Hox Cluster Evolution in the Highly Derived Pipefish & Seahorse Family
Loading...
Date
2019-04-30
Authors
Fuiten, Allison
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
A central question in evolutionary biology is how organisms evolve highly derived and novel morphologies. More specifically, what changes to conserved developmental genes lead to the evolution of divergent morphologies? Here, I investigate the genetic and genomic changes to the developmentally important Hox genes using comparative genomics, gene expression and gene editing approaches. Hox genes code for homeodomain transcription factors that are responsible for determining the body plan of an embryo along the anterior-posterior axis, and changes to these genes have paralleled the rise of morphological diversity in the vertebrate animals. I focus my studies in a group of fish that exhibit a striking departure from the typical fish body plan: the pipefish and seahorse family, Syngnathidae. The evolution of syngnathid fish involved major modifications to their vertebrate body plan, but the developmental genetic basis of those changes is largely unknown.
I describe the genomic organization of Hox clusters in a species of syngnathid pipefish—the Gulf pipefish (Syngnathus scovelli). I present an initial investigation on phenotypic consequences to the loss of hox7 genes in teleost fish—a group of Hox genes that are missing in syngnathids—using of the CRISPR/Cas9 system to induce indels in all hox7 genes (hoxa7a, hoxb7a) in the threespine stickleback (Gasterosteus aculeatus). In the second half of my thesis, I investigate noncoding changes in the syngnathid Hox clusters. I use syngnathid representative species and compared their conserved noncoding sequences within the Hox clusters to other teleost fish, non-teleost fish, and non-fish vertebrates. I present a detailed study regarding the nature of the loss of one conserved non-coding element.
Results from this research indicate that the divergent syngnathid body plan is not due to rampant change in throughout Hox clusters. Also, these data do not argue for the absence of any role of genetic changes in Hox clusters. Instead, the findings presented here support the intermediate hypothesis that certain key changes to the Hox genes, microRNAs, and regulatory elements have probably contributed to their body plan developmental evolution in this unique family of fish.
This work includes published co-authored material.