Scientists find new protein potentially linked to human infertility

WASHINGTON, Feb. 7– American researchers have identified a
protein in mice eggs that is proved crucial to fertility, lending a new
clue to unexplained causes of female infertility since humans also have the
same protein.

In a study published on Monday in the journal Developmental Cell,
scientists at University of California San Diego found that mice eggs
without the protein called L2, appear ordinary, but cannot be fertilized by
sperm. Heidi Cook-Andersen, the paper’s senior author, who worked with
couples struggling with infertility, said, “it’s frustrating that for many
of them, we have no idea why it’s difficult for them to conceive. All of
their tests come back normal.” “That’s why this study is so exciting to us.
It’s another clue,” Cook-Andersen said.

The study shows that L2 plays a role in cells by turning off gene
expression when the proteins encoded by the mRNAs are no longer needed. The
mRNA is the messenger that carries DNA’s recipe to the cell’s
protein-making machinery. To determine what effect the L2 lacking had on
fertility, Cook-Andersen’s team set up an equal number of fertile male mice
with 10 females lacking L2 in their eggs and 10 normal females. Then they
tracked the groups for six months. In that time, the normal mice produced
regularly but the female mice lacking the L2 protein in their eggs didn’t
have a single pup. The team found that L2-deficient eggs were unable to
shut off the global transcription, a process that normally happens in the
final stages of egg growth. It means that eggs lacking L2 continued
transcribing genes into mRNA and producing proteins. “Many research groups
are looking at how genes are regulated from the perspective of which genes
need to be turned ‘on’ for a cell to advance to the next stage of
development, but now we see that it’s just as important to know which genes
need to be turned ‘off,'” Cook-Andersen said. In the future, the team plans
to determine if L2 plays a role in human infertility. Currently, the
underlying causes for approximately 15 percent of human infertility cases
is not known. – XINHUA