The role of telomeres in 3D organization of the genome within the nucleus

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The goal of the proposed research project is to understand how telomere localization within the nucleus regulates chromosome structure and genome organization, both in normal cells as well as in disease states and during the process of cellular aging. The human genome is organized into chromosome territories within the nucleus, in which chromosomes occupy a defined volume to facilitate processes such as transcription, gene expression, DNA repair and recombination. Despite intense research into the structural organization of the nucleus during the past 25 years, it is still entirely unclear how chromosome territories are established and maintained throughout cell divisions and cellular lifespan. Specifically, very little is known about how these territories are re-established following chromosome decondensation post mitosis. Telomeres, nucleoprotein complexes that make up the physical ends of eukaryotic linear chromosomes, serve to mask the exposed DNA from being recognized as double-strand breaks. Human telomeres have been shown to localize to the nuclear periphery specifically after mitosis, when the nucleus reassembles. Telomere anchoring to the envelope could therefore present one possible way to reorganize chromatin domains. I will employ Hi-C, an extension of chromosome conformation capture (3C) that is followed by high-throughput sequencing, to determine interactions between telomeres and genomic regions in an unbiased, genome-wide manner. This will allow me to investigate how nuclear organization and long-range chromatin interactions are changed during the cell cycle and reestablished after cell division. In addition, changes during cellular aging and in cells with disease mutations will be investigated. Last, I will address the molecular mechanisms of the physical telomere tethering in order to be able to directly test the role of telomere anchoring in the determination of genome architecture and organization. Importantly, changes in territories would represent an efficient way for altering genome wide transcription signatures and the whole nucleus during aging, cellular transformation, or in disease states. The proposed work is therefore expected to contribute to a more detailed understanding of these processes. I propose that it is possible that the synergistic onset of age-associated diseases could be a result of failing to establish territories efficiently, thereby changing transcription pathways throughout the nucleus. Our goal is to identify the molecular pathways that are required for the establishment and maintenance of chromosomal territories, with the ultimate goal of counteracting pathologic changes in these pathways, and thereby preventing the onset of disease.