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On page 545, Strachan and Condic show that neural crest cells (NCCs) can be speedy if they remember to recycle receptors. The speed gained from their conservation efforts may expose them to differentiation pathways that other NCCs miss out on.
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( t+ W$ _+ C0 x, x! T* e n9 WPopulations of NCCs differ in their speed on various matrices. Cranial NCCs, for instance, pick up speed on higher concentrations on laminin, whereas trunk NCCs keep a slow pace. The new results show that the cranial population is able to move quickly because they both recycle and reduce the numbers of their laminin-binding integrin receptors.% T' A$ H5 m" g0 [
; V# Z0 [8 a+ j8 V g! G- t" GMore laminin might actually slow cells by promoting strong adhesions. But cranial NCCs avoided this slowdown by removing laminin receptors (integrin 6) from the cell surface. The removed 6 receptors were internalized into recycling endosomes and sent back to the surface. Through this recycling pathway, receptors that are freed from adhesions at the trailing edge may be quickly moved to the leading edge, where new adhesions are needed. Indeed, inhibition of 6 receptor recycling slowed NCC migration on high concentrations of laminin, but had no affect on low laminin levels.
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On fibronectin, which binds to integrin 5, the surface levels of integrins 5 and 6 were unchanged, and 5 recycling was not increased. The lack of 5 recycling may explain why the speed of cranial NCCs does not vary based on fibronectin concentrations.$ q! A0 Q! Q8 M. F0 Y8 q- _- Y5 D
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Integrin recycling may explain in part how some sets of NCCs acquire their fate. Upon emerging from the neural tube, NCCs migrate throughout the body and differentiate into cell types as varied as bone, nerves, and pigment cells. NCCs that move quickly on laminin may receive one set of differentiation instructions at their destination. By the time latecomers arrive, the environment may have changed such that these NCCs are told to adopt a different fate.(Integrin 6 (green) is returned to the ce) |
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发表于 2009-3-6 08:17
发表于 2015-6-10 21:00
