| 1. |
- Bergquist, Annika, et al.
(författare)
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Impact on follow-up strategies in patients with primary sclerosing cholangitis
- 2023
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Ingår i: Liver international (Print). - Chichester, United Kingdom : Wiley-Blackwell Publishing Inc.. - 1478-3223 .- 1478-3231. ; 43:1, s. 127-138
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND & AIMS: Evidence for the benefit of scheduled imaging for early detection of hepatobiliary malignancies in primary sclerosing cholangitis (PSC) is limited. We aimed to compare different follow-up strategies in PSC with the hypothesis that regular imaging improves survival.METHODS: We collected retrospective data from 2,975 PSC patients from 27 centers. Patients were followed from the start of scheduled imaging or in case of clinical follow-up from January 1, 2000, until death or last clinical follow-up alive. The primary endpoint was all-cause mortality.RESULTS: A broad variety of different follow-up strategies were reported. All except one center used regular imaging, ultrasound (US) and/or magnetic resonance imaging (MRI). Two centers used scheduled ERCP in addition to imaging for surveillance purposes. The overall HR (CI95%) for death, adjusted for sex, age and start year of follow-up, were 0.61 (0.47-0.80) for scheduled imaging with and without ERCP; 0.64 (0.48-0.86) for US/MRI and 0.53 (0.37-0.75) for follow-up strategies including scheduled ERCP. The lower risk of death remained for scheduled imaging with and without ERCP after adjustment for cholangiocarcinoma (CCA) or high-grade dysplasia as a time-dependent covariate, HR 0.57 (0.44-0.75). Hepatobiliary malignancy was diagnosed in 175 (5.9%) of the patients at 7.9 years follow-up. Asymptomatic patients (25%) with CCA had better survival if scheduled imaging had been performed.CONCLUSIONS: Follow-up strategies vary considerably across centers. Scheduled imaging was associated with improved survival. Multiple factors may contribute to this result including early tumor detection and increased endoscopic treatment of asymptomatic benign biliary strictures.
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| 2. |
- Cockerill, Christopher Alan, 1994-, et al.
(författare)
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Genomic Consequences of Fragmentation in the Endangered Fennoscandian Arctic Fox (Vulpes lagopus)
- 2022
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Ingår i: Genes. - : MDPI AG. - 2073-4425. ; 13:11
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Tidskriftsartikel (refereegranskat)abstract
- Accelerating climate change is causing severe habitat fragmentation in the Arctic, threatening the persistence of many cold-adapted species. The Scandinavian arctic fox (Vulpes lagopus) is highly fragmented, with a once continuous, circumpolar distribution, it struggled to recover from a demographic bottleneck in the late 19th century. The future persistence of the entire Scandinavian population is highly dependent on the northernmost Fennoscandian subpopulations (Scandinavia and the Kola Peninsula), to provide a link to the viable Siberian population. By analyzing 43 arctic fox genomes, we quantified genomic variation and inbreeding in these populations. Signatures of genome erosion increased from Siberia to northern Sweden indicating a stepping-stone model of connectivity. In northern Fennoscandia, runs of homozygosity (ROH) were on average ~1.47-fold longer than ROH found in Siberia, stretching almost entire scaffolds. Moreover, consistent with recent inbreeding, northern Fennoscandia harbored more homozygous deleterious mutations, whereas Siberia had more in heterozygous state. This study underlines the value of documenting genome erosion following population fragmentation to identify areas requiring conservation priority. With the increasing fragmentation and isolation of Arctic habitats due to global warming, understanding the genomic and demographic consequences is vital for maintaining evolutionary potential and preventing local extinctions.
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| 3. |
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| 4. |
- Díez-del-Molino, David, et al.
(författare)
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Population genomics reveals lack of greater white-fronted introgression into the Swedish lesser white-fronted goose
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Interspecific introgression is considered a potential threat to endangered taxa. One example where this has had a major impact on conservation policy is the lesser white-fronted goose (LWfG). After a dramatic decline in Sweden, captive breeding birds were released between 1981–1999 with the aim to reinforce the population. However, the detection of greater white-fronted goose (GWfG) mitochondrial DNA in the LWfG breeding stock led to the release program being dismantled, even though the presence of GWfG introgression in the actual wild Swedish LWfG population was never documented. To examine this, we sequenced the complete genomes of 21 LWfG birds from the Swedish, Russian and Norwegian populations, and compared these with genomes from other goose species, including the GWfG. We found no evidence of interspecific introgression into the wild Swedish LWfG population in either nuclear genomic or mitochondrial data. Moreover, Swedish LWfG birds are genetically distinct from the Russian and Norwegian populations and display comparatively low genomic diversity and high levels of inbreeding. Our findings highlight the utility of genomic approaches in providing scientific evidence that can help improve conservation management as well as policies for breeding and reinforcement programmes.
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| 5. |
- Dussex, Nicolas, et al.
