Sengupta Lab - Sarah E. Hall Profile

Sarah E. Hall

Postdoctoral fellow

PhD, University of Chicago, 2004

BS, Texas A&M University, 1998

sehall@brandeis.edu

Experiences during a critical period of early developmental stages have been shown to shape adult behaviors in many species. I am interested in how organisms create a ‘cellular memory’ of these experiences, and how this memory is translated into changes in gene expression that result in altered adult behaviors.

To examine this phenomenon, I use the model organism C. elegans, which can have variable developmental programs depending on its environment during early larval stages. In C. elegans, overcrowding of animals, scarce amounts of food, and high temperatures during the L1/L2 larval stage may trigger entry into the alternative dauer developmental stage (Figure 1).

Animals exit from the dauer stage and resume reproductive growth when conditions become more favorable. During the dauer stage, many tissue types are remodeled and gene expression patterns are altered. However, post-dauer animals appear grossly similar to animals that bypassed the dauer stage. Thus, whether post-dauer animals retain a cellular memory of their developmental history remains unclear.

Expression of an osm-9::gfp fusion gene in adult animals is an example of a gene regulated by developmental history. osm-9 encodes a TRPV channel, and is expressed in multiple cell types, including the ADL and AWA chemosensory neurons. Interestingly, osm-9::gfp expression is eliminated in the ADL, but not the AWA neurons in post-dauer animals (Figure 2). This alteration in gene expression does not appear to be regulated merely by starvation, L1 arrest, or by exposure to pheromone in early larval stages, suggesting that passage through the dauer stage is necessary for the ‘memory’ of its developmental history and the observed changes in osm-9::gfp expression. I am currently in the process of determining the pathways that regulate the expression of osm-9 in post-dauer animals. In addition, since OSM-9 is required for sensory transduction, I am interested if behaviors of animals that have passed through the dauer stage differ from those that have bypassed the dauer stage.

Figure 2 osm-9::gfp expression is seen in AWA, OLQ, and ADL neurons in control animals, but is only seen in AWA and OLQ neurons in post-dauer animals.

To identify additional genes that may be regulated in a similar manner, I have performed expression profiling of post-dauer adult and control animals. Using this method, I have identified genes that are both significantly up and down regulated in post-dauer animals that may also retain a ‘memory’ of animals developmental history. I expect that this work will allow me to understand how early environmental and developmental experiences affect adult phenotypes by identifying the required molecules and pathways for developmental ‘memory’.

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Sarah E. Hall Postdoctoral fellow PhD, University of Chicago, 2004 BS, Texas A&M University, 1998 *sehall@brandeis.edu***
Experiences during a critical period of early developmental stages have been shown to shape adult behaviors in many species. I am interested in how organisms create a ‘cellular memory’ of these experiences, and how this memory is translated into changes in gene expression that result in altered adult behaviors. To examine this phenomenon, I use the model organism C. elegans, which can have variable developmental programs depending on its environment during early larval stages. In C. elegans, overcrowding of animals, scarce amounts of food, and high temperatures during the L1/L2 larval stage may trigger entry into the alternative dauer developmental stage (Figure 1). Animals exit from the dauer stage and resume reproductive growth when conditions become more favorable. During the dauer stage, many tissue types are remodeled and gene expression patterns are altered. However, post-dauer animals appear grossly similar to animals that bypassed the dauer stage. Thus, whether post-dauer animals retain a cellular memory of their developmental history remains unclear. Expression of an osm-9::gfp fusion gene in adult animals is an example of a gene regulated by developmental history. osm-9 encodes a TRPV channel, and is expressed in multiple cell types, including the ADL and AWA chemosensory neurons. Interestingly, osm-9::gfp expression is eliminated in the ADL, but not the AWA neurons in post-dauer animals (Figure 2). This alteration in gene expression does not appear to be regulated merely by starvation, L1 arrest, or by exposure to pheromone in early larval stages, suggesting that passage through the dauer stage is necessary for the ‘memory’ of its developmental history and the observed changes in osm-9::gfp expression. I am currently in the process of determining the pathways that regulate the expression of osm-9 in post-dauer animals. In addition, since OSM-9 is required for sensory transduction, I am interested if behaviors of animals that have passed through the dauer stage differ from those that have bypassed the dauer stage. Figure 2 osm-9::gfp expression is seen in AWA, OLQ, and ADL neurons in control animals, but is only seen in AWA and OLQ neurons in post-dauer animals. To identify additional genes that may be regulated in a similar manner, I have performed expression profiling of post-dauer adult and control animals. Using this method, I have identified genes that are both significantly up and down regulated in post-dauer animals that may also retain a ‘memory’ of animals developmental history. I expect that this work will allow me to understand how early environmental and developmental experiences affect adult phenotypes by identifying the required molecules and pathways for developmental ‘memory’.