Project description:Gene regulation can evolve either by cis-acting local changes to regulatory element DNA sequences or by global changes to the trans-acting regulatory environment; however, the modes favored during recent human evolution are unknown. To date, studies investigating gene regulatory divergence between closely-related species have produced limited estimates on the relative contributions of cis and trans effects on DNA regulatory element activities at a global-scale. By leveraging a comparative ATAC-STARR-seq framework, we identified 10,779 regulatory regions with divergent activity in cis and 10,608 regulatory regions with divergent activity in trans between human and rhesus macaque lymphoblastoid cell lines (LCLs). This revealed substantially more trans effects than predicted and indicates trans-regulatory mechanisms play a larger role in human evolution than previously expected. We also discover that most species-specific regulatory elements (67%) diverge in both cis and trans, suggesting these two mechanisms jointly drive divergent regulatory activity in a single sequence.
Project description:Gene-expression divergence between species shapes morphological evolution, but the molecular basis is largely unknown. Here we show cis- and trans-regulatory elements and chromatin modifications on gene-expression diversity in genetically tractable Arabidopsis allotetraploids. In Arabidopsis thaliana and Arabidopsis arenosa, both cis and trans with predominant cis-regulatory effects mediate gene-expression divergence. The majority of genes with both cis- and trans-effects are subjected to compensating interactions and stabilizing selection. Interestingly, chromatin modifications correlate with cis - and trans -regulation. In F1 allotetraploids, Arabidopsis arenosa trans factors predominately affect allelic expression divergence. Arabidopsis arenosa trans factors tend to upregulate Arabidopsis thaliana alleles, whereas Arabidopsis thaliana trans factors up- or down-regulate Arabidopsis arenosa alleles. In resynthesized and natural allotetraploids, trans effects drive expression of both homoeologous loci into the same direction. We provide evidence for natural selection and chromatin regulation in shaping gene-expression diversity during plant evolution and speciation. Examination of gene expression in 5 tetraploid Arabidopsis using mRNA-seq
Project description:Gene-expression divergence between species shapes morphological evolution, but the molecular basis is largely unknown. Here we show cis- and trans-regulatory elements and chromatin modifications on gene-expression diversity in genetically tractable Arabidopsis allotetraploids. In Arabidopsis thaliana and Arabidopsis arenosa, both cis and trans with predominant cis-regulatory effects mediate gene-expression divergence. The majority of genes with both cis- and trans-effects are subjected to compensating interactions and stabilizing selection. Interestingly, chromatin modifications correlate with cis - and trans -regulation. In F1 allotetraploids, Arabidopsis arenosa trans factors predominately affect allelic expression divergence. Arabidopsis arenosa trans factors tend to upregulate Arabidopsis thaliana alleles, whereas Arabidopsis thaliana trans factors up- or down-regulate Arabidopsis arenosa alleles. In resynthesized and natural allotetraploids, trans effects drive expression of both homoeologous loci into the same direction. We provide evidence for natural selection and chromatin regulation in shaping gene-expression diversity during plant evolution and speciation.
Project description:Gene expression evolution can be caused by changes in cis- or trans-regulatory elements or both. As cis and trans regulation operate through different molecular mechanisms, cis and trans mutations may show different inheritance patterns and may be subjected to different selective constraints. To investigate these issues, we obtained and analyzed gene expression data from two Saccharomyces cerevisiae strains and their hybrid, using high-throughput sequencing. Our data indicate that compared to other types of genes, those with antagonistic cis-trans interactions are more likely to exhibit over- or under-dominant inheritance of expression level. Moreover, in accordance with previous studies, genes with trans variants tend to have a dominant inheritance pattern while cis variants are enriched for additive inheritance. In addition, cis regulatory differences contribute more to expression differences between species than within species, whereas trans regulatory differences show a stronger association between divergence and polymorphism. Our data indicate that in the trans component of gene expression differences genes subjected to weaker selective constraints tend to have an excess of polymorphism over divergence compared to those subjected to stronger selective constraints. In contrast, in the cis component, this difference between genes under stronger and weaker selective constraint is mostly absent. To explain these observations, we propose that purifying selection more strongly shapes trans polymorphism than cis polymorphism. Study the gene expression patterns in two strains of yeast (BY and RM)
Project description:The basic body plan and major physiological axes have been highly conserved during mammalian evolution, yet only a small fraction of the human genome sequence appears to be subject to evolutionary constraint. To quantify cis- versus trans-acting contributions to mammalian regulatory evolution, we performed genomic DNase I footprinting of the mouse genome across 25 cell and tissue types, collectively defining ~8.6 million transcription factor (TF) occupancy sites at nucleotide resolution. Here we show that mouse TF footprints conjointly encode a regulatory lexicon that is ~95% similar with that derived from human TF footprints. However, only ~20% of mouse TF footprints have human orthologues. Despite substantial turnover of the cis-regulatory landscape, nearly half of all pairwise regulatory interactions connecting mouse TF genes have been maintained in orthologous human cell types through evolutionary innovation of TF recognition sequences. Furthermore, the higher-level organization of mouse TF-to-TF connections into cellular network architectures is nearly identical with human. Our results indicate that evolutionary selection on mammalian gene regulation is targeted chiefly at the level of trans-regulatory circuitry, enabling and potentiating cis-regulatory plasticity. We performed genomic DNase I footprinting of the mouse genome across 25 cell and tissue types, collectively defining ~8.6 million transcription factor (TF) occupancy sites at nucleotide resolution.
