Positive selection in the human lineage across time scales

Thesis (Ph.D.)--University of Washington, 2016-08Understanding the evolutionary history of humankind has long been a central goal of biology. This history extends over millions of years- beginning with the events that led to our divergence from chimpanzees and other primate relatives, and ending with the ongoing migration patterns that give rise to the diverse human populations we see today. DNA sequencing and other molecular techniques for ascertaining genetic variation have been instrumental in reconstructing the timeline of this history. However, these technologies can also be leveraged to answer more fundamental questions about the ways that natural selection has shaped human evolution. For instance, studying patterns of DNA variation can elucidate the genetic basis of traits that were selected for in the human lineage across time scales. Although many methods have been developed to identify these signatures that natural selection has left on our genomes, there are still many cases of positive selection that current methods are not designed to detect. Here I present novel genome-wide approaches for detecting natural selection at two different points in human history. In the first, I extended methods to identify regulatory elements that show elevated rates of human-specific substitutions, and may thus underlie unique human phenotypes that evolved after our divergence from other apes. In the second, I characterized haplotypes inherited from interbreeding events with archaic hominin species that facilitated modern human adaptation to out of Africa environments. Both of these approaches build significantly on previous work to identify positive selection in the human genome, and provide an extensive catalogue of loci to study using more targeted hypotheses in the future

SNP_in_haDHS(from 1000 human genome project)

This file showed all the SNPs(data from 1000 human genome project) that located in TRIM haDHSs, with their information such as the positions of SNPs and allele frequencies

Data from: Positive selection of the TRIM family regulatory region in primate genomes

Viral selection pressure has acted on restriction factors that play an important role in the innate immune system by inhibiting the replication of viruses during primate evolution. Tripartite motif-containing (TRIM) family members are some of these restriction factors. It is becoming increasingly clear that gene expression differences, rather than protein-coding regions changes, could play a vital role in the anti-retroviral immune mechanism. Increasingly, recent studies have created genome-scale catalogues of DNase I hypersensitive sites (DHSs), which demark potentially functional regulatory DNA. To improve our understanding of the molecular evolution mechanism of antiviral differences between species, we leveraged 14 130 DHSs derived from 145 cell types to characterize the regulatory landscape of the TRIM region. Subsequently, we compared the alignments of the DHSs across six primates and found 375 DHSs that are conserved in non-human primates but exhibit significantly accelerated rates of evolution in the human lineage (haDHSs). Furthermore, we discovered 31 human-specific potential transcription factor motifs within haDHSs, including the KROX and SP1, that both interact with HIV-1. Importantly, the corresponding haDHS was correlated with antiviral factor TRIM23. Thus, our results suggested that some viruses may contribute, through regulatory DNA differences, to organismal evolution by mediating TRIM gene expression to escape immune surveillance

Exploring signatures of positive selection in pigmentation candidate genes in populations of East Asian ancestry

Abstract Background Currently, there is very limited knowledge about the genes involved in normal pigmentation variation in East Asian populations. We carried out a genome-wide scan of signatures of positive selection using the 1000 Genomes Phase I dataset, in order to identify pigmentation genes showing putative signatures of selective sweeps in East Asia. We applied a broad range of methods to detect signatures of selection including: 1) Tests designed to identify deviations of the Site Frequency Spectrum (SFS) from neutral expectations (Tajima’s D, Fay and Wu’s H and Fu and Li’s D* and F*), 2) Tests focused on the identification of high-frequency haplotypes with extended linkage disequilibrium (iHS and Rsb) and 3) Tests based on genetic differentiation between populations (LSBL). Based on the results obtained from a genome wide analysis of 25 kb windows, we constructed an empirical distribution for each statistic across all windows, and identified pigmentation genes that are outliers in the distribution. Results Our tests identified twenty genes that are relevant for pigmentation biology. Of these, eight genes (ATRN, EDAR, KLHL7, MITF, OCA2, TH, TMEM33 and TRPM1,) were extreme outliers (top 0.1% of the empirical distribution) for at least one statistic, and twelve genes (ADAM17, BNC2, CTSD, DCT, EGFR, LYST, MC1R, MLPH, OPRM1, PDIA6, PMEL (SILV) and TYRP1) were in the top 1% of the empirical distribution for at least one statistic. Additionally, eight of these genes (BNC2, EGFR, LYST, MC1R, OCA2, OPRM1, PMEL (SILV) and TYRP1) have been associated with pigmentary traits in association studies. Conclusions We identified a number of putative pigmentation genes showing extremely unusual patterns of genetic variation in East Asia. Most of these genes are outliers for different tests and/or different populations, and have already been described in previous scans for positive selection, providing strong support to the hypothesis that recent selective sweeps left a signature in these regions. However, it will be necessary to carry out association and functional studies to demonstrate the implication of these genes in normal pigmentation variation

Exploring signatures of positive selection in pigmentation candidate genes in populations of East Asian ancestry

Background: Currently, there is very limited knowledge about the genes involved in normal pigmentation variation in East Asian populations. We carried out a genome-wide scan of signatures of positive selection using the 1000 Genomes Phase I dataset, in order to identify pigmentation genes showing putative signatures of selective sweeps in East Asia. We applied a broad range of methods to detect signatures of selection including: 1) Tests designed to identify deviations of the Site Frequency Spectrum (SFS) from neutral expectations (Tajima’s D, Fay and Wu’s H and Fu and Li’s D* and F*), 2) Tests focused on the identification of high-frequency haplotypes with extended linkage disequilibrium (iHS and Rsb) and 3) Tests based on genetic differentiation between populations (LSBL). Based on the results obtained from a genome wide analysis of 25 kb windows, we constructed an empirical distribution for each statistic across all windows, and identified pigmentation genes that are outliers in the distribution. Results: Our tests identified twenty genes that are relevant for pigmentation biology. Of these, eight genes (ATRN, EDAR, KLHL7, MITF, OCA2, TH, TMEM33 and TRPM1,) were extreme outliers (top 0.1% of the empirical distribution) for at least one statistic, and twelve genes (ADAM17, BNC2, CTSD, DCT, EGFR, LYST, MC1R, MLPH, OPRM1, PDIA6, PMEL (SILV) and TYRP1) were in the top 1% of the empirical distribution for at least one statistic. Additionally, eight of these genes (BNC2, EGFR, LYST, MC1R, OCA2, OPRM1, PMEL (SILV) and TYRP1) have been associated with pigmentary traits in association studies. Conclusions: We identified a number of putative pigmentation genes showing extremely unusual patterns of genetic variation in East Asia. Most of these genes are outliers for different tests and/or different populations, and have already been described in previous scans for positive selection, providing strong support to the hypothesis that recent selective sweeps left a signature in these regions. However, it will be necessary to carry out association and functional studies to demonstrate the implication of these genes in normal pigmentation variation

Transposable elements within TRIM DHS

This files showed the transposable elements that overlapped with TRIM haDHSs and conversed DHSs and their detailed information. The first three columns represented the position of DHS, the fourth to sixth columns represented the position of transposable elements. The annotation file of transposable elements came from ReapeatsMasker output file in UCSC