Date Thesis Awarded

4-2017

Document Type

Honors Thesis

Degree Name

Bachelors of Science (BS)

Department

Neuroscience

Advisor

Margaret S. Saha

Committee Member

Randolph A. Coleman

Committee Member

Mark H. Forsyth

Committee Member

Oliver Kerscher

Abstract

The establishment of the anterior-posterior (AP) axis is an essential step in the development of the central nervous system. In the model vertebrate organism Xenopus laevis, AP neural patterning begins during the late blastula stage and continues through gastrulation. Although the patterning of the nervous system in normal conditions has been extensively studied, less is known about how this process is able to regulate in the face of environmental perturbations. This study aims to characterize the extent and molecular basis of neural axis plasticity in Xenopus laevis by investigating the response of embryos to a 180-degree rotation of their AP neural axis during gastrulation. Embryos were assessed for the expression of regional marker genes using in situ hybridization, and also underwent global gene expression analysis using RNA-Sequencing. Our results suggest that there is a window of time between the mid- and late-gastrula stage during which embryos are able to recover from a 180-degree rotation of their neural axis and then lose this ability. At the mid-gastrula stage, embryos are able to recover from neural axis rotation and correctly express regional marker genes. By the late-gastrula stage, embryos show misregulation of regional marker genes following neural axis rotation and differential expression of genes important for neural development and patterning. Heterochronic transplants between donor and host embryos of different stages indicate that both the presumptive neural ectoderm and the underlying mesoderm play an important role in this plasticity.

Available for download on Sunday, May 05, 2019

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