Posts tagged genetics
Articles and news from the latest research reports.
Perfect Pitch: Knowing the Note May Be in Your Genes
People with perfect pitch seem to possess their own inner pitch pipe, allowing them to sing a specific note without first hearing a reference tone. This skill has long been associated with early and extensive musical training, but new research suggests that perfect pitch may have as much to do with genetics as it does with learning an instrument or studying voice.
Previous research does draw a connection between early musical training and the likelihood of a person developing perfect pitch, which is also referred to as absolute pitch. This is especially true among speakers of tonal languages, such as Mandarin. Speakers of English and other non-tonal languages are far less likely to develop perfect pitch, even if they were exposed to early and extensive musical training.
“We have wondered if perfect pitch is as much about nature or nurture,” said Diana Deutsch, a professor of psychology at the University of California, San Diego. “What is clear is that musically trained individuals who speak a non-tone language can acquire absolute pitch, but it is still a remarkably rare talent. What has been less clear is why most others with equivalent musical training do not.” Deutsch and her colleague Kevin Dooley present their findings at the 164th meeting of the Acoustical Society of America (ASA), held Oct. 22 – 26 in Kansas City, Missouri.
To shine light on this question, the researchers studied 27 English speaking adults, 7 of whom possessed perfect pitch. All began extensive musical training at or before the age of 6. The researchers tested the subjects’ memory ability using a test known as the digit span, which measures how many digits a person can hold in memory and immediately recall in correct order. They presented the digits either visually or auditorily; for the auditory test, the subject listened to the numbers through headphones, and for the visual test the digits were presented successively at the center of a computer screen.
The people with perfect pitch substantially outperformed the others in the audio portion of the test. In contrast, for the visual test, the two groups exhibited very similar performance, and their scores were not significantly different from each other. This is significant because other researchers have shown previously that auditory digit span has a genetic component.
“Our finding therefore shows that perfect pitch is associated with an unusually large memory span for speech sounds,” said Deutsch, “which in turn could facilitate the development of associations between pitches and their spoken languages early in life.”
(Source: newswise.com)
Evolution of new genes captured
Like job-seekers searching for a new position, living things sometimes have to pick up a new skill if they are going to succeed. Researchers from the University of California, Davis, and Uppsala University, Sweden, have shown for the first time how living organisms do this.
The observation, published Oct. 19 in the journal Science, closes an important gap in the theory of natural selection.
Scientists have long wondered how living things evolve new functions from a limited set of genes. One popular explanation is that genes duplicate by accident; the duplicate undergoes mutations and picks up a new function; and, if that new function is useful, the gene spreads.
"It’s an old idea and it’s clear that this happens," said John Roth, a distinguished professor of microbiology at UC Davis and co-author of the paper.
The problem, Roth said, is that it has been hard to imagine how it occurs. Natural selection is relentlessly efficient in removing mutated genes: Genes that are not positively selected are quickly lost.
How then does a newly duplicated gene stick around long enough to pick up a useful new function that would be a target for positive selection?
Experiments in Roth’s laboratory and elsewhere led to a model for the origin of a novel gene by a process of “innovation, amplification and divergence.” This model has now been tested by Joakim Nasvall, Lei Sun and Dan Andersson at Uppsala.
About face: Study shows long-ignored segments of DNA play role in coordinating early stages of face development
The human face is a fantastically intricate thing. The billions of people on the planet have faces that are individually recognizable because each has subtle differences in its folds and curves. How is the face put together during development so that, out of billions of people, no two faces are exactly the same?
School of Medicine researcher Joanna Wysocka, PhD, and her colleagues have discovered key genetic elements that guide the earliest stages of the process.
Their research, published in the Sept. 13 issue of Cell Stem Cell, provides a resource for others studying facial development and could give insights to the cause of some facial birth defects. Because there is not enough genetic information in the body to define exactly where each cell will go, development of the face proceeds much like origami: genes provide instructions for folding, crimping, and movement of cells. As with origami, following a sequence of simple instructions can result in a complex, intricate object.
Wysocka focused on the first critical fold in the process of making an embryo, when the whole of the embryo is a flat sheet of cells that creases and closes over on itself to make a tube. Much of the tube eventually becomes the foundation of the brain and the spinal column, but one end sets the stage for the formation of the head and face. This process is driven by a small population of remarkable cells called neural crest cells.
