Professor, Department of Biology
Ph.D. Case Western Reserve
B.S. Stanford Univeristy
Research Interests: Genetic regulation of animal development including development of the nervous system, the mechanisms of sex determination, the origin of novel morphologies in evolution and the evolution of the vertebrate genome.
Overview: Our laboratory is interested in the genetic, genomic, and evolutionary principles that guide animal development. We investigate several aspects of this main problem:
Genome Duplication: The evolution of gene functions in development after genome duplication, focusing on skeletal development.
Fanconi anemia: A small molecule screen for compounds to rescue zebrafish Fanconi Anemia mutants as a way to identify potential therapeutics for human FA patients and to understand disease mechanisms.
MicroRNAs: The roles of microRNAs in embryonic (especially skeletal) development, including evolving miRNA functions after genome duplication.
Icefish: The genetic basis for the evolution of osteopenia or osteoporosis in Antarctic icefish.
Sex determinaion:The developmental genetic basis for sex determination in zebrafish.
Speciation: The roles of genome duplication in lineage divergence, focusing on the evolution of cis and trans acting regulation in the radiation of the danio lineage, including zebrafish, and on variation among populations of stickleback.
Oikopleura: Retaining a chordate body plan as an adult, the larvacean urochordate Oikopleura dioica represents the sister lineage to the vertebrates, diverging before the R1 and R2 rounds of genome duplication that led to the origin of vertebrate innovations.
Perchlorate toxicity and sex determination: Perchlorate is a pervasive environmental contaminant that can cause partial sex reversal in stickleback. We are investigating the hypotheses that perchlorate alters sex development through the thyroid or a non-thyroidal mechanism.
Drosophila developmental genetics: Work on Drosophila homeotic mutants, pattern formation, and ovary development.
Skeletal development in the heterocercal caudal fin of spotted gar (Lepisosteus oculatus) and other Lepisosteiformes.
Dev Dyn. 2018 Jan 13;:
Authors: Desvignes T, Carey A, Braasch I, Enright T, Postlethwait JH
BACKGROUND: The caudal fin of actinopterygians experienced substantial morphological changes during evolution. In basal actinopterygians, the caudal fin skeleton supports an asymmetrical heterocercal caudal fin, while most teleosts have a symmetrical homocercal caudal fin. The transition from the ancestral heterocercal form to the derived homocercal caudal fin remains poorly understood. Few developmental studies provide an understanding of derived and ancestral characters among basal actinopterygians. To fill this gap, we examined the development of the caudal fin of spotted gar Lepisosteus oculatus, one of only eight living species of Holostei, the sister group to the teleosts.
RESULTS: Our observations of animals from fertilization to more than a year old provide the most detailed description of the developmentof caudal fin skeletal elements in any Holostean species. We observed two different types of distal caudal radials replacing two transient plates of connective tissue, identifying two hypaxial ensembles separated by a space between hypurals 2 and 3. These features have not been described in any gar species, but can be observed in other gar species, and thus represent anatomical structures common to lepisosteiformes.
CONCLUSION: The present work highlights the power and importance of ontogenic studies, and provides bases for future evolutionary and morphological investigations on actinopterygians fins. This article is protected by copyright. All rights reserved.
PMID: 29330942 [PubMed - as supplied by publisher]
Endocrine disruption and differential gene expression in sentinel fish on St. Lawrence Island, Alaska: Health implications for indigenous residents.
Environ Pollut. 2017 Nov 25;234:279-287
Authors: von Hippel FA, Miller PK, Carpenter DO, Dillon D, Smayda L, Katsiadaki I, Titus TA, Batzel P, Postlethwait JH, Buck CL
People living a subsistence lifestyle in the Arctic are highly exposed to persistent organic pollutants, including polychlorinated biphenyls (PCBs). Formerly Used Defense (FUD) sites are point sources of PCB pollution; the Arctic contains thousands of FUD sites, many co-located with indigenous villages. We investigated PCB profiles and biological effects in freshwater fish (Alaska blackfish [Dallia pectoralis] and ninespine stickleback [Pungitius pungitius]) living upstream and downstream of the Northeast Cape FUD site on St. Lawrence Island in the Bering Sea. Despite extensive site remediation, fish remained contaminated with PCBs. Vitellogenin concentrations in males indicated exposure to estrogenic contaminants, and some fish were hypothyroid. Downstream fish showed altered DNA methylation in gonads and altered gene expression related to DNA replication, response to DNA damage, and cell signaling. This study demonstrates that, even after site remediation, contaminants from Cold War FUD sites in remote regions of the Arctic remain a potential health threat to local residents - in this case, Yupik people who had no influence over site selection and use by the United States military.
PMID: 29182972 [PubMed - as supplied by publisher]
The Spotted Gar: Genomic Journeys into a Lost World.
J Exp Zool B Mol Dev Evol. 2017 Nov;328(7):593-595
Authors: Braasch I, Postlethwait JH
PMID: 29059506 [PubMed - in process]