Posts tagged evolution
Articles and news from the latest research reports.
Eat crow if you think I’m a bird-brain
Scientists have long suspected that corvids – the family of birds including ravens, crows and magpies – are highly intelligent. Now, Tübingen neurobiologists Lena Veit und Professor Andreas Nieder have demonstrated how the brains of crows produce intelligent behavior when the birds have to make strategic decisions. Their results are published in the latest edition of Nature Communications.
Crows are no bird-brains. Behavioral biologists have even called them “feathered primates” because the birds make and use tools, are able to remember large numbers of feeding sites, and plan their social behavior according to what other members of their group do. This high level of intelligence might seem surprising because birds’ brains are constructed in a fundamentally different way from those of mammals, including primates – which are usually used to investigate these behaviors.
The Tübingen researchers are the first to investigate the brain physiology of crows’ intelligent behavior. They trained crows to carry out memory tests on a computer. The crows were shown an image and had to remember it. Shortly afterwards, they had to select one of two test images on a touchscreen with their beaks based on a switching behavioral rules. One of the test images was identical to the first image, the other different. Sometimes the rule of the game was to select the same image, and sometimes it was to select the different one. The crows were able to carry out both tasks and to switch between them as appropriate. That demonstrates a high level of concentration and mental flexibility which few animal species can manage – and which is an effort even for humans.
The crows were quickly able to carry out these tasks even when given new sets of images. The researchers observed neuronal activity in the nidopallium caudolaterale, a brain region associated with the highest levels of cognition in birds. One group of nerve cells responded exclusively when the crows had to choose the same image – while another group of cells always responded when they were operating on the “different image” rule. By observing this cell activity, the researchers were often able to predict which rule the crow was following even before it made its choice.
The study published in Nature Communications provides valuable insights into the parallel evolution of intelligent behavior. “Many functions are realized differently in birds because a long evolutionary history separates us from these direct descendants of the dinosaurs,” says Lena Veit. “This means that bird brains can show us an alternative solution out of how intelligent behavior is produced with a different anatomy.” Crows and primates have different brains, but the cells regulating decision-making are very similar. They represent a general principle which has re-emerged throughout the history of evolution. “Just as we can draw valid conclusions on aerodynamics from a comparison of the very differently constructed wings of birds and bats, here we are able to draw conclusions about how the brain works by investigating the functional similarities and differences of the relevant brain areas in avian and mammalian brains,” says Professor Andreas Nieder.
Big brains are all in the genes
Scientists have moved a step closer to understanding genetic changes that permitted humans and other mammals to develop such big brains.
During evolution, different mammal species have experienced variable degrees of expansion in brain size. An important goal of neurobiology is to understand the genetic changes underlying these extraordinary adaptations.
The process by which some species evolved larger brains – called encephalization – is not well understood by scientists. The puzzle is made more complex because evolving large brains comes at a very high cost.
Dr Humberto Gutierrez, from the School of Life Sciences, University of Lincoln, UK, led research which examined the genomes of 39 species of mammals with the aim of better understanding how brains became larger and more complex in mammals.
To do this, the scientists focussed on the size of gene families across these species. Gene families are groups of related genes which share similar characteristics, often linked with common or related biological functions. It is believed that large changes in the size of gene families can help to explain why related species evolved along different paths.
The researchers found a clear link between increased brain size and the expansion of gene families related to certain biological functions.
Dr Gutierrez said: “We found that brain size variations are associated with changes in gene number in a large proportion of families of closely related genes. These gene families are preferentially involved in cell communication and cell movement as well as immune functions and are prominently expressed in the human brain. Our results suggest that changes in gene family size may have contributed to the evolution of larger brains in mammals.”
Mammalian species in general tend to have large brains compared to their body size which represent an evolutionary costly adaptation as they require large amounts of energy to function.
Dr Gutierrez explained: “The brain is an extremely expensive organ consuming a large amount of energy in proportion to its volume, so large brains place severe metabolic demands on animals. Larger brains also demand higher parental investment. For example, humans require many years of nurturing and care before their brains are fully matured.”
