Project description:To investigate how organisms mitigate the deleterious effects of mistranslation during evolution, a mutant tRNA was expressed in S. cerevisiae. The expression of Candida Ser-tRNACAG from a low copy plasmid in S. cerevisiae promoted mistranslation events by random incorporation of both serine and leucine at CUG codons. As mistranslation causes an overload of the protein quality pathways, it disrupts cellular protein homeostasis leading to a major fall in fitness. Laboratory evolutionary experiments were performed to study whether the fitness cost of mistranslation can be lowered. We also wanted to identify the cost-reduction strategy: reducing the frequencies of errors (mitigation), or increasing tolerance to errors (robustness), either by global or local activities. Gene expression was measured in the ancestor (non-evolved) lineage in two different situations: 1) carrying an empty vector and 2) expressing the mutant Ser-tRNACAG. Gene expression was also measured in three ambiguously evolved lineages (B3, D11, H9) in both situations (carrying an empty vector and expressing the mutant tRNA). Three independent experiments were performed for each lineage. Non-evolved strain with empty vector was used as control sample.
Project description:The interplay between phenotypic plasticity and adaptive evolution has long been an important topic of evolutionary biology. This process is critical to our understanding of a species evolutionary potential in light of rapid climate changes. Despite recent theoretical work, empirical studies of natural populations, especially in marine invertebrates, are scarce. In this study, we investigated the relationship between adaptive divergence and plasticity by integrating genetic and phenotypic variation in Pacific oysters from its natural range in China. Genome resequencing of 371 oysters revealed unexpected fine-scale genetic structure that is largely consistent with phenotypic divergence in growth, physiology, thermal tolerance and gene expression across environmental gradient. These findings suggest that selection and local adaptation are pervasive and together with limited gene flow shape adaptive divergence. Plasticity in gene expression is positively correlated with evolved divergence, indicating that plasticity is adaptive and likely favored by selection in organisms facing dynamic environments such as oysters. Divergence in heat response and tolerance implies that the evolutionary potential to a warming climate differs among oyster populations. We suggest that trade-offs in energy allocation are important to adaptive divergence with acetylation playing a role in energy depression under thermal stress.
Project description:Recent discussions of human brain evolution have largely focused on increased neuron numbers and changes in their connectivity and expression. However, it is increasingly appreciated that oligodendrocytes play important roles in cognitive function and disease. Whether both cell types follow distinctive evolutionary trajectories is not known. We examined the transcriptomes of neurons and oligodendrocytes in the frontal cortex of humans, chimpanzees, and rhesus macaques. We identified human-specific trajectories of gene expression in oligodendrocytes and show that oligodendrocytes have undergone accelerated gene expression evolution in the human lineage. The signature of acceleration is enriched for cell type-specific expression alterations in schizophrenia. These results underscore the importance of oligodendrocytes in human brain evolution.
Project description:We examined adaptive morphological divergence and epigenetic variation in genetically impoverished asexual populations of a freshwater snail, Potamopyrgus antipodarum from distinct environments. These populations exhibit environment-specific adaptive divergence in shell shape and significant genome wide DNA methylation differences among differentially adapted lake and fast water flow river populations. The epigenetic variation correlated with adaptive phenotypic variation in rapidly adapting asexual animal populations. This provides one of the first examples of environmentally-driven differences in epigenetics that associates with adaptive phenotypic divergence.
Project description:We examined adaptive morphological divergence and epigenetic variation in genetically impoverished asexual populations of a freshwater snail, Potamopyrgus antipodarum from distinct environments. These populations exhibit environment-specific adaptive divergence in shell shape and significant genome wide DNA methylation differences among differentially adapted lake and fast water flow river populations. The epigenetic variation correlated with adaptive phenotypic variation in rapidly adapting asexual animal populations. This provides one of the first examples of environmentally-driven differences in epigenetics that associates with adaptive phenotypic divergence.
Project description:Here we derive human and chimpanzee cranial neural crest cells (CNCCs) and profile histone modifications, transcription factors, chromatin accessibility and gene expression to systematically and quantitatively annotate evolutionary divergence of craniofacial cis-regulatory landscapes.
Project description:Long noncoding RNA sequences evolve relatively rapidly, but it is unclear whether this is due to relaxed constraint or accelerated evolution. Here, we trace the recent evolutionary history of human lncRNAs, using genomes of multiple individuals from all great ape species to map fixed lineage-specific nucleotide variants. We find that the lower conservation of lncRNAs compared to protein coding genes partially arises from lncRNA’s more recent evolutionary origin. We identify more than one hundred lncRNAs that show some evidence of accelerated evolution in at least one primate species, including 17 in human. Several of these display transcriptional regulatory activity in an RNA-specific reporter assay. By experimentally reconstructing the ancestral lncRNA sequence, we find that this activity has been altered by human-specific nucleotide substitutions. Functional analysis of accelerated lncRNAs with specific expression in blood suggests lncRNAs have participated in adaptive regulatory changes in the immune system during recent human evolution. Together our results provide evidence that accelerated evolution of lncRNAs may have contributed, through regulatory changes, to human-specific phenotypes.