Contact Information:

Media Contact

Jennie Dusheck

Twitter: sumedicine

Kredyty mieszkaniowe Kredyty mieszkaniowe

Sprawdź aktualny ranking najlepszych kredytów mieszkaniowych w Polsce - atrakcyjne kredytowanie nieruchomości. - Press Release Distribution
RSS - Press News Release
Add Press Release

Unique genes in Khoe-San people may lower risk of some pregnancy hazards

( An examination of the immune genes of the southern African Khoe-San people has revealed a completely new kind of mutation, according to researchers at the Stanford University School of Medicine. The gene variant likely contributes to healthier babies, although the variant can also lower resistance to disease.

The findings grew out of a long-term effort by Peter Parham, PhD, professor of structural biology and of microbiology and immunology, to understand how immune system genes make us reject organ transplants.

A paper detailing the findings will be published online Aug. 20 in PLOS Genetics. The gene variant was one of two they found that would be expected to alter the formation of the placenta during early pregnancy, leading to larger, healthier babies and a reduced risk of pre-eclampsia, a major cause of maternal death.

"Only a handful of studies have investigated the function of immune genes in African populations. As a result, we have probably greatly underestimated the breadth of human immune variation," said Parham, the study's senior author. "So we were excited to investigate the Khoe-San, a divergent, modern human population known to harbor enormous genetic diversity."

A genetic 'railway' switch

Mutations can alter genes in all kinds of ways. A mutation can have no effect on how a gene operates, it can change functionality in minor or important ways, or it can completely destroy normal function. Geneticists have never seen this type of mutation before, the researchers said. Originating among the Khoe-San, the mutation does two things at once: It simultaneously turns off one function and turns on another, much like a railway switch, pushing gene function off one track and onto another.

The Khoe-San -- known for the unusual clicking sounds in their language -- harbor unusually high genetic diversity, about 10 times more among their 100,000 people than among modern Europeans.

"The Khoe-San is one of the oldest populations of humans, so every population that's branched off from them has just a part of their genetic diversity. Every time the human population splits, there's slightly less diversity. So that's the reason the Khoe-San were so interesting to us," said co-author Paul Norman, PhD, a senior research scientist. One reason the Khoe-San are so diverse is that they are descended from an ancient population that was much larger.

Khoe-San genomes are an excellent place to look for unusual human genes. "We knew we'd find novel genes," said Hugo Hilton, DVM, a research scientist and lead author of the paper. "Our work has allowed us to understand the evolution of these genes, not only in the Khoe-San but in populations around the world."

The immune system genes of interest to Parham's team code for two sets of proteins. On the surfaces of ordinary cells are proteins called HLAs, which mark cells in ways so specific that a person's immune system recognize cells as self or not self. If a surgeon transplants a kidney, the recipient's immune system can tell that the kidney is someone else's -- just from its cell surface HLA proteins -- and the patient's immune system signals its natural killer cells, or NK cells, to attack the transplanted kidney.

The most varied genes

HLA genes are the most variable of the genome. So Parham and others have been trying to measure how much HLA genes vary within and between populations around the world. If you look at the population of the Bay Area, for example, you'll find hundreds of variants, because people come from all over the world. "In the Khoe-San, there are 10 or 11 variations of one of these genes, whereas when we looked at Amerindians a few years ago, they basically only had one version," said Norman. Doing organ transplants among people with few variants is relatively easy, whereas doing the same transplant among the Khoe-San would be difficult.

To recognize HLA proteins, NK cells deploy receptor molecules called killer-cell immunoglobulin-like receptors, or KIRs, which bind to foreign HLA proteins. In most people in the world, one kind of KIR receptor binds to HLA C2 cell surface proteins, and another kind binds to HLA C1 proteins. The difference between the two kinds of proteins is critical. If you have an infection, you might want those NK cells to latch onto C2 molecules. If you are carrying a baby, however, you don't.

That's because special NK cells in the uterus play an important role in reproduction by regulating the blood supply to a developing embryo. "The NK cells are involved at the beginning of pregnancy in helping develop the maternal blood vessels in the placenta, where they can supply a lot more blood to the developing embryo," said Parham.

