Chun Han
Nancy M. and Samuel C. Fleming Term Assistant Professor
Chun Han

Phone

607-255-7855

Address

Department of Molecular Biology & Genetics
Cornell University
435 Weill Hall
Ithaca, NY 14853

Email

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Background

Chun Han is an Assistant Professor in the Department of Molecular Biology and Genetics. He received a B.S. degree from Peking University in 1999 and a Ph.D. degree from the College of Medicine, University of Cincinnati, in 2006. He did his postdoctoral research at the University of California, San Francisco in the laboratory of Dr. Yuh Nung Jan.

Research Description

We are interested in understanding the molecular and cellular mechanisms of dendrite morphogenesis and dendrite degeneration, especially from the perspective of dendrite-environment interaction. Dendrite morphogenesis is a fundamental aspect of neural development and lies at the foundation of neural circuit formation. During the early phase of dendrite morphogenesis, a neuron develops a dendritic arbor with a particular size, shape, and branching pattern. The dendritic arbor is then maintained over time in order to carry out its function in information collection and processing. Some neurons remodel their dendritic arbors in response to changes in the neuronal environment and functional demands of the nervous system, which may involve removal of dendrites through local degeneration. All of these processes take place in a complex cellular environment in which the neuron interacts with many other cells. We are interested to discover the neuron-environment interactions that shape every step of dendrite morphogenesis.

Establishment of a mature dendritic arbor from a newly born neuron involves a drastic increase of cell membrane surface and deployment of organized cytoskeletal architecture. Membrane trafficking and cytoskeletal reorganization are carried out under instructions coming from the neuronal environment. How do diverse neuronal types existing in a similar neuronal environment develop drastically different dendrite morphologies? Does each neuronal type only sense a unique subset of environmental cues? How is the environmental information collected by each type of neuron translated into unique instructions to shared and neuronal type-specific membrane trafficking and cytoskeletal machineries within dendrites?

Han research image 1

Han research image 2We try to answer these questions by using Drosophila dendritic arborization (da) neurons as a model system. Da neurons are peripheral sensory neurons attached to the body wall and they exhibit stereotypic yet diverse dendrite morphologies. We use a strategy called GEEM (for gene expression with an independent enhancer-driven cellular marker) to dissect the interaction between dendrites and surrounding tissues. In the GEEM system, dendrites are labeled by class-specific membrane markers while gene activities in dendrite-interacting tissues, such as glia or epidermal cells, are controlled by the UAS/Gal4 binary system. By using advanced cell biological tools, we hope to decipher the secret behind the formation of diverse dendrite morphologies.

During dendrite degeneration, either in dendrite remodeling or after neuronal injury, dendrite debris resulting from this degeneration needs to be promptly removed to maintain tissue homeostasis and to prevent inflammatory response. We have found that Drosophila epidermal cells function as phagocytes to engulf and degrade degenerating dendrites of da neurons during dendrite remodeling and after dendrite injury. We are interested in understanding the phagocyte-dendrite interaction during dendrite degeneration and using this system to study phagocytosis.

Publications

Han, C., Song, Y., Xiao, H., Wang, D., Franc, N.C., Jan, L.Y. and Jan, Y.N. (2014) Epidermal cells are the primary phagocytes in the fragmentation and clearance of degenerating dendrites in Drosophila. Neuron 81, 544-560.

Han, C., Wang, D., Soba, P., Zhu, S., Lin, X., Jan, L. Y. and Jan, Y. N. (2012). Integrins regulate repulsion-mediated dendritic patterning of Drosophila sensory neurons by restricting dendrites in a 2D space. Neuron 73, 64-78.

This paper was reviewed by Flight, MH. in Nature Reviews Neuroscience 13, 152-153 (2012), Kurshan, PT. and Shen, K. in Current Biology 22(6), R192-4 22 (2012), and Burgess, RW., Garrett, AM., and Tadenev, AL. in Developmental Cell 22(1), 5-6 (2012).

Peng, Y., Han, C., and Axelrod, J.D. (2012). Planar Polarized Protrusions Break the Symmetry of EGFR Signaling during Drosophila Bract Cell Fate Induction. Dev Cell 23, 507-518.

Song, Y., Ori-McKenney, K. M., Zheng, Y., Han, C., Jan, L. Y. and Jan, Y. N. (2012). Regeneration of Drosophila sensory neuron axons and dendrites is regulated by the Akt pathway involving Pten and microRNA bantam. Genes Dev 26, 1612-25.

Yuan, Q., Xiang, Y., Yan, Z., Han, C., Jan, L. Y. and Jan, Y. N. (2011). Light-induced structural and functional plasticity in Drosophila larval visual system. Science 333, 1458-62.

Han, C., Jan, L. Y. and Jan, Y. N. (2011). Enhancer-driven membrane markers for analysis of nonautonomous mechanisms reveal neuron-glia interactions in Drosophila. Proc Natl Acad Sci U S A 108, 9673-8.

Han, C. and Lin, X. (2005). Shifted from Wnt to Hedgehog signaling pathways. Mol Cell 17, 321-2

Han, C., Yan, D., Belenkaya, T. Y. and Lin, X. (2005). Drosophila glypicans Dally and Dally-like shape the extracellular Wingless morphogen gradient in the wing disc. Development 132, 667-79.

Han, C., Belenkaya, T. Y., Wang, B. and Lin, X. (2004). Drosophila glypicans control the cell-to-cell movement of Hedgehog by a dynamin-independent process. Development 131, 601-11.

This paper was reviewed by Tromans, A. in Nature Reviews Molecular Cell Biology 5, 256 (2004) and recommended by Faculty of 1000.

Han, C., Belenkaya, T. Y., Khodoun, M., Tauchi, M. and Lin, X. (2004). Distinct and collaborative roles of Drosophila EXT family proteins in morphogen signalling and gradient formation. Development 131, 1563-75.

Belenkaya, T. Y., Han, C., Yan, D., Opoka, R. J., Khodoun, M., Liu, H. and Lin, X. (2004). Drosophila Dpp morphogen movement is independent of dynamin-mediated endocytosis but regulated by the glypican members of heparan sulfate proteoglycans. Cell 119, 231-44.

Ran, R., Lu, A., Zhang, L., Tang, Y., Zhu, H., Xu, H., Feng, Y., Han, C., Zhou, G., Rigby, A. C. et al. (2004). Hsp70 promotes TNF-mediated apoptosis by binding IKK gamma and impairing NF-kappa B survival signaling. Genes Dev 18, 1466-81.

Belenkaya, T. Y., Han, C., Standley, H. J., Lin, X., Houston, D. W. and Heasman, J. (2002). Pygopus encodes a nuclear protein essential for wingless/Wnt signaling. Development 129, 4089-101. (The first three authors have contributed equally to the work.)

Liu, C., Li, Y., Semenov, M., Han, C., Baeg, G. H., Tan, Y., Zhang, Z., Lin, X. and He, X. (2002). Control of beta-catenin phosphorylation/degradation by a dual-kinase mechanism. Cell 108, 837-47.