The most common type of arthritis, osteoarthritis, occurs due to accumulated wear and tear – welcome to old age! – or from repetitive movements or injury.  Rheumatoid arthritis, on the other hand, is caused by an autoimmune attack on the lining of the joints, resulting in stiffness, muscle aches, and general fatigue. Approximately two million people in the U.S. suffer from rheumatoid arthritis, and although women are affected more often than men, men tend to have more severe symptoms.

Research has identified a number of genetic factors that contribute to one’s risk of developing rheumatoid arthritis, and new studies continue to reveal more genes that seem to be involved in this complex disease. In a report published this week in Nature Genetics, a team led by Soumya Raychaudhuri and Robert Plenge of Brigham and Women’s Hospital in Boston describe three new genetic associations with rheumatoid arthritis risk.

Using a computational algorithm that incorporates information from the scientific literature, Raychaudhuri and his colleagues identified 22 candidate SNPs that have a large number of connections to previously validated genetic risk factors for rheumatoid arthritis. When they tested these SNPs in a set of almost 8,000 Caucasians with rheumatoid arthritis and 12,000 controls, seven emerged as highly significant associations. After combining this study population with that from a previous study – for a total of more than 11,000 individuals with rheumatoid arthritis and 22,000 without  – three of the variants rose to the top.

All three variants are in genes not previously linked to rheumatoid arthritis. Each copy of a C at rs1980422 and each copy of a G  at rs11586238 increased an individual’s odds of developing the condition by 1.13 times. Similarly, each copy of a C at rs548234 increased the odds of rheumatoid arthritis by 1.11 times.

(23andMe customers can see their data for the SNPs currently covered by 23andMe’s service by using the Browse Raw Data feature. 23andMe currently does not report on rs11586238, but does report on a SNP that acts as a perfect proxy for it, rs12405671. The A version of rs12405671 corresponds to the G version of rs11586238.)

These three SNPs are located near genes involved in the immune response, and, in some cases, near genetic variations that have been associated with other autoimmune disorders, such as Crohn’s disease and type 1 diabetes. Although a detailed, cohesive picture of the causes underlying rheumatoid arthritis remains elusive, each new association discovered by researchers contributes to our understanding of the biological players involved in this autoimmune disease.

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

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In autoimmune disorders, the immune system — which normally protects us from harmful, foreign substances — goes into overdrive and starts attacking the body’s own cells, causing inflammation and organ damage.

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by chronic, widespread inflammation that can result in arthritis, fever, skin rashes, muscle aches, seizures and fatigue, among other symptoms. Some symptoms can even be life-threatening. Between one and seven out of every 10,000 people is affected by SLE. The disease affects women nine times more frequently than men, and tends to be more prevalent and severe in people of non-European descent. The exact causes of SLE are unknown and there is currently no cure.

For several decades now, researchers have probed the genetic underpinnings of this mysterious disease. Two studies published this week in Nature Genetics identify new genetic variants associated with SLE in European and Asian populations.

In the first study, a team led by Vesela Gateva and Robert Graham of Genentech identified ten novel genetic variants associated with SLE in a European group consisting of more than 3,000 people with the disease and 10,000 people without SLE. Half of these variants were previously associated with other autoimmune diseases, but this is the first time they have been associated with SLE. In addition, the researchers confirmed nine variants previously linked to SLE in other studies.

(23andMe customers can see their data for the SNPs currently covered by 23andMe’s service by using the Browse Raw Data feature. See table at the end of this post.)

Of the previously reported autoimmune variants, Gateva and colleagues note that the A version of rs641153, a known risk variant for age-related macular degeneration, seems to be protective against SLE, although additional research will be needed to confirm this effect.

One of the SNPs not previously associated with SLE or any other autoimmune disease, rs7708392, is in the gene that encodes TNIP1.  The TNIP1 protein is known to interact with TNFAIP3, a protein that genetic studies have previously linked to rheumatoid arthritis, psoriasis and type 1 diabetes — all autoimmune disorders — suggesting that the TNIP1-TNFAIP3 association may play a general role in autoimmunity.

