Yixian Zheng is Director of the Department of Embryology. Her lab has a long-standing interest in cell division. In recent years, their findings have broadened their research using animal models, to include the study of stem cells, genome organization, and lineage specification—how stem cells differentiate into their final cell forms. They use a wide range of tools, including genetics in different model organisms, cell culture, biochemistry, proteomics, and genomics.
Cell division is essential for all organisms to grow and live. During a specific time in a cell’s cycle the elongated apparatus consisting of string-like micro-tubules called the spindle is assembled to move the chromosomes into two new cells. Another structure near the cell’s nucleus, the centrosome, is important for creating the microtubules and for assembling the spindle. Researchers are trying to understand the regulation of the spindle assembly, the structure of the centrosome, and how it organizes the microtubules and participates in spindle assembly.
The scientists use the frog Xenopus for their research. The centrosome consists of a pair of cylinder-shaped structures called centrioles, which are surrounded by a material called pericentriolar material (PCM). Microtubules arise from this PCM. The Zheng scientists discovered a ring complex containing an essential protein component of microtubules called γ -tubulin. They found that the ring complex, named γ TuRC, is essential for centrosomes to form microtubules. They also uncovered an important signaling pathway controlled by a protein made in the nucleolus called GTPase Ran that regulates multiple aspects of cell division.
To study genome organization in development and aging, they use various tools to study how genomes obtain their organization in stem cells and during development. To understand the influence of the process of the cell beginning to shape, called cell morphogenesis, on the eventual type of cell it turns into, the researchers use a technique called pre-implantation mouse embryos. The development of a pre-implanted embryo allows them to discern the first type of cell differentiation, or lineage specification, in a small number of initially similar cells independent of any influence from other tissues. By using live-imaging and computational modeling and tracking, they uncovered unique cellular behaviors that are associated with lineage specification during pre-implantation development, key to analyzing how various physical and chemical changes in the developing cell influence which genes are turned on.
Zheng was a Howard Hughes Medical Investigator from 2000 to 2012. She studied biology as an undergraduate in China before moving to Ohio State University where she received a PhD in 1992. She was a postdoctoral fellow at the University of California, San Francisco from 1992 to 1996, when she moved to Carnegie as a staff scientist and became Acting Director of the department in early 2016. For more see the Zheng lab
