Project description:Frogs are an ecologically diverse and phylogenetically ancient group of anuran amphibians that include important vertebrate cell and developmental model systems, notably the genus Xenopus. Here we report a high-quality reference genome sequence for the western clawed frog, Xenopus tropicalis, along with draft chromosome-scale sequences of three distantly related emerging model frog species, Eleutherodactylus coqui, Engystomops pustulosus and Hymenochirus boettgeri. Frog chromosomes have remained remarkably stable since the Mesozoic Era, with limited Robertsonian (i.e., centric) translocations and end-to-end fusions found among the smaller chromosomes. Conservation of synteny includes conservation of centromere locations, marked by centromeric tandem repeats associated with Cenp-a binding, surrounded by pericentromeric LINE/L1 elements. We explored chromosome structure across frogs, using a dense meiotic linkage map for X. tropicalis and chromatin conformation capture (Hi-C) data for all species. Abundant satellite repeats occupy the unusually long (~20 megabase) terminal regions of each chromosome that coincide with high rates of recombination. Both embryonic and differentiated cells show reproducible association of centromeric chromatin, and of telomeres, reflecting a Rabl-like configuration. Our comparative analyses reveal 13 conserved ancestral anuran chromosomes from which contemporary frog genomes were constructed.
Project description:Macaque species share over 93% genome homology with humans and develop many disease phenotypes similar to those of humans, making them valuable animal models for the study of human diseases (e.g.,HIV and neurodegenerative diseases). However, the quality of genome assembly and annotation for several macaque species lags behind the human genome effort. To close this gap and enhance functional genomics approaches, we employed a combination of de novo linked-read assembly and scaffolding using proximity ligation assay (HiC) to assemble the pig-tailed macaque (Macaca nemestrina) genome. This combinatorial method yielded large scaffolds at chromosome-level with a scaffold N50 of 127.5 Mb; the 23 largest scaffolds covered 90% of the entire genome. This assembly revealed large-scale rearrangements between pig-tailed macaque chromosomes 7, 12, and 13 and human chromosomes 2, 14, and 15. We subsequently annotated the genome using transcriptome and proteomics data from personalized induced pluripotent stem cells (iPSCs) derived from the same animal. Reconstruction of the evolutionary tree using whole genome annotation and orthologous comparisons among three macaque species, human and mouse genomes revealed extensive homology between human and pig-tailed macaques with regards to both pluripotent stem cell genes and innate immune gene pathways. Our results confirm that rhesus and cynomolgus macaques exhibit a closer evolutionary distance to each other than either species exhibits to humans or pig-tailed macaques. These findings demonstrate that pig-tailed macaques can serve as an excellent animal model for the study of many human diseases particularly with regards to pluripotency and innate immune pathways.
Project description:During embryonic development, maintenance of cell identity and lineage commitment requires the Polycomb-group PRC2 complex, which catalyzes histone H3 K27 trimethylation (H3K27me3). However, the developmental origins of this regulation are unknown. Here, we report on H3K27me3 deposition dynamics in Xenopus embryos, on sequence elements that initiate deposition during pluripotency, and the sequence characteristics that segregate Polycomb-regulated domains from the rest of the genome. Strikingly, although PRC2 binds widely to active enhancers, H3K27me3 is only deposited at a small subset of these sites. Using a Support Vector Machine algorithm these sequences can be predicted accurately on basis of DNA sequence alone, with a sequence signature conserved between humans, frog and fish. The results suggest a genetic-default model in which genomic sequence constrains Polycomb regulation. ChIP-seq profiles of three histone modifications (H3K4me3, H3K27me3 and H3K4me1) and RNA Polymerase II, EZH2 and Jarid2 of Xenopus tropicalis embryos during development
Project description:During embryonic development, maintenance of cell identity and lineage commitment requires the Polycomb-group PRC2 complex, which catalyzes histone H3 K27 trimethylation (H3K27me3). However, the developmental origins of this regulation are unknown. Here, we report on H3K27me3 deposition dynamics in Xenopus embryos, on sequence elements that initiate deposition during pluripotency, and the sequence characteristics that segregate Polycomb-regulated domains from the rest of the genome. Strikingly, although PRC2 binds widely to active enhancers, H3K27me3 is only deposited at a small subset of these sites. Using a Support Vector Machine algorithm these sequences can be predicted accurately on basis of DNA sequence alone, with a sequence signature conserved between humans, frog and fish. The results suggest a genetic-default model in which genomic sequence constrains Polycomb regulation.
2013-11-28 | GSE41161 | GEO
Project description:Engystomops pustulosus (Tungara frog) genome, aEngPut1, sequence data