Preserver of Reproductive Integrity: ABC Transporters and Their Potential Roles in the Human Germ Line

Abstract

Cellular defense systems are fundamental to life and dictate survival in an increasingly polluted world. Organisms are continuously exposed to xenobiotics (naturally occurring toxins or anthropogenic compounds) that persist in their environment. I seek to identify the threshold of xenobiotic protection available in mammalian primordial germ cells (PGCs): the embryonic stem cells to eggs and sperm. Most animals and model organisms “set aside” PGCs early in the embryo and maintain it until the adult stage of gamete development is reached. However, little is known about the protective toolkit of PGCs at the plasma membrane. This is important to understand because early-life encounters with xenobiotics could negatively impact reproductive potential of the adult.

Ubiquitous environmental chemicals commonly found in human blood include plasticizers, polyaromatic hydrocarbons, and perfluorochemicals. Pivotal to the front lines of cellular defenses are transporters of the ATP-binding cassette superfamily. ABC transporters’ primary conserved function is to export xenobiotics and small molecules out of the cell. Using an in-vitro derivation protocol, I am testing which ABC transporters are present in and most utilized by human PGCs. This will improve our understanding of how organisms protect their reproductive capability at the earliest developmental stage possible. Using immunolocalization and cell sorting techniques with trans- porter-specific antibodies, I have identified that ABCC1 and ABCG2 are enriched in hPGCs. This is the first description of these proteins in this cell type.

To knockout ABCC1 in these cells, I will design and deliver sgRNA guides against ABCC1 alongside Cas9 and GFP-reporter constructs in our hESC lines (UCLA1 [46XX] and UCLA2 [46XY]), via transfection and selection protocols that have proven successful in these cells. I will then test how sensitive ABCC1-knockout PGCs are to known cord blood contaminants.

This proposed work provides an exciting opportunity to elucidate the role of ABCC1/ ABCG2 in the development and/or protection of human PGCs against toxicants that pose a known threat to reproductive function. Therefore, the potential findings of this study can inform researchers studying germ lines in other organisms and broaden the community’s understanding of how animals can maintain reproductive output in light of xenobiotic exposures.