M. Smith et al., TRUNK NEURAL CREST ORIGIN OF CAUDAL FIN MESENCHYME IN THE ZEBRAFISH BRACHYDANIO-RERIO, Proceedings - Royal Society. Biological Sciences, 256(1346), 1994, pp. 137-145
The origin of fin mesenchyme and the cells forming the distal fin ray
skeleton in fishes is unknown, but is often assumed to be the neural c
rest. To test this possibility, a series of experiments have been done
using a vital cell marking technique to label candidate progenitor ce
ll populations in early zebrafish embryos. Injections of the fluoresce
nt membrane probe DiI were made in discrete focal points into the dors
al aspect of the caudal neural keel before trunk neural crest cell emi
gration at that axial level in embryos at the 15-20 somite stage. As c
ontrols, injections were made into both paraxial, unsegmented mesoderm
, and semitic mesoderm before somite elevation, ventral and lateral to
the dorsal keel injection site. Only after injection into the neural
keel site were labelled cells subsequently found in the fin mesenchyme
(along with labelling of other cells types traditionally regarded as
crest derived). These data provide the first experimental evidence tha
t early fin bud mesenchyme contains a contribution from the trunk neur
al crest, and support the hypothesis that the dermal skeleton depends
upon a crest-derived mesenchyme for its formation. We suggest that a c
ausal link between neural crest-derived mesenchyme and the development
of the exoskeleton has been evolutionary conserved throughout the neu
ral crest of teleosts but has been lost in the trunk crest of higher v
ertebrates.