Project description:How modification of gene expression generates novel traits is key to understanding the evolutionary process. Here we investigated the genetic basis for the origin of the piscine gas bladder from lungs of ancestral bony vertebrates. Distinguishing these homologous organs is the direction of budding from the foregut during development; lungs bud ventrally and the gas bladder buds dorsally. We investigated whether this morphological inversion is associated with the molecular inversion of conserved genes regulating lung and gas bladder development. Using laser-capture microdissection and RNA-seq, we assayed transcript abundance and compared expression patterns between dorsal and ventral foregut tissues at three developmental stages spanning gasbladder development. Our focal taxon, bowfin (Amia calva), representing the sistergroup to teleosts, is an early diverging ray-finned fish with a gas bladder. We discovered a number of genes with unknown function during lung development that are differentially expressed during gas bladder development and annotated to functions relevant for organ budding. We also identified several known lung-regulatory genes that exhibit inverted dorsoventral expression during gasbladder development relative to lung development. In particular, we found Tbx5 is strongly expressed in the dorsal mesoderm surrounding the gas bladder during bowfin development, and several interacting genes are co-expressed dorsally with Tbx5. In contrast, in mouse and bichir (Polypterus senegalus), the only ray-finned fish that have lungs, Tbx5 is expressed in the ventral lung mesoderm during lung development. Our data demonstrating dorsoventral inversion of conserved genes suggest that these genes may have contributed to the evolutionary transition between ventral lungs and a dorsal gas bladder in ray-finned fishes.
Project description:The six species of lungfish possess both lungs and gills and are the closest extant relatives of tetrapods. Here, we report a single-cell transcriptome atlas of the West African lungfish (Protopterus annectens). This species manifests the most extreme form of terrestrialization, a life history strategy to survive dry periods in five lungfish species that can last for years, characterized by dormancy and reversible adaptive changes of the gills and lungs. Our atlas highlights the cell type diversity of the West African lungfish, including gene expression consistent with phenotype changes of terrestrialization. Comparisons with terrestrial tetrapods and ray-finned fishes revealed broad homology between the swim bladder and lung cell types as well as shared and idiosyncratic changes of the external gills of the West African lungfish and the internal gills of Atlantic salmon. The single-cell atlas presented here provides a valuable resource for further exploring the evolution of the vertebrate respiratory system and the diversity of lungfish terrestrialization.
2023-08-05 | GSE240094 | GEO
Project description:FishPIE: a universal phylogenetically informative exon markers set for ray-finned fishes