(23andMe does not currently report data for rs7708392.)

In the second study, Jian-Wen Han and Xue-Jun Zhang’s team from Anhui Medical University in China identified 21 genetic variants associated with SLE in more than 4,000 Chinese individuals with the disease and 8,200 individuals without autoimmune disorders. About half of the associations confirmed previous reports in European populations, and half represented novel findings.

Interestingly, one of the new variants they identified — rs10036748 — is also in the TNIP1 gene. Here, each copy of a T increased odds of SLE by about 1.24 times. Many other SNPs associated with SLE in the Chinese study were located in or near genes involved in immune response.

The TNIP1-TNFAIP3 connection and association of variants known to be linked to other autoimmune diseases add to growing evidence that common genetic factors contribute to autoimmunity. These findings may help pave the way for novel therapeutics for autoimmune disease that exploit this shared genetic basis.

Novel SNPs associated with SLE in Europeans (Gateva et al. study)

Novel SNPs associated with SLE in Asians (Han et al. study)

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Previously in The Spittoon, we discussed two papers that identified genetic variants associated with hemoglobin levels in circulating blood.

But blood consists of much more than hemoglobin, and it is responsible for much more than just transporting oxygen. This week Nature Genetics published the results of two of the largest blood studies to date, which together identified dozens of new variants associated with nine blood-related traits.

In addition to red blood cells, which carry hemoglobin, whole blood contains white blood cells—a crucial part of our immune system—and platelets, which are important for clotting. All of these cellular components are suspended in a protein-rich plasma that makes up most of the volume of blood, and maintains the pressure needed to deliver the blood’s cargo throughout a person’s body.

Like hemoglobin levels, measurements of other blood traits can be informative about health. An abnormally high white blood cell count and platelet volume have both been linked to an increased risk for heart attack. These measurements can also indicate the presence of infectious disease, immunological disorders or cancers.

Nicole Soranzo and her colleagues in the HaemGen consortium measured hemoglobin concentration (Hb), red blood cell count (RBC), red blood cell volume (MCV), platelet count (PLT), platelet volume (MPV), white blood cell count (WBC), the amount of hemoglobin per red blood cell (mean corpuscular hemoglobin content, or MCH), and the amount of hemoglobin relative to the size of the cell (mean corpuscular hemoglobin concentration, or MCHC) in more than 14,000 healthy individuals from Europe. They found sixteen new genetic associations with blood traits from fifteen genomic regions not previously thought to be involved.

Santhi Ganesh and her colleagues in the CHARGE consortium measured Hb, MCV, RBC, MCH, MCHC, and the percent of red blood cells in whole blood (hematocrit, or Hct) in more than 24,000 Caucasian individuals from the U.S. and Europe. Here, they found nine new associated variants from eleven previously unassociated genomic regions.

(23andMe customers can see their data for the SNPs currently covered by 23andMe’s service using the Browse Raw Data feature. See table at the end of this post.)

One of the advantages of these studies is the number of traits that they analyzed.

“Until now, few genome-wide association studies have looked beyond single traits,” Soranzo’s co-author Christian Geiger said in a press release. “But, through a systematic analysis of correlated traits we can begin to discover such shared genetic variants, forming the basis for understanding how these processes interact to influence health and disease.”

Both teams noted several genomic regions that play a broad role in blood-related health. The HBS1L-MYB, TFR2-EPO, TMPRSS6 and HFE regions were all associated with at least three different traits. These regions have also been connected to fetal hemoglobin levels and the iron-overload condition hemochromatosis. Of these newly associated variants, many are close to genes that present promising candidates for further research.

Soranzo’s team went further by investigating whether two of the variants associated with increased platelet volume (PLT) rs11066301 and rs11065987, were also associated with coronary artery disease. They analyzed these SNPs in about 9,500 people with coronary artery disease and 10,500 healthy controls. They found that at both SNPs, each copy of a G increased odds of coronary artery disease by about 1.15 times.

(23andMe customers can see their data for rs11065987 by using the Browse Raw Data feature. 23andMe does not report on rs11066301, but we do report on rs11066320, which correlates perfectly with rs110066301. For rs110066320, the A allele corresponds to increased PLT and higher odds of coronary artery disease.)

