Chapter 32 - Proteomic Approach to the Reprogramming Machinery of the Mouse Oocyte

Abstract

The mature oocyte is the only cell of the body that can incorporate either sperm or somatic nuclei and express developmental totipotency. In order to prepare for these tasks, the oocyte stockpiles dedicated molecules during oogenesis. If one aims to solve the special properties of oocytes, one should consider that information on the transcriptomic level is of limited use, as ultimately proteins are the main functional units of any given cell type. Therefore, an in-depth characterization of the oocyte proteome is a promising approach to advance our understanding of reprogramming and germ cell biology. To date, limitations on oocyte numbers and proteomic technology have impeded this task, and the search for reprogramming factors has instead been conducted in embryonic stem cells (ESCs). Here we highlight the importance of proteomics in the field of mouse oocyte-mediated reprogramming. We present data on the proteome of mouse metaphase II oocytes and ESCs to a depth of 3699 and 4723 proteins, respectively. Active reprogramming molecules should reside in the nucleus, act on chromatin, and function as enzymes. Following these criteria, we analyzed and filtered the shared proteome of oocytes and ESCs for proteins matching the gene ontology (GO) terms nuclear localization, chromatin modification, and catalytic activity. As a result, we identified 28 oocyte proteins that match the criteria of our multilevel approach to screen for putative active reprogramming factors and thus advance the definition of the “reprogrammome.”