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Marc Wallace Kirschner (born February 28, 1945) is an American cell biologist and biochemist and the founding chair of the Department of Systems Biology at Harvard Medical School. He is known for major discoveries in cell and developmental biology related to the dynamics and function of the cytoskeleton, the regulation of the cell cycle, and the process of signaling in embryos, as well as the evolution of the vertebrate body plan. He is a leader in applying mathematical approaches to biology. He is the John Franklin Enders University Professor at Harvard University. In 1989 he was elected to the National Academy of Sciences. In 2021 he was elected to the American Philosophical Society.
Kirschner studies how cells divide, how they generate their shape, how they control their size, and how embryos develop. In his eclectic lab, developmental work on the frog coexists with biochemical work on mechanism of ubiquitination, cytoskeleton assembly or signal transduction.
At Princeton, his early work on microtubules established their unusual molecular assembly from tubulin proteins and identified the first microtubule-stabilizing protein Tau protein, later shown to be a major component of the neurofibrillary tangles in Alzheimer's disease. In studies at UC San Francisco of the frog embryo as a model system of cell development, Kirschner identified the first inducer of embryonic differentiation, fibroblast growth factor (FGF), an early finding in the field of signal transduction.
Kirschner's lab is also known for uncovering basic mechanisms of the cell cycle in eukaryotic cells. Working in Xenopus (frog) egg extracts, Kirschner and Andrew Murray showed that cyclin synthesis drives the cell cycle Pulverer, Bernd "Milestones in cell division (12): Surfing the cyclin wave" Nature Publishing Group (retrieved 16 May 2012) and, later, that ubiquitin regulates levels of cyclin by marking the cell-cycle molecule for destruction.Brooksbank, Cath "Milestones in cell division (20): Disappearing Act" Nature Publishing Group (retrieved 16 May 2012) His lab discovered and purified many of the components involved in cell cycle progression, including anaphase promoting complex (APC), the complex that ubiquitinates cyclin B.
A second notedLewin, B "Great experiments: Dynamic instability of microtubules - Marc Kirschner and Tim Mitchison" , CELLS! The web site accompanying the Cells textbook (Jones and Bartlett Publishers (2007) finding was his discovery, with Tim Mitchison, of the dynamic instability of microtubules, In mitosis, for example, microtubules form the spindle that separates the chromosomes. The first step in spindle formation is the nucleation of microtubules by microtubule-organizing centers, which then grow in all directions. Microtubules that attach to a chromosome are stabilized and are therefore retained to form part of the spindle. Because of dynamic instability, some individual microtubules that are not stabilized are at risk of collapse (or "catastrophe" as Kirschner named it), allowing re-use of the tubulin monomers. This recognition of self-organization in biological systems has been highly influential, and helped shape the view of the cytoplasm as a collection of dynamic molecular machines.
Kirschner is also interested in the evolutionary origins of the vertebrate body plan. Together with John Gerhart, he was instrumental in developing the acorn worm Saccoglossus kowalevskii into a model system that could be used to study the divergence between and , and the evolution of the chordate nervous system.
Kirschner is a pioneer in using mathematical approaches to learn about central biological questions. For example, a model of the Wnt pathway he developed in collaboration with the late Reinhart Heinrich showed that new properties and constraints emerge when the individual biochemical steps are combined into a complete pathway. A talk he gave on mathematics and the future of medicine at a retreat for Department Chairs at Harvard Medical School in 2003 inspired the Dean, Joseph B. Martin, to found a new Department, the Department of Systems Biology, with Kirschner as founding chair. Since then, Kirschner's lab has attracted many students and post-docs from theoretical backgrounds who wish to make the transition into biology. His lab is now a leader in using mathematical tools to analyze signaling pathways, cell size control, and the selectivity of drugs.
In two books co-authored with John Gerhart, Kirschner has described the cellular and developmental underpinnings of the evolution of organisms, and the concept of "evolvability". In the most recent book, Kirschner and Gerhart proposed a new theory of "facilitated variation" that aims to answer the question: How can small, random genetic changes be converted into useful changes in complex body parts?
Kirschner helped launch the monthly, peer-reviewed journal PLoS Biology in October 2003 as a member of the editorial board and senior author of a paper in the inaugural issue. The journal was the first publishing venture from the San Francisco-based Public Library of Science (PLoS), which had begun three years previously as a grassroots organization of scientists advocating free and unrestricted access to the scientific literature
target="_blank" rel="nofollow"> Marc W. Kirschner, Ph.D., (Faculty page), Harvard Department of Systems Biology.
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