Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Single-Cell Analysis May Shed New Lights on the Role of LncRNAs in Chemoresistance in Gastrointestinal Cancers

International audienceA major challenge in the treatment of cancer is dealing with intrinsic and/or acquired chemoresistance and with the development of metastatic lesions. The underlying mechanisms of chemoresistance are complex as a consequence of cancer heterogeneity, such as different tumour tissue origin, inter-tumour heterogeneity between patients and intra-tumour heterogeneity within cell populations of tumours. Classifying tumours according to gene expression-based molecular subtypes predicts the response to therapy and has been proposed to innovate towards personalized therapy. We here highlight the molecular subtypes observed in gastrointestinal cancers. In addition, we discuss the implication of long non-coding RNAs (lncRNAs), a class of RNAs without protein-coding sequence and over 200 nucleotides long, in chemoresistance of gastrointestinal cancers.Furthermore, with the development of single-cell RNA sequencing technologies 10 years ago, it has become clear that intercellular transcriptome heterogeneity of similar cell types may contribute to intra-tumour heterogeneity. Single-cell transcriptome profiling may identify specific cell phenotypes prone to develop chemoresistance that previously remained undistinguished by global gene expression or cell morphology. CRISPR/Cas9 methods may permit to elucidate the role of lncRNAs in chemoresistance at a single-cell level. The single-cell approach may take cancer treatment a step closer towards personalized, or even cell-specific, therapy