Regulation of neural crest cell emigration in turtle embryos (541.9)

Turtle plastron bones develop by intramembranous ossification, suggesting that they are derived, like the facial bones, from neural crest cells. Using cell‐labeling and neural tube explant cultures, we have shown that cells expressing neural crest markers emerge from the trunk neural tube in the turtle Trachemys scripta for a greatly extended period compared other model amniotes. The neural crest cells that emerge in a second wave, well beyond the stage of neural crest emigration in chick or mouse embryos, appear to migrate ventrally to form an ectomesenchymal dermis that gives rise to the bones of the plastron. The specification of premigratory neural crest cells and the epithelial‐mesenchymal transition that produces migratory neural crest cell is controlled by a gene regulatory network including the transcription factors Snail2, FoxD3, Sox9, and Sox10. We are currently examining the expression of markers of premigratory and early migratory neural crest cells to examine whether the premigratory domain persists during the period in between the early and late migratory phases. If the expression of these markers persist throughout this period, it will suggest that the premigratory region is maintained, and that the lack of neural crest cell migration may be due to the lack of a supportive environment. In contrast, if these genes are only expressed during the periods of active neural crest cell emigration, then the second wave of neural crest cell migration would require a second inductive signal not found in chick embryos. Grant Funding Source : NSF