When the researchers looked more closely at the region where rs11066301 and rs11065987 are located, they found a block of ten SNPs that tend to be inherited together, and which are all associated with increased PLT and risk of coronary artery disease. They also confirmed previous findings from other researchers of association between celiac disease and type 1 diabetes with SNPs in this block.

Data for chimpanzees and multiple human populations point to a relatively recent event in human evolution where the above-mentioned genetic variants swept across European populations — but not East Asian or African populations. Because the block of SNPs is located in an area of the genome involved in immune response, the authors suggest that these mutations may have given some populations a survival advantage against infection, despite increasing the risk for certain diseases.

SNPs associated with blood-related traits

* In some cases, 23andMe does not cover the original SNP, so a proxy SNP that correlates perfectly with the original in Europeans is reported instead.

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

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Doctors routinely order the complete blood count (CBC) for their patients because they can learn a lot about a person’s health by measuring the numbers of different types of blood cells in the circulation, their sizes and the ratios between them.

One component of the CBC is usually a measure of the total amount of hemoglobin, the oxygen carrying protein found in red blood cells.  Low levels of hemoglobin can be a sign of nutritional deficiency, autoimmune disease or bone marrow problems, and may result in fatigue, irregular heartbeat and poor growth in children.  Abnormally high levels of hemoglobin can be caused by heart failure, COPD or kidney cancer and are associated with increased risk of stroke.

New research published online in the journal Nature Genetics this week identifies two SNPs that account for a small amount of the variation in hemoglobin levels seen in the population and may help scientists find new ways to treat blood disorders.

John Chambers and colleagues analyzed the DNA from more than 11,000 Europeans in England and Finland and more than 16,000 Indian Asians living in London.  They found rs855791 and rs198846 both impacted hemoglobin levels.

In both the European and Indian study groups, each A at rs855791 and each G at rs198846 led to an approximately 0.1 gram per deciliter (g/dL) decrease in hemoglobin levels. The normal range for hemoglobin levels in adults is 12 to 18 g/dL.

(23andMe does not currently offer data for rs198846.  Customers can use rs1799945 as a proxy for this SNP.  The C version of rs1799945 corresponds to the lower hemoglobin levels G version of rs198846.)

Approximately 25% of the world’s population has hemoglobin levels low enough to be considered anemic.  The World Health Organization has deemed anemia a severe public health problem in India.  Although nutritional iron deficiencies are a large part of the problem in this and other countries with high levels of anemia, it is interesting to note that the versions of rs855791 and rs198846 that lead to lower hemoglobin levels were found at higher frequencies in the Indian study subjects.

Both SNPs identified in this study are in or near genes involved in regulating the body’s iron levels.

Rs198846 is near the HFE gene.  Mutations in this gene cause hereditary hemochromatosis, a condition that can result in iron overload.  The researchers found, however, that the effect of rs198846 is not related to these mutations.

Rs855791 is located in the TMPRSS6 gene.  Mutations in this gene have been shown to cause a serious form of anemia that does not respond to treatment with oral iron supplements.  Chambers says that learning more about how this gene contributes to hemoglobin levels could lead to new treatments for people suffering from chronic hemoglobin problems.

“The enzyme protein produced by the TMPRSS6 gene is a good target for drug development. Designing a drug that enhances TMPRSS6 activity could augment hemoglobin in people such as cancer and kidney failure patients, who suffer from chronically low levels. A different drug that blocked TMPRSS6 enzyme production might bring down high hemoglobin levels,” he said in a statement.

Several other reports published online this week in Nature Genetics (Benyamin et al., Soranzo et al. and Ganesh et al.) also examined genetic contributions to blood traits.  These will be covered later this week here in the Spittoon.  Benyamin et al. and Ganesh et al. also both found evidence for an association between rs855791 and hemoglobin concentration.

