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Andrew Chisholm

Research

Morphogenesis and regeneration of skin and neurons in C. elegans

My lab’s interests are in the early development of epidermal and neuronal tissues, and in the responses of epidermal and neuronal cells to damage. We are studying these processes in the nematode worm Caenorhabditis elegans. C. elegans is an excellent organism for analyzing fundamental aspects of development. Worm genetics is simple and cheap; gene function can also be probed using genome wide RNA interference screens. Embryogenesis takes 12 hours and its dynamics can be studied using timelapse microscopy and fluorescent markers.

We are interested in epidermal (skin) development as a model for epithelial morphogenesis. The worm epidermis is a simple epithelium that encases the animal. In embryogenesis the epidermis spreads out over substrate cells to enclose the embryo (enclosure) and subsequently undergoes elongation (Chisholm and Hardin 2005). Pathways involved in these processes are evolutionarily conserved, and several are implicated in cancer or other genetic diseases.

Eph signaling and the role of the neuronal substrate in epidermal enclosure

We showed that signaling via the C. elegans Eph receptor tyrosine kinase and its ephrin ligands are required for enclosure (Chin-Sang et al., 1999). Ephrin signaling acts to promote earlier movements of neuroblasts that form a substrate for epidermal enclosure. We are currently using genetics, laser microsurgery and quantitative timelapse microscopy to define the cellular and molecular basis of these neuroblast migrations. Using advanced imaging and new image analysis algorithms we have been able to track the migrations of all nuclei in the embryo during epidermal morphogenesis. We plan to use mathematical modeling to understand how forces are generated in the substrate and in the epidermis to promote spreading.

figure 1

Movements of epidermal cells (green) and neurons (red) during epidermal enclosure (Claudiu Giurumescu and Alan Kang)

The extracellular matrix and epidermal cell shape change

In large-scale genetic screens for epidermal morphogenesis mutants we identified numerous genes affecting epidermal cell-matrix attachments and the extracellular matrix, in many cases providing the first genetic models for a conserved gene family. Among these we identified peroxidasin, a poorly understood enzyme affecting the extracellular matrix (Gotenstein et al., 2010), as essential for elongation and later tissue adhesion. We are currently focusing on peroxidasin and its interactors, with the goal of identifying substrates of peroxidasin activity.

Epidermal wound healing responses

The epidermis forms the first line of defense against injury and microbial pathogens. In collaboration with Jonathan Ewbank (Marseille) we have developed C. elegans as a model for epidermal wound responses and repair pathways (Pujol et al., 2008). We have identified mutants in which the epidermal damage response is constitutively activated (Tong et al., 2009). We are focusing on the role of calcium signals in damage sensing and how injury signals are interpreted by the epidermis.

figure 2

A ring of actin bundles forms after wounding (Suhong Xu)

C. elegans is a genetically accessible model for axon regeneration

The ability of axons to regrow after injury has been known for decades, yet axon regrowth mechanisms remain poorly understood owing in part to the lack of genetically tractable models. In collaboration with Yishi Jin’s lab (UCSD) we have developed C. elegans as a genetically accessible model for axon regeneration (Wu et al., 2007). C. elegans neurons display robust regenerative responses that critically depend on the DLK-1 MAP kinase pathway and second messenger cascades (Ghosh-Roy et al., 2010). We are performing large-scale screens to identify new regeneration genes; results from a pilot screen of 650 genes have identified a large number of new genes whose role in axon regrowth was not previously suspected (Chen et al., 2011). We are continuing to expand this screen and to dissect the roles of these novel regeneration factors.

figure 3

Axon regeneration after laser injury (Lizhen Chen)

Select Publications

Chisholm Lab selected publications, arranged by topic:

Morphogenesis

  • Gotenstein JR, Swale RE, Fukuda T, Wu Z, Giurumescu CA, Goncharov A, Jin Y, Chisholm A.D. 2010. The C. elegans peroxidasin PXN-2 is essential for embryonic morphogenesis and inhibits adult axon regeneration. Development 137: 3603-3613. PMID: 20876652.
  • Dejima, K., Kang, S.-R., Mitani, S., Cosman, P., and Chisholm, A.D. 2014. Syndecan defines precise spindle orientation by modulating Wnt signaling in C. elegans. Development. 141: 4354-65. PMID: 25344071
  • Gotenstein, J.R., Koo, C.C., Ho, T.W., and Chisholm. A.D. 2018. Genetic suppression of extracellular matrix defects in C. elegans by gain of function in extracellular matrix and cell-matrix attachment proteins. Genetics, 208(4):1499-1512. PMID: 29440357

Reviews:

  • Zheng, S.L., Adams, J.G., and Chisholm A.D. 2020. Form and function of the apical extracellular matrix: new insights from C. elegans, Drosophila, and the vertebrate inner ear. Faculty Opinions, in press.