The placenta is the interface between the embryo and the mother. Early in pregnancy, when the placenta is forming, the mother's NK cells bind to the embryo's placental cells. Sometimes, the mother doesn't have the gene for the C2 protein but the embryo does, having received the gene from its father. In that case, the mother's NK cells attack the C2-marked cells, leading to a poorly formed placenta that delivers insufficient blood to the fetus, a common problem that leads to low birthweight babies. The problem is also associated with dangerous high blood pressure, or pre-eclampsia, in the mother.

Binding more C1 and less C2 reduces these risks, and the novel version of the KIR gene that Parham's team found does just that. It no longer binds to C2 and instead has switched to binding C1. Immune cells are renowned for their ability to respond with great specificity to other molecules, so the researchers said it's remarkable that a small mutation could completely reverse the specificity of a receptor.

Parham's team also found a second variant of the KIR gene among the Khoe-San. This KIR allele simply makes a damaged receptor that does not bind to C2. Together, these two gene alleles greatly reduce the frequency of C2 receptors and increase C1 receptors in Khoe-San, presumably making for healthier babies.


Other Stanford-affiliated authors of the paper are research assistant Neda Nemat-Gorgani, MS; postdoctoral scholars Ana Goyos, PhD and Christopher Gignoux, PhD; and senior research scientist Lisbeth Guethlein, PhD.

The work was supported by the National Institutes of Health (grants AI17892, AI090905 and GM109030), the March of Dimes Prematurity Research Center at Stanford University and the School of Medicine.

Information about Stanford's Department of Structural Biology, Department of Microbiology and Immunology and Department of Genetics, all of which also supported the work, is available at, and, respectively.

The Stanford University School of Medicine consistently ranks among the nation's top medical schools, integrating research, medical education, patient care and community service. For more news about the school, please visit The medical school is part of Stanford Medicine, which includes Stanford Health Care and Lucile Packard Children's Hospital Stanford. For information about all three, please visit


Regulatory, certification systems creating paralysis in use of genetically altered trees

CORVALLIS, Ore. - Myriad regulations and certification requirements around the world are making it virtually impossible to use genetically engineered trees to combat catastrophic forest threats, according to a new policy analysis published this week in the journal Science. In the United States, the time is ripe to consider regulatory changes, the authors say, because the federal government recently initiated an update of the overarching Coordinated Framework for the Regulation of Biotechnology, which governs use of genetic engineering. North American forests are suffering ...

The unique ecology of human predators

The unique ecology of human predators
Are humans unsustainable 'super predators'? Want to see what science now calls the world's "super predator"? Look in the mirror. Research published today in the journal Science by a team led by Dr. Chris Darimont, the Hakai-Raincoast professor of geography at the University of Victoria, reveals new insight behind widespread wildlife extinctions, shrinking fish sizes and disruptions to global food chains. "These are extreme outcomes that non-human predators seldom impose," Darimont's team writes in the article titled "The Unique Ecology of Human Predators." "Our ...

Discovery of trigger for bugs' defenses could lead to new antibiotics

Scientists have exposed a chink in the armour of disease-causing bugs, with a new discovery about a protein that controls bacterial defences. Bacteria react to stressful situations - such as running out of nutrients, coming under attack from antibiotics or encountering a host body's immune system - with a range of defence mechanisms. These include constructing a resistant outer coat, growing defensive structures on their surface or producing enzymes that break down the DNA of an attacker. The new research shows that a protein called sigma54 holds a bacterium's defences ...

A detector shines in search for dark matter

WEST LAFAYETTE, Ind. -- Results of the XENON100 experiment are a bright spot in the search for dark matter. The team of international scientists involved in the project demonstrated the sensitivity of their detector and recorded results that challenge several dark matter models and a longstanding claim of dark matter detection. Papers detailing the results will be published in upcoming issues of the journals Science and Physical Review Letters. Dark matter is an abundant but unseen matter in the universe considered responsible for the gravitational force that keeps the ...

School vacations and humidity linked to multiple waves of influenza in Mexico during the 2009 H1N1 pandemic

Scientists studying the 2009 A/H1N1 influenza pandemic have found that the inconsistent regional timing of pandemic waves in Mexico was the result of interactions between school breaks and regional variations in humidity. The research published in PLOS Computational Biology, led by Dr. James Tamerius at the University of Iowa and Dr. Gerardo Chowell at Georgia State University, applied mathematical models to understand the social and environmental processes that generated two distinct pandemic outbreaks ("waves") in Mexico during the summer and fall of 2009. The summer ...

Maltreated children's brains show 'encouraging' ability to regulate emotions

Children who have been abused or exposed to other types of trauma typically experience more intense emotions than their peers, a byproduct of living in volatile, dangerous environments. But what if those kids could regulate their emotions? Could that better help them cope with difficult situations? Would it impact how effective therapy might be for them? A University of Washington-led team of researchers sought to address those questions by studying what happens in the brains of maltreated adolescents when they viewed emotional images, and then tried to control their ...

Cellphone data can track infectious diseases

Cellphone data can track infectious diseases
PRINCETON, N.J.--Tracking mobile phone data is often associated with privacy issues, but these vast datasets could be the key to understanding how infectious diseases are spread seasonally, according to a study published in the Proceedings of the National Academy of Sciences. Princeton University and Harvard University researchers used anonymous mobile phone records for more than 15 million people to track the spread of rubella in Kenya and were able to quantitatively show for the first time that mobile phone data can predict seasonal disease patterns. Harnessing ...

Study finds e-cigarette use linked to cough reflex sensitivity

Glenview, Ill. (August 20, 2015)--The popularity of electronic cigarettes has steadily increased worldwide, but little is known about their effects on health. New research suggests that the single use of an electronic cigarette approximating the nicotine exposure of one tobacco cigarette reduces the sensitivity of the cough reflex. The study tested 30 adult lifetime nonsmokers with no history of asthma or respiratory diseases and used cough tests to determine how e-cigarettes affect the cough reflex. Capsaicin, the pungent extract of red peppers, was used to induce a ...

Patent expirations for blockbuster antipsychotic meds could save billions

Medicaid is expected to save billions of dollars a year as patents for several blockbuster antipsychotic medications expire and use of generic versions of these drugs increases, according to a new study by researchers at the University of Maryland School of Medicine. These savings may provide relief from the high costs of these medications and allow policymakers to lift restrictions on patients' access, the researchers argue. The study forecast that annual Medicaid payments for antipsychotic medicines will decrease by nearly $1.8 billion (or nearly 50 percent) by 2016 ...

Laser-burned graphene gains metallic powers

Laser-burned graphene gains metallic powers
HOUSTON - (Aug. 20, 2015) - Rice University chemists who developed a unique form of graphene have found a way to embed metallic nanoparticles that turn the material into a useful catalyst for fuel cells and other applications. Laser-induced graphene, created by the Rice lab of chemist James Tour last year, is a flexible film with a surface of porous graphene made by exposing a common plastic known as polyimide to a commercial laser-scribing beam. The researchers have now found a way to enhance the product with reactive metals. The research appears this month in the ...


How your brain decides blame and punishment -- and how it can be changed

Uniquely human brain region enables punishment decisions

Pinpointing punishment

Chapman University publishes research on attractiveness and mating

E-cigarettes: Special issue from Nicotine & Tobacco Research

Placental problems in early pregnancy associated with 5-fold increased risk of OB & fetal disorders

UT study: Invasive brood parasites a threat to native bird species

Criminals acquire guns through social connections

Restoring ocean health

Report: Cancer remains leading cause of death in US Hispanics

Twin study suggests genetic factors contribute to insomnia in adults

To be fragrant or not: Why do some male hairstreak butterflies lack scent organs?

International team discovers natural defense against HIV

Bolivian biodiversity observatory takes its first steps

Choice of college major influences lifetime earnings more than simply getting a degree

Dominant strain of drug-resistant MRSA decreases in hospitals, but persists in community

Synthetic biology needs robust safety mechanisms before real world application

US defense agencies increase investment in federal synthetic biology research

Robots help to map England's only deep-water Marine Conservation Zone

Mayo researchers identify protein -- may predict who will respond to PD-1 immunotherapy for melanoma

How much water do US fracking operations really use?

New approach to mammograms could improve reliability

The influence of citizen science grows despite some resistance

Unlocking secrets of how fossils form

What happens on the molecular level when smog gets into the lungs?

Using ultrasound to clean medical instruments

Platinum and iron oxide working together get the job done

Tiny silica particles could be used to repair damaged teeth, research shows

A quantum lab for everyone

No way? Charity's logo may influence perception of food in package

[] Unique genes in Khoe-San people may lower risk of some pregnancy hazards is a service of DragonFly Company. All Rights Reserved.
Issuers of news releases are solely responsible for the accuracy of their content.