Stem cell self-renewal: centrosomes on the move

Three recent studies show that centrosome asymmetry correlates with self-renewal of Drosophila neural and germline stem cells and that equalizing centrosomes disrupts asymmetric cell division.     

Semaphorins command cells to move

Semaphorins are secreted or transmembrane proteins that regulate cell motility and attachment in axon guidance, vascular growth, immune cell regulation and tumour progression. The main receptors for semaphorins are plexins, which have established roles in regulating Rho-family GTPases. Recent work shows that plexins can also influence R-Ras, which, in turn, can regulate integrins. Such regulation is probably a common feature of semaphorin signalling and contributes substantially to our understanding of semaphorin biology.     

Stem cells on patrol

Hematopoietic stem cells (HSCs) exist in the bone marrow and circulate in the blood. In this issue, Massberg et al. (2007) report that HSCs also travel through the lymphatic system. Furthermore, migration of HSCs--which express Toll-like receptors--allows the recognition of pathogenic molecules in peripheral tissues thereby promoting the local generation of innate immune cells at the site of infection.     

Blebs on the move

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Butterflies on the move

The Fourth International Conference on the Biology of Butterflies and the Fragland Symposium were held at Leeuwenhorst, The Netherlands, from 23–28 March 2002.