Chromosome anchors form hollow shells before cell division, imaging reveals
Whenever a cell divides, it has to split its chromosomes perfectly between two daughter cells, and even a single mistake can be disastrous. Now, researchers from Japan have found that one of the key structures that makes this possible takes a surprising shape: a hollow sphere.
Cells divide by splitting their chromosomes evenly between two daughter cells; errors in this process can be catastrophic. Researchers from the University of Osaka have discovered that a protein complex called the constitutive centromere-associated network (CCAN) forms a hollow, spherical shell structure within the nucleus, which is crucial for proper chromosome segregation during cell division.
CCAN is located at the centromere of each chromosome, where it forms part of the kinetochore, a "tow hitch" that connects chromosomes to the cellular ropes pulling them apart during division. While the structure of a single CCAN unit has been detailed in previous studies, the arrangement of dozens of these units into a working kinetochore inside the cell has been unclear.
To investigate this, the team used supercomputer simulations to model how CCAN units behave when linked by a protein called CENP-C, suggesting that CENP-C clusters at the center and binds to DNA, organizing other CCAN proteins into an orderly shell around it. High-resolution imaging techniques confirmed the existence of this CCAN shell-like structure in chicken cells, particularly during the period leading up to cell division.
The researchers found that when CENP-C is removed or prevented from binding to DNA, the shell fails to form properly, leading to defective chromosome segregation. This finding highlights the essential role of CCAN's ordered shell-like structure in ensuring accurate chromosome distribution during cell division. Understanding this process could provide insights into the origin of chromosome segregation errors, which are common in many cancers.
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