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

Explore Carnegie Science

June 17, 2019

Meredith Wilson, a postdoctoral associate in Steve Farber’s lab at the Department of Embryology, has been awarded Carnegie’s thirteenth Postdoctoral Innovation and Excellence Award. These prizes are given to postdocs for their exceptionally creative approaches to science, strong mentoring, and contributing to the sense of campus community. The nominations are made by the departments and are chosen by the Office of the President. The recipients receive a cash prize and are celebrated at an event at their departments.  

Wilson came to Carnegie in 2014 from the University of Pennsylvania with a background in cell biology investigating how motor proteins position

Illustration of a thymus in a human chest courtesy of Navid Marvi.
May 29, 2019

Washington, DC—Aging-related inflammation can drive the decline of a critical structural protein called lamin-B1, which contributes to diminished immune function in the thymus, according to research from Carnegie’s Sibiao Yue, Xiaobin Zheng, and Yixian Zheng published in Aging Cell.

Each of our cells is undergirded by a protein-based cellular skeleton. And each of our tissues is likewise supported by a protein matrix holding the cells that comprise it together. These protein scaffolds or structures are necessary for organs and tissues to be constructed during development.

“Since organ building and maintenance require this protein-based structural support

Steve Farber photo by Navid Marvi, courtesy of the Carnegie Institution for Science
May 1, 2019

Baltimore, MD—This week Carnegie’s Steve Farber will be recognized by New England Biolabs Inc. with its Passion in Science Award in the category of Mentorship and Advocacy. The company, which supplies research tools for sequencing, synthetic biology, and cellular and molecular research, launched the prize in 2014.  

The 12 honorees were chosen for their “innovative work that goes above and beyond the boundaries of pure science to make a profound impact on other fields.”

In announcing the 2019 class, CEO Jim Ellard described them as individuals “who are enriching lives in ways that go well beyond the traditional definition of success for a

Michael Diamreyan with Yixian Zheng, Frederick Tan, and Minjie Hu courtesy of Navid Marvi, Carnegie Embryology.
March 21, 2019

Baltimore, MD—Michael Diamreyan, a Johns Hopkins University undergraduate biophysics student with a Carnegie connection, has been awarded two prestigious research grants to further his independent investigations.  He is a member of Carnegie Embryology Director Yixian Zheng’s laboratory team, in collaboration with the department’s bioinformatician, Frederick Tan.

Diamreyan received an ASPIRE Grant (formerly called DURA grants), which recognizes “exceptional undergraduate students” from the Krieger School of Arts and Sciences at Johns Hopkins University (JHU) with funding for independent research projects. He was also named an Amgen Scholar, which

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The Zheng lab studies cell division including the study of stem cells, genome organization, and lineage specification. They study the mechanism of genome organization in development, homeostasis—metabolic balance-- and aging; and the influence of cell morphogenesis, or cell shape and steructure,  on cell fate decisions. They use a wide range of tools and systems, including genetics in model organisms, cell culture, biochemistry, proteomics, and genomics.

 

The Spradling laboratory studies the biology of reproduction. By unknown means eggs reset the normally irreversible processes of differentiation and aging. The fruit fly Drosophila provides a favorable multicellular system for molecular genetic studies. The lab focuses on several aspects of egg development, called oogenesis, which promises to provide insight into the rejuvenation of the nucleus and surrounding cytoplasm. By studying ovarian stem cells, they are learning how cells maintain an undifferentiated state and how cell production is regulated by microenvironments known as niches. They are  also re-investigating the role of steroid and prostaglandin hormones in controlling

Stem cells make headline news as potential treatments for a variety of diseases. But undertstanding the nuts and bolts of how they develop from an undifferentiated cell  that gives rise to cells that are specialized such as organs, or bones, and the nervous system, is not well understood. 

The Lepper lab studies the mechanics of these processes. overturned previous research that identified critical genes for making muscle stem cells. It turns out that the genes that make muscle stem cells in the embryo are surprisingly not needed in adult muscle stem cells to regenerate muscles after injury. The finding challenges the current course of research into muscular dystrophy,

The Marnie Halpern laboratory studies how left-right differences arise in the developing brain and discovers the genes that control this asymmetry. Using the tiny zebrafish, Danio rerio, they explores how regional specializations occur within the neural tube, the embryonic tissue that develops into the brain and spinal cord.

The zebrafish is ideal for these studies because its basic body plan is set within 24 hours of fertilization. By day five, young larvae are able to feed and swim, and within three months they are ready to reproduce. They are also prolific breeders. Most importantly the embryos are transparent, allowing scientists to watch the nervous system develop and to

Evolutionary geneticist Moises Exposito-Alonso joins the Department of Plant Biology as a staff associate in the summer of 2019. He investigates whether and how plants will evolve to keep pace with climate change by conducting large-scale ecological and genome sequencing experiments. He also develops computational methods to derive fundamental principles of evolution, such as how fast natural populations acquire new mutations and how past climates shaped continental-scale biodiversity patterns. His goal is to use these first principles and computational approaches to forecast evolutionary outcomes of populations under climate change to anticipate potential future

Staff Associate Kamena Kostova joined the Department of Embryology in November 2018. She studies ribosomes, the factory-like structures inside cells that produce proteins. Scientists have known about ribosome structure, function, and biogenesis for some time. But, a major unanswered question is how cells monitor the integrity of the ribosome itself. Problems with ribosomes have been associated with diseases including neurodegeneration and cancer. The Kostova lab investigates the fundamental question of how cells respond when their ribosomes break down using mass spectrometry, functional genomics methods, and CRISPR genome editing.

Kostova received a B.S. in Biology from the

Sally June Tracy applies cutting-edge experimental and analytical techniques to understand the fundamental physical behavior of materials at extreme conditions. She uses dynamic compression techniques with high-flux X-ray sources to probe the structural changes and phase transitions in materials at conditions that mimic impacts and the interiors of terrestrial and exoplanets. She is also an expert in nuclear resonant scattering and synchrotron X-ray diffraction. She uses these techniques to understand novel behavior at the electronic level.  Tracy received her Ph.D. from the California Institute of

The Ludington lab investigates complex ecological dynamics from microbial community interactions using the fruit fly  Drosophila melanogaster. The fruit fly gut carries numerous microbial species, which can be cultured in the lab. The goal is to understand the gut ecology and how it relates to host health, among other questions, by taking advantage of the fast time-scale and ease of studying the fruit fly in controlled experiments.