The long-term objective of this research is to use cell biological and biochemical techniques to understand the molecular nature of the kinetochore-microtubule (MT) interface in vertebrate cells. For chromosomes to properly segregate during mitosis, they must firmly attach to dynamically growing and shortening MT plus- ends. They do so via the kinetochore, a large protein assemblage built at the primary constriction of mitotic chromosomes. This linkage is likely complicated, as it must be robust to resist the forces of chromosome bi- orientation, yet flexible to allow for fluid growth and shortening of bound MT plus-ends. Kinetochores must also regulate the strength of this attachment, since incorrectly attached MTs must be released, and those that are correctly attached must be stabilized. The kinetochore-associated NDC80 complex is required for generating stable kinetochore-MT attachments in eukaryotic cells, but how this complex builds and regulates binding sites for the plus-ends of spindle MTs remains one of the most important unanswered questions in the mitosis field. This proposal is designed to answer the following questions: What domains of the NDC80 complex make up the direct points of contact with MT plus-ends? Are the complexes tethered together in a """"""""sleeve"""""""" for the MT plus-ends to insert into? If so, how are the complexes tethered together? Do weakly-associated NDC80 complexes diffuse along the MT lattice to facilitate chromosome congression? Or, alternatively, are the points of contact between kinetochores and MTs made up of high affinity binding interactions that require continual release and re-binding to drive chromosome movement? Is kinetochore-MT binding strength regulated through phosphorylation of the NDC80 complex by Aurora B kinase? What phosphatase counter-acts the kinase activity to ensure kinetochore-MT stabilization? These questions will be answered using the following approaches: First, a gene silence/rescue strategy for NDC80 complex components will be developed in PtK1 cells to unambiguously assess kinetochore-MT attachment phenotypes in cells expressing mutant NDC80 complexes. Second, biochemical and biophysical experiments using NDC80 mutants will be carried out to understand mechanistically how NDC80 complexes bind to and translocate along MTs, and which features of the complex are responsible for physically coupling plus-end MT dynamics to force production for chromosome movement. Third, protein-protein interactions will be mapped at the kinetochore-MT interface for the first time in vivo through the development of kinetochore-specific fluorescence interaction assays. These studies will provide answers to a critical set of unresolved questions in the mitosis field, and the developed techniques will be applicable to further study of mitotic proteins and processes. Relevance: Progression through mitosis with incorrect kinetochore-MT attachments is a major cause of aneuploidy, which has been linked to the initiation and progression of human tumors and also to the formation of birth defects. Thus, understanding how cells generate and regulate kinetochore-MT attachments is of critical importance to human health.

Public Health Relevance

During mitosis, chromosomes must segregate correctly in order to prevent the formation of aneuploid cells, which contain an incorrect number of chromosomes. This is critical for human health, as aneuploidy is well-known for causing birth defects and has been implicated as a causative factor in the initiation and progression of tumors. Understanding the mechanisms that cells use to correctly divide their chromosomes equally into two daughter cells is essential to understand the pathways leading to the emergence of aneuploid cells.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
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Deatherage, James F
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Colorado State University-Fort Collins
Schools of Arts and Sciences
Fort Collins
United States
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DeLuca, Keith F; Meppelink, Amanda; Broad, Amanda J et al. (2018) Aurora A kinase phosphorylates Hec1 to regulate metaphase kinetochore-microtubule dynamics. J Cell Biol 217:163-177
Wiggan, O'Neil; Schroder, Bryce; Krapf, Diego et al. (2017) Cofilin Regulates Nuclear Architecture through a Myosin-II Dependent Mechanotransduction Module. Sci Rep 7:40953
DeLuca, Jennifer G (2017) Aurora A Kinase Function at Kinetochores. Cold Spring Harb Symp Quant Biol 82:91-99
Heasley, Lydia R; Markus, Steven M; DeLuca, Jennifer G (2017) ""Wait anaphase"" signals are not confined to the mitotic spindle. Mol Biol Cell 28:1186-1194
Shirnekhi, Hazheen K; Kelley, Erin P; DeLuca, Jennifer G et al. (2017) Spindle assembly checkpoint signaling and sister chromatid cohesion are disrupted by HPV E6-mediated transformation. Mol Biol Cell 28:2035-2041
Ruggeri, Elena; DeLuca, Keith F; Galli, Cesare et al. (2017) Use of Confocal Microscopy to Evaluate Equine Zygote Development After Sperm Injection of Oocytes Matured In Vivo or In Vitro. Microsc Microanal 23:1197-1206
DeLuca, Keith F; Herman, Jacob A; DeLuca, Jennifer G (2016) Measuring Kinetochore-Microtubule Attachment Stability in Cultured Cells. Methods Mol Biol 1413:147-68
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Abe, Yusuke; Sako, Kosuke; Takagaki, Kentaro et al. (2016) HP1-Assisted Aurora B Kinase Activity Prevents Chromosome Segregation Errors. Dev Cell 36:487-97
Maeshima, Kazuhiro; Rogge, Ryan; Tamura, Sachiko et al. (2016) Nucleosomal arrays self-assemble into supramolecular globular structures lacking 30-nm fibers. EMBO J 35:1115-32

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