Skin Wound Healing

  • Xu, S., and Chisholm, A.D. 2011. A Gαq – Ca2+ signaling pathway promotes actin-mediated epidermal wound closure in C. elegans. Curr. Biol. 21: 1960-7. PMID: 25313960.
  • Xu, S., and Chisholm, A.D. 2014. Skin wounding triggers a mitochondrial ROS burst that promotes wound repair. Dev. Cell. 31: 48-60. PMID: 25313960
  • Chuang, M., Hsiao, T.I., Tong, A., Xu, S., Chisholm, A.D. 2016. DAPK interacts with Patronin and the microtubule cytoskeleton in C. elegans epidermal development and wound repair. eLife, Sep 23;5. pii: e15833. PMID: 27661253.

Reviews:

  • Chisholm, A.D., and Xu, S. 2012. The C. elegans epidermis as a model skin II: differentiation and physiological roles. Wiley Interdiscip Rev Dev Biol. 1(6): 879-902. PMID: 23539358

Axon Repair and Regeneration

  • Chen, L., Wang, Z., Ghosh-Roy, A., Hubert, T., Yan, D., O’Rourke, S., Bowerman, B., Wu, Z., Jin, Y., Chisholm, A.D. 2011. Axon regeneration pathways identified by systematic genetic screening in C. elegans. Neuron. 71: 1043-1057. PMID: 21943602
  • Kim KW, Tang NH, Piggott CA, Andrusiak MG, Park S, Zhu M, Kurup N, Cherra SJ 3rd, Wu Z, Chisholm AD, Jin Y. 2018. Expanded genetic screening in Caenorhabditis elegans identifies new regulators and an inhibitory role for NAD+ in axon regeneration. eLife. pii: e39756. doi: 10.7554/eLife.39756. PMID: 3046142
  • Tang, N.H., Kim, K.W., Xu, S., Blazie, S.M., Yee, B.A., Yeo, G., Jin, Y., Chisholm, A.D. 2020. The mRNA decay factor CAR-1/LSM14 regulates axon regeneration via mitochondrial Ca dynamics. Curr. Biol, Jan 15. PMID: 31983639

Reviews:

  • Chisholm, A.D., Hutter, H., Jin, Y., and Wadsworth, W.G. 2016. The genetics of axon guidance and axon regeneration in Caenorhabditis elegans. Genetics (WormBook). Nov;204(3):849-882. PMID: 28114100

Methods and Tools

  • Giurumescu, C.A, Kang, S., Planchon, T.A., Betzig, E., Bloomekatz, J., Yelon, D., Cosman, P., and Chisholm, A.D. 2012. Quantitative semi-automated analysis of morphogenesis with single cell resolution in complex embryos. Development 139: 4271-9. PMID: 23052905
  • Xu, S., and Chisholm, A.D. 2016. Highly efficient optogenetic cell ablation in C. elegans using miniSOG. Sci. Rep. 6: 21271. PMID: 26861262
  • Wang S, Tang NH, Lara-Gonzalez P, Zhao Z, Cheerambathur DK, Prevo B, Chisholm AD, Desai A, Oegema K. 2017. A toolkit for GFP-mediated tissue-specific protein degradation in C. elegans. Development. 144(14): 2694-2701. PMID: 28619826

For a complete list search Pubmed for Chisholm AD[Author], or search Google Scholar for Andrew Chisholm.

Biography

Andrew Chisholm received his Ph.D. in 1989 from Cambridge University, working at the MRC Laboratory of Molecular Biology. He did postdoctoral research with H. Robert Horvitz at the Massachusetts Institute of Technology where he held a Lucille P Markey postdoctoral fellowship. He was on the faculty of the University of California Santa Cruz where he rose to the rank of Professor before moving to UC San Diego in 2007. From 2016-2019 he was Head of Cellular and Developmental Sciences at the Wellcome Trust in London. From 2019 he has served as Associate Dean of the Division of Biological Sciences.

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