Investigating the role of DNA structure in centromere specification

PROJECT SUMMARY Centromeres are chromosomal loci that bind to meiotic or mitotic spindles to facilitate chromosome segregation and faithful inheritance of genetic information. Errors arising during chromosome segregation can be detrimental to the cell and cause aneuploidies. The location of the centromere is well maintained; however, how centromeric DNA encodes the centromere position is not well understood. Centromeric DNA is defined by the presence of unique centromeric nucleosomes that act as a molecular loading dock for other protein complexes involved in chromosome segregation. Centromeric nucleosomes contain a histone H3 variant, centromere protein A (CENP- A). All human centromeres contain repetitive DNA elements known as alpha satellites; however, alpha satellite sequences vary within a chromosome and between chromosomes. Despite the lack of conserved sequences, the identity of the centromere is highly maintained. In rare cases, centromeres can form outside of their native locus, causing the formation of a stable centromere elsewhere in the genome. The formation of ectopic centromeres, also called neocentromeres, is often associated with chromosomal rearrangements that are found in developmental disorders and cancers. Patient-derived neocentromeres exhibit a non-random distribution in the genome, indicating a targeting mechanism to these sites; however, conserved features of the DNA or chromatin at these sites and at the endogenous centromere have not been discovered yet. This raises interesting questions about how centromeric DNA is encoded. I hypothesize that the CENP-A nucleosomes that define the location of the centromere are targeted to unique DNA structures. To address the existing gap in knowledge, this proposal will use a genomic-based approach to investigate DNA structures and centromere specification. Understanding the requirements for centromere formation that is necessary for chromosome separation can be applied to the development of gene therapies and will provide valuable insights into genomic instability that contributes to disease. This work will allow us to address longstanding questions in the field about how the localization of centromeres is determined in humans, and through this we will better understand how unique DNA structures contribute to cellular function and disease.