Tag: John Postlethwait

Genomic News From an Old Fish: Understanding Gene Regulation by Sequencing the Genome of a Living Fossil, the Spotted Gar (Lepisosteus oculatus)

Presenter: Margo Werner, Biology

Poster: D-3

Mentor: Ingo Braasch, John Postlethwait Biology

Cis-regulatory elements (CREs) are important regions of the genome that modulate the expression of nearby genes. However, their role in the evolution of genes is not yet well understood. To examine the function and evolution of CREs in fish, we study the spotted gar (Lepisosteus oculatus). The gar is a ‘living fossil’ that diverged from teleost fishes just before a teleost-specific whole genome duplication. Comparing the genome sequence of gar to teleosts allows us to investigate the appearance of CREs in relation to this genome duplication. We screen a genomic library of the gar in order to find regions of the genome containing developmentally relevant genes and their CREs. These genomic regions are then sequenced using next generation sequencing techniques. The results will potentially help us to understand the evolution of gene regulation in fish.accurate indicators of ancient local species distribution.

Effect of Elevated Temperature on Embryonic Skeletal Development in Antarctic Bullhead Notothen, Notothenia coriiceps

Presenter(s): Natalie Mosqueda − Biology

Faculty Mentor(s): John Postlethwait, Thomas Desvignes

Poster 70

Research Area: Developmental Biology

Funding: SPUR NIH Grant

Among adapted species is the Antarctic Bullhead Notothen, Notothenia coriiceps, a Notothenoid only found in the secluded waters of the Southern Ocean. The Antarctic Peninsula in particular is one of the faster warming areas, warming at a rate 10 times faster than the global average and is expected to rise 4°C from the normal -1/0°C at the end of the century. It is important to investigate the effects of the warming temperature on embryogenesis and more specifically on early skeletal development of the Antarctic fish, N. coriiceps. We hypothesize that fish embryos raised at the higher temperature of +4°C will develop faster compared to embryos raised at the normal water temperature of about -1°C. In addition, we hypothesize that elevated temperature will result in asynchronous and abnormal development of various skeletal elements in embryos compared to control embryos raised at normal temperature. For this study, reproductive adult Notothenia coriiceps were collected around the Antarctic Peninsula in 2014 and 2016. Half of the embryos obtained by in vitro fertilization were raised at +4°C and composed the “heated” group, while the other half were raised at natural temperature between -1 and 0°C and formed the “control” group. We collected embryos at regular intervals during the first four months of development, fixed them and preserved them in 80% ethanol. The development and morphology of skeletal elements was recorded with a numbering system and results showed that the “heated” embryos had a faster embryonic and skeletal development compared to the “control” embryos, confirming our hypotheses. Our results therefore indicate that elevated water temperatures impact the normal skeletal development of the Antarctic fish larvae and could alter their survival if global warming predictions prove to be accurate. Additionally, there is asynchronous development between the cranial facial skeletal features and the axial skeleton among the two sample groups that could lead to later development issues

Life With White Blood: Histological Analysis of Antarctic Icefish Elucidates its Unique Adaptation to Loss of Hemoglobin, Fueling Inquir into The Regulatory Role Of Mirnas in Hematopoiesis

Presenter(s): Leandro Marx − Biology

Faculty Mentor(s): Thomas Desvignes, John Postlethwait

Poster 53

Research Area: Biology

Funding: University of Oregon Presidential Scholarship, National Science Foundation

Antarctic icefish (Channichthyidae), belong to a family of ray-finned fish endemic to the Southern Ocean (1). With an astonishing set of adaptations, the enigmatic icefish have inspired curiosity since their discovery in 1927 (2). The defining feature of this 16-species family is their “white blood”, which is devoid of hemoglobin — the iron-containing protein that facilitates oxygen transport throughout the body (3,4). Through a series of histological analyses, genetic analyses, and reverse genetic screens, the aim of this research is to identify phenotypic and genotypic adaptations that mitigate the consequences of the unique physiology of the icefish as well as to understand the role of miRNAs (small, regulatory RNA molecules) in red blood cell production (hematopoiesis). Current questions focus primarily on the regulatory role of miRNAs in hematopoiesis. Through differential analysis of miRNA expression between icefish and other ray-finned species, we will select candidate genes that may be involved in the hematopoietic process. Using these target miRNAs, we will generate genetic knockouts in zebrafish using the CRISPR/Cas-9 system and will observe the effects of these genes on hematopoiesis. Although work is currently in progress, successful completion of this research will develop a greater understanding of the unique physiology of icefish and the role of understudied miRNAs in the genetic regulation of hematopoiesis. In addition to helping us understand the evolution of developmental mechanisms, results may be relevant to human anemia diseases because miRNAs circulating in the bloodstream are thought to be potential disease therapies (5).

Impaired Erythropoiesis in Notothenioids Predated the Loss of Hemoglobin in White- blooded Antarctic Icefish

Presenter(s): Leandro Marx-Albuquerque

Faculty Mentor(s): John Postlethwait & Thomas Desvignes

Poster 28

Session: Sciences

The 16 recognized white-blooded Antarctic icefishes (Channichthyidae) are the only known vertebrates living without hemoglobin– the protein packed into red blood cells and responsible for oxygen transport throughout an organism. Red-blooded dragonfishes (Bathydraconidae), plunderfishes (Artedidraconidae), and “notothens” (Nototheniidae) are close relatives of icefishes and all possess hemoglobin. All four families are part of the Notothenioidei suborder. While the genetic mechanism that led to the loss of hemoglobin genes in icefish is well understood, whether icefish possess mature red blood cells remains contested. Therefore, our purpose was to decipher if red blood cell development (erythropoiesis) in icefishes progresses as it does in their red-blooded relatives. These investigations were conducted using head kidney histology samples and blood smears from six species of white-blooded icefishes and seven closely related red-blooded fish species (four dragonfish species, one plunderfish species, and two notothen species). We conducted a morphological analysis of erythropoietic cells using principal component analyses to differentiate and compare cell types across species. Our results indicate that icefishes have Pro-erythroblasts and some more advanced cells morphologically similar to red-blooded erythroblasts. Additionally, we observed that in plunderfishes and two of the four dragonfishes, the most developed erythropoietic cells are morphologically akin to erythroblasts. These results suggest that while hemoglobin was lost at the origin of the icefish radiation, the erythropoietic pathway was impaired earlier– likely in the common ancestor of plunderfishes, dragonfishes, and icefishes. Thus, our investigation provides a new perspective into the evolutionary history that led to the unique white-blooded icefish phenotype.