CELL BIOLOGY: A Dead-End Shortcut

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Science  24 Oct 2003:
Vol. 302, Issue 5645, pp. 535c
DOI: 10.1126/science.302.5645.535c

Flagella and cilia project from the cell surface. They can provide a means of propulsion for single cells, and they are an integral component of the signaling apparatus in some sensory organs. The prototypical structure of the flagellum is conserved from unicellular organisms through to higher mammals.

Kohl et al. have examined the contribution of the flagellum to cellular architecture in the protozoan parasite Trypanosoma brucei. Using RNA interference, they blocked the production of proteins required for intraflagellar transport—a critical step in flagellum assembly. During the early stages of gene silencing, before assembly had been completely abolished, they noticed that cells with short flagella were correspondingly shorter than their sisters who had full-length flagella. This unexpected observation suggests that the flagellum is involved in sensing the size of the cell and in promoting cytokinesis—the separation of daughter cells after mitosis. It appears that the tip of the flagellum, which sits on the cell surface, defines the site of cleavage during cytokinesis, probably by virtue of its connections to the cytoskeleton. Hence, cells completely devoid of flagella and the intracellular flagellum attachment zone (FAZ) cannot divide. — SMH

EMBO J. 22, 5336 (2003).

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