A more detailed understanding of cell divisions giving rise to sperm and egg cells could lead to infertility treatments

May 17, 2017, Agency for Science, Technology and Research (A*STAR), Singapore
A more detailed understanding of cell divisions giving rise to sperm and egg cells could lead to infertility treatments
Researchers have identified a ‘speedy’ protein that plays an important role in the cell division process called meiosis. Credit: SCIEPRO/Science Photo Library

Researchers have shown that a recently identified protein, called Speedy A, plays an essential role in the early stages of meiosis—a special type of cell division that produces sperm and egg cells.

In meiosis, a single cell divides twice, producing four , known as sperm or , which contain half the genetic information of the original cell. When a sperm fertilizes an egg, the resultant embryo contains a full set of chromosomes. In the early stages of meiosis, chromosomes residing in the nucleus undergo a process called recombination, which involves the exchange of genetic material that leads to genetic diversity.

"Recombination can only happen when the ends of the chromosomes, called telomeres, are attached to the ," explains Philipp Kaldis of the A*STAR Institute of Molecular and Cell Biology.

Kaldis, in collaboration with Kui Liu of Sweden's University of Gothenburg, and colleagues in China and the US, wanted to understand how chromosomal telomeres attach to the or 'envelope', during meiosis.

Using immunofluorescent staining of mouse spermatocytes, they found that a called Speedy A is localized to telomeres. Speedy A is a member of the Speedy/RINGO protein family, which activate cyclin-dependent kinase 2 (Cdk2), an important cell division-related protein which is also localized to telomeres, but whose role in meiosis is not fully understood.

The researchers then bred mice that were deficient in the gene for Speedy A and found that mice lacking Speedy A were infertile, similar to mice that were previously bred lacking Cdk2.

By comparing telomere–nuclear envelope attachment in mice with and without Speedy A, the team found that a specific portion of the Speedy A protein, called its RINGO domain, facilitated binding to Cdk2. Speedy A also bound to telomeres via its N terminus (the end that has a free amine group) and this, together with the RINGO domain, form Speedy A's 'telomere localization domain', which the researchers believe mediates the initial binding of chromosomal telomeres to the nuclear envelope.

Speedy A's other end, the C terminus (which has a free carboxyl group), is responsible for activating Cdk2 and is unlikely to affect attachment to the nuclear membrane. Speedy A may also recruit Cdk2 to telomeres and later activate it together with other cyclins. Activated Cdk2 may then help regulate chromosome movements along the nuclear envelope.

"Our work is basic research, but you wonder whether a man with fertility defects may have defects associated with Cdk2 and Speedy A," says Kaldis. The team's "ultimate goal is to develop treatments for males with fertility issues," he says.

Explore further: How two telomere proteins interact with each other and the functional effects of cancer-associated mutations

More information: Zhaowei Tu et al. Speedy A–Cdk2 binding mediates initial telomere–nuclear envelope attachment during meiotic prophase I independent of Cdk2 activation, Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1618465114

Related Stories

How two telomere proteins interact with each other and the functional effects of cancer-associated mutations

April 11, 2017
Scientists at The Wistar Institute have unveiled part of the protein complex that protects telomeres—the ends of our chromosomes. The study, published online in Nature Communications, explains how a group of genetic mutations ...

Scientists discover master regulator of cellular aging

January 12, 2017
Scientists at The Scripps Research Institute (TSRI) have discovered a protein that fine-tunes the cellular clock involved in aging.

Aging and cancer: An enzyme protects chromosomes from oxidative damage

December 20, 2016
EPFL scientists have identified a protein that caps chromosomes during cell division and protect them from oxidative damage and shortening, which are associated with aging and cancer.

Recommended for you

New blood test to detect liver damage in under an hour

May 24, 2018
A quick and robust blood test that can detect liver damage before symptoms appear has been designed and verified using clinical samples by a team from UCL and University of Massachusetts.

Selective neural connections can be reestablished in retina after injury, study finds

May 24, 2018
The brain's ability to form new neural connections, called neuroplasticity, is crucial to recovery from some types of brain injury, but this process is hard to study and remains poorly understood. A new study of neural circuit ...

Space-like gravity weakens biochemical signals in muscle formation

May 23, 2018
Astronauts go through many physiological changes during their time in spaceflight, including lower muscle mass and slower muscle development. Similar symptoms can occur in the muscles of people on Earth's surface, too. In ...

Eating at night, sleeping by day swiftly alters key blood proteins

May 21, 2018
Staying awake all night and sleeping all day for just a few days can disrupt levels and time of day patterns of more than 100 proteins in the blood, including those that influence blood sugar, energy metabolism, and immune ...

Hotter bodies fight infections and tumours better—researchers show how

May 21, 2018
The hotter our body temperature, the more our bodies speed up a key defence system that fights against tumours, wounds or infections, new research by a multidisciplinary team of mathematicians and biologists from the Universities ...

Deep space radiation treatment reboots brain's immune system

May 21, 2018
Planning a trip to Mars? You'll want to remember your anti-radiation pills.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.