Determination of Telomere Sequence in Atlantic Horseshoe Crabs, Limulus polyphemus

Student: Jessica Brideau*, Kevin Hess* and Jenna Lynch*
Mentor: Suzanne Deschênes
Major: Biology

Telomeres are repeating sequences at the end of eukaryotic chromosomes that protect the DNA from deterioration over time during replication. The telomere sequences for some chelicerates, insects, and crustaceans are known; however, the sequence in horseshoe crabs (Limulus polyphemus), a chelicerate, has not been investigated. We performed this experiment in order to determine the telomere sequence in Limulus. We isolated the genomic DNA from amebocytes, used agarose gel electrophoresis to determine its quality, and digested the genomic DNA with Rsa1 and Hinf1, or EcoRI and HindIII, to release telomere fragments. Digested DNAs were electrophoresed and southern blotted. The Limulus sequences were detected using the digoxygenin-labeled probe (CCTAA)3 and compared to positive control chelicerate and insect sequences and negative insect and vertebrate controls. The telomere sequence of Limulus polyphemus hybridized to the probe complementary to the insect motif, (TTAGG)n, but not to the probe complementary to the vertebrate telomeric repeat sequence, (TTAGGG)n. These results indicate that Limulus polyphemus contains the insect telomeric repeat sequence. Eventually, we hope to use telomere restriction fragment length analysis to determine relative differences in length of telomeres in animals of different ages.

*Honors Senior