Project description:The little skate, a cartilaginous fish evolutionarily distal from tetrapods, displays walking-like behavior and has conserved genetic programs and neuronal substrates for land-walking. Studies on little skate have been limited due to lack of high-quality genome assembly. Here, we generated an improved genome assembly of little skate reflecting precise gene annotation and structures and performed integrated analysis of gene expression and chromatin accessibility to investigate molecular mechanisms of fin motor neuron development. Through interspecies comparison of RNA expression, common and species-specific genes expressed in fin/limb/wing level motor neurons were identified. Moreover, by performing chromatin accessibility analysis with a pure fin motor neuron population the potential regulators controlling the gene expression in fin motor neurons were identified. Interspecies comparison of genomic data, gene expression, and chromatin accessibility assay suggest that the little skate has highly conserved gene regulatory mechanisms controlling tetrapod locomotion, which was not previously expected.
Project description:Sea urchins are emblematic marine animals with a rich fossil record and represent instrumental models for developmental biology. As echinoderms, sea urchins display several characteristics that set them apart from other deuterostomes such as their highly regulative embryonic development and their unique pentaradial adult body plan. To determine whether these characteristics are linked to particular genomic rearrangement or gene regulatory rewiring, we introduce a chromosome-scale genome assembly for sea urchin Paracentrotus lividus as well as extensive transcriptomic and epigenetic profiling during its embryonic development. We found that sea urchins show opposite modalities of genome evolution as compared to those of vertebrates: they retained ancestral chromosomal linkages that otherwise underwent mixing in vertebrates, while their intrachromosomal gene order has evolved much faster between sea urchin species that split 60 Myr ago than it did in vertebrates. We further assessed the conservation of the cis-regulatory program between sea urchins and chordates and identified conserved modules despite the developmental and body plan differences. We documented regulatory events underlying processes like zygotic genome activation and transition to larval stage in sea urchins. We also identified a burst of gene duplication in the echinoid lineage and showed that some of these expanded genes are involved in organismal novelties, such as Aristotle's lantern, tube feet, or in the specification of lineages through for instance the pmar1 and pop genes. Altogether, our results suggest that gene regulatory networks controlling development can be conserved despite extensive gene order rearrangement.
Project description:YerA41 is a myoviridae bacteriophage that was originally isolated due its ability to infect Yersinia ruckeri bacteria, the causative agent of enteric redmouth disease of salmonid fish. Several attempts to determine its genomic DNA sequence using traditional and next generation sequencing technologies failed, indicating that the phage genome is modified such way that it is an unsuitable template for PCR amplification and sequencing. To determine the YerA41 genome sequence we isolated RNA from phage-infected Y. ruckeri cells at different time points post-infection, and sequenced it. The host-genome specific reads were substracted and de novo assembly was performed on the unaligned reads.
Project description:The little skate, a cartilaginous fish evolutionarily distal from tetrapods, displays walking-like behavior and has conserved genetic programs and neuronal substrates for land-walking. Studies on little skate have been limited due to lack of high-quality genome assembly. Here, we generated an improved genome assembly of little skate reflecting precise gene annotation and structures and performed integrated analysis of gene expression and chromatin accessibility to investigate molecular mechanisms of fin motor neuron development. Through interspecies comparison of RNA expression, common and species-specific genes expressed in fin/limb/wing level motor neurons were identified. Moreover, by performing chromatin accessibility analysis with a pure fin motor neuron population the potential regulators controlling the gene expression in fin motor neurons were identified. Interspecies comparison of genomic data, gene expression, and chromatin accessibility assay suggest that the little skate has highly conserved gene regulatory mechanisms controlling tetrapod locomotion, which was not previously expected.
2022-10-24 | GSE180336 | GEO
Project description:Genome assembly of Pearlspot fish
Project description:The naked mole-rat (NMR; Heterocephalus glaber) has recently gained considerable attention in the scientific community for its unique potential to unveil novel insights in the fields of medicine, biochemistry, and evolution. NMRs exhibit unique adaptations that include protracted fertility, cancer resistance, eusociality, and anoxia. This suite of adaptations is not found in other rodent species, suggesting that interrogating conserved and accelerated regions in the NMR genome will find regions of the NMR genome fundamental to their unique adaptations. However, the current NMR genome assembly has limits that make studying structural variations, heterozygosity, and non-coding adaptations challenging. We present a complete diploid naked-mole rat genome assembly by integrating long-read and 10X-linked read genome sequencing of a male NMR and its parents, and Hi-C sequencing in the NMR hypothalamus (N=2). Reads were identified as maternal, paternal or ambiguous (TrioCanu). We then polished genomes with Flye, Racon and Medaka. Assemblies were then scaffolded using the following tools in order: Scaff10X, Salsa2, 3d-DNA, Minimap2-alignment between assemblies, and the Juicebox Assembly Tools. We then subjected the assemblies to another round of polishing, including short-read polishing with Freebayes. We assembled the NMR mitochondrial genome with mitoVGP. Y chromosome contigs were identified by aligning male and female 10X linked reads to the paternal genome and finding male-biased contigs not present in the maternal genome. Contigs were assembled with publicly available male NMR Fibroblast Hi-C-seq data (SRR820318). Both assemblies have their sex chromosome haplotypes merged so that both assemblies have a high-quality X and Y chromosome. Finally, assemblies were evaluated with Quast, BUSCO, and Merqury, which all reported the base-pair quality and contiguity of both assemblies as high-quality. The assembly will next be annotated by Ensembl using public RNA-seq data from multiple tissues (SRP061363). Together, this assembly will provide a high-quality resource to the NMR and comparative genomics communities.