Engineered LINE-1 retrotransposition in nondividing human neurons

Half the human genome is made of transposable elements (TEs), whose ongoing activity continues to impact our genome. LINE-1 (or L1) is an autonomous non-LTR retrotransposon in the human genome, comprising 17% of its genomic mass and containing an average of 80-100 active L1s per average genome that provide a source of inter-individual variation. New LINE-1 insertions are thought to accumulate mostly during human embryogenesis. Surprisingly, the activity of L1s can further impact the somatic human brain genome. However, it is currently unknown whether L1 can retrotranspose in other somatic healthy tissues or if L1 mobilization is restricted to neuronal precursor cells (NPCs) in the human brain. Here, we took advantage of an engineered L1 retrotransposition assay to analyze L1 mobilization rates in human mesenchymal (MSCs) and hematopoietic (HSCs) somatic stem cells. Notably, we have observed that L1 expression and engineered retrotransposition is much lower in both MSCs and HSCs when compared to NPCs. Remarkably, we have further demonstrated for the first time that engineered L1s can retrotranspose efficiently in mature nondividing neuronal cells. Thus, these findings suggest that the degree of somatic mosaicism and the impact of L1 retrotransposition in the human brain is likely much higher than previously thought.We thank current members of the J.L.G.-P. laboratory for helpful discussions. We also thank Drs. Geoffrey Faulkner (Mater Research, Australia) and John V. Moran (University of Michigan) for sharing unpublished data and for critical input during the project; Ms. Raquel Marrero (Microscopy Unit, Genyo) for technical support; Simon Mendez-Ferrer (CNIC, Spain) for providing total RNA isolated from human mesenspheres; Dr. Oliver Weichenrieder (Max-Planck, Tubingen, Germany) for providing a polyclonal L1-ORF1p antibody; and Dr. Aurelien Doucet (IRCAN, Nice, France) for providing a plasmid containing an UBC-driven EGFP retrotransposition indicator cassette. J.L.G. was funded by the US Department of Defense, Breast Cancer Research Program (award #BC051386), the National Institutes of Health (NIH) National Institute of Neurological Disorders and Stroke (1R03NS087290-01), and the ALS Therapy Alliance (2013-F-067). A.M. has been partially funded by a Marie Curie IRG project (FP7-PEOPLE-2007-4-3-IRG: SOMATIC LINE-1). J.L.G.-P's laboratory is supported by CICE-FEDER-P09-CTS-4980, CICE-FEDER-P12-CTS-2256, Plan Nacional de I+D+I 2008–2011 and 2013–2016 (FIS-FEDER-PI11/01489 and FIS-FEDER-PI14/02152), PCIN-2014-115-ERA-NET NEURON II, the European Research Council (ERC-Consolidator ERC-STG-2012-233764), by an International Early Career Scientist grant from the Howard Hughes Medical Institute (IECS-55007420), and by The Wellcome Trust–University of Edinburgh Institutional Strategic Support Fund (ISFF2).S

Laser writing of coherent colour centres in diamond

Optically active point defects in crystals have gained widespread attention as photonic systems that can find use in quantum information technologies [1,2]. However challenges remain in the placing of individual defects at desired locations, an essential element of device fabrication. Here we report the controlled generation of single nitrogen-vacancy (NV) centres in diamond using laser writing [3]. The use of aberration correction in the writing optics allows precise positioning of vacancies within the diamond crystal, and subsequent annealing produces single NV centres with up to 45% success probability, within about 200 nm of the desired position. Selected NV centres fabricated by this method display stable, coherent optical transitions at cryogenic temperatures, a pre-requisite for the creation of distributed quantum networks of solid-state qubits. The results illustrate the potential of laser writing as a new tool for defect engineering in quantum technologies

Laser writing of coherent colour centres in diamond

Optically active point defects in crystals have gained widespread attention as photonic systems that can find use in quantum information technologies. However challenges remain in the placing of individual defects at desired locations, an essential element of device fabrication. Here we report the controlled generation of single negatively charged nitrogen-vacancy (NV-) centres in diamond using laser writing. Aberration correction in the writing optics allows precise positioning of vacancies within the diamond crystal, and subsequent annealing produces single NV- centres with up to (45 ± 15)% success probability, within about 200 nm of the desired position in the transverse plane. Selected NV- centres display stable, coherent optical transitions at cryogenic temperatures, a pre-requisite for the creation of distributed quantum networks of solid-state qubits. The results illustrate the potential of laser writing as a new tool for defect engineering in quantum technologies, and extend laser processing to the single defect domain