Dr Gutierrez’s research concluded that variations in the size of gene families associated with encephalization provided an evolutionary support for the specific physiological demands associated with increased brain size in mammals.
(Source: lincoln.ac.uk)
Snakes on the brain: Are primates hard-wired to see snakes?
Was the evolution of high-quality vision in our ancestors driven by the threat of snakes? Work by neuroscientists in Japan and Brazil is supporting the theory originally put forward by Lynne Isbell, professor of anthropology at the University of California, Davis.
In a paper published Oct. 28 in the journal Proceedings of the National Academy of Sciences, Isbell; Hisao Nishijo and Quan Van Le at Toyama University, Japan; and Rafael Maior and Carlos Tomaz at the University of Brasilia, Brazil; and colleagues show that there are specific nerve cells in the brains of rhesus macaque monkeys that respond to images of snakes.
The snake-sensitive neurons were more numerous, and responded more strongly and rapidly, than other nerve cells that fired in response to images of macaque faces or hands, or to geometric shapes. Isbell said she was surprised that more neurons responded to snakes than to faces, given that primates are highly social animals.
"We’re finding results consistent with the idea that snakes have exerted strong selective pressure on primates," Isbell said.
Isbell originally published her hypothesis in 2006, following up with a book, “The Fruit, the Tree and the Serpent” (Harvard University Press, 2009) in which she argued that our primate ancestors evolved good, close-range vision primarily to spot and avoid dangerous snakes.
Modern mammals and snakes big enough to eat them evolved at about the same time, 100 million years ago. Venomous snakes are thought to have appeared about 60 million years ago — “ambush predators” that have shared the trees and grasslands with primates.
Nishijo’s laboratory studies the neural mechanisms responsible for emotion and fear in rhesus macaque monkeys, especially instinctive responses that occur without learning or memory. Previous researchers have used snakes to provoke fear in monkeys, he noted. When Nishijo heard of Isbell’s theory, he thought it might explain why monkeys are so afraid of snakes.
"The results show that the brain has special neural circuits to detect snakes, and this suggests that the neural circuits to detect snakes have been genetically encoded," Nishijo said.
The monkeys tested in the experiment were reared in a walled colony and neither had previously encountered a real snake.
"I don’t see another way to explain the sensitivity of these neurons to snakes except through an evolutionary path," Isbell said.
Isbell said she’s pleased to be able to collaborate with neuroscientists.
"I don’t do neuroscience and they don’t do evolution, but we can put our brains together and I think it brings a wider perspective to neuroscience and new insights for evolution," she said.
(Source: news.ucdavis.edu)
Primate brain development follows a predictable pattern
In a breakthrough for understanding brain evolution, neuroscientists have shown that differences between primate brains - from the tiny marmoset to human – can be largely explained as consequences of the same genetic program.
In research published in the Journal of Neuroscience, Professor Marcello Rosa and his team at Monash University’s School of Biomedical Sciences and colleagues at Universidade Federal do Rio de Janeiro, in Brazil, used computer modelling to demonstrate that the substantial enlargement of some areas of the human brain, vital to advanced cognition, reflected a consistent pattern that is seen across primate species of all sizes.
This finding suggests how the neural circuits responsible for traits that we consider uniquely human – such as the ability to plan, make complex decisions and speak – could have emerged simply as a natural consequence of the evolution of larger brains.
“We have known for a long time that certain areas of the human brain are much larger than one would expect based on how monkey brains are organised,” Professor Rosa said.
“What no one had realised is that this selective enlargement is part of a trend that has been present since the dawn of primates.”
Using publicly available brain maps, MRI imaging data and modelling software, the neuroscientists compared the sizes of different brain areasin humans and three monkey species: marmosets, capuchins and macaques. They found that two regions, the lateral prefrontal cortex and the temporal parietal junction, expand disproportionally to the rest of the brain.
The prefrontal cortex is related to long term planning, personality expression, decision-making, and behaviour modification. The temporal parietal junction is related to self-awareness and self-other distinction.
Lead author Tristan Chaplin, from the Department of Physiology will commence his PhD next year. He said the findings showed that those areas of the brain grew disproportionately in a predictable way.
“We found that the larger the brain is, the larger these areas get,” Tristan said.