Project description:Both cis- and trans-acting changes could accumulate and participate in complex interactions, so to isolate the cis-regulatory component of patterning evolution, we measured allele-specific spatial gene expression patterns in Drosophila melanogaster × D. simulans hybrid embryos. RNA-seq of cryosectioned slices revealed 55 genes with strong spatially-varying allele-specific expression, and several hundred more with weaker but significant spatial divergence. Combined with mathematical modeling and regulatory locus editing, we determine the SNP responsible for the allele-specific expression observed in the gene hunchback.
Project description:Gene expression differences between species are driven by both cis and trans effects. Whereas cis effects on gene expression are due to nearby genetic variants, trans effects are due to distal genetic variants that affect diffusible elements such as transcription factors. However, as previous studies have mostly assessed the impacts of cis and trans effects at the gene level, how cis and trans effects differentially impact regulatory elements such as enhancers and promoters remains poorly understood. Here, we used massively parallel reporter assays to directly measure cis and trans effects between human and mouse embryonic stem cells at thousands of individual regulatory elements, including enhancers as well as promoters of both protein-coding and long non-coding RNA genes. Our approach revealed that cis effects are widespread across regulatory elements, and the strongest cis effects are associated with the disruption of motifs recognized by strong transcriptional activators. Conversely, we found that trans effects are rare but stronger in enhancers than promoters, and can be attributed to a subset of transcription factors that are differentially expressed between human and mouse. While previous gene-based studies have found extensive co-occurrence of cis and trans effects in opposite directions that stabilize gene expression between species—or compensatory cis-trans effects—we find that cis-trans compensation is uncommon within individual regulatory elements. Moreover, regulatory elements that do show compensatory cis-trans effects are often less redundant than regulatory elements lacking compensatory cis-trans effects. Thus, our results are consistent with a model wherein compensatory cis-trans effects occur more often through crosstalk between multiple redundant regulatory elements than within a single individual regulatory element. Together, these results indicate that studying the evolution of individual regulatory elements is pivotal to understand the tempo and mode of gene expression evolution.
Project description:Modification of cis regulatory elements to produce differences in gene expression level, localization, and timing is an important mechanism by which organisms evolve divergent adaptations. To examine gene regulatory change during the domestication of maize from its wild progenitor, teosinte, we assessed allele-specific expression in a collection of maize and teosinte inbreds and their F1 hybrids using three tissues from different developmental stages. Our use of F1 hybrids represents the first study in a domesticated crop and wild progenitor that dissects cis and trans regulatory effects to examine characteristics of genes under various cis and trans regulatory regimes. We find evidence for consistent cis regulatory divergence that differentiates maize from teosinte in approximately 4% of genes. These genes are significantly correlated with genes under selection during domestication and crop improvement, suggesting an important role for cis regulatory elements in maize evolution. We assayed genome-wide cis and trans regulatory differences between maize and its wild progenitor, teosinte, using deep RNA sequencing in F1 hybrid and parent inbred lines for three tissue types (ear, leaf and stem) followed by assessment of allele-specific gene expression.