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AMACHER/ELSEVIER
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: l- Y% R3 i. ?$ mAs slow-twitch muscle cells migrate through fast-twitch muscle precursor cells, they act as morphogenesis tutors, according to Clarissa Henry and Sharon Amacher (University of California, Berkeley, CA).
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! x' A1 B% H' `; e) M lFast-twitch muscle cells in zebrafish start off life as round blobs but must undergo anterio-posterior elongation to become functional myofibers. Henry and Amacher had noticed that this elongation process spreads in a medial-to-lateral wave, i.e., cells near the midline change shape first.* d1 H3 I3 ?9 Y& p4 t! d6 t0 u
; a: T$ h3 ~+ a) L2 u1 S& ^The authors first established that elongation required Hedgehog signaling. Transplantation experiments showed, however, that this effect was indirect. To restore fast-twitch elongation in a Hedgehog-signaling mutant, the critical ingredient was wild-type slow-twitch cells not wild-type fast-twitch cells.5 P3 c5 S) y8 `$ _
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In response to the Hedgehog signal, transplanted slow-twitch cells extended across the anterior–posterior width of a somite and migrated outwards from the notochord. Fast-twitch cells in their wake elongated. The effect could be relayed to other fast-twitch cells as long as the targets were in the same somite. In the wild type there are probably enough migrating cells to contact directly all of the fast-twitch cells., M, p( y, K3 ?, b5 U7 b2 A
. T+ K9 S! r. M2 d; v7 z) F& FFuture work will show if the slow-twitch cell or its discarded extracellular matrix is acting as a scaffolding for the fast-twitch cell, or if other signals are at work. In other sites of cell migration, such as the developing limb and early embryo, there may be similar drop-offs of differentiation and morphogenesis cues.
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" J! P* Q* ~9 i$ q0 @+ `9 lReference:
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Henry, C.A., and S.L. Amacher. 2004. Dev. Cell. 7:917–923.(Ovoid fast muscle cells (white arrow) st) |
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发表于 2009-3-6 08:41
发表于 2015-5-26 16:59