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

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Our bones are amazing structures, capable of supporting tremendous force through complex motions. They do this day in and day out, year after year as we sit, stand, walk, run, lift, work, and play. But as the elderly among us know all too well, bones are not invincible and become more fragile as we age. As the natural, continuous cycle of bone turnover slows down and becomes unbalanced, bone is broken down faster than it is replaced — and important bone-strengthening minerals like calcium are lost.

Low bone mineral density (BMD) is one of the hallmarks of osteoporosis (literally “porous bones”), a disease that impacts nearly 45 million people in US and is responsible for more than one million fractures each year. Women develop osteoporosis much more frequently than men, especially after menopause. The burden on the health care system is significant and is expected to double over the next 10-15 years as the population ages.

Although it is natural to lose bone mass as we get older, genetic factors are known to play a large role in determining bone mass and the rate at which bone mineral density decreases. The relationship between genetics and BMD is complex, and association studies have implicated many different genes that may play a role. New research published this week in Nature Genetics continues the search for genetic factors and has identified more than a dozen SNPs associated with BMD in Europeans.

The team of researchers, led by Fernando Rivadeneira and Andre Uitterlinden of the Erasmus Medical Center in The Netherlands, used data from the Genetic Factors for Osteoporosis (GEFOS) Consortium containing lumbar spine BMD and femoral neck BMD measurements for almost 20,000 individuals. About half of the variants they identified replicated previously reported genetic associations with BMD, but the other half were new.

Some of the SNPs were associated with lower BMD while others were associated with higher BMD. For instance, individuals with one or more copies of the C allele at rs1366594 tended to have lower lumbar spine BMD than those without, and individuals with one or more copies of the C allele at rs2566755 tended to have higher lumbar and femoral neck BMD.

(23andMe customers can see their data for the SNPs currently covered by 23andMe’s service using the Browse Raw Data feature. See the table at the end of this post.)

The exact biological processes affected by these variants are still unclear, but increasing evidence points to several signaling pathways known to be important in bone biology.

One of these pathways is mediated by the “Wnt” family of proteins; Wnt signaling is important both for proper differentiation of cells responsible for breaking down bone and for the development of cartilage, required for new bone formation. rs87939, for instance, is near the gene that encodes β-catenin, an important node through which Wnt proteins influence cellular processes such as gene expression (this SNP is not on 23andMe’s platform but correlates perfectly with one that is, rs450615). Wnt proteins can also act through other channels potentially affected by additional SNPs identified by this study.

Another pathway implicated by the growing body of research is estrogen signaling. There is no doubt that the drop in estrogen following menopause in women leads to increased risk for osteoporosis, and hormone replacement therapy can have a protective effect. Not surprisingly, estrogen affects numerous biological processes – including bone maintenance – mainly through its role in gene expression. Variants in ESR1, the major estrogen receptor found in bone, have been associated with BMD and osteoporosis, though results are far from conclusive. Rivadeneira and colleagues confirmed the association of a SNP in ESR1, rs2504063, with lumbar spine BMD. Several other SNPs are also located in or near genes that may influence the regulation of bone development.

Osteoporosis is the most common bone disorder in developed countries. One in two women and one in four men over the age of 50 will experience a bone fracture due to the disease. Diets rich in calcium (especially before your mid-30s) and regular exercise can help combat bone loss. Meanwhile, the search carries on for clues that could lead to greater understanding of bone disease and potential avenues for treatment.

SNPs associated with bone mineral density (BMD):

* In some cases, 23andMe does not cover the original SNP, so a proxy SNP that correlates perfectly with the original in Europeans is reported instead.

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

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In the United States, prostate cancer affects about one in every six men.  Genomewide association studies aimed at finding common genetic variants associated with this common disease have been particularly successful. More than a dozen SNPs have been associated with prostate cancer, but researchers calculate that these variants represent only a tiny fraction of the genetic component of the disease.

To fill in the genetic gaps, researchers are turning to studies that include larger numbers of participants than ever before.  The hard work is paying off, as can be seen in four recent reports published in the journal Nature Genetics.  These analyses, based on the DNA of tens of thousands of men, have added at least 12 new variants to the roster of prostate cancer-associated SNPs.

