Project description:Gene copy-number variation, which provides the raw material for the evolution of novel genes, is surprisingly widespread in natural populations. Experimental evolution studies have demonstrated an extremely high spontaneous rate of origin of gene duplications. When organisms are suboptimally adapted to their environment, gene duplication may compensate for reduced fitness by amplifying promiscuous activity of a gene, or increasing dosage of a suboptimal gene. The overarching goal of this study is to inverstigate whether CNVs constitute a common mechanism of adaptive genetic change during compensatory evolution and to further characterize the role of natural selection in dictating their evolutionary spread at a population-genomic level. Outcrossing populations of C. elegans with low fitness were evolved for >200 generations and the frequencies of CNVs in these populations were analyzed by oligonucleotide array comparative genome hybridization, quantitative PCR, and single-worm PCR. Multiple duplications and deletions were detected in intermediate to high frequencies and several lines of evidence suggest that the changes in frequency were adaptive. 1) Many copy-number changes reached high frequency, were near fixation, or were fixed in a short time. 2) Many independent duplications and deletions in high frequency harbor overlapping regions which likely include genes that are under selection for either higher or lower rates of expression. 3) The size spectrum of deuplications and deletions in the adaptive recovery populations is significantly larger than that of spontaneous copy-number variants in mutation accumulation experiments. This is expected if larger CNVs are more likely to encompass genes that are being selected for altered gene dosage. Out results validate the great potential borne by gene copy-number changes for compensatory evolution and adaptation. Experimental genome evolution of copy-number variants in 25 experimental lines compared to 5 ancestral control lines.
Project description:Gene copy-number variation, which provides the raw material for the evolution of novel genes, is surprisingly widespread in natural populations. Experimental evolution studies have demonstrated an extremely high spontaneous rate of origin of gene duplications. When organisms are suboptimally adapted to their environment, gene duplication may compensate for reduced fitness by amplifying promiscuous activity of a gene, or increasing dosage of a suboptimal gene. The overarching goal of this study is to inverstigate whether CNVs constitute a common mechanism of adaptive genetic change during compensatory evolution and to further characterize the role of natural selection in dictating their evolutionary spread at a population-genomic level. Outcrossing populations of C. elegans with low fitness were evolved for >200 generations and the frequencies of CNVs in these populations were analyzed by oligonucleotide array comparative genome hybridization, quantitative PCR, and single-worm PCR. Multiple duplications and deletions were detected in intermediate to high frequencies and several lines of evidence suggest that the changes in frequency were adaptive. 1) Many copy-number changes reached high frequency, were near fixation, or were fixed in a short time. 2) Many independent duplications and deletions in high frequency harbor overlapping regions which likely include genes that are under selection for either higher or lower rates of expression. 3) The size spectrum of deuplications and deletions in the adaptive recovery populations is significantly larger than that of spontaneous copy-number variants in mutation accumulation experiments. This is expected if larger CNVs are more likely to encompass genes that are being selected for altered gene dosage. Out results validate the great potential borne by gene copy-number changes for compensatory evolution and adaptation.
Project description:Gene duplication and deletion are pivotal processes shaping the structural and functional repertoire of genomes, with implications for disease, adaptation and evolution. We employed an experimental evolution framework partnered with high-throughput genomics to assess the molecular and transcriptional characteristics of novel gene copy-number variants (CNVs) in Caenorhabditis elegans populations subjected to varying intensity of selection. Here, we report a direct spontaneous genome-wide rate of gene duplication of 2.9 × 10-5 /gene/generation in C. elegans, the highest for any species to date. The increase in average transcript abundance of new duplicates arising under minimal selection is significantly greater than two-fold compared to single-copies of the same gene, suggesting that genes in segmental duplications are frequently overactive at inception. The average increase in transcriptional activity of gene duplicates is greater in MA lines that passed through single individual bottlenecks than in MA lines with larger population bottlenecks. Furthermore, there is an inverse relationship between the ancestral transcription levels of newly originating gene duplicates and population size, with duplicate copies of highly expressed genes less likely to accumulate in larger populations. The results demonstrate that there is a fitness cost of superfluous gene expression and purifying selection against new gene duplicates. However, on average, duplications also provide a significant increase in gene expression that can facilitate adaptation to novel environmental challenges.
Project description:Copy-number variants (CNVs) are large-scale amplifications or deletions of DNA that can drive rapid adaptive evolution and result in large-scale changes in gene expression. Whereas alterations in the copy number of one or more genes within a CNV can confer a selective advantage, other genes within a CNV can decrease fitness when their dosage is changed. Dosage compensation - in which the gene expression output from multiple gene copies is less than expected - is one means by which an organism can mitigate the fitness costs of deleterious gene amplification. Previous research has shown evidence for dosage compensation at both the transcriptional level and at the level of protein expression; however, the extent of compensation differs substantially between genes, strains, and studies. Here, we investigated sources of dosage compensation at multiple levels of gene expression regulation by defining the transcriptome, translatome and proteome of experimentally evolved yeast (Saccharomyces cerevisiae) strains containing adaptive CNVs.
Project description:Genome replication follows a defined temporal programme that can change during cellular differentiation and disease onset. DNA replication results in an increase in DNA copy number that can be measured by high-throughput sequencing (HTS). Here we present a protocol to determine genome replication dynamics using DNA copy number measurements. Cell populations can be obtained in three variants of the method. First, sort-seq uses fluorescence activated cell sorting (FACS) to isolate replicating and non-replicating subpopulations from asynchronous cells. Second, sync-seq uses cell synchronisation to obtain samples before and during DNA replication. Third, marker frequency analysis (MFA-seq) assesses copy number differences in rapidly replicating asynchronous cells. These approaches have been used to reveal genome replication dynamics in prokaryotes, archaea, and a wide range of eukaryotes, including mammalian cells. The whole protocol can be performed in 7-10 days.
Project description:we used Caenorhabditis elegans as a model organism, to investigate the effect of mannose on the lifespan. Using nematode RNAi methods, RT-PCR, RNA-seq and other experimental method, we explored the possible mechanism for how mannose change the lifespan of Caenorhabditis elegans.