The timing of bone formation in frog skulls

Ryan Kerney
AAAS Science and Technology Policy Fellow
Presented in the Embryo Physics Course, December 21, 2011


My goal in this presentation is to explore the evidence that physical forces influence the order and timing of skull bone formation in frogs. A combination of comparative and experimental evidence suggests a link between bone formation and metamorphic shape changes. In metamorphosing frogs the braincase and otic capsules consistently form bone before other regions of the skull. These are also the regions that undergo the least amount of metamorphic remodeling. Additionally, this order of bone formation is modified in some lineages of terrestrial direct-developing frogs, which have lost their free-living tadpole stage. I will also discuss on-going experimental work in developing transgene reporters, specific to cartilage and bone, in the model frog genus Xenopus. These reporters were developed to investigate cellular origins of the post-metamorphic skeleton. However, they will also be useful isolating skeletogenic cell populations and testing their sensitivity to physical perturbations. These latter experiments are just underway, and I look forward to gaining research insights from the Embryo Physics community on further testing how physical forces can influence these developmental processes.



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