Profiles

Kyuhyung Kim, Ph.D.

Postdoctoral Fellow

Ph.D., Boston University

khkim [at] brandeis.edu

Plasticity in chemosensory neuron-specific gene expression and behavior

Plasticity in sensory responses enables animals to appropriately modulate their behaviors and developmental programs in response to constantly changing environmental conditions. In addition to acute neuronal plasticity, cues experienced during specific developmental stages are critical in shaping adult behaviors.

The nematode C. elegans responds to conditions of overcrowding, limited food and high temperature by arresting development as a dauer larva. A primary signal triggering entry into the dauer stage is high levels of secreted dauer pheromone. We and others (Nolan et al., 2002; Peckol et al., 1999) showed previously that exposure to dauer pheromone at any developmental stage reversibly alters the expression of olfactory receptor genes in the ASI chemosensory neurons, suggesting that acute modulation of chemoreceptor expression by environmental cues may be a mechanism by which C. elegans can rapidly alter its sensory behaviors. We have now shown that similar to the chemoreceptor genes, expression of additional signaling molecules in chemosensory neurons is also similarly affected by exposure to dauer pheromone. Interestingly, we have also found that exposure to low levels of dauer pheromone only at early developmental stages appears to be sufficient to irreversibly alter a subset of gene expression in the chemosensory neurons. Moreover, adult animals exposed to dauer pheromone at early stages, or animals that have transiently passed through the dauer stage, exhibit sensory behaviors that are distinct from those of animals that have not experienced these environmental and developmental conditions. These results suggest that the gene expression pattern in sensory neurons and sensory behaviors may reflect a 'memory' of the animals' developmental and environmental history.

To identify the signaling pathways and genes required for environmental and developmental plasticity, we performed a genetic screen utilizing dauer pheromone-mediated downregulation of chemoreceptor gene expression in the ASI neurons. In a genetic screen of ~40,000 haploid genomes, we isolated several mutants which are currently being further mapped and haracterized (see Figure).

Sengupta Lab Publications

Kim, K., Sato, K., Shibuya, M., Butcher, R.A., Ragains, J.R., Clardy, J., Thomas, J.H., Touhara, K. and Sengupta, P. (2008) Identification of two chemoreceptors mediating responses to dauer-inducing pheromone in C. elegans. Submitted.

van der Linden, A.M., Wiener, S., You, Y-J., Kim, K., Avery L., and Sengupta, P. (2008) The EGL-4 PKG acts with the KIN-29 SIK and KIN-2 PKA to regulate chemoreceptor gene expression and sensory behaviors in C. elegans. Genetics. In Press. [PubMed]

Kim, K., Colosimo, M.E., Yeung, H., and Sengupta, P. (2005). The UNC-3 Olf/EBF protein represses alternate neuronal programs to specify chemosensory neuron identity. Dev Biol 286, 136-148. [PubMed]