Project description:Mechanisms of X chromosome dosage compensation have been studied extensively in a few model species representing clades of shared sex chromosome ancestry. However, the diversity within each clade as a function of sex chromosome evolution is largely unknown. Here, we anchor ourselves to the nematode Caenorhabditis elegans, for which a well-studied mechanism of dosage compensation occurs through a specialized structural maintenance of chromosomes (SMC) complex, and explore the diversity of dosage compensation in the surrounding phylogeny of nematodes. Through phylogenetic analysis of the C. elegans dosage compensation complex and a survey of its epigenetic signatures, including X-specific topologically associating domains (TADs) and X-enrichment of H4K20me1, we found that the condensin-mediated mechanism evolved recently in the lineage leading to Caenorhabditis through an SMC-4 duplication. Intriguingly, an independent duplication of SMC-4 and the presence of X-specific TADs in Pristionchus pacificus suggest that condensin-mediated dosage compensation arose more than once. mRNA-seq analyses of gene expression in several nematode species indicate that dosage compensation itself is ancestral, as expected from the ancient XO sex determination system. Indicative of the ancestral mechanism, H4K20me1 is enriched on the X chromosomes in Oscheius tipulae, which does not contain X-specific TADs or SMC-4 paralogs. Together, our results indicate that the dosage compensation system in C. elegans is surprisingly new, and condensin may have been co-opted repeatedly in nematodes, suggesting that the process of evolving a chromosome-wide gene regulatory mechanism for dosage compensation is constrained.
Project description:Mechanisms of X chromosome dosage compensation have been studied extensively in a few model species representing clades of shared sex chromosome ancestry. However, the diversity within each clade as a function of sex chromosome evolution is largely unknown. Here, we anchor ourselves to the nematode Caenorhabditis elegans, for which a well-studied mechanism of dosage compensation occurs through a specialized structural maintenance of chromosomes (SMC) complex, and explore the diversity of dosage compensation in the surrounding phylogeny of nematodes. Through phylogenetic analysis of the C. elegans dosage compensation complex and a survey of its epigenetic signatures, including X-specific topologically associating domains (TADs) and X-enrichment of H4K20me1, we found that the condensin-mediated mechanism evolved recently in the lineage leading to Caenorhabditis through an SMC-4 duplication. Intriguingly, an independent duplication of SMC-4 and the presence of X-specific TADs in Pristionchus pacificus suggest that condensin-mediated dosage compensation arose more than once. mRNA-seq analyses of gene expression in several nematode species indicate that dosage compensation itself is ancestral, as expected from the ancient XO sex determination system. Indicative of the ancestral mechanism, H4K20me1 is enriched on the X chromosomes in Oscheius tipulae, which does not contain X-specific TADs or SMC-4 paralogs. Together, our results indicate that the dosage compensation system in C. elegans is surprisingly new, and condensin may have been co-opted repeatedly in nematodes, suggesting that the process of evolving a chromosome-wide gene regulatory mechanism for dosage compensation is constrained.
Project description:In Caenorhabditis elegans, the dosage compensation complex (DCC) specifically binds to and represses transcription from both X chromosomes in hermaphrodites. The DCC is composed of an X-specific condensin complex that interacts with several proteins. During embryogenesis, DCC starts localizing to the X chromosomes around the 40-cell stage, and is followed by X-enrichment of H4K20me1 between 100-cell to comma stage. Here, we analyzed dosage compensation of the X chromosome between sexes, and the roles of dpy-27 (condensin subunit), dpy-21 (non-condensin DCC member), set-1 (H4K20 monomethylase) and set-4 (H4K20 di-/tri-methylase) in X chromosome repression using mRNA-seq and ChIP-seq analyses across several developmental time points. We found that the DCC starts repressing the X chromosomes by the 40-cell stage, but X-linked transcript levels remain significantly higher in hermaphrodites compared to males through the comma stage of embryogenesis. Dpy-27 and dpy-21 are required for X chromosome repression throughout development, but particularly in early embryos dpy-27 and dpy-21 mutations produced distinct expression changes, suggesting a DCC independent role for dpy-21. We previously hypothesized that the DCC increases H4K20me1 by reducing set-4 activity on the X chromosomes. Accordingly, in the set-4 mutant, H4K20me1 increased more from the autosomes compared to the X, equalizing H4K20me1 level between X and autosomes. H4K20me1 increase on the autosomes led to a slight repression, resulting in a relative effect of X derepression. H4K20me1 depletion in the set-1 mutant showed greater X derepression compared to equalization of H4K20me1 levels between X and autosomes in the set-4 mutant, indicating that H4K20me1 level is important, but X to autosomal balance of H4K20me1 contributes only slightly to X-repression. Thus H4K20me1 by itself is not a downstream effector of the DCC. In summary, X chromosome dosage compensation starts in early embryos as the DCC localizes to the X, and is strengthened in later embryogenesis by H4K20me1.