"We were interested in identifying the portions of the human genome that are responsible for the behavior of the neural crest," Wysocka said.
What they discovered is that the modification of a collection of DNA sequences called “enhancers” can dial up or down the activity of the genes governing which cells eventually become the face. It’s almost as if they have discovered how the instructions for a piece of origami can be modified — slightly change how a fold is made and you may end up with something very different looking.
Replicating Risk Genes in Bipolar Disorder
One of the biggest challenges in psychiatric genetics has been to replicate findings across large studies.
Scientists at King’s College London, Institute of Psychiatry have now performed one of the largest ever genetic replication studies of bipolar affective disorder, with 28,000 subjects recruited from 36 different research centers. Their findings provide compelling evidence that the chromosome 3p21.1 locus contains a common genetic risk for bipolar disorder, the PBRM1 gene.
The locus at 3p21.1 has also been previously associated with depression and schizophrenia. Using a separate dataset of over 34,000 subjects, they did not confirm association of this same variant with schizophrenia.
Thus, they replicated the association of the marker with bipolar disorder, but not with schizophrenia. This is an interesting finding, in that it distinguishes the heritable risk for bipolar disorder and schizophrenia. It contrasts with the majority of studies that have found that schizophrenia risk genes also contribute to the risk for bipolar disorder.
"This study adds to the recent rapid progress in identifying genes for mental illness. The last few years have seen the identification of about two dozen genetic loci for bipolar disorder and schizophrenia," commented first author Evangelos Vassos. "About half of these are shared between these two disorders, indicating they share some, but not all, genetic causes."
Due to the conflicting results, it is clear that more work is needed to determine the role this locus plays in psychosis, but the evidence seems solid that it is associated with bipolar disorder.
A Gene Implicated In Schizophrenia Risk Is Also Associated With Risk for Cannabis Dependence
A paper by Shizhong Han and colleagues in the current issue of Biological Psychiatry implicates a new gene in the risk for cannabis dependence. This gene, NRG1, codes for the ErbB4 receptor, a protein implicated in synaptic development and function.
The researchers set out to investigate susceptibility genes for cannabis dependence, as research has already shown that it has a strong genetic component.
To do this, they employed a multi-stage design using genetic data from African American and European American families. In the first stage, a linkage analysis, the strongest signal was identified in African Americans on chromosome 8p21. Then using a genome-wide association study dataset, they identified one genetic variant at NRG1 that showed consistent evidence for association in both African Americans and European Americans. Finally, they replicated the association of that same variant in an independent sample of African-Americans.
All together, the findings suggest that NRG1 may be a susceptibility gene for cannabis dependence.
An interesting feature of this paper is that these findings may also suggest a link between the genetics of schizophrenia and the genetics of cannabis dependence. NRG1 emerged into public awareness after a series of genetic studies implicated it in the heritable risk for schizophrenia. Subsequent studies in post-mortem brain tissue also suggested that the regulation of NRG1 was altered in the brains of individuals diagnosed with schizophrenia.
Thus, the current findings may help to explain the already established link between cannabis use and the risk for developing schizophrenia. A number of epidemiologic studies have attributed the association of cannabis use and schizophrenia to the effects of cannabis on the brain rather than a common genetic link between these two conditions.
"The current data provide a potentially important insight into the heritable risk for schizophrenia and raise the possibility that there are some common genetic contributions to these two disorders," commented Dr. John Krystal, Editor of Biological Psychiatry.
However, further research will be necessary to further confirm the role that NRG1 plays in cannabis dependence and the potential link between cannabis use and psychosis.
(Source: alphagalileo.org)
Researchers Find Regenerated Lizard Tails Are Different From Originals
Just because a lizard can grow back its tail, doesn’t mean it will be exactly the same. A multidisciplinary team of scientists from the University of Arizona and Arizona State University examined the anatomical and microscopic make-up of regenerated lizard tails and discovered that the new tails are quite different from the original ones. The findings are published in a pair of articles featured in a special October edition of the journal, The Anatomical Record.
“The regenerated lizard tail is not perfect replica,” said Rebecca Fisher, an associate professor at the UA College of Medicine-Phoenix. “There are key anatomical differences including the presence of a cartilaginous rod and elongated muscle fibers spanning the length of the regenerated tail.”
