The Tiny Molecules That Say If Your Boy/Daughter Is Fertile or Not

A very tiny protein can make the difference if you will have grandchildren or not. A new research published in the Nature journal has discovered a previously unknown chemical which makes the embryonic germ cells, that would later grow into sperm or ova, to pass through a period of "transcriptional silence," when the cell's DNA cannot be copied (a possible protection against mutations). Without this silence typical just for the germ cells, an organism will have sterile offspring.

The study was led by Dr. Akira Nakamura at the RIKEN Center for Developmental Biology (CDB) in Kobe (Japan) and by Dr. Paul Lasko, Chair of McGill University's Department of Biology, Montreal, Canada.

"A fundamental characteristic of embryonic germ cells in all organisms is that they don't transcribe their own genes for a certain time during embryonic development. They are transcriptionally silent; that's what makes them special. It's not fully understood why this is the case, but if that silencing doesn't happen, then the germ cells don't work. They don't migrate correctly and they don't make their way into the gonads," said Lasko.

In the mid-90s, the Nakamura-Lasko team discovered the Polar Granule Component (PGC) gene in the fruit fly. Females lacking PGC produced offspring unable to generate germ cells, both sperms or eggs. Only current technology allowed Nakamura to find the protein encoded by the PGC. This molecule controls the Transcription Elongation Factor B (TEF-B), involved in expressing proteins.

"It's a very small, 71-amino acid protein. The average length of a protein is about 400 to 500 amino acids, so this is extremely small. Back when we did the initial research, there weren't very many genes known that encoded such a short protein. The significance of this is that Nakamura has shown that this little protein seems to be the key regulator that keeps gene expression shut off in germ cells. What the study argues is that this regulation of TEF-B might be very important for germ cell development in a variety of organisms. That's something people will want to look at in mammals," said Lasko.