Embryos begin development by forming a simple epithelium. Cells fated to become connective tissue then undergo an epithelial-mesenchymal transition (EMT) to leave that early epithelium and populate the interstitial regions of the embryo. This project seeks to understand how the EMT works, specifically how the cells de-adhere from the epithelium, how they become motile to leave the epithelium, and how they invade through the basement membrane beneath the epithelium. Previous work identified the transcriptional subcircuits of the gene regulatory networks responsible for controlling the EMT. In the model system studied, each of the three EMT components ? de-adhesion, motility, and invasion ? are driven by distinct subcircuits of transcription factors. The goal of the project is to identify and functionally understand the effector molecules that are directly regulated downstream of the transcription factors in the subcircuits. Thus, the three aims of the project are: 1) What are the effector molecules, controlled by the de-adhesion subcircuit, that initiate and conduct the deadhesion from the epithelium, and how do they function? 2) What are the effector molecules, controlled by the motility subcircuit, that initiate the motility necessary to move the nascent mesenchymal cell out of the epithelium and through the basal lamina? And, 3) What are the effector molecules, driven by the invasion subcircuit, that are necessary to provide access through the basement membrane for the nascent mesenchyme cells. RNA-seq databases of those targeted cells at different time points of the EMT were obtained, and also RNA-seq databases of the same cells following the same temporal trajectories, but after knockdown of transcription factors in the subcircuits, were obtained to provide a group of candidate effector molecules for the experiments. Three different assays were developed for direct analysis of control and perturbed (knockdowns) of the candidate molecules in an effort to identify participants in controlling the de-adhesion, motility onset, and invasion. In addition to wanting to understand how these three EMT components function in the model system the findings will be pertinent to understand how EMTs operate with high fidelity in embryos to avoid birth defects such as cleft palate. And, the data will be useful to understand progression of disease states where the invasive property similar to normal embryonic cells, is co-opted by cells as they develop metastatic properties.

Public Health Relevance

to public health: This project seeks to understand details of how an epithelial- mesenchymal transition (EMT) works. EMTs occur normally during development and must occur with high fidelity to avoid birth defects, and elements of EMTs are co-opted by tumor cells in the invasive process. Thus, an understanding of how the EMT process functions in detail is valuable for potential intervention approaches.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Research Project (R01)
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Study Section
Development - 2 Study Section (DEV2)
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Mukhopadhyay, Mahua
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Duke University
Schools of Arts and Sciences
United States
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Slota, Leslie A; McClay, David R (2018) Identification of neural transcription factors required for the differentiation of three neuronal subtypes in the sea urchin embryo. Dev Biol 435:138-149
McClay, David R; Miranda, Esther; Feinberg, Stacy L (2018) Neurogenesis in the sea urchin embryo is initiated uniquely in three domains. Development 145:
Martik, Megan L; McClay, David R (2017) New insights from a high-resolution look at gastrulation in the sea urchin, Lytechinus variegatus. Mech Dev 148:3-10
Martik, Megan L; Lyons, Deirdre C; McClay, David R (2016) Developmental gene regulatory networks in sea urchins and what we can learn from them. F1000Res 5:
Warner, Jacob F; Miranda, Esther L; McClay, David R (2016) Contribution of hedgehog signaling to the establishment of left-right asymmetry in the sea urchin. Dev Biol 411:314-324
Israel, Jennifer W; Martik, Megan L; Byrne, Maria et al. (2016) Comparative Developmental Transcriptomics Reveals Rewiring of a Highly Conserved Gene Regulatory Network during a Major Life History Switch in the Sea Urchin Genus Heliocidaris. PLoS Biol 14:e1002391
Martik, Megan L; McClay, David R (2015) Deployment of a retinal determination gene network drives directed cell migration in the sea urchin embryo. Elife 4:
Saunders, Lindsay R; McClay, David R (2014) Sub-circuits of a gene regulatory network control a developmental epithelial-mesenchymal transition. Development 141:1503-13
Warner, Jacob F; McClay, David R (2014) Perturbations to the hedgehog pathway in sea urchin embryos. Methods Mol Biol 1128:211-21
Lyons, Deirdre C; Martik, Megan L; Saunders, Lindsay R et al. (2014) Specification to biomineralization: following a single cell type as it constructs a skeleton. Integr Comp Biol 54:723-33

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