Tough Babies:
By Amro Hamdoun

Embryos are tough. With no more than a single cell, these earliest stages of life must survive in the ocean. Their strategy is to have heavy duty mechanisms to ward off infection, keep out toxic chemicals, shield from the sun, prevent breaking in the waves and survive when food or air are scarce. These mechanisms determine the success or failure of development in the real world.

My research seeks to understand how embryos use cellular and molecular tools to solve everyday environmental challenges. To learn more about the biology of the embryo defenses in animal embryos I primarily use sea urchins as a model. These animals produce millions of eggs that can be easily manipulated in the laboratory to produce robust embryos. The sea urchin has thus served as a major model for embryology for the past century, providing us with many insights into the functioning of embryos and cells.

A key tool is a group of proteins called multidrug transporters. These molecules are cellular pumps, keeping chemicals from building up inside the embryo and “flooding” the cell. They can be thought of as cellular “bouncers”, determining which chemicals get in and which ones are kept out. Sea urchins have large amounts of the multidrug transporter proteins stored in the egg, inactive, before fertilization. Minutes after fertilization the transporters move to the surface of the embryo and become active.

Once active, the transporters can keep a variety of chemicals from building up inside the embryo. This has important implications for the ability of these embryos to keep both natural and man-made toxic chemicals out of the cell. If these transporters are overwhelmed by chemicals, or fail to recognize them, the chemicals enter the cell and build up inside embryos.

Both environmental contaminants and pharmaceutical drugs can defeat transporters in this way. Some of these same chemicals can also adversely affect the survival or embryos in the environment. By unraveling the mysteries of how embryo defenses work we gain insights into why myriad chemicals in the environment and our bodies, are problematic for these tough babies.