Meeting Abstract

P1.63  Tuesday, Jan. 4  Late Emerging Trunk Neural Crest Cells Form the Turtle Plastron CEBRA-THOMAS, J.A.; TERRELL, A.; YIN, M.; SHAH, S.P.; BETTERS, E.; DOLES, T.; GILBERT, S.F*; Millersville Univ., Millersville, PA; Millersville Univ., Millersville, PA; Swarthmore College, Swarthmore, PA; Millersville Univ., Millersville, PA; Swarthmore College, Swarthmore, PA; Swarthmore College, Swarthmore, PA; Swarthmore College, Swarthmore, PA sgilber1@swarthmore.edu

Turtle plastron bones develop by intramembranous ossification, suggesting that they are derived, like the facial bones, from neural crest cells. At Greenberg stage 17, well after the initial wave of neural crest migration, cells expressing HNK1 and the early neural crest marker FoxD3, begin accumulating in the thickened dermis of the carapace and migrating to the developing plastron. These cells possess the defining attribute of neural crest cells, that of emerging from the neural tube. However, they emerge from the neural tube in a second, later wave. HNK1+ cells can also be observed migrating away from cultured neural tubes from St.17 embryos. In contrast to the neural crest cells migrating away from stage 12 neural tubes, these late emerging neural crest cells also express PDGFRα, which is typically expressed by cranial neural crest cells. Plastron mesenchyme cells also express neural crest cell markers (HNK1, PDGFRα and p75). When the lipophilic dye DiI was injected into the lumen of the neural tube of St.16-17 turtle embryos, DiI-positive cells were observed in the carapacial ridge neural crest “staging area” within a day. After several days, DiI-positive cells reached the ventral mesenchyme. These data support our hypothesis that the plastron of the turtle is formed by a late emerging population of neural crest cells that collect dorsally in the carapace, migrate ventrally to the plastron, and undergo intramembranous osification. Plastron mesenchyme cells appear to have functional similarities to cranial neural crest cells as they differentiate readily in culture to form clusters of collagen I-positive cells.