Understanding the role of mitochondrial specialization in early development

PROJECT SUMMARY Embryogenesis is an energetically demanding process in which a single cell initiates divisions, giving rise to progeny that undergo diverse cell fate decisions and complex morphogenetic behaviors to form a multicellular organism with distinct tissues. Mitochondrial oxidative phosphorylation (OXPHOS) and subsequent ATP production play a central role in meeting the dynamic energetic and ROS-mediated signaling demands of embryogenesis. OXPHOS consists of four ETC complexes that each contain multiple protein subunits (~100 total). Importantly, when the function of ETC proteins is impaired, variable developmental defects occur, suggesting that development is dependent on specific ETC proteins. However, how the mitochondrial ETC is regulated to meet the varying energetic and signaling demands of development remains unclear because of the vast complexity of the ETC and difficulty of studying the ETC in development. The Sherwood lab has recently created the first in vivo mitochondrial ETC toolkit in C. elegans, through endogenous fluorophore tagging of ~20 nuclear encoded ETC components from the four ETC complexes. Through whole embryo analysis of fluorescence levels, I have found that ETC complex expression increases ~1.5-3 fold per mitochondria from the two-cell to the two-fold stage when major tissues have formed. ETC protein levels differ between the developing primordial tissues, with striking divergence in the increased levels of ETC proteins per mitochondria in the epidermis compared to the intestine. Overall, this proposal will test the hypotheses that unique mitochondrial ETC levels develop after tissue specification to meet the distinct energetic and possibly signaling demands of the tissue and that these unique mitochondria are essential to tissue differentiation. Completion of the proposed aims will develop C. elegans as a new model to understand mitochondrial ETC regulation and specialization in development, which has important implications to our understanding of development, mitochondrial biology, and metabolic disorders.