Yun Zhang, Ph.D.

Assistant Professor of Biology

Harvard University
Dept. Organismic and Evolutionary Biology,

     Center for Brain Research
16 Divinity Avenue
Cambridge, MA 02138
Telephone: 617-405-1107
Fax: 617-405-1018
Email: yzhang@oeb.harvard.edu
Lab website: The Zhang Lab

Neural plasticity is a remarkable feature of the nervous system.  Molecular pathways that regulate learning and memory are conserved.  However, what is less clear is how learning behaviors are organized at the circuit level.  What are the smallest units of circuitry that regulate learning?  What is the functional relationship of different neurons in a learning circuit?  Does learning result from a localized change or concerted modulations of the circuit?  In the long term, we would like to understand these intrinsic properties of neural circuits and how these mechanisms regulate learning processes.

My postdoctoral work in Caenorhabditis elegans established an olfactory learning paradigm.  I found that C. elegans is able to learn to avoid the smell of pathogenic bacteria after aversive esperiences with pathogens.  I asked how this learning behavior is regulated by the underlying neural circuitry.  I discovered that a serotonin signaling from a pair of serotonergic neurons ADF is essential to direct this learning.  The physiological stress of infection enhances ADF serotonin signals by activating the key enzyme for serotonin synthesis, TPH-1, both transcriptional and post-transcriptionally.  The enhanced serotonin signaling promotes learning through a serotonin signaling modulates the properties of the olfactory circuit, resulting in a change in olfaction.  We are asking the following questions to address fundamental aspects of learning acquisition:

• What are the cellular components of the aversive olfactory learning circuitry?
• How does the aversive experience regulate the serotonin neuromodulatory pathway?
• How does the neuromodulatory pathway spatially and temporally regulate the circuit, resulting in learning behavior?

References:

• Zhang Y, Chalfie M. MTD-1, a touch-cell-specific membrane protein with a subtle effect on touch sensitivity. Mechanisms of Developement 119, 3-7 (2002).
• Zhang Y, Ma C, Delohery T, Nasipak B, Foat BC, Bounoutas A, Bussemaker HJ, Kim SK, Chalfie, M. Idenification of genes expressed in C. elegans touch receptor neurons. Nature 418, 331-335 (2002).
• Zhang Y, Lu H. Bargmann CI.  Pathogenic bacteria induce aversive olfactory learning in C. elegans. Nature 438, 179-184 (2005).
• Pradel E*, Zhang Y*, Pujol N, Maysuyana T, Bargmann CI, Ewbank JJ. Detection nd avoidance of a naturl product from the pathogenic bacterium Serratia Marcescens by Caenorhabditis elegans. Proc Natl Acad Sci USA 104, 2295-2300 (2007). *:Equal Contributions.

Previous faculty member (Junying Yuan)