Much of the vertebrate embryonic body forms from a recently discovered neuromesodermal progenitor cell population located at the most posterior end of the early embryo, in a region called the Progenitor Zone (PZ). The PZ gradually releases mesodermal cells that populate the somites (primarily muscle) as well as the neural cells that form the spinal cord, until the complete anterior-posterior axis of the embryo has been established. While the mechanisms controlling the differentiation of the neuromesodermal cells are increasingly understood, how these cells regulate the completion of the epithelial to mesenchymal transition (EMT) and directional migration from the PZ into the body largely remains a mystery, yet this process is essential for the embryo to form its anterior-posterior axis correctly. Based on our analysis of a zebrafish mutant that specifically disrupts the migration of mesodermal cells from the PZ, we have identified a unique set of PZ-expressed Progenitor Cytoskeletal Regulatory Genes (PCRGs) that we propose must be down-regulated for cells to complete the EMT and migrate from the PZ into the presomitic mesoderm (PSM). Using a novel explant assay we recently developed that allows in vivo imaging of the migrating cells at very high resolution, in Aim 1 we will determine how the PCRGs are used to regulate the directional movement of cells into the PSM using a combination of gain and loss of function studies, as well as examining how the PCRGs control Rho activity.
In Aim 2 we will determine how the posterior hox genes, which through unknown mechanisms control the orderly movement of cells from the PZ into the embryonic body, specifically regulate cell movements using our novel explant system to examine directional cell migration and protrusive activity of the hox-expressing cells. We will test the hypothesis that the hox genes act to sustain the expression of the PCRGs, and thereby regulate the timing of cell entry into the PSM. Collectively, these studies will examine the premise that the migration of cells from the PZ into the PSM is regulated by the action of the PCRGs and posterior hox genes, which acting together control the orderly anteriorward migration of newly differentiating mesodermal cells, thus allowing the vertebrate embryonic body to form with remarkable fidelity. With the ease of making transgenic lines that allow temporally controlled expression of the PCRGs and hox genes as well as CRISPR mutant lines, combined with our innovative explant system for high resolution imaging, zebrafish is an excellent system for understanding the mechanisms that control the early formation of the vertebrate body.

Public Health Relevance

The formation of an embryo starting from a single cell is a very complex process involving massive cell proliferation, the differentiation of subsets of cells into specific cell types, and the highly orchestrated movements of cells to form the basic embryonic body plan. Failures in any of these processes leads to a distorted embryo resulting in either the death of the embryo or various types of birth defects. This project uses zebrafish as a model system for understanding vertebrate development, taking advantage of the outstanding utility of zebrafish embryos for imaging cell movements at very high resolution, as well as the ease of manipulating gene expression as the embryo develops. The goal of this project is to understand how cells migrate from a newly discovered progenitor population that produces the spinal cord and musculature of the embryonic body. The results from the study will provide essential insight into the mechanisms that normally form the embryonic body as well as the alterations in this process that lead to birth defects.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM079203-09
Application #
9403120
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Gibbs, Kenneth D
Project Start
2008-07-01
Project End
2021-07-31
Budget Start
2017-08-01
Budget End
2018-07-31
Support Year
9
Fiscal Year
2017
Total Cost
Indirect Cost
Name
University of Washington
Department
Biochemistry
Type
Schools of Medicine
DUNS #
605799469
City
Seattle
State
WA
Country
United States
Zip Code
98195
Kimelman, David; Smith, Natalie L; Lai, Jason Kuan Han et al. (2017) Regulation of posterior body and epidermal morphogenesis in zebrafish by localized Yap1 and Wwtr1. Elife 6:
Kimelman, David (2016) A novel cold-sensitive mutant of ntla reveals temporal roles of brachyury in zebrafish. Dev Dyn 245:874-80
Yoshimatsu, Takeshi; D'Orazi, Florence D; Gamlin, Clare R et al. (2016) Presynaptic partner selection during retinal circuit reassembly varies with timing of neuronal regeneration in vivo. Nat Commun 7:10590
Kimelman, David (2016) Tales of Tails (and Trunks): Forming the Posterior Body in Vertebrate Embryos. Curr Top Dev Biol 116:517-36
Manning, Alyssa J; Kimelman, David (2015) Tbx16 and Msgn1 are required to establish directional cell migration of zebrafish mesodermal progenitors. Dev Biol 406:172-85
Bouldin, Cortney M; Manning, Alyssa J; Peng, Yu-Hsuan et al. (2015) Wnt signaling and tbx16 form a bistable switch to commit bipotential progenitors to mesoderm. Development 142:2499-507
Bouldin, Cortney M; Snelson, Corey D; Farr 3rd, Gist H et al. (2014) Restricted expression of cdc25a in the tailbud is essential for formation of the zebrafish posterior body. Genes Dev 28:384-95
Bouldin, Cortney M; Kimelman, David (2014) Dual fucci: a new transgenic line for studying the cell cycle from embryos to adults. Zebrafish 11:182-3
Bouldin, Cortney M; Kimelman, David (2014) Cdc25 and the importance of G2 control: insights from developmental biology. Cell Cycle 13:2165-71
Suli, Arminda; Guler, Ali D; Raible, David W et al. (2014) A targeted gene expression system using the tryptophan repressor in zebrafish shows no silencing in subsequent generations. Development 141:1167-74

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