Project description:In Caenorhabditis elegans, the dosage compensation complex (DCC) specifically binds to and represses transcription from both X chromosomes in hermaphrodites. The DCC is composed of an X-specific condensin complex that interacts with several proteins. During embryogenesis, DCC starts localizing to the X chromosomes around the 40-cell stage, and is followed by X-enrichment of H4K20me1 between 100-cell to comma stage. Here, we analyzed dosage compensation of the X chromosome between sexes, and the roles of dpy-27 (condensin subunit), dpy-21 (non-condensin DCC member), set-1 (H4K20 monomethylase) and set-4 (H4K20 di-/tri-methylase) in X chromosome repression using mRNA-seq and ChIP-seq analyses across several developmental time points. We found that the DCC starts repressing the X chromosomes by the 40-cell stage, but X-linked transcript levels remain significantly higher in hermaphrodites compared to males through the comma stage of embryogenesis. Dpy-27 and dpy-21 are required for X chromosome repression throughout development, but particularly in early embryos dpy-27 and dpy-21 mutations produced distinct expression changes, suggesting a DCC independent role for dpy-21. We previously hypothesized that the DCC increases H4K20me1 by reducing set-4 activity on the X chromosomes. Accordingly, in the set-4 mutant, H4K20me1 increased more from the autosomes compared to the X, equalizing H4K20me1 level between X and autosomes. H4K20me1 increase on the autosomes led to a slight repression, resulting in a relative effect of X derepression. H4K20me1 depletion in the set-1 mutant showed greater X derepression compared to equalization of H4K20me1 levels between X and autosomes in the set-4 mutant, indicating that H4K20me1 level is important, but X to autosomal balance of H4K20me1 contributes only slightly to X-repression. Thus H4K20me1 by itself is not a downstream effector of the DCC. In summary, X chromosome dosage compensation starts in early embryos as the DCC localizes to the X, and is strengthened in later embryogenesis by H4K20me1. RNA-Seq profiles of C. elegans wild type hermaphrodite, mixed sex, at 5 time points and dpy-27, set-4, dpy-21, set-1 and RNAi at 2-3 time points with 3-4 replicates each. RNA-Seq profiles of C. elegans. Strains are N2 (wild type), BS553 fog-2(oz40) V, CB428 dpy-21(e428) V, MK4 dpy-27(y56) III, MT14911 set-4 (n4600) II, SS1075 set-1(tm1821)/hT2g[bli-4(e937) let-?(q782) qIs48] (I;III). Set-1 collections made as heterozygotes and dpy-27(y56) homozygotes. Spike in RNA-seq libraries have AF16 wild type C. briggsae L1s added at a 1:10 ratio. Timepoints are early embryos (synchronized collection, <40 cells), comma embryos (synchronized early embryos aged for 4 hours), mixed embryos (mixed stage embryos from unsynchronized population), L1 (synchronized L1 larvae), L3 (synchronized L3 larvae), and YA (synchronized young adults, collected before embryos present in hermaphrodite gonad). Biological replicates for each strain/stage listed separately. ChIP-seq profiles of C. elegans DCC subunit dpy-27, H4K20me1 histone modification and RNA pol II large subunit ama-1 in 3-6 replicates from mixed stage (unsynchronized) embryos and synchronized L3 larvae. Corresponding inputs are labelled with "Input_" plus ChIP name.
Project description:Dosage Compensation is required to correct for uneven gene dose between the sexes. We utilized global run-on sequencing (GRO-seq) to examine how Caenorhabditis elegans dosage compensation reduces transcription of X-linked genes. To facilitate these experiments, we required accurate 5’-ends of genes that have been missing due to a co-transcriptional trans-splicing event common in nematodes. We developed a modified GRO-seq protocol to identify TSSs that are supported by transcription, and determined that TSSs lie more than 1 kb upstream of the previously annotated TSS for nearly one-quarter of all genes. We then investigated the changes that occur in transcriptionally engaged RNA Polymerase when dosage compensation is disrupted, and find that dosage compensation controls recruitment of RNA Polymerase to X-linked genes.