One of the most striking features of these new studies is that they have identified two new SNPs on chromosome eight in a region known as 8q24.  Three other variants in this same region have already been linked to prostate cancer in both African American and European samples.  Other SNPs in the 8q24 region have been associated with breast, bladder and colorectal cancer.

(The new 8q24 SNPs as well as the others associated with prostate cancer are detailed in a table at the end of this post.)

The bounty of cancer-related SNPs in the 8q24 region is puzzling to scientists because there are no actual genes in this stretch of DNA.  The closest gene, MYC, is known to be involved in cancer, but so far there is no evidence that the cancer-associated 8q24 SNPs are affecting MYC. Future research will hopefully identify what these SNPs are doing and how they affect cancer risk.

Even though prostate cancer genomewide association studies have been fruitful, critics such as John Witte of UCSF argue that the findings may not be clinically useful (read his February Nature Genetics review of prostate cancer genomics here).

But that doesn’t mean that looking for variants associated with prostate cancer should be abandoned.  Finding SNPs associated with the disease could lead scientists to new treatments.

There is also the possibility of finding variants that don’t just predict whether someone is at risk for prostate cancer, but whether they are at risk for a particularly aggressive form of the disease. This could help doctors discriminate between those men whose cancers require immediate treatment and those who can avoid the side effects of surgery and radiation in favor of “watchful waiting.”

“There is clear clinical utility in identifying markers that can distinguish which prostate tumors will progress rapidly and be life-threatening versus those that are relatively latent and may not substantively impact a man’s health,” Witte writes.

As has been the case with most other studies looking for genetic variants associated with prostate cancer, none of the four new studies found an association between the identified SNPs and disease severity. Scientists have suggested that this indicates the studies are mainly finding variations associated with increased risk for the initiation of cancer. To find disease aggression-associated variants, more large studies will be needed, and researchers will need to focus on SNPs correlated with disease recurrence following treatment and/or mortality instead of just presence or absence of disease.

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

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Unlike the flu virus, which the body is generally able to fight off completely, infection with hepatitis C is often chronic.  That means for most of the three to four million people worldwide who are newly infected each year the virus will persist in the body, where it greatly increases risk for chronic liver diseases including cirrhosis and cancer. The only treatment currently available — an almost year long course of drugs — often causes severe side-effects. Worse yet, it fails in about half of all patients.

Last month, a study published online in the journal Nature showed that DNA variations in and around the IL28B gene influence whether a person chronically infected with the hepatitis C virus will fully respond to the standard treatment regimen. Now three new reports further support the importance of IL28B variations in the body’s response to hepatitis C, a finding that has implications for the future of hepatitis treatment and drug development.

An Australian group headed up by Vijayaprakash Suppiah analyzed the DNA of more than 800 people with European ancestry from Australia, the UK, Germany and Italy infected with hepatitis C.  They found that having one or two copies of the less-common G version of rs8099917, a SNP near the IL28B gene, doubled the odds that a person would fail to have a sustained response to treatment.

A group headed up by Yasuhito Tanaka studied 326 Japanese hepatitis C patients and also found that rs8099917 predicts whether or not a person will respond to treatment.  In this population, however, the effect was much greater.  Carrying a G increased the odds of treatment failure by at least twelve times.

“This SNP has such a strong association with response that, in combination with other parameters, genotyping it and other genetic variants should be a useful part of  clinical management,” write Suppiah et al., who along with Tanaka et al. published their results online this week in the journal Nature Genetics.

Another study, this one published online in Nature, found that variation near IL28B might be part of what allows a minority of people infected with hepatitis C to clear the virus naturally, without any treatment.

David Thomas and colleagues found that individuals with European or African ancestry were about three times more likely to spontaneously clear a hepatitis C infection if they carried two copies of the C version of rs12979860 than if they had CT or TT at this SNP.

Twenty-eight percent of the people with the CT or TT genotypes were able to fight off their hepatitis C infection without treatment, a number very close to the population average.  But 53% of those with the CC genotype were able to become naturally virus-free.

In a commentary published in Nature, Shawn Iadonato and Michael Katze express doubts about the importance of these new discoveries.