Researchers studied the regenerated tails of the green anole lizard (Anolis carolinensis), which can lose its tail when caught by a predator and then grow it back. The new tail had a single, long tube of cartilage rather than vertebrae, as in the original. Also, long muscles span the length of the regenerated tail compared to shorter muscle fibers found in the original.
"These differences suggest that the regenerated tail is less flexible, as neither the cartilage tube nor the long muscle fibers would be capable of the fine movements of the original tail, with its interlocking vertebrae and short muscle fibers," said Fisher, who also is an associate professor in the School of Life Sciences at ASU. "The regrown tail is not simply a copy of the original, but instead is a replacement that restores some function."
Film explores struggles with rare diseases
There may be only a few thousand people in the United States who suffer from Hermansky-Pudlak syndrome, a disease so rare that most doctors have never even heard of it, much less know how to treat it.
But this very unusual condition is the focus of a documentary airing on public television this weekend, made by two Stanford filmmakers who are trying to draw attention to the plight of patients who suffer from rare diseases.
The documentary “Rare” airs at 6 p.m. Sunday on KQED. For more information about the film, and to see a preview, go to www.rarefilm.org
The Date of Interbreeding between Neandertals and Modern Humans
Comparisons of DNA sequences between Neandertals and present-day humans have shown that Neandertals share more genetic variants with non-Africans than with Africans. This could be due to interbreeding between Neandertals and modern humans when the two groups met subsequent to the emergence of modern humans outside Africa. However, it could also be due to population structure that antedates the origin of Neandertal ancestors in Africa. We measure the extent of linkage disequilibrium (LD) in the genomes of present-day Europeans and find that the last gene flow from Neandertals (or their relatives) into Europeans likely occurred 37,000–86,000 years before the present (BP), and most likely 47,000–65,000 years ago. This supports the recent interbreeding hypothesis and suggests that interbreeding may have occurred when modern humans carrying Upper Paleolithic technologies encountered Neandertals as they expanded out of Africa.
New de novo Genetic Mutations in Schizophrenia Identified
Columbia University Medical Center (CUMC) researchers have identified dozens of new spontaneous genetic mutations that play a significant role in the development of schizophrenia, adding to the growing list of genetic variants that can contribute to the disease. The study, the largest and most comprehensive of its kind, was published today in the online edition of the journal Nature Genetics.
Although schizophrenia typically onsets during adolescence and early adulthood, many of the mutations were found to affect genes with higher expression during early-to-mid fetal development. Together, the findings show that both the function of the mutated gene and when the gene is expressed are critically important in determining the risk for schizophrenia.
The findings inform epidemiologic studies showing that environmental factors, such as malnutrition or infections during pregnancy, can contribute to the development of schizophrenia. “Our findings provide a mechanism that could explain how prenatal environmental insults during the first and second trimester of pregnancy increase one’s risk for schizophrenia,” said study leader Maria Karayiorgou, MD, professor of psychiatry at CUMC, and acting chief, division of Psychiatric and Medical Genetics, New York State Psychiatric Institute. “Patients with these mutations were much more likely to have had behavioral abnormalities, such as phobias and anxiety in childhood, as well as worse disease outcome.”
Intelligence Is in the Genes, but Where?
You can thank your parents for your smarts—or at least some of them. Psychologists have long known that intelligence, like most other traits, is partly genetic. But a new study led by psychological scientist Christopher Chabris of Union College reveals the surprising fact that most of the specific genes long thought to be linked to intelligence probably have no bearing on one’s IQ. And it may be some time before researchers can identify intelligence’s specific genetic roots.
Chabris and David Laibson, a Harvard economist, led an international team of researchers that analyzed a dozen genes using large data sets that included both intelligence testing and genetic data.
In nearly every case, the researchers found that intelligence could not be linked to the specific genes that were tested. The results are published online in Psychological Science, a journal of the Association for Psychological Science.
“In all of our tests we only found one gene that appeared to be associated with intelligence, and it was a very small effect. This does not mean intelligence does not have a genetic component. It means it’s a lot harder to find the particular genes, or the particular genetic variants, that influence the differences in intelligence,” said Chabris.