Kathryn W. Tosney

    Neural Crest

In axon guidance 'general cues' guide multiple axonal populations along common pathways. These general cues are also crucial for guiding cells, particularly the neural crest cells, a migratory population that colonizes wide reaches of the embryo. Studying these cells identifies intriguing similarities and differences in axonal and cell guidance, particularly in one path that crest cells travel unaccompanied by axons, the dorsal path between the somite and ectoderm.

In investigating neural crest migration we showed that, in the somitic environment, the general guidance cues guide neural crest migration in a highly intricate pattern. That pattern is a product of the detailed patial and temporal development of the somite. A series of permisive and inhibitory clues delineate the pathway. However, in neural crest cells, these cues are deployed in time as well as in space. The temporal control assures that proper population dispersion at a choice point, where ventral and dorsal paths diverge. Crest cells initially migrate ventrally. The dorsal path becomes acessible only after this ventral population has completed migration. The temporal control has two components. First, the entire dorsal path initially inhibits advance; later it loses its inhibitory qualities. Interestingly, the glycoconjugate, chondroitin-6-sulfate that correlates with inhibition in other tissues, also characterizes inhibition in this system (figure). It is expressed transiently, during the period of inhibition. It disappears following surgeries that ameliorate the inhibition. This tight correlation suggests that molecular as well as cellular mechanisms of guidance are likely the same for many populations guided by general cues.

In addition, my most recent study shows that a second temporally-regulated cue, aids neural crest entry into the dorsal path. This cue is positive. It is a chemotactic cue. It arises from emerging dermis, which emits a diffusible cue that attracts from a distance.

Delayed entry correlates with glycoconjugate expression
C shows an inhibition marker chondroitin-6-sulfate immuno-reactivity, in the dorsal path
D shows HNK-1 positive cells in the same section. Neural crest cells have migrated ventrally but have yet to enter the dorsal path.


  • Tosney KW (2004). Long-distance cue from emerging dermis stimulates neural crest melanoblast migration. Dev. Dynamics 229: 99-108
  • Tosney KW, Dehnbostel DB and Erickson CA (1994). Crest cells prefer the myotome's basal lamina over the sclerotome as a substratum in the intact chicken embryo. Dev. Bio. 163: 389-406.
  • Oakley RA, Lasky CJ, Erickson CA and Tosney KW(1994). Gycoconjugates identify a transient barrier to neural crest migration in the chicken embryo. Development 120: 103-114
  • Erickson CA, Duong TD, and Tosney KW (1992). Descriptive and experimental analysis of the dispersion of neural crest cells along the dorsolateral path and their entry into ectoderm in the chick embryo. Dev. Biol. 151: 251-172
  • Tosney KW (1982). The segregation and early migration of cranial neural crest cells in the avian embryo. Dev. Biol. 89:13-24.
  • Erickson CA, Tosney KW and Weston JA (1980). Analysis of migratory behavior of neural crest and fibroblastic cells in embryonic tissues. Dev. Biol. 7:142-161.
  • Tosney KW (1978). The early migration of neural crest cells in the trunk region of the avian embryo: an electron microscopic study. Dev. Biol. 62:317-333.