Project description:Dosage Compensation is required to correct for uneven gene dose between the sexes. We utilized global run-on sequencing (GRO-seq) to examine how Caenorhabditis elegans dosage compensation reduces transcription of X-linked genes. To facilitate these experiments, we required accurate 5M-bM-^@M-^Y-ends of genes that have been missing due to a co-transcriptional trans-splicing event common in nematodes. We developed a modified GRO-seq protocol to identify TSSs that are supported by transcription, and determined that TSSs lie more than 1 kb upstream of the previously annotated TSS for nearly one-quarter of all genes. We then investigated the changes that occur in transcriptionally engaged RNA Polymerase when dosage compensation is disrupted, and find that dosage compensation controls recruitment of RNA Polymerase to X-linked genes. GRO-seq experiments (two biological replicates) were performed in nuclei from many wild-type states and a dosage compensation mutant
Project description:Dosage Compensation is required to correct for uneven gene dose between the sexes. We utilized global run-on sequencing (GRO-seq) to examine how Caenorhabditis elegans dosage compensation reduces transcription of X-linked genes. To facilitate these experiments, we required accurate 5M-bM-^@M-^Y-ends of genes that have been missing due to a co-transcriptional trans-splicing event common in nematodes. We developed a modified GRO-seq protocol to identify TSSs that are supported by transcription, and determined that TSSs lie more than 1 kb upstream of the previously annotated TSS for nearly one-quarter of all genes. We then investigated the changes that occur in transcriptionally engaged RNA Polymerase when dosage compensation is disrupted, and find that dosage compensation controls recruitment of RNA Polymerase to X-linked genes. Two biological replicates of ChIP with DPY-27 and a random rabbit IgG
Project description:Dosage Compensation is required to correct for uneven gene dose between the sexes. We utilized global run-on sequencing (GRO-seq) to examine how Caenorhabditis elegans dosage compensation reduces transcription of X-linked genes. To facilitate these experiments, we required accurate 5’-ends of genes that have been missing due to a co-transcriptional trans-splicing event common in nematodes. We developed a modified GRO-seq protocol to identify TSSs that are supported by transcription, and determined that TSSs lie more than 1 kb upstream of the previously annotated TSS for nearly one-quarter of all genes. We then investigated the changes that occur in transcriptionally engaged RNA Polymerase when dosage compensation is disrupted, and find that dosage compensation controls recruitment of RNA Polymerase to X-linked genes.
Project description:Dosage Compensation is required to correct for uneven gene dose between the sexes. We utilized global run-on sequencing (GRO-seq) to examine how Caenorhabditis elegans dosage compensation reduces transcription of X-linked genes. To facilitate these experiments, we required accurate 5’-ends of genes that have been missing due to a co-transcriptional trans-splicing event common in nematodes. We developed a modified GRO-seq protocol to identify TSSs that are supported by transcription, and determined that TSSs lie more than 1 kb upstream of the previously annotated TSS for nearly one-quarter of all genes. We then investigated the changes that occur in transcriptionally engaged RNA Polymerase when dosage compensation is disrupted, and find that dosage compensation controls recruitment of RNA Polymerase to X-linked genes.
Project description:Dosage Compensation is required to correct for uneven gene dose between the sexes. We utilized global run-on sequencing (GRO-seq) to examine how Caenorhabditis elegans dosage compensation reduces transcription of X-linked genes. To facilitate these experiments, we required accurate 5M-bM-^@M-^Y-ends of genes that have been missing due to a co-transcriptional trans-splicing event common in nematodes. We developed a modified GRO-seq protocol to identify TSSs that are supported by transcription, and determined that TSSs lie more than 1 kb upstream of the previously annotated TSS for nearly one-quarter of all genes. We then investigated the changes that occur in transcriptionally engaged RNA Polymerase when dosage compensation is disrupted, and find that dosage compensation controls recruitment of RNA Polymerase to X-linked genes. GRO-cap reactions were performed with TAP, and without TAP as a control.