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• 1. [Article] Epigenetic Regulation of Alternative Developmental Trajectories

  The annual killifish, Austrofundulus limnaeus, is capable of entering into a state of metabolic and developmental dormancy during embryogenesis termed diapause. However, individuals may also follow an ...

  Citation × Citation Citation Abstract Copy Title: Epigenetic Regulation of Alternative Developmental Trajectories Author: Romney, Arnie Lynn T., Podrabsky, Jason E. Year: 2017 The annual killifish, Austrofundulus limnaeus, is capable of entering into a state of metabolic and developmental dormancy during embryogenesis termed diapause. However, individuals may also follow an alternative phenotypic trajectory and instead "escaped" entry into diapause and develop continuously until hatching. Early development along the two trajectories is morphologically indistinguishable, and gene regulatory mechanisms are currently unknown. Phenotype appears to be influenced by maternal provisioning based on the observation that young females produce predominately escape embryos and older females produce diapausing embryos. Additionally, the incubation temperature of embryos can override this maternal pattern and alter trajectory. Maternal provisioning is known in many vertebrates to direct early development prior to the initiation of embryonic gene transcription. Using RNA-seq, we have generated transcriptomic profiles of messenger RNAs (mRNAs) during embryogenesis of A. limnaeus. Embryos that are destined for either the diapause or escape phenotypes have unique profiles of mRNA isoforms at fertilization; well before they are morphologically distinct. We hypothesize that maternally packaged gene products coordinate the cellular events that determine developmental trajectory in A. limnaeus. In addition, we propose the expression of environmentally responsive microRNAs during development that can override maternal provisioning. RNA-seq data during early development, after the maternal-to-zygotic transition, suggest distinct profiles of microRNA expression that are phenotype specific. Our findings suggest maternal programming of diapause through the packaging of specific mRNAs as well as temperature induced microRNAs that target maternal transcripts allowing an escape from the diapause trajectory. This presents a novel example of maternal-embryonic-conflict in gene regulation that provides the embryo with alternatives in developmental trajectories in the face of fluctuating environmental patterns. These results will not only impact our understanding of genetic mechanisms that regulate entrance into diapause, but will also provide insight into epigenetic control of development. Title: Epigenetic Regulation of Alternative Developmental Trajectories Author: Romney, Arnie Lynn T., Podrabsky, Jason E. Year: 2017 The annual killifish, Austrofundulus limnaeus, is capable of entering into a state of metabolic and developmental dormancy during embryogenesis termed diapause. However, individuals may also follow an alternative phenotypic trajectory and instead "escaped" entry into diapause and develop continuously until hatching. Early development along the two trajectories is morphologically indistinguishable, and gene regulatory mechanisms are currently unknown. Phenotype appears to be influenced by maternal provisioning based on the observation that young females produce predominately escape embryos and older females produce diapausing embryos. Additionally, the incubation temperature of embryos can override this maternal pattern and alter trajectory. Maternal provisioning is known in many vertebrates to direct early development prior to the initiation of embryonic gene transcription. Using RNA-seq, we have generated transcriptomic profiles of messenger RNAs (mRNAs) during embryogenesis of A. limnaeus. Embryos that are destined for either the diapause or escape phenotypes have unique profiles of mRNA isoforms at fertilization; well before they are morphologically distinct. We hypothesize that maternally packaged gene products coordinate the cellular events that determine developmental trajectory in A. limnaeus. In addition, we propose the expression of environmentally responsive microRNAs during development that can override maternal provisioning. RNA-seq data during early development, after the maternal-to-zygotic transition, suggest distinct profiles of microRNA expression that are phenotype specific. Our findings suggest maternal programming of diapause through the packaging of specific mRNAs as well as temperature induced microRNAs that target maternal transcripts allowing an escape from the diapause trajectory. This presents a novel example of maternal-embryonic-conflict in gene regulation that provides the embryo with alternatives in developmental trajectories in the face of fluctuating environmental patterns. These results will not only impact our understanding of genetic mechanisms that regulate entrance into diapause, but will also provide insight into epigenetic control of development. Close

• 2. [Article] Mitochondrial DNA Sequence and Lack of Response to Anoxia in the Annual Killifish <i>Austrofundulus limnaeus</i>

  The annual killifish Austrofundulus limnaeus inhabits ephemeral ponds in regions of Venezuela, South America. Permanent populations of A. limnaeus are maintained by production of stress-tolerant embryos ...

