have characterized the transcriptional and epigenetic landscapes of the PTGS pathway genes in normal and cancer cells.ResultsData from four independent series of CRC patients (502 tumors including adenomas and carcinomas and 222 adjacent normal tissues) and two series of colon mucosae from 69 healthy donors have been included in the study. Gene expression was analyzed by real-time PCR and Affymetrix U219 arrays. DNA methylation was analyzed by bisulfite sequencing, dissociation curves, and HumanMethylation450K arrays. Most CRC patients show selective transcriptional deregulation of the enzymes involved in the synthesis of prostanoids and their receptors in both tumor and its adjacent mucosa. DNA methylation alterations exclusively affect the tumor tissue (both adenomas and carcinomas), redirecting the transcriptional deregulation to activation of prostaglandin E2 (PGE2) function and blockade of other biologically active prostaglandins. In particular, PTGIS, PTGER3, PTGFR, and AKR1B1 were hypermethylated in more than 40 % of all analyzed tumors.ConclusionsThe transcriptional and epigenetic profiling of the PTGS pathway provides important clues on the biology of the tumor and its microenvironment. This analysis renders candidate markers with potential clinical applicability in risk assessment and early diagnosis and for the design of new therapeutic strategies.Electronic supplementary materialThe online version of this article (doi:10.1186/s13148-015-0110-4) contains supplementary material, which is available to authorized users.

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DNA fluorescence in situ hybridization (DNA FISH) has emerged as a powerful microscopy technique that allows a unique view into the composition and arrangement of the genetic material in its natural context-be it the cell nucleus in interphase, or chromosomes in metaphase spreads. The core principle of DNA FISH is the ability of fluorescently labeled DNA probes (either double- or single-stranded DNA fragments) to bind to their complementary sequences in situ in cells or tissues, revealing the location of their target as fluorescence signals detectable with a fluorescence microscope. Numerous variants and improvements of the original DNA FISH method as well as a vast repertoire of applications have been described since its inception more than 4 decades ago. In recent years, the development of many new fluorescent dyes together with drastic advancements in methods for probe generation (Boyle et al., Chromosome Res 19:901-909, 2011; Beliveau et al., Proc Natl Acad Sci U S A 109:21301-21306, 2012; Bienko et al., Nat Methods 10:122-124, 2012), as well as improvements in the resolution of microscopy technologies, have boosted the number of DNA FISH applications, particularly in the field of genome architecture (Markaki et al., Bioessays 34:412-426, 2012; Beliveau et al., Nat Commun 6:7147, 2015). However, despite these remarkable steps forward, choosing which type of DNA FISH sample preparation protocol, probe design, hybridization procedure, and detection method is best suited for a given application remains still challenging for many research labs, preventing a more widespread use of this powerful technology. Here, we present a comprehensive platform to help researchers choose which DNA FISH protocol is most suitable for their particular application. In addition, we describe computational pipelines that can be implemented for efficient DNA FISH probe design and for signal quantification. Our goal is to make DNA FISH a versatile and streamlined technique that can be easily implemented by both research and diagnostic labs.