Sequencing and de novo assembly of 150 genomes from Denmark as a population reference

Hundreds of thousands of human genomes are now being sequenced to characterize genetic variation and use this information to augment association mapping studies of complex disorders and other phenotypic traits. Genetic variation is identified mainly by mapping short reads to the reference genome or by performing local assembly. However, these approaches are biased against discovery of structural variants and variation in the more complex parts of the genome. Hence, large-scale de novo assembly is needed. Here we show that it is possible to construct excellent de novo assemblies from high-coverage sequencing with mate-pair libraries extending up to 20 kilobases. We report de novo assemblies of 150 individuals (50 trios) from the GenomeDenmark project. The quality of these assemblies is similar to those obtained using the more expensive long-read technology. We use the assemblies to identify a rich set of structural variants including many novel insertions and demonstrate how this variant catalogue enables further deciphering of known association mapping signals. We leverage the assemblies to provide 100 completely resolved major histocompatibility complex haplotypes and to resolve major parts of the Y chromosome. Our study provides a regional reference genome that we expect will improve the power of future association mapping studies and hence pave the way for precision medicine initiatives, which now are being launched in many countries including Denmark

Genome sequence and genetic diversity of European ash trees

Eurofins MWG provided a discounted service for Illumina and 454 sequencing of the reference genome, funded by Natural Environment Research Council (NERC) Urgency Grant NE/K01112X/1 to R.J.A.B. The associative transcriptomic and metabolomic work was part of the ‘Nornex’ project led by J.A.D. funded jointly by the UK Biotechnology and Biological Sciences Research Council (BBSRC) (BBS/E/J/000CA5323) and the Department for Environment, Food & Rural Affairs. The Earlham Institute, Norwich, UK, sequenced ‘Tree 35’ funded by ‘Nornex’ and the European Diversity Panel funded by the Earlham Institute National Capability in Genomics (BB/J010375/1) grant. W. Crowther assisted with DNA extractions for the KASP assay; The John Innes Centre contributed KASP analyses. J. F. Miranda assisted with RNA extractions and quantitative PCR with reverse transcription (qRT–PCR) at the University of York. H. V. Florance, N. Smirnoff and the Exeter Metabolomics Facility developed metabolomic methods and ran samples, and T. P. Howard helped with statistics. L.J.K. and R.J.A.B. were partly funded by Living with Environmental Change (LWEC) Tree Health and Plant Biosecurity Initiative - Phase 2 grant BB/L012162/1 to R.J.A.B., S.L. and P. Jepson funded jointly by a grant from the BBSRC, Defra, Economic and Social Research Council, the Forestry Commission, NERC and the Scottish Government, under the Tree Health and Plant Biosecurity Initiative. G.W. was funded by Teagasc Walsh Fellowship 2014001 to R.J.A.B. and G.C.D. E.D.C. was funded by a Marie Skłodowska-Curie Individual Fellowship ‘FraxiFam’ (grant agreement 660003) to E.D.C. and R.J.A.B. E.S.A.S. and J.Z. were funded by the Marie Skłodowska-Curie Initial Training Network INTERCROSSING. J.A.D. received a John Innes Foundation fellowship. We thank A. Joecker for supervising E.S.A.S. at Qiagen and for helpful discussions. R.H.R.G. is supported by a Norwich Research Park PhD Studentship and Earlham Institute Funding and Maintenance Grant. This research used Queen Mary’s MidPlus computational facilities, supported by QMUL Research-IT and funded by Engineering and Physical Sciences Research Council grant EP/K000128/1 and NERC EOS Cloud. D.J.S. acknowledges the support of BBSRC grant BB/N021452/1, which partly supported M.G., C.M.S. and D.J.S. during this work