The goal of this project is to elucidate redox-responsive developmental pathways and gene regulatory networks that mediate susceptibility to environmental redox stressors. Redox chemistry is at the core of biology, providing the energy that fuels life but also producing toxic byproducts in the form of reactive oxygen species (ROS). ROS production can lead to oxidative stress, a hallmark of many human diseases (such as diabetes) and environmentally-induced pathologies (such as those associated with alcohol abuse). Biological signaling systems are therefore often responsive to redox chemistry. While many environmental redox stressors are also known to cause developmental malformations in humans, particularly in the developing nervous system, the redox-sensitive regulatory networks that mediate this susceptibility are largely unknown. The sea urchin embryo provides a useful comparative model for addressing this problem, as its genome has been sequenced and annotated, and because of the fact that it is a deuterostome and hence developmentally more similar to humans than other invertebrate model organisms. A number of findings indicate that ectodermal cell fate along the oral-aboral axis of the sea urchin embryo is specified via a redox-sensitive regulatory network, and can be specifically perturbed (radialized) by redox stressors such as metal ions and hypoxia. Ectodermal cell fate specification is mediated by Nodal signaling, which in turn is dependent on p38 mitogen activated protein kinase (MARK). The specific aims of this project are to (1) test the hypothesis that p38 mitogen activated protein kinase (MARK) activity is regulated by redox signaling in the developing ectoderm;(2) identify redox-responsive cis-elements and transcription factors that regulate Nodal activity;and (3) identify pathways through which redox stressors perturb ectodermal patterning and affect human development and disease. To achieve these aims, the project will make use of highly specific molecular reagents including mitochondrially-targeted enzymatic anti-oxidants, morpholino-antisense mediated knockdown, and cis-regulatory analysis of the Nodal gene. In addition, a microarray approach will be used to identify the redox-sensitive transcriptome. Finally, the Comparative Toxicogenomics Database (CTD) at MDIBL will be used to determine the relevance of the pathways discovered in sea urchins to human health, and to generate hypotheses that might explain specific human diseases.