“Although these findings raise the tantalizing prospect of a more personalized approach to treating [hepatitis C] by tailoring treatment to patients who are most likely to benefit, the reality is more sobering,” they write.

Iadonato and Katze worry that testing for IL28B variations would not provide doctors with a straightforward yes-or-no answer to the question of whether a patient will respond to hepatitis C treatment.  This is because not all carriers of the advantageous versions of the variants clear the virus, nor do all patients lacking them fail to benefit from treatment.  Furthermore, they point out, there is currently no alternative hepatitis C treatment available.

What they do not consider, however, is how this new research may help change that. In a separate commentary in Nature Genetics, Thomas O’Brien suggests that the current findings could increase the interest in developing hepatitis therapies based on the protein encoded by IL28B, interferon-λ3.  He notes that an early clinical trial testing the effects of a related protein, interferon-λ1, has already had some success.  And certain properties of interferon-λs may cause them to have fewer side effects than current treatments.

O’Brien is still cautious about the findings linking IL28B variations to hepatitis C treatment response.  He says that more research in this area is needed in diverse populations and in people infected with different forms of hepatitis C.  He also stresses that researchers need to consider how these genetic findings fit in with other factors that affect treatment response, including age and gender.

Overall, however, his view is optimistic.  He concludes: “With these caveats, predictive models of HCV treatment response hold the potential to inform treatment decisions for millions of patients who are infected with HCV.”

(Rs12979860 was also described in the original paper linking IL28B to hepatitis C.  23andMe does not currently provide data for this SNP.  As pointed out in the previous Spittoon post on this topic, rs12980275 is very near to this SNP.  The A version of rs12980275 usually corresponds to the C version of rs12979860.  The other SNP discussed in this post, rs8099917, is located close to both rs12979860 and rs12980275.  23andMe customers can look up their data for rs8099917 using the Browse Raw Data feature.  Keep in mind that because all of these SNPs are so closely linked to each other, they are all probably representing the same effect.  More research will be needed to zero in on the exact variation(s) that are important for hepatitis C.)

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

Map: PhilippN

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Scientists are narrowing in on two regions of the human genome that could be responsible for ALS (amyotrophic lateral sclerosis), also known as Lou Gehrig’s disease.

ALS is a neurodegenerative disorder that weakens muscles and paralyzes patients within three years of onset, and has no known cure. The available drug treatment delays progression by only three to five months.

Despite several attempts to find genetic variations associated with the sporadic form of the disease (which accounts for 95% of ALS cases), no association has been found.

A team of researchers from Netherlands, Van Es et al., analyzed the genes of nearly 20,000 people of European descent, including 5,000 ALS patients. Their results, published online this week in Nature Genetics, identified several genetic variations on two chromosomes suspected to affect ALS and other neurological functions.

The study revealed that each copy of the C version of rs12608932, a SNP on chromosome 19, is associated with a 1.2 times increased odds of ALS compared to having two copies of A. This SNP is found near UNC13A, a gene that may be involved in the function of motor neurons, which degenerate and die in ALS patients.

Each copy of the T version SNP rs2814707, located on chromosome 9, is associated with a 1.16 times increased odds of ALS compared to having two copies of C. This SNP was found in a region of the genome previously associated with the rare familial (non-sporadic) version of ALS. Researchers also found an association between the disease and a third SNP located very close to rs2814707.

(23andMe customers can check their data for rs12608932 and rs2814707 using the Browse Raw Data feature.)

There is increasing evidence that ALS belongs to a broader spectrum of neurodegenerative disorders, including Parkinson’s disease, so researchers speculate that genetic associations with ALS may also lead to clues about other disorders of the nervous system.

(Note: A previous genetic association listed in 23andMe’s ALS Research Report, which provides information about lower-impact and preliminary research results, was not replicated in this study.)

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

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Acute lymphoblastic leukemia (ALL) is the most common childhood cancer in developed nations, affecting between 30 and 45 out of every one million kids.  But not much is known about the genetics of the disease.

