Meeting Abstract
Repetitive DNA has been implicated in chromatin organization, genome replication, expression regulation, and cell proliferation. Chromosomal regions that contain large tandem repeats such as ribosomal genes, telomeres, and centromeres are often not included in the reference genomes of most model organisms. We are currently sequencing and assembling the genome of Hydractinia, an organism that has proven to be a valuable model for the study of regenerative medicine, early development processes, and allorecognition. Like human embryonic stem cells, Hydractinia stem cells are pluripotent; homologs for many genes associated with the ability to self-renew and differentiate in bilaterians have already been identified in Hydractinia, reinforcing its value in the study of development and regeneration. Importantly, the regenerative process also depends on both the maintenance of telomere integrity throughout numerous cycles of cell division and the role of ribosome biogenesis in cell growth and proliferation. To better understand the role of repetitive DNA in regeneration and stem cell maintenance in Hydractinia, we are characterizing the large tandem repeats in these de novo assemblies, as well as studying protein complexes that interact with and help regulate their function. We have already identified a ribosomal gene consensus sequence and prospective junction sequences on either side of rDNA clusters that may play a role in ribosome regulation. Using the eukaryotic telomeric sequence, we have also identified scaffolds that flank the telomere and contain new tandem repeats up to 380 bp in length. These findings represent a critical first step towards understanding how differences in the genomic structure of these highly repetitive regions may confer and control regenerative capacity.
