Protein Held to Direct Egg Development

Harvard University researchers announced Friday they had discovered a key protein that plays a pivotal role in directing a fertilized egg to develop into a complex animal.

The protein, known as an activin, induced a fertilized frog egg to develop in the laboratory into a miniature embryo, with head, eyes and muscles, the researchers said.

Although human applications are still far off, the finding answers part of the longstanding question of how an egg develops into the wide variety of specialized cells that form a body’s parts and organs.

Furthermore, the frog egg was induced to develop with activin from mice, demonstrating that protein activators cross species lines, said the researchers, led by Douglas Melton, a Harvard professor of biochemistry and molecular biology.

“It’s unlikely that activins or closely related compounds are not involved in setting up the development plan for mice and, probably, for humans,” Melton said.

The team discovered that an egg contains the basic development plan before it is fertilized with sperm, in the form of different molecules in different parts of the cell.

The sperm carries instructions for designating the left and right sides of the body and contains half of the genes that direct construction and maintenance. At this point, activins apparently turn on and begin directing genes to make muscles, a heart and other tissues and organs.