Presenter(s): Colin Maxwell − Biology
Faculty Mentor(s): Diana Libuda, Nicole Kurhanewicz Codd
Oral Session 3M
Research Area: Biological Science
Meiosis is a specialized form of cell division that sexually reproducing organisms use to generate haploid sex cells. Developing sperm are particularly sensitive to temperature fluctuations, with some studies indicating that exposure to elevated temperature increases DNA damage in spermatocytes, but not oocytes. Although temperature-induced DNA damage has been observed, the underlying molecular mechanisms remain unknown. DNA transposons are mobile genetic elements that produce double-strand DNA breaks (DSBs) when excised from the genome. Additionally, transposons can excise from the genome under heat stress.
I hypothesize that heat stress causes transposon excision which may be observed as a linear relationship between transposon copy number and the quantity of DSBs in developing spermatocytes exposed to elevated temperature. To test this hypothesis, I conducted an immunofluorescence screen of wild type Caenorhabditis elegans strains with varying transposon copy numbers. Using deconvolution microscopy, DSBs were visualized via the recombinase RAD-51, a protein involved in the early stages of meiotic DSB repair. Quantification of RAD-51 foci was performed to determine the frequency of temperature-induced DSB formation. Preliminary results demonstrate that the CB4856 strain with ~15 copies of Tc1, a class of transposons active in C. elegans, exhibited half the amount of DSBs as the Bristol N2 strain with ~30 copies of Tc1 displayed upon heat shock. In contrast, comparisons of DSB quantities between additional strains with varying Tc1 copy numbers show no clear relationships. Taken together, these results indicate temperature-induced DNA damage in spermatocytes has multiple mechanisms, with excision of Tc1 transposons as one possible mechanism.