| 1. |
- Naboulsi, Rakan
(författare)
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Animal genomics – gene discovery and gene characterization
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis involves two projects. The aim in the first project was to identify genomic regions associated with spontaneous autoimmune thyroiditis (SAT), which is a hereditary autoimmune disease that affects the obese strain (OS) of chicken, an animal model for human Hashimoto’s thyroiditis (HT). In the second project, we study ZBED6, a highly conserved protein unique to placental mammals. Here we explore the functional significance of ZBED6 in general, and its effect on the regulation of Igf2 and miR483 in specific. To identify genomic regions predisposing to SAT, a nine-generation intercross between OS and their wild ancestor, the red junglefowl (RJF), was previously generated. In paper I, we developed a cell-based assay to phenotype the F9 chickens by measuring the TSH levels in their serum. We found that 1) SAT is similar to HT in the sense that the serum-TSH levels increase in affected individuals, and 2) that TSH levels in SAT-affected chickens starts to increase after 20 weeks of age. In paper II, a whole genome sequencing experiment was performed to compare a healthy and a severely SAT-affected groups of chicken. This analysis revealed 12 genomic loci to be significantly different between the two groups. In the second project, we utilized a mouse myoblast cell line, C2C12, to characterize the function of ZBED6. In paper III, we affect ZBED6 function, by either mutating its binding site in Igf2 (Igf2dGGCT), or by completely knocking it out (Zbed6-/-). Functional analysis of the mutant cells revealed that ZBED6 overexpression induces cell cycle arrest and apoptosis, that ZBED6 directly affects mitochondrial activity, and that ZBED6 in myoblast cells mainly exerts its effect through regulating Igf2. In paper IV, we use ZBED6 knock-out and knock-in mice to investigate the effect of ZBED6 on the regulation of miRNA expression. We found that ZBED6 is not a general regulator for miRNA, with the exception of miR483, which exists in an intron of Igf2. Thereafter, we generated miR483-/- cells, using the Igf2dGGCT cell line. In this analysis we found that the main function of miR483 in myoblast cells is to regulate the expression of Igf2, and that ZBED6 partially regulates Igf2 through regulating miR483.
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| 2. |
- Han, Fan
(författare)
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Genetic Adaptation and Speciation in Darwin’s Finches and Atlantic Herring
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Natural selection acts on existing genetic variation to drive genetic adaptation of organisms to various ecological niches. Interaction between closely related populations, through processes such as competition and hybridization, may either lead to their divergence or population fusion, which has consequences for adaptation and the formation of species. This thesis aims to use two natural populations, Darwin’s finches and Atlantic herring, as models to explore the genetic mechanisms underlying ecological adaptation and speciation.The ecological adaptation of Darwin’s finches across the Galápagos Islands is primarily reflected by variation in beak morphology. Using whole-genome re-sequencing of all Darwin’s finch species, we discover that a locus, HMGA2, is highly associated with variation in beak size. Data collected before and after a severe drought show that this locus plays a critical role for ecological character displacement in large ground finches Geospiza magnirostris and medium ground finches G. fortis.Genomic islands of divergence refer to genomic regions of elevated divergence when comparing the genomes of closely related taxa. Establishment of these genomic islands can reflect a role in reproductive isolation or be related to ecological adaptation or background selection. Investigating their properties can shed light on how new species evolve. We study the landscape of genomic islands in Darwin’s finches, and find that the most pronounced genomic islands are likely ancient balanced polymorphisms, which govern adaptive variation in beak morphology.Hybridization is increasingly recognized as an important evolutionary process which may lead to speciation. We study two cases of hybridization in Darwin’s finches. In the first case, a new lineage of Darwin’s finches was founded through hybridization between a resident medium ground finch G. fortis and an immigrant Española cactus finch G. conirostris. In the second case, female-biased introgression occurred predominantly from medium ground finches G. fortis to common cactus finches G. scandens. Our genetic analysis on the mosaic genomes of hybrid finches show that non-random mating and natural selection primarily determine the outcome of hybridization.We generate a chromosome-level assembly of the Atlantic herring with a total size of 726 Mb, which coincides with a high-resolution linkage map and an LD-based recombination map. This facilitates the identification of an ~8Mb inversion, which is likely to be associated with ecological adaptation in herring to differences in water temperature. The contiguity of the assembly sorts placement of loci under selection that were identified based on a previous, highly fragmented draft assembly of the herring genome.
