Analysis of the mitotic spindle proteome reveals conserved cell division factors in Caenorhabditis elegans

Cell division is important for many cellular processes including cell growth, reproduction, wound healing and stem cell renewal. Failures in cell division can lead to tumors and birth defects. Numerous proteins ensure the proper allocation of chromosomes to daughter cells in cell division. However, despite our knowledge about the main components in cell division, questions remain as to exactly how many factors play a role in cell division and what their functions are.;In this dissertation, I identified and profiled the mitotic spindle proteome in Chinese Hamster Ovary (CHO) cells for likely cell division candidates. The assembled mitotic spindle proteome totaled 1155 proteins, and profiling the spindle proteins by subcellular localization yielded 313 cell division candidates in the categories of membrane-associated, microtubule-associated, actin-associated and unknown localization. Additionally, comparative proteomics was performed to the previously published CHO midbody proteome and the HeLa mitotic spindle proteome.;In the subsequent study, I identified cell division factors from the initial list of cell division candidates from the mitotic spindle proteome. I found that 72% of mitotic spindle candidates had homologs in Caenorhabditis elegans and that 34 out of the 143 homologs tested were required for embryonic survival in C. elegans. Of the 34 embryonic lethal genes, 21 were determined to be necessary for cell division in a visual screen. A membrane protein whose homologs are involved in glycosylation, OSTD-1, was characterized further. Depletion of OSTD-1 resulted in cell cycle defects, spindle orientation defects, aberrant karyomere fusion, extra cleavage furrows, alterations in cleavage furrow positioning and cytokinesis failures. OSTD-1 also may play a role in ER morphology during mitosis.;Together, my work identified OSTD-1 as a cell division factor from the mitotic spindle proteome and offered an initial characterization of its role in cell division. My work reinforced the connections between membrane proteins, glycosylation and cell division in C. elegans, which is likely conserved in other organisms.