Meeting Abstract

29.6  Wednesday, Jan. 4  Persistence of embryonic axial patterning markers in adult Eurycea cirrigera tails SWEARINGEN, R.L.*; VAGLIA, J.L.; DePauw University, Greencastle, IN; DePauw University, Greencastle, IN jvaglia@depauw.edu

Post-embryonic addition of segments in salamanders (Amphibia:Urodela) suggests that the tail tip retains aspects of embryonic cell organization and gene expression throughout life. Knowledge of how spinal cord and associated tissues continue to develop, and what genes are expressed could reveal mechanisms that also underlie tail regeneration. Our research investigates tissue organization and protein expression in the posterior tail of the salamander Eurycea cirrigera (Plethodontidae). Our goals were to 1. Describe relations amongst tissues such as spinal cord, notochord and muscle in the posterior tail 2. Determine when during development MF20, Pax6, and Pax7 are expressed in the tail, and 3. Document expression of those proteins along the posterior tail. Embryo, larval and adult specimens were collected from field sites in central Indiana and fixed and processed for whole mount (MF20) or frozen section immunostaining (MF20, Pax6, Pax7). Whole mounts were visualized using a DAB conjugated secondary antibody; sections were visualized using fluorescence. Notochord and spinal cord were present in tails of all life stages, and spinal cord consistently extended more posterior than notochord. Somites were not present in post-embryonic tails, suggesting that ongoing patterning of the spinal cord originates from either within the cord, or from nearby progenitor cells. MF20 expression was absent from tail tips of all stages, but present in differentiated muscle cells positioned more anteriorly in the tail. Dorsolateral spinal cord exhibited Pax6 expression; however, only neural crest expressed Pax7. Consistent with MF20, neither Pax6 nor Pax7 were expressed in tail tips. Our study suggests that genes important for axial patterning in embryos are relevant to post-embryonic development.