“When you go from a small to big monkey - the marmoset to macaque - the prefrontal cortex and temporal parietal junction get larger relative to the rest of the cortex, and we see the same thing again when you compare macaques to humans.”
“This trend argues against the view that specific human mutations gave us these larger areas and advanced cognition and behaviour, but are a consequence of what happens in development when you grow a larger brain,” Tristan said.
Professor Rosa said the pattern held for primate species that evolved completely separately.
"If you compare the capuchin of South America and the macaque of Asia, their brains are almost identical, although they developed on opposite sides of the world. They both reflect the genetic plan of how a primate brain grows," Professor Rosa said.
This is the first computational comparative study conducted across several primate species. Tristan now hopes, in collaboration with zoos, to check if our closest primate relatives, the chimpanzees and gorillas, also have brain areas organised as his theory predicts.
(Source: monash.edu.au)
What evolved first - a dexterous hand or an agile foot?
Resolving a long-standing mystery in human evolution, new research from the RIKEN Brain Science Institute indicates that early hominids developed finger dexterity and tool use ability before the development of bipedal locomotion.
Combining monkey and human behavior, brain imaging, and fossil evidence, a research team led by neurobiologist Dr. Atsushi Iriki and including Dr. Gen Suwa, an anthropologist from the University of Tokyo Museum, have overturned the common assumption that manual dexterity evolved after the development of bipedal locomotion freed hominid hands to use fingers for tool manipulation.
In a study published today in Philosophical Transactions of the Royal Society B, the researchers employed functional magnetic resonance imaging in humans and electrical recording from monkeys to locate the brain areas responsible for touch awareness in individual fingers and toes, called somatotopic maps. With these maps, the researchers confirmed previous studies showing that single digits in the hand and foot have discrete neural locations in both humans and monkeys.
However, the researchers found new evidence that monkey toes are combined into a single map, while human toes are also fused into a single map, but with the prominent exception of the big toe, which has its own map not seen in monkeys. These findings suggest that early hominids evolved dexterous fingers when they were still quadrupeds. Manual dexterity was not further expanded in monkeys, but humans gained fine finger control and a big toe to aid bipedal locomotion.
“In early quadruped hominids, finger control and tool use were feasible, while an independent adaptation involving the use of the big toe for functions like balance and walking occurred with bipedality,” the authors explained.
The brain study was supported by analysis of the well-preserved hand and feet bones of a 4.4 million year-old skeleton of the quadruped hominid Ardipithecus ramidus, a species with hand dexterity that preceded the human-monkey lineage split.
The findings suggest that the parallel evolution of two-legged locomotion and manual dexterity in hands and fingers in the human lineage were a consequence of adaptive pressures on ancestral quadrupeds for balance control by foot digits while retaining the critical capability for fine finger specialization.
“Evolution is not usually thought of as being accessible to study in the laboratory”, stated Dr. Iriki, “but our new method of using comparative brain physiology to decipher ancestral traces of adaptation may allow us to re-examine Darwin’s theories”.
The song of songbirds is a learned, complex behavior and subject to strong selective forces. However, it is difficult to tease apart the influence of the genetic background and the environment on the expression of individual variation in song. Scientists from the Max Planck Institute for Ornithology in Seewiesen in collaboration with international researchers now compared song and brain structure of parents and offspring in zebra finches that have been raised either with their genetic or foster parents. They also varied the amount of food during breeding. Remarkably, both song and the underlying brain structure had a low heritability and were strongly influenced by environmental factors.
A central topic in behavioral biology is the question, which aspects of a behavior are learned or expressed due to genetic predisposition. Today it is known that our personality and behavior are far less determined by the genetic background. Especially during development environmental factors can shape brain and behavior via so-called epigenetic effects. Thereby hormones play an important role. A shift in hormone concentrations in early life can have long lasting effects for an organism, whereas the same change in adults often may show only short-term changes. However, whether the influence of the environment has either strong or weak effects can largely depend on the individual genetic predisposition. However, it is relatively hard to discriminate the effects of the environment from that of the genes.
