Cold Spring Harbor, NY Infertility is generally thought of as a woman's problem. In fact, more than 3 million men across America also experience it. Today, researchers from Cold Spring Harbor Laboratory (CSHL) describe a key event during sperm development that is essential for male fertility. A team led by CSHL Professor Alea Mills explains how a protein controls DNA packaging to protect a man's genetic information.
The sperm is a simple delivery vehicle for a man's genetic information. The highly specialized cell is little more than a DNA bundle powered by molecular motors. As such, it is necessarily tiny: from head to tail a sperm cell is only about 50 micrometers long (1/500th of an inch), invisible to the naked eye. An egg is 30 times larger. The sperm's small size has its benefits less bulk to carry while searching for an egg but it also presents significant challenges. A man's genetic material must be very tightly packaged to fit within a minuscule space.
This organizational problem is not unique to sperm. Every cell in our body contains a full human genome, which spans nearly two meters (6 feet) if unfurled. To contain this massive length of DNA, cells tightly compress our genetic information. In every cell nucleus, DNA is wrapped like thread around protein spools, called histones. The thread can be easily unwound at any time to allow access to the genetic information. In sperm, the packaging problem is much more acute, as its DNA is even more condensed. The spool-like histones are replaced with tiny proteins called protamines. This repackaging process, called chromatin remodeling, is absolutely essential for male fertility.
In work published today in Nature Communications, Mills and her team identify a protein, called Chd5, as a key regulator of chromatin remodeling during sperm development. Mills and Wangzhi Li, PhD, lead author on the study, removed both copies of the Chd5 gene from male mice. They discovered that
|Contact: Jaclyn Jansen|
Cold Spring Harbor Laboratory