(författare)
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Complete genomes of two extinct New Zealand passerines show responses to climate fluctuations but no evidence for genomic erosion prior to extinction
- 2019
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Ingår i: Biology Letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 15:9
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Tidskriftsartikel (refereegranskat)abstract
- Human intervention, pre-human climate change (or a combination of both), as well as genetic effects, contribute to species extinctions. While many species from oceanic islands have gone extinct due to direct human impacts, the effects of pre-human climate change and human settlement on the genomic diversity of insular species and the role that loss of genomic diversity played in their extinctions remains largely unexplored. To address this question, we sequenced whole genomes of two extinct New Zealand passerines, the huia (Heteralocha acutirostris) and South Island kokako (Callaeas cinereus). Both species showed similar demographic trajectories throughout the Pleistocene. However, the South Island kokako continued to decline after the last glaciation, while the huia experienced some recovery. Moreover, there was no indication of inbreeding resulting from recent mating among closely related individuals in either species. This latter result indicates that population fragmentation associated with forest clearing by Maori may not have been strong enough to lead to an increase in inbreeding and exposure to genomic erosion. While genomic erosion may not have directly contributed to their extinctions, further habitat fragmentation and the introduction of mammalian predators by Europeans may have been an important driver of extinction in huia and South Island kokako.
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| 6. |
- Dussex, Nicolas, et al.
(författare)
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Full Mitogenomes in the Critically Endangered Kakapo Reveal Major Post-Glacial and Anthropogenic Effects on Neutral Genetic Diversity
- 2018
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Ingår i: Genes. - : MDPI AG. - 2073-4425. ; 9:4
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how species respond to population declines is a central question in conservation and evolutionary biology. Population declines are often associated with loss of genetic diversity, inbreeding and accumulation of deleterious mutations, which can lead to a reduction in fitness and subsequently contribute to extinction. Using temporal approaches can help us understand the effects of population declines on genetic diversity in real time. Sequencing pre-decline as well as post-decline mitogenomes representing all the remaining mitochondrial diversity, we estimated the loss of genetic diversity in the critically endangered kakapo (Strigops habroptilus). We detected a signal of population expansion coinciding with the end of the Pleistocene last glacial maximum (LGM). Also, we found some evidence for northern and southern lineages, supporting the hypothesis that the species may have been restricted to isolated northern and southern refugia during the LGM. We observed an important loss of neutral genetic diversity associated with European settlement in New Zealand but we could not exclude a population decline associated with Polynesian settlement in New Zealand. However, we did not find evidence for fixation of deleterious mutations. We argue that despite high pre-decline genetic diversity, a rapid and range-wide decline combined with the lek mating system, and life-history traits of kakapo contributed to a rapid loss of genetic diversity following severe population declines.
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| 7. |
- Dussex, Nicolas, et al.
(författare)
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Integrating multi-taxon palaeogenomes and sedimentary ancient DNA to study past ecosystem dynamics
- 2021
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 288:1957
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Forskningsöversikt (refereegranskat)abstract
- Ancient DNA (aDNA) has played a major role in our understanding of the past. Important advances in the sequencing and analysis of aDNA from a range of organisms have enabled a detailed understanding of processes such as past demography, introgression, domestication, adaptation and speciation. However, to date and with the notable exception of microbiomes and sediments, most aDNA studies have focused on single taxa or taxonomic groups, making the study of changes at the community level challenging. This is rather surprising because current sequencing and analytical approaches allow us to obtain and analyse aDNA from multiple source materials. When combined, these data can enable the simultaneous study of multiple taxa through space and time, and could thus provide a more comprehensive understanding of ecosystem-wide changes. It is therefore timely to develop an integrative approach to aDNA studies by combining data from multiple taxa and substrates. In this review, we discuss the various applications, associated challenges and future prospects of such an approach.
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| 8. |
- Dussex, Nicolas, et al.
(författare)
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Population genomics of the critically endangered kākāpō
- 2021
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Ingår i: Cell Genomics. - : Elsevier BV. - 2666-979X. ; 1:1
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Tidskriftsartikel (refereegranskat)abstract
- Summary The kākāpō is a flightless parrot endemic to New Zealand. Once common in the archipelago, only 201 individuals remain today, most of them descending from an isolated island population. We report the first genome-wide analyses of the species, including a high-quality genome assembly for kākāpō, one of the first chromosome-level reference genomes sequenced by the Vertebrate Genomes Project (VGP). We also sequenced and analyzed 35 modern genomes from the sole surviving island population and 14 genomes from the extinct mainland population. While theory suggests that such a small population is likely to have accumulated deleterious mutations through genetic drift, our analyses on the impact of the long-term small population size in kākāpō indicate that present-day island kākāpō have a reduced number of harmful mutations compared to mainland individuals. We hypothesize that this reduced mutational load is due to the island population having been subjected to a combination of genetic drift and purging of deleterious mutations, through increased inbreeding and purifying selection, since its isolation from the mainland ∼10,000 years ago. Our results provide evidence that small populations can survive even when isolated for hundreds of generations. This work provides key insights into kākāpō breeding and recovery and more generally into the application of genetic tools in conservation efforts for endangered species.
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| 9. |
- Feuerborn, Tatiana R., et al.
(författare)
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Competitive mapping allows for the identification and exclusion of human DNA contamination in ancient faunal genomic datasets
- 2020
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Ingår i: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: After over a decade of developments in field collection, laboratory methods and advances in high-throughput sequencing, contamination remains a key issue in ancient DNA research. Currently, human and microbial contaminant DNA still impose challenges on cost-effective sequencing and accurate interpretation of ancient DNA data.Results: Here we investigate whether human contaminating DNA can be found in ancient faunal sequencing datasets. We identify variable levels of human contamination, which persists even after the sequence reads have been mapped to the faunal reference genomes. This contamination has the potential to affect a range of downstream analyses.Conclusions: We propose a fast and simple method, based on competitive mapping, which allows identifying and removing human contamination from ancient faunal DNA datasets with limited losses of true ancient data. This method could represent an important tool for the ancient DNA field.
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| 10. |
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