Abstract
In avians and mice, trunk neural crest migration is restricted to the anterior half of each somite. Sclerotome has been shown to play an essential role in this restriction; the potential role of other somite components in specifying neural crest migration is currently unclear. By contrast, in zebrafish trunk neural crest, migration on the medial pathway is restricted to the middle of the medial surface of each somite. Sclerotome comprises only a minor part of zebrafish somites, and the pattern of neural crest migration is established before crest cells contact sclerotome cells, suggesting other somite components regulate the pattern of zebrafish neural crest migration. Here, we use mutants to investigate which components regulate the pattern of zebrafish trunk neural crest migration on the medial pathway. The pattern of trunk neural crest migration is aberrant in spadetail mutants that have very reduced somitic mesoderm, in no tail mutants injected with spadetail morpholino antisense oligonucleotides that entirely lack somitic mesoderm and in somite segmentation mutants that have normal somite components but disrupted segment borders. Fast muscle cells appear dispensable for patterning trunk neural crest migration. However, migration is abnormal in Hedgehog signaling mutants that lack slow muscle cells, providing evidence that slow muscle cells regulate the pattern of trunk neural crest migration. Consistent with this idea, surgical removal of adaxial cells, which are slow muscle precursors, results in abnormal patterning of neural crest migration; normal patterning can be restored by replacing the ablated adaxial cells with ones transplanted from wild-type embryos.
Highlights
All vertebrates have a similar body plan, the early cell movements that establish that body plan can differ considerably in different vertebrate subgroups
They migrate through the somite and, by the stage shown in Fig. 2, they form a monolayer of slow muscle fibers on the lateral surface of each somite (Devoto et al, 1996)
Research article test this hypothesis, we examined neural crest migration in embryos with mutations in genes required for proper somite segmentation, including beamter, fused somites [fss] (Nikaido et al, 2002), after eight [aei] (Holley et al, 2000) and deadly seven [des] (Holley et al, 2002)
Summary
All vertebrates have a similar body plan, the early cell movements that establish that body plan can differ considerably in different vertebrate subgroups. Neural crest cells, a defining feature of vertebrates, migrate from their origin in the region of the dorsal neural tube throughout the body and differentiate into a well-characterized set of derivatives (Le Douarin and Kalcheim, 1999; Kalcheim, 2000; Eisen and Weston, 1993). The pathways of neural crest migration are highly regulated, but differ between amniotes, such as avians and mice, and anamniotes, such as zebrafish. The equivalent migration pathway in avians and mice is restricted to the anterior half of each somite. Despite these differences in migration path in amniotes and anamniotes, early-migrating crest cells in both groups generate similar neuronal derivatives (Le Douarin and Kalcheim, 1999; Kalcheim, 2000; Christiansen et al, 2000)
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