An attempt to tease apart these effects has been conducted by researchers from the Max Planck Institute for Ornithology in collaboration with an international team of scientists in zebra finch breeding pairs. Using partial cross-fostering the researchers exchanged half of the eggs within a nest making them to “cuckoo’s eggs”. Therefore half of the hatchlings were raised by their genetic parents, whereas the other half was raised by their foster parents. In addition they modified the availability of food by mixing the seeds with husks so that the parents had to spend more time searching for food. When the male offspring were adult at 100 days the researchers recorded their songs and analyzed the underlying neuroanatomy. This partial cross-fostering design enabled the researchers to tease apart the involvement of genotype, the rearing environment and nutritional effects to variation in song behavior and brain structure.
The results showed that heritability values were low for most song characteristics, except the number of song syllables and maximum frequency. On the other hand the common rearing environment including the song of the foster father mainly predicted the proportion of unique syllables in the songs of the sons, moreover this relationship was dependent on food availability. Even more striking results were found when the researchers investigated the brain anatomy. Heritability of brain variables was very low and strongly controlled by the environment. For example, an emergence of a clear relationship between brain mass and genotype is prevented by varying environmental quality.
This result was quite surprising as previous studies have found a high heritability of the song control system in the songbird brain, however these studies did not account for variation of the rearing environment. ”Being highly flexible in response to environmental conditions can maintain genetic variation and influences song learning and brain development” says Stefan Leitner, senior author of the study.
Striking Patterns: Skill for Forming Tools and Words Evolved Together
When did humans start talking? There are nearly as many answers to this perplexing question as there are researchers studying it. A new brain imaging study claims to support the hypothesis that language emerged long before Homo sapiens and coevolved with the invention of the first finely made stone tools nearly 2 million years ago. However, some experts think it’s premature to draw sweeping conclusions.
Unlike ancient bones and stone tools, language does not fossilize. Researchers have to guess about its origins based on proxy indicators. Does painting cave walls indicate the capacity for language? How about the ability to make a fancy tool? Yet, in recent years, scientists have made some progress. A series of brain imaging studies by Dietrich Stout, an archaeologist at Emory University in Atlanta, and Thierry Chaminade, a cognitive neuroscientist at Aix-Marseille University in France, have shown that toolmaking and language use similar parts of the brain, including regions involved in manual manipulations and speech production. Moreover, the overlap is greater the more sophisticated the toolmaking techniques are. Thus, there was little overlap when modern-day flint knappers were making stone tools using the oldest known techniques, dated to 2.5 million years ago and called the Oldowan technology. But when knappers used a more sophisticated approach, called Acheulean technology and dating to as much as 1.75 million years ago, the parallels between toolmaking and language were more evident. Stout and Chaminade have used functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) scans, although not on the same subjects at the same time.
In the new work, published online today in PLOS ONE, archaeologist Natalie Uomini and experimental psychologist Georg Meyer, both at the University of Liverpool in the United Kingdom, attempted to advance these earlier studies in several ways. They applied a technique called functional transcranial Doppler ultrasonography (fTCD), which measures blood flow to the brain’s cerebral cortex and which—unlike fMRI and PET—is highly portable and can be used on subjects in the field through a device attached to their heads (see video). The fTCD approach makes it much easier to monitor subjects’ brains during vigorous activity, such as the somewhat violent motions that are required to make stone tools. Uomini and Meyer are also the first to study both toolmaking and language tasks in the same subjects.
The researchers recruited 10 expert flint knappers and gave them two different tasks. In the first, the knappers crafted an Acheulean hand ax, a symmetrical tool that requires considerable planning and skill. The procedure involves shaping a flint core with another stone called a hammerstone. While wearing the fTCD monitor, the knappers worked on the tool for periods of about 30 seconds each, interspersed with control periods of about 20 seconds in which they simply struck the core with the hammerstone without trying to make a tool.
In the second task, the knappers were asked to silently think up words beginning with a given letter. The control periods consisted of simply resting quietly and not thinking of words.
The team found that the pattern of blood flow changes in the brain during the critical first 10 seconds of each experimental period—when the knappers were strategizing about how to shape the core or thinking up their first words—was very similar, again involving areas of the brain implicated in manual manipulations and language. Moