A major challenge in developmental biology is to understand the intricate cellular interactions between tissues that underlie morphogenesis of complex organs. To dissect the molecular basis of morphogenesis it s advantageous to study simple model tissues or organs. The long term objective of this proposal is a molecular and cellular explanation of embryonic morphogenesis of epidermis of the nematode C. elegans. In embryonic development the epidermis spreads over substrate cells, the ventral neuroblasts. Our previous work showed that signaling via the Eph receptor tyrosine kinase and its ephrin ligands is required for movements of substrate ventral neuroblasts. A specific form of Eph signaling involving both receptor and igand activation (bidirectional signaling) likely promotes adhesion or attraction among ventral neuroblasts. Here we propose to investigate how Eph signaling and parallel pathways regulate neuroblast adhesion and movements. 1. We will analyze the cellular basis of ventral neuroblast motility by a combination of confocal timelapse analysis, genetics, pharmacological interventions, and laser microsurgery. The results will allow us to interpret how the signaling pathways affect motility. 2. Reverse signaling by GPI-linked ephrins is poorly understood. In RNAi enhancer screens we identified a G protein subunit as a potential component of ephrin reverse signaling. We will define the role of this G protein in ephrin signaling using genetic and biochemical tests. 3. Eph signaling functions partly redundantly with several other pathways that provide cell adhesion in the embryo and in axon guidance. To address the nature of this redundancy we will analyze one such parallel pathway involving KAL-1, the C. elegans ortholog of anosmin-1. We have shown KAL-1 interacts with the cell surface heparan sulfated proteoglycans syndecan and glypican. We will define the regulatory pathway of KAL-1 and HSPGs and whether they are required in the same cells. HSPGs are essential for C. elegans embryonic morphogenesis. We will identify the other core proteins that account for this essential function by a combination of candidate gene testing and biochemical purification. 4. Epidermal cells migrate over the ventral neuroblast substrate. The molecules involved in epidermal- substrate adhesion are not known. Our preliminary data suggest netrin signaling has functions both in neuroblast migration and in epidermal substrate attachment. We will define the roles of netrin signaling in morphogenesis and test the hypothesis that netrin acts over short range in epidermal substrate adhesion. Relevance: An understanding of morphogenesis is relevant to treatment of human birth defects, to the development of artificial organs and tissue repair, and to tumor development. Eph signaling in particular has been implicated in human genetic disease, cancer, and in maintenance of neural stem cell niches.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Development - 1 Study Section (DEV1)
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Haynes, Susan R
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University of California San Diego
Schools of Arts and Sciences
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Chen, Fei; Chisholm, Andrew D; Jin, Yishi (2017) Tissue-specific regulation of alternative polyadenylation represses expression of a neuronal ankyrin isoform in C. elegans epidermal development. Development 144:698-707
Wang, Shaohe; Tang, Ngang Heok; Lara-Gonzalez, Pablo et al. (2017) A toolkit for GFP-mediated tissue-specific protein degradation in C. elegans. Development 144:2694-2701
Schwieterman, Alicia A; Steves, Alyse N; Yee, Vivian et al. (2016) The Caenorhabditis elegans Ephrin EFN-4 Functions Non-cell Autonomously with Heparan Sulfate Proteoglycans to Promote Axon Outgrowth and Branching. Genetics 202:639-60
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Chuang, Marian; Hsiao, Tiffany I; Tong, Amy et al. (2016) DAPK interacts with Patronin and the microtubule cytoskeleton in epidermal development and wound repair. Elife 5:
Xu, Suhong; Chisholm, Andrew D (2016) Highly efficient optogenetic cell ablation in C. elegans using membrane-targeted miniSOG. Sci Rep 6:21271
Chisholm, Andrew D; Hutter, Harald; Jin, Yishi et al. (2016) The Genetics of Axon Guidance and Axon Regeneration in Caenorhabditis elegans. Genetics 204:849-882
Xu, Suhong (2015) The application of CRISPR-Cas9 genome editing in Caenorhabditis elegans. J Genet Genomics 42:413-21
Kang, Sukryool; Lee, Chen-Yu; Gonçalves, Monira et al. (2015) Tracking epithelial cell junctions in C. elegans embryogenesis with active contours guided by SIFT flow. IEEE Trans Biomed Eng 62:1020-33
Loer, Curtis M; Calvo, Ana C; Watschinger, Katrin et al. (2015) Cuticle integrity and biogenic amine synthesis in Caenorhabditis elegans require the cofactor tetrahydrobiopterin (BH4). Genetics 200:237-53

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