Scientists deconstruct cell division( Baltimore MDThe last step of the ce...)

Baltimore, MDThe last step of the cell cycle is the brief but spectacularly dynamic and complicated mitosis phase, which leads to the duplication of one mother cell into two daughter cells. In mitosis, the chromosomes condense and the nucleus breaks down. Fibrous structures called spindles form, which then move the chromosomal material toward opposite ends of a cell and help partition other cell contents. If something goes wrong, diseases such as cancer can arise. Scientists have tried for years to unravel the process of spindle assembly. Now, researchers at Carnegie's Department of Embryology have found that two proteins dynein and Nudelinvolved in other cell-division functions, are essential to regulate assembly of the spindle matrix.

"The mechanisms that cells use during division to partition both chromosomes and regulatory factors into their daughters are widely recognized as among the most fundamental processes in all of biology. During the last several years no one has done more than Yixian Zheng to broaden our understanding of how dividing cells control these critical events," said Allan Spradling, Department of Embryology director.

"To ensure proper cell division, the mother cell needs to separate its genetic materials, the chromosomes, equally, but also partition its cellular content properly into daughter cells," explained co-author Yixan Zheng. "Cell division allows a fertilized egg to develop into multicellular organisms with different types of cells. It also replenishes adult tissues, such as skin and bones. Forming a spindle requires the assembly of a 'skeleton' from tube-like microtubules and the construction of a poorly defined scaffold called a spindle matrix."

In 2006, Zheng and colleagues discovered that a protein found in the nucleus during the interphase of the cell division cycle, called lamin-B, is a structural component of the spindle matrix (Science 31 March 2006, 311: 1887-1893). Based on this findin
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