Scholar: Fernanda Bosada
Faculty Mentor: Dr. Scott Clark
Research Topic: "When the Maintenance Man Fails: Maintaining the Expression and State of Differentiation of an Interneuron in C. Elegans"
Abstract: During differentiation, neurons extend axons to targets, form synaptic connections, and begin to exhibit the attributes of mature, functional neurons. Neurons must retain their differentiated state and express the correct complement of 'terminal differentiation' genes throughout the life of the organism to maintain function of the nervous system. In the nematode C. elegans the two PVQ neurons are located in the tail and each extends an axon along the ventral nerve cord to the head.
PVQ can be visualized in living animals using a transcriptional sra-6::gfp reporter. The gene sra-6 encodes an odorant receptor and is expressed exclusively in PVQ and in two other neurons (ASH, ASI) in the head starting soon after the cells are born during embryogenesis. As such, the sra-6::gfp reporter is a terminal differentiation marker for PVQ. Mutations in six genes (tba-1, unc-14, unc-33, unc-44, unc-51, unc-119) that disrupt axon outgrowth were found to eliminate expression of the sra-6::gfp reporter in PVQ soon after hatching.
Expression of the sra-6::gfp reporter in PVQ was high in embryos and newly hatched L1 larvae yet the GFP signal was greatly reduced within 2-3 hours and was typically not detectable after 5-6 hours. Expression in ASI and ASH was not altered and other axon outgrowth mutations did not affect sra-6::gfp expression in PVQ, indicating that axon outgrowth defects per se did not alter sra-6::gfp expression.
These observations suggest that these six genes act in a process that maintains sra-6 expression or the differentiated state of PVQ. I plan to examine the expression of other genes that are expressed in PVQ to determine whether they are also affected by mutations in these six axon guidance genes. I will also express the gene unc-119 specifically in PVQ to determine whether the sra-6 expression phenotype is cell autonomous and when unc-119 activity is needed. These experiments will address how these six genes function in maintaining sra-6 expression in PVQ.
Earned Baccalaureate Degree: Spring 2010
Doctoral Program Update: Enrolled in Ph.D. program, Molecular Biology and Genetics, University of Oregon