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| 3. |
- Rancilhac, Loïs, et al.
(författare)
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Introgression Underlies Phylogenetic Uncertainty But Not Parallel Plumage Evolution in a Recent Songbird Radiation
- 2023
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Ingår i: Systematic Biology. - : Oxford University Press. - 1063-5157 .- 1076-836X.
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Tidskriftsartikel (refereegranskat)abstract
- Instances of parallel phenotypic evolution offer great opportunities to understand the evolutionary processes underlying phenotypic changes. However, confirming parallel phenotypic evolution and studying its causes requires a robust phylogenetic framework. One such example is the “black-and-white wagtails,” a group of 5 species in the songbird genus Motacilla: 1 species, Motacilla alba, shows wide intra-specific plumage variation, while the 4r others form 2 pairs of very similar-looking species (M. aguimp + M. samveasnae and M. grandis + M. maderaspatensis, respectively). However, the 2 species in each of these pairs were not recovered as sisters in previous phylogenetic inferences. Their relationships varied depending on the markers used, suggesting that gene tree heterogeneity might have hampered accurate phylogenetic inference. Here, we use whole genome resequencing data to explore the phylogenetic relationships within this group, with a special emphasis on characterizing the extent of gene tree heterogeneity and its underlying causes. We first used multispecies coalescent methods to generate a “complete evidence” phylogenetic hypothesis based on genome-wide variants, while accounting for incomplete lineage sorting (ILS) and introgression. We then investigated the variation in phylogenetic signal across the genome to quantify the extent of discordance across genomic regions and test its underlying causes. We found that wagtail genomes are mosaics of regions supporting variable genealogies, because of ILS and inter-specific introgression. The most common topology across the genome, supporting M. alba and M. aguimp as sister species, appears to be influenced by ancient introgression. Additionally, we inferred another ancient introgression event, between M. alba and M. grandis. By combining results from multiple analyses, we propose a phylogenetic network for the black-and-white wagtails that confirms that similar phenotypes evolved in non-sister lineages, supporting parallel plumage evolution. Furthermore, the inferred reticulations do not connect species with similar plumage coloration, suggesting that introgression does not underlie parallel plumage evolution in this group. Our results demonstrate the importance of investing genome-wide patterns of gene tree heterogeneity to help understand the mechanisms underlying phenotypic evolution. [Gene tree heterogeneity; incomplete lineage sorting; introgression; parallel evolution; phylogenomics; plumage evolution; wagtails.]
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| 4. |
- Semenov, Georgy A., et al.
(författare)
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Asymmetric introgression reveals the genetic architecture of a plumage trait
- 2021
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Genome-wide variation in introgression rates across hybrid zones offers a powerful opportunity for studying population differentiation. One poorly understood pattern of introgression is the geographic displacement of a trait implicated in lineage divergence from genome-wide population boundaries. While difficult to interpret, this pattern can facilitate the dissection of trait genetic architecture because traits become uncoupled from their ancestral genomic background. We studied an example of trait displacement generated by the introgression of head plumage coloration from personata to alba subspecies of the white wagtail. A previous study of their hybrid zone in Siberia revealed that the geographic transition in this sexual signal that mediates assortative mating was offset from other traits and genetic markers. Here we show that head plumage is associated with two small genetic regions. Despite having a simple genetic architecture, head plumage inheritance is consistent with partial dominance and epistasis, which could contribute to its asymmetric introgression. Hybrid zones are windows into the evolutionary process. Semenov et al. find that the head plumage differences between white wagtail subspecies have a simple genetic basis involving two small genetic regions, in which partially dominant and epistatic interactions help to explain how this sexual signal has become decoupled from other plumage traits.
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