Cranial neural crest contributes to the bony skull vault in adult Xenopus laevis: insights from cell labeling studies.
As a step toward resolving the developmental origin of the ossified skull in adult anurans, we performed a series of cell labeling and grafting studies of the cranial neural crest (CNC) in the clawed frog, Xenopus laevis. We employ an indelible, fixative-stable fluorescent dextran as a cell marker to follow migration of the three embryonic streams of cranial neural crest and to directly assess their contributions to the bony skull vault, which forms weeks after hatching. The three streams maintain distinct boundaries in the developing embryo. Their cells proliferate widely through subsequent larval (tadpole) development, albeit in regionally distinct portions of the head. At metamorphosis, each stream contributes to the large frontoparietal bone, which is the primary constituent of the skull vault in adult anurans. The streams give rise to regionally distinct portions of the bone, thereby preserving their earlier relative position anteroposteriorly within the embryonic neural ridge. These data, when combined with comparable experimental observations from other model species, provide insights into the ancestral pattern of cranial development in tetrapod vertebrates as well as the origin of differences reported between birds and mammals.
Gross
Joshua B
JB
Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts 02138, USA. jgross@fas.harvard.edu
Hanken
James
J
D000818:Animals; D002465:Cell Movement / Q000502:physiology*; D003911:Dextrans; D016332:Fetal Tissue Transplantation; D019793:Fluorescein; D006652:Histological Techniques; D007091:Image Processing, Computer-Assisted; D008856:Microscopy, Fluorescence; D009432:Neural Crest / Q000196:embryology* / Q000637:transplantation; D010802:Phylogeny; D012886:Skull / Q000033:anatomy & histology* / Q000196:embryology; D014982:Xenopus laevis / Q000196:embryology*
D003911:Dextrans; D019793:Fluorescein