  Citation × Citation Citation Abstract Copy Title: Mitochondrial DNA Sequence and Lack of Response to Anoxia in the Annual Killifish <i>Austrofundulus limnaeus</i> Author: Wagner, Josiah T., Chavez, Florisela H., Podrabsky, Jason E. Year: 2016 The annual killifish Austrofundulus limnaeus inhabits ephemeral ponds in regions of Venezuela, South America. Permanent populations of A. limnaeus are maintained by production of stress-tolerant embryos that are able to persist in the desiccated sediment. Previous work has demonstrated that A. limnaeus have a remarkable ability to tolerate extended periods of anoxia and desiccating conditions. After considering temperature, A. limnaeus embryos have the highest known tolerance to anoxia when compared to any other vertebrate yet studied. Oxygen is completely essential for the process of oxidative phosphorylation by mitochondria, the intracellular organelle responsible for the majority of adenosine triphosphate production. Thus, understanding the unique properties of A. limnaeus mitochondria is of great interest. In this work, we describe the first complete mitochondrial genome (mtgenome) sequence of a single adult A. limnaeus individual and compare both coding and non-coding regions to several other closely related fish mtgenomes. Mitochondrial features were predicted using MitoAnnotator and polyadenylation sites were predicted using RNAseq mapping. To estimate the responsiveness of A. limnaeus mitochondria to anoxia treatment, we measure relative mitochondrial DNA copy number and total citrate synthase activity in both relatively anoxia-tolerant and anoxia-sensitive embryonic stages. Our cross-species comparative approach identifies unique features of ND1, ND5, ND6, and ATPase-6 that may facilitate the unique phenotype of A. limnaeus embryos. Additionally, we do not find evidence for mitochondrial degradation or biogenesis during anoxia/reoxygenation treatment in A. limnaeus embryos, suggesting that anoxia-tolerant mitochondria do not respond to anoxia in a manner similar to anoxia-sensitive mitochondria. Title: Mitochondrial DNA Sequence and Lack of Response to Anoxia in the Annual Killifish <i>Austrofundulus limnaeus</i> Author: Wagner, Josiah T., Chavez, Florisela H., Podrabsky, Jason E. Year: 2016 The annual killifish Austrofundulus limnaeus inhabits ephemeral ponds in regions of Venezuela, South America. Permanent populations of A. limnaeus are maintained by production of stress-tolerant embryos that are able to persist in the desiccated sediment. Previous work has demonstrated that A. limnaeus have a remarkable ability to tolerate extended periods of anoxia and desiccating conditions. After considering temperature, A. limnaeus embryos have the highest known tolerance to anoxia when compared to any other vertebrate yet studied. Oxygen is completely essential for the process of oxidative phosphorylation by mitochondria, the intracellular organelle responsible for the majority of adenosine triphosphate production. Thus, understanding the unique properties of A. limnaeus mitochondria is of great interest. In this work, we describe the first complete mitochondrial genome (mtgenome) sequence of a single adult A. limnaeus individual and compare both coding and non-coding regions to several other closely related fish mtgenomes. Mitochondrial features were predicted using MitoAnnotator and polyadenylation sites were predicted using RNAseq mapping. To estimate the responsiveness of A. limnaeus mitochondria to anoxia treatment, we measure relative mitochondrial DNA copy number and total citrate synthase activity in both relatively anoxia-tolerant and anoxia-sensitive embryonic stages. Our cross-species comparative approach identifies unique features of ND1, ND5, ND6, and ATPase-6 that may facilitate the unique phenotype of A. limnaeus embryos. Additionally, we do not find evidence for mitochondrial degradation or biogenesis during anoxia/reoxygenation treatment in A. limnaeus embryos, suggesting that anoxia-tolerant mitochondria do not respond to anoxia in a manner similar to anoxia-sensitive mitochondria. Close