Two research groups set out to learn more by looking for common genetic variations associated with the disease.  Their results, published online this week in Nature Genetics, provide new insight into the development of ALL.

British researchers led by Elli Papaemmanuil studied a total of 907 ALL cases and 2,398 controls with European ancestry.  They identified three genetic variants associated with increased risk for the disease.

The strongest of these, rs4132601, is near the IKZF1 gene, which encodes a protein involved in the development of white blood cells.  Deletions of the region of DNA containing this gene are common in forms of ALL that have a poor prognosis.  Each copy of a G at rs4132601 increases the odds of ALL by 1.69 times.

The second most strongly associated SNP was rs7089424 in ARID5B, a gene previously linked to a different form of blood cancer called acute promyelocytic leukemia.  Each copy of a G at rs7089424 was associated with 1.65 times increased odds of ALL.

Finally, Papaemmanuil et al. found that each copy of a G at rs2239633 was associated with 1.34 times increased odds of ALL.

(23andMe customers can check their data for all three SNPs using the links to the Browse Raw Data feature above.)

All three SNPs were even more strongly associated with ALL when the researchers restricted their analysis to a subtype of the disease called B-cell ALL.  Within this form of the disease, rs7089424 in ARID5B seems to be highly associated with a further subtype called hyperdiploid ALL.  This form of the disease has a better response to methotrexate chemotherapy than other subtypes of ALL.

The authors conclude that the variations they identified underlie approximately 64% of all cases of ALL.

“Our findings provide the first unambiguous evidence that common genetic variation influences the risk of developing pediatric ALL and strong rationale for searching for additional risk variants through further GWA [genomewide association] scans,” the authors write.

In a separate study of 441 ALL cases and 16,912 controls, Lisa Trevino and colleagues from the United States also found evidence for the involvement of variants in and around the ARID5B gene in B-hyperdiploid ALL.  The riskier versions of SNPs closely related to rs7089424 were not only correlated with disease risk, but also with a response to methotrexate that at least partially underlies its greater efficacy in B-hyperdiploid ALL.

“The data…suggest that the same genetic variation that predisposes to B-hyperdiploid ALL may underlie the superior response of this subtype to chemotherapy.  Thus, genomic variation may affect not only disease risk but treatment outcome as well,” they write.

Photo: VashiDonsk

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A new genetic study has added more evidence to a decades-old association between blood type and the risk for pancreatic cancer.

Close to 42,500 men and women are expected to be diagnosed with pancreatic cancer in the United States this year.  Because there is no effective screening test for the disease and it is often not detected until it has spread, the five-year survival rate for people with pancreatic cancer is only about 5%. The new results, published online this week in the journal Nature Genetics, represent one of the first associations of a common genetic variant with this deadly disease.

Researchers from Harvard and the National Cancer Institute studied more than 4,300 people with pancreatic cancer and 4,500 controls.  They found that each copy of the C version of rs505922 is associated with 1.2 times increased odds of pancreatic cancer compared to two Ts at this SNP.  The study subjects were mainly of European descent, but this association was essentially the same when the small number of people from other ethnic groups (mainly Asian and African American) was also included in the analysis.

(23andMe customers can check their data for rs505922 using the Browse Raw Data feature.)

The non-risk T version of rs505922 is linked to the variation in the ABO gene that results in type O blood.  People with two Ts are type O.  The riskier C version of the SNP is found in people with type A, B and AB blood.

Epidemiological studies from the 1950s and 1960s, as well as more recent reports, have suggested that people with type O blood are at lower risk for pancreatic cancer compared to those with type A or type B blood.  Finding the association of rs505922 with the disease in a genetic study adds more credence to these previous results. What’s still not understood, however, is why people with type O blood are less likely to get pancreatic cancer.

In their concluding remarks, the authors of the study stressed the need for further research into the genetic risk factors for cancer of the pancreas.

“As there are few known risk factors, improved diagnostics and a finer understanding of the molecular pathogenesis are urgently needed…. The discovery of additional genetic risk variants for this highly lethal cancer could contribute to improvements in … prevention, early detection and therapeutic approaches to pancreatic cancer,” the authors write.

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