I have evaluated the following article for F1000:
J Azimzadeh, ML Wong,…, A Sánchez Alvarado, WF Marshall Science 2012 Jan 27 335 6067:461-3 DOI 10.1126/science.1214457 PMID 22223737
Developmental Evolution,Morphogenesis & Cell Biology,Developmental Molecular Mechanisms,Cell Growth & Division,Cytoskeleton
The key finding here is that planarians lack centrosomes. In a series of careful phylogenetic analyses and gene-depletion experiments, the authors show that centrioles, the core components of centrosomes, are not necessary for cell division and tissue formation in planarians. In contrast, centrioles are assembled in planarians during the differentiation of ciliated cells, which they use for locomotion. Furthermore, many of the typical proteins required for human centrosome formation (e.g. Plk4, SAS4) are required for centriole assembly and ciliogenesis during differentiation of ciliated cells. The elegantly crafted final sentence of this paper sums up its importance perfectly: “ selective pressure to maintain the centrosome in animals comes from the need to coordinate specific developmental processes rather than a fundamental cellular requirement for the organelle”.
My evaluation at the F1000 cite can be found here.