Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Disease-causing genetic mutations in sperm increase with men’s age

18.10.2002


Scientists from the McKusick-Nathans Institute for Genetic Medicine at Johns Hopkins may have discovered why a rare genetic disease is more common in children born to older fathers. The disease, Apert syndrome, leads to webbed fingers and early fusion of the skull bones and must be corrected by surgery.



While Apert syndrome itself affects only 1 in 160,000 births, the scientists believe their findings could extend to many of the 20 or so other genetic conditions similarly linked to older fathers. The researchers are scheduled to present their findings Oct. 17 at the annual meeting of the American Society for Human Genetics in Baltimore.

"It makes sense that the mutations causing these diseases would occur more frequently in older men, and indeed that’s what we saw for Apert syndrome," says Ethylin Jabs, M.D., director of the Center for Craniofacial Development and Disorders at Johns Hopkins.


Importantly, disorders linked to advancing paternal age begin to increase rapidly at about the same time as maternal risks increase -- age 33 to 35. Until now, the only evidence for paternal age effects has come from determining how many children with these diseases are born to fathers of various ages.

To obtain the first genetic explanation for these effects, the scientists studied sperm from about 60 men of various ages and looked for two genetic changes responsible for 99 percent of the cases of Apert syndrome. They found that men over 50 were, on average, three times as likely as men under 30 to have sperm with at least one of these changes. The mutations were not more common in blood samples as men aged.

The scientists say it’s likely that the number of cell divisions that go into making a sperm plays a large role in the link between Apert syndrome and paternal age, and represents a fundamental difference between how aging egg and sperm can impact the health of a child.

"In the men we studied, these mutations had not been inherited, but rather collected over time in the reservoir of primitive cells that become sperm," says first author Rivka Glaser, a graduate student in human genetics at the Johns Hopkins School of Medicine.

Cells that mature into eggs are essentially frozen in time from puberty until the time the egg is signaled to develop. Because of the stage at which they are "frozen," the most likely error in an egg is to have an abnormal partitioning of chromosomes, producing an egg with an extra copy or a missing copy, Glaser says. For example, in Down syndrome, an extra copy of chromosome 21 is inherited from the mother.

Sperm, on the other hand, are continually produced throughout a male’s lifetime from a reservoir of primitive cells. These primitive cells, like other kinds of so-called stem cells, can either replicate themselves or take a step closer to becoming a sperm, a process called differentiation. All told, these cells divide every 21 days after puberty, and at each cell division the opportunity exists for an error in copying the DNA.

"Literally hundreds of millions of sperm are made in each batch, so in most cases there are still many normal sperm available," says Jabs, also a professor of pediatrics. Their study showed that "high levels" of mutations among men who had no children with Apert syndrome amounted to roughly 3 sperm with the mutation among 100,000 sperm.

If an error is made in any of the steps toward becoming a sperm, the only cells affected are the resulting sperm for that batch. However, if an error appears in a primitive cell as it replicates itself and the mistake isn’t fixed, the mutation will continue to be passed on to all of its progeny, including subsequent primitive cells and other batches of semen.

As men age, more of these primitive cells have collected mutations that cause Apert syndrome, leading to more sperm with the mutations in each batch of semen, the scientists suggest. The risk of having a child with Apert is about six times higher for a man age 52 than for someone who’s 27.


Authors on the study are Glaser, Jabs, and Rebecca Schulman, of Johns Hopkins School of Medicine, and Karl Broman, of the Johns Hopkins Bloomberg School of Public Health.

Abstract # 1127 "Molecular evidence for the paternal age effect in sperm." R. Glaser, et al.

Joanna Downer | EurekAlert!
Further information:
http://www.ashg.org
http://www.hopkinsmedicine.org/craniofacial/Home/

More articles from Health and Medicine:

nachricht How cancer metastasis happens: Researchers reveal a key mechanism
19.01.2018 | Weill Cornell Medicine

nachricht Researchers identify new way to unmask melanoma cells to the immune system
17.01.2018 | Duke University Medical Center

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Optical Nanoscope Allows Imaging of Quantum Dots

Physicists have developed a technique based on optical microscopy that can be used to create images of atoms on the nanoscale. In particular, the new method allows the imaging of quantum dots in a semiconductor chip. Together with colleagues from the University of Bochum, scientists from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute reported the findings in the journal Nature Photonics.

Microscopes allow us to see structures that are otherwise invisible to the human eye. However, conventional optical microscopes cannot be used to image...

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks Industry & Economy
Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Researchers reveal how microbes cope in phosphorus-deficient tropical soil

23.01.2018 | Earth Sciences

Opening the cavity floodgates

23.01.2018 | Life Sciences

Siberian scientists suggested a new method for synthesizing a promising magnetic material

23.01.2018 | Materials Sciences

VideoLinks Science & Research
Overview of more VideoLinks >>>