Nasopharyngeal cancer (NPC) arises in the upper part of the throat, behind the nose.  It is rare in most areas of the world—affecting only about 1 in every 100,000 people—but about 25 times more common in southern China, earning it the name “Cantonese Cancer.”  NPC rates are also high in southeastern Asia, northern Africa and the Arctic.

Environmental factors play a very large role in NPC.  Smoking increases risk, as does infection with the Epstein-Barr virus.  Diets high in salt cured food, which are common in many of the areas where increased rates of NPC are seen, have also been shown to increase risk.  These foods can be very high in nitrates and nitrites, which react with protein to form DNA-damaging chemicals.

It’s also been known for quite some time, however, that genetics contribute to NPC susceptibility.  In 1970s, certain immune markers were associated with increased risk.  Now a large genomewide association study has revealed three more immune related areas of the genome that are associated with risk for NPC.  These results, published online this week in the journal Nature Genetics, could eventually help develop models for prediction and screening, which in turn would help with early diagnosis. Continue Reading »

Tags: Africa, Arctic, Asia, cancer, Cantonese Cancer, Chinese, glioma, leukemia, nasopharyngeal carcinoma, Nature Genetics, NPC, salt, throat

Today 23andMe received a letter from the Committee on Energy and Commerce of the United States House of Representatives asking that along with Navigenics and Pathway Genomics, we provide information about our genetic testing services. The letter was signed by Congressmen Henry A. Waxman from California, Chairman of the Committee, Ranking Member Joe Barton from Texas, and the Chairman and Ranking Member of the Subcommittee on Oversight and Investigations, Bart Stupak from Michigan and Michael C. Burgess from Texas.  A link to the letters can be found here.  We look forward to providing information to the Committee and Subcommittee and engaging with them on the topic of personal genetic testing, explaining how our services connect people to information about their own bodies, and highlighting the meaningful scientific research we facilitate through our services.

We believe that genetics has an important role to play in the coming age of personalized medicine and we view this inquiry as an opportunity to discuss real and important issues that include technology and data quality, scientific rigor, privacy, and accessibility as applied to the rapidly growing body of genetic knowledge.

Through our blog we will keep you informed of progress on this topic.

Tags: 23andMe, Committee on Energy and Commerce of the United States House of Representatives, Congress, personal genomics, personalized medicine

Aching joints and bones aren’t always just a normal part of aging.  For some, they are a symptom of Paget’s disease of bone (PDB), a condition that affects more than one million people over the age of 45 in the United States.

Bone tissue is constantly being recycled.  As old bone is broken down, new bone grows in to replace it.  In PDB, the breakdown process is sped up, so the rate of new bone generation must also increase.  This rapidly grown bone tends to be softer and weaker than normal.  In most people this doesn’t lead to any symptoms, but for some it can cause bone or joint pain, deformities or fractures.  Tingling or weakness can occur if deformed bones impinge on nerves.

The cause of PDB isn’t known, but there is thought to be a genetic component to the disease.  Between 15% and 40% of people with the disease have an affected mother, father, sibling or child, and mutations in the SQSTM1 gene have been linked to some cases.  To find the remaining genes that predispose a person to PDB, an international team led by researchers at the University of Edinburgh analyzed the DNA of close to 1,200 people with the disease and more than 1,500 controls.  Their results, published online recently in the journal Nature Genetics, identify common variations in three separate regions of the genome contribute to differences in risk of developing the disease. Continue Reading »

Tags: arthritis, bones, Paget's disease of bone, pain

Rheumatoid arthritis is a common autoimmune disease in which the individual’s own immune system attacks the lining of the joints, causing stiffness and muscle aches. Like other autoimmune diseases, development of rheumatoid arthritis is likely caused by a complex combination of genetic and environmental factors. Recent research into the genetics of the disease has identified many of the genetic factors, and new studies continue to implicate additional variants that may influence risk.

A pair of such studies published this week in Nature Genetics found several new genetic variants associated with rheumatoid arthritis. Continue Reading »

Tags: immune system, Rheumatoid Arthritis

Understanding Alzheimer’s disease, the most common cause of dementia in people 65 years and older, is of the utmost importance as the population of the United States (and many other nations) becomes increasingly older.  Currently more than five million Americans are thought to have the disease, but by the year 2050 that number is estimated to reach 14 million unless a cure or prevention method is developed.

Until very recently, mutations in only one gene—APOE—had been conclusively associated with the more common late-onset form of Alzheimer’s (there are others associated with early-onset disease).  In September 2009 two groups studying large numbers of people identified variants in three new genes that had small effects on the disease.

Now researchers have pulled together the results of several studies and found variations in two more genes associated with increased risk.  The scientists, whose results appear online today in the Journal of the American Medical Association, suggest that these variants may be important for unraveling the underlying biology of Alzheimer’s, which will be essential in the quest to find new methods of treatment. Continue Reading »

Tags: Alzheimer's disease, APOE, JAMA, plaques, tangles, tau

The author during her time as a Peace Corps volunteer in Kenya.

As a Peace Corps volunteer teaching in Kenya 25 years ago, I was fascinated by the cultural, linguistic, and physical differences among the people of eastern Africa. One of our Kenyan trainers took us to a “boma” where his tall, cattle-herding Maasai-speaking family lived.  Once I began working, I lived with a Luo-speaking fellow teacher who emphasized the cultural differences, for instance in circumcision practices, between the Luo and other ethnic groups.  Later I taught Bantu-speaking children of farmers and fishermen along the coast of Kenya. Physical features hinted at ethnic identity and, even within the village where I taught, skin color ranged from quite light to relatively dark.  At the time I saw patterns, but understood little of the history behind those patterns.

Upon returning to the United States, I was fortunate to join the lab of geneticist Luca Cavalli-Sforza, who was studying the genetics of people across Africa. At that time, relatively little was known about human genetic diversity, in particular for Africa. I leaped at the opportunity to compare the hidden dimension of genetic diversity with the linguistic and cultural variation that I had observed in Kenya. In the 25 years since then, the study of diversity in Africa has blossomed. Thanks to advances in DNA technology, researchers have begun to augment information about the cultural and linguistic variation with information about how Africans differ at the genetic level. Online last week in the Proceedings of the National Academy of Sciences, authors Laura Scheinfeldt, Sameer Soi and Sarah Tishkoff pulled together recent discoveries about the population history of Africa based on languages, artifacts and DNA. Their paper paints the prehistory of the continent in broad strokes, beginning over 100,000 years ago. Continue Reading »

Tags: Africa, artifacts, Genes, Kenya, language, Laura Scheinfeldt, Peace Corps, PNAS, Sameer Soi, Sarah Tishkoff

Latin America is the home of dances as varied as the stately rumba and the racy salsa. It ranges over searing deserts, rocky heights, and sultry jungles. Perhaps it should not be a surprise, as a new study published this week in the Proceedings of the National Academy of Sciences shows, that its people run the genetic gamut as well.

Researchers from NYU and Stanford gathered DNA from 100 people, each with ancestry from one of four Latin American populations: Colombian, Dominican, Ecuadorian, and Puerto Rican. History tells us to expect that these Latino populations should be a mixture of Native American, European, and African populations. By comparing the Latino DNA with reference individuals’ DNA from these three source populations, using an analysis similar to that of 23andMe’s Ancestry Painting feature, the researchers found stark genetic differences between the Latino groups, and between individuals within each group. Continue Reading »

Tags: ancestry, DNA, hispanic, latino

This picture shows three bones (Vi33.16, Vi33.25, Vi33.26) from Vindija cave, Croatia. Most of the Neandertal genome sequence was retrieved from these bones./ Image courtesy of Max-Planck-Institute EVA

A new study of the Neanderthal genome, published online today in the journal Science, presents strong evidence that humans and Neanderthals interbred.

There’s been a lot of debate about this subject in scientific circles (see this Spittoon post and the links within it) over the last few years.  Even some of the researchers involved in the current study previously said they thought human-Neanderthal couplings were unlikely.

ScienceNews and Ars Technica’s Nobel Intent both have good overviews of the new study and what it means.  Ars Technica’s John Timmer gives a great summary of why scientists now think that rather than replace Neanderthals, our human ancestors instead assimilated them:

At the same time, the genome sequence does provide evidence that humans and Neanderthals have interbred. This became apparent when the Neanderthal genome was paired against human genomes from different parts of the globe. The Neanderthal DNA consistently matched European and Asian samples better than it did African; the difference was small, but consistent. It suggested that the Neanderthals, which were restricted to Europe and Asia at the time modern humans originated in Africa, had interbred with humans once they began migrating out of Africa.

Because African human populations are older, they tend to have more divergent genomes. But the human-Neanderthal split is older still, so the authors figured that any areas of the genome where variation was larger in populations outside of Africa may have entered the human genome through interbreeding. If they did arise through interbreeding, then the non-African segments should match Neanderthals. Researchers found at least 10 regions that fit these predictions.

Although they can’t rule out the possibility that modern humans had already started diverging from Neanderthals before leaving Africa, the research team favors the idea of interbreeding in the Mid-East as the first modern humans left Africa. This would ensure that both the Asian and European populations picked up some Neanderthal DNA.

Be sure to check out the Science Magazine Neanderthal Genome Special Feature (free).

Tags: genome sequence, interbreeding, Neanderthals

Multiple sclerosis (MS) is an autoimmune disease that affects the central nervous system, causing unpredictable and varying symptoms that differ from person to person. About 1 in 700 people in the United States is affected by the disease. Because MS often runs in families, it’s thought that there is a substantial genetic component to the disease.

But genetics aren’t the whole story.  If one identical twin has MS, the chance that the other twin will also have the disease is increased by only 30%. Although this is more than the 5% increase in risk seen in non-identical twins, the fact that identical twins (who are theoretically completely the same at the DNA level) are not always concordant for MS has led researchers to assume that environmental factors of some sort must also play an important role.  Everything from viral infections to vitamin D deficiency due to low sun exposure has been suggested.

But the true identical-ness of identical twins has been called into question in recent years.  Research has shown that there may be subtle differences in their genomes.  To test whether tiny changes—either in DNA sequence, gene expression, or chemical modifications to the genome—might play a role in determining why one twin gets MS while the other is spared, researchers from the University of California, San Francisco and the National Center for Genome Resources used a variety of methods to go over the genomes of three sets of MS-discordant identical twins in unprecedented detail. Continue Reading »

Tags: DNA, epigenetics, multiple sclerosis, sequencing, twins

New research, published recently in the journal Neurology, has found the surprising result that a genetic variant previously associated with better cognitive function in young people appears to have the opposite effect as people get older.

Alexandra Fiocco and colleagues from the University of California, San Francisco, studied 2,858 men and women (1,679 white and 1,179 black) who were between the ages of 70 and 79 upon recruitment to the study in 1997.  All were in generally good health and had no difficulty with day-to-day activities.

Each person was given two tests at various points over an eight year follow up period: 1) the Modified Mini-Mental State Examination, a measure of global cognitive performance; and 2) the Digit Symbol Substitution Test, which measures response speed, sustained attention, visual spatial skills and set shifting, and has been reported to distinguish mild dementia from healthy aging.

The study participants’ cognitive test results were then compared with their genotypes for SNP rs4680.  This genetic variant is found in the COMT (catechol-O-methyltransferase) gene, which encodes an enzyme involved in a variety of chemical conversions in the body, including the degradation of the neurotransmitter dopamine.  The different versions of rs4680 encode COMT proteins with either a valine (Val) or methionine (Met) at amino acid 158.  The Val version of COMT (G at rs4680) is associated with higher COMT enzyme activity, and therefore lower levels of dopamine in the brain, while the Met version (A at rs4680) is associated with lower enzyme activity and higher dopamine levels.

(23andMe Complete Edition customers can check their data for rs4680 using the Browse Raw Data feature.) Continue Reading »

Tags: African American, cognition, COMT, elderly, Neurology