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Microtubules and Their Plus-ends

Microtubules are long, tube-shaped (25 nm in diameter) protein polymers that are present in all eukaryotic cells. An important function of microtubules is to drive the movement of cellular organelles such as chromosomes. During mitosis, microtubules attach their end structures, called plus-ends in this case, to chromosomes via kinetochore (a secondary structure of chromosomes), illustrated in the left figure. As the microtubules grow and shrink, the chromosomes are pulled around inside the cell. Because of their vital roles in cells, microtubules have been under intensive investigation in both cell biology and molecular medicine. For example, a direction in anti-cancer drug development is to disrupt microtubule dynamics to stop cells from proliferating.               

Problems and Challenges

Biologists study the functions of microtubules and plus-ends by observing their structures. For this purpose, electron microscope tomography is used to produce high-resolution 3D volume image. However, in the low contrast tomography volume, the interpretation of the volume data is rather challenging since the microtubules and plus-end features are in close contact with the cellular environment and are densely surrounded by proteins of similar appearance, as shown in both the left and right figures. Consequently, practical segmentation of the tomography volume is dominated by time-consuming manual operation.

A selected slice in the volume, microtubules are indicated by arrows

A close-up view of one microtubule, plus-end indicated by arrow

Summary | Background | Methods | Results | Publications