Scientists Discover Protein Associated With Male Infertility, Shedding Light on Sperm Development

Typically thought of exclusively as a woman's issue, infertility also affects a large number of men: over 3 million in the United States. Researchers at the Cold Spring Harbor Laboratory in New York uncovered new information about sperm development.

Led by Professor Alea Mills, the research team discovered that a protein controls DNA packaging to protect a man's genetic information, a key event in sperm development that is essential for fertility. The protein, Chd5, was present in the sperm of fertile mice and absent in the sperm of infertile mice.

Infertility in men is caused by a number of different factors: varicoceles (large veins on a man's scrotum); diseases such as diabetes, cystic fibrosis, trauma, infection, testicular failure, or treatment with chemotherapy or radiation; poor habits such as smoking, heavy drinking, illicit drug use, etc.; and exposure to environmental toxins. More information on male infertility can be found on the Centers for Disease Control and Prevention website.

Chd5 is a key regulator of chromatin remodeling during sperm development. Chromatin remodeling is a repackaging process that tightly compresses a man's genetic information in the sperm. When Chromodomain helicase DNA binding protein 5 (Chd5) was removed from sperm in male mice the researchers found that the mice suffered from low sperm count, decreased sperm motility, and inability to fertilize eggs.

The researchers' study, "Chd5 Orchestrates Chromatin Remodeling During Sperm Development," was published today in the journal Nature Communications.

The absence of Chd5 affects chromatin remodeling because the histones (the protein spools in which DNA is wrapped) are not properly replaced with protamines (tiny proteins that help further condense the DNA), which lead to an array of issues. Histones can be easily unwound at any time and they require help from protamines to maintain the DNA structure.

"So in addition to infertility, loss of Chd5 may put future generations - the rare embryos that do get fertilized with defective sperm - at risk for disease," said Professor Mills in this EurekAlert! news release. "Chd5 may protect a person from medical conditions related to DNA damage and spontaneous mutations, like cancer and autism."

You can read more about the Cold Spring Harbor Laboratory study in the Nature Communications journal.