Accurate detection of complex structural variations using single-molecule sequencing

Structural variations are the greatest source of genetic variation, but they remain poorly understood because of technological limitations. Single-molecule long-read sequencing has the potential to dramatically advance the field, although high error rates are a challenge with existing methods. Addressing this need, we introduce open-source methods for long-read alignment (NGMLR; https://github.com/philres/ngmlr ) and structural variant identification (Sniffles; https://github.com/fritzsedlazeck/Sniffles ) that provide unprecedented sensitivity and precision for variant detection, even in repeat-rich regions and for complex nested events that can have substantial effects on human health. In several long-read datasets, including healthy and cancerous human genomes, we discovered thousands of novel variants and categorized systematic errors in short-read approaches. NGMLR and Sniffles can automatically filter false events and operate on low-coverage data, thereby reducing the high costs that have hindered the application of long reads in clinical and research settings

Genetic population structure in prickly sculpin (Cottus asper) reflects isolation-by-environment between two life-history ecotypes

Life-history transitions have evolved repeatedly in numerous taxa, although the ecological and evolutionary conditions favouring such transitions in the presence of gene flow remain poorly understood. The present study aimed to disentangle the effects of isolation-by-distance and isolation-by-environment on genetic differentiation between two sympatric life-history ecotypes. Using 14 microsatellite loci, we first characterized amphidromous and freshwater groups of Cottus asper in a high gene flow setting in the Lower Fraser River system (south-western British Columbia, Canada) to test for the effects of habitat and geographical distance on the distribution of life-history ecotypes. Within the main river channel, no genetic differentiation was found, whereas tributaries even close to the estuary were genetically differentiated. Partial mantel tests confirmed that genetic differentiation between river tributaries and the main channel was independent from geographical distance, with distance-scaled migration rates indicating reduced gene flow from the main channel into the tributaries. Our results suggest that isolation-by-environment can play an important role for the early stage of life-history transitions, and may promote differentiation among life-history ecotypes despite the presence of gene flo

Phylogeography of the prickly sculpin (Cottus asper) in north-western North America reveals parallel phenotypic evolution across multiple coastal–inland colonizations

Aim Glacial cycles during the Pleistocene may have frequently contributed to parallel evolution of phenotypes across independently evolving genetic lineages associated with separate glacial refugia. Previous studies based on morphology suggested that the prickly sculpin (Cottus asper) survived the Last Glacial Maximum (LGM) in southern coastal and inland refugia, favouring allopatric divergence between coastal and inland prickling phenotypes, which vary in the degree to which spine-like scales cover the body of the fish. Herein, we aimed to test whether parallel evolution across multiple genetic lineages rather than a single-lineage origin of highly prickled inland sculpins could serve as an explanation for the biogeographical distribution of prickling phenotypes. Location North-western North America, Southeast Alaska and Canada (British Columbia). Methods We used data from mitochondrial haplotypes and 19 microsatellite loci to identify distinct genetic lineages as a basis to interpret patterns of phenotypic evolution. Results The occurrence of multiple mtDNA groups suggests that highly prickled inland phenotypes comprise more than one genetic lineage. Both mtDNA and microsatellite data are consistent with post-glacial dispersal along the coast and repeated coastal to inland colonization events, as opposed to inland dispersal of a single lineage from a southern refugium to northern regions. Main conclusions Our results suggest that highly prickled inland phenotypes evolved repeatedly following multiple inland colonization events, probably via coastal rivers. The prickly sculpin therefore provides an example of recent (post-glacial) parallel evolution, potentially facilitated by standing genetic variation already present in the ancestral coastal populations

Conservation genetics of prickly sculpin (Cottus asper) at the periphery of its distribution range in Peace River, Canada

Populations at the edge of their range often invoke taxonomic confusion and are increasingly considered to harbour cryptic genetic diversity of significant adaptive potential. In the Peace River region of northwestern Canada, three sculpin species have been reported: spoonhead (Cottus ricei), slimy (Cottus cognatus) and prickly (Cottus asper) sculpin. Prickly sculpin occurrence in this region represents the most eastern edge of its distribution, but its status has remained uncertain following its initial discovery in 1989. These populations may represent an independently evolving lineage of special conservation concern, or be the consequence of an ongoing range expansion, possibly accompanied by interspecific hybridization with local species. Using a combination of mtDNA sequencing and microsatellite analyses, we did not find peripheral population differentiation or interspecific hybridization, suggesting that the Albertan Peace River population belongs to the same genetic group as its western counterparts. Future studies will benefit from a greater understanding of whether demographically independent prickly sculpin populations established in Alberta without the typical genetic signatures of expansion at the periphery of their range

Adaptive genomic divergence under high gene flow between freshwater and brackish-water ecotypes of prickly sculpin (Cottus asper) revealed by Pool-Seq

Understanding the genomic basis of adaptive divergence in the presence of gene flow remains a major challenge in evolutionary biology. In prickly sculpin (Cottus asper), an abundant euryhaline fish in northwestern North America, high genetic connectivity among brackish-water (estuarine) and freshwater (tributary) habitats of coastal rivers does not preclude the build-up of neutral genetic differentiation and emergence of different life history strategies. Because these two habitats present different osmotic niches, we predicted high genetic differentiation at known teleost candidate genes underlying salinity tolerance and osmoregulation. We applied whole-genome sequencing of pooled DNA samples (Pool-Seq) to explore adaptive divergence between two estuarine and two tributary habitats. Paired-end sequence reads were mapped against genomic contigs of European Cottus, and the gene content of candidate regions was explored based on comparisons with the threespine stickleback genome. Genes showing signals of repeated differentiation among brackish-water and freshwater habitats included functions such as ion transport and structural permeability in freshwater gills, which suggests that local adaptation to different osmotic niches might contribute to genomic divergence among habitats. Overall, the presence of both repeated and unique signatures of differentiation across many loci scattered throughout the genome is consistent with polygenic adaptation from standing genetic variation and locally variable selection pressures in the early stages of life history divergence. © 2016 John Wiley Sons Ltd

Tabla genealógica de la familia de Ribadeneyra, marqueses de la Vega de Boecillo. [Manuscrito]

Empieza en Hernando Salido de Ribadeneyra. Termina en su quinta nieta doña Casilda Teresa de Ribadeneyra y Niño de Castro, II marquesa de la Vega de Boecillo.Pertenece a la Colección Salazar y Castro de la RA

Genome-wide patterns of transposon proliferation in an evolutionary young hybrid fish

Hybridization can induce transposons to jump into new genomic positions, which may result in their accumulation across the genome. Alternatively, transposon copy numbers may increase through non-allelic (ectopic) homologous recombination in highly repetitive regions of the genome. The relative contribution of transposition bursts versus recombination-based mechanisms to evolutionary processes remains unclear because studies on transposon dynamics in natural systems are rare. We assessed the genome-wide distribution of transposon insertions in a young hybrid lineage ("invasive Cottus", n=11) and its parental species Cottus rhenanus (n=17) and Cottus perifretum (n=9) using a reference genome assembled from long single molecule PacBio reads. An inventory of transposable elements was reconstructed from the same data and annotated. Transposon copy numbers in the hybrid lineage increased in 120 (15.9%) out of 757 transposons studied here. The copy number increased on average by 69% (range: 10 - 197%). Given the age of the hybrid lineage, this suggests that they have proliferated within a few hundred generations since admixture began. However, frequency spectra of transposon insertions revealed no increase of novel and rare insertions across assembled parts of the genome. This implies that transposons were added to repetitive regions of the genome that remain difficult to assemble. Future studies will need to evaluate whether recombination-based mechanisms rather than genome-wide transposition may explain the majority of the recent transposon proliferation in the hybrid lineage. Irrespectively of the underlying mechanism, the observed over-abundance in repetitive parts of the genome suggests that gene-rich regions are unlikely to be directly affected. This article is protected by copyright. All rights reserved

J. Virol.

Phosphorylation of hepatitis B virus (HBV) core protein has recently been shown to be a prerequisite for pregenomic RNA encapsidation into viral capsids, but the host cell kinases mediating this essential step of the HBV replication cycle have not been identified. We detected two kinases of 95 and 115 kDa in HuH-7 total cell lysates which interacted specifically with the HBV core protein and phosphorylated its arginine-rich C- terminal domain. The 95-kDa kinase was purified and characterized as SR protein-specific kinase I (SRPK1) by mass spectrometry. Based on this finding, the 115-kDa kinase could be identified as the related kinase SRPK2 by immunoblot analysis. In vitro, both SRPKs phosphorylated HBV core protein on the same serine residues which are found to be phosphorylated in vivo. Moreover, the major cellular HBV core kinase activity detected in the total cell lysate showed biochemical properties identical to those of SRPK1 and SRPK2, as examined by measuring binding to a panel of chromatography media. We also clearly demonstrate that neither the cyclin- dependent kinases Cdc2 and Cdk2 nor protein kinase C, previously implicated in HBV core protein phosphorylation, can account for the HBV core protein kinase activity. We conclude that both SRPK1 and SRPK2 are most likely the cellular protein kinases mediating HBV core protein phosphorylation during viral infection and therefore represent important host cell targets for therapeutic intervention in HBV infection