The Role of ptp-3, a Protein Tyrosine Phosphatase, in the Modulation of GLD-1 Protein Levels in the Caenorhabditis elegans Germline

Mackenzie Esch, Biology

Faculty Mentor: Dr. Sudhir Nayak

              The expression of the Defective in Germline Development 1 (gld-1) gene in Caenorhabditis elegans is restricted to cells entering and progressing through meiosis.  Visible expression of gld-1 tagged with green fluorescent protein declines rapidly in the oocytes as meiosis nears completion.  It is believed that gld-1 is expressed throughout the germline and is regulated by rapid degradation of the newly transcribed protein; consequently, it is inferred that some sort of signal initiates this degradation process.  Thus, when the activity of the proteins that regulate the signal is interrupted, abnormal gld-1 expression should result.

              Post-translational modification of polypeptides is common, where alterations are made to certain amino acids after their linear sequence has been assembled.  These modifications may be used to bring the protein to an active form or serve as signals for interactions with other proteins, localization to a certain area of the cell, or a plethora of other processes.  Protein Tyrosine Phosphatase 3 (ptp-3) is one such modifier; it removes a phosphate group from the amino acid tyrosine, a change that can serve as a signal for a certain pathway to begin.  Because it is expressed in the germline, ptp-3 may be a modifier of gld-1 activity or levels.  Since phosphorylation is a common degradation signal, it is possible that ptp-3 is involved in ensuring adequate gld-1 expression before the loop; conversely, ptp-3 may remove a phosphate group integral for the stabilization of gld-1, thus expediting its degradation beyond the loop.

              We use a technique called RNA Interference (RNAi) to reduce the activity of ptp-3 and observed its affect on GLD-1 protein expression.  Preliminary findings indicate that interrupting the activity of ptp-3 leads to misexpression of gld-1, suggesting that ptp-3 is involved in the degradation signal pathway of the germline protein.  However, abnormal expression was not observed in the majority of worms, indicating that the RNAi technique requires optimization in order to bring it to its peak effectiveness for further analysis.  In the future, more specific observations of the ptp-3 RNAi phenotypes are needed in order to precisely deduce the function of ptp-3 in the regulation of gld-1. 

Personal Statement

              The Summer Undergraduate Research Program has allowed me to work with my professors and fellow students in a manner that is not feasible during the academic year.  I have been fortunate to have had the opportunity to further my skills and interest in research by working closely under a mentor who has encouraged me to find the answers to my own questions.  The experiences in troubleshooting problems, utilizing databases for research, and presenting my findings to an audience not familiar with biological research will be taken with me as I further my academic career.  Through social events, SURP granted me the opportunity to discuss my studies with other research-oriented students in an informal, comfortable setting.  SURP was a unique chance to immerse myself in research and I believe it is an essential component of TCNJ’s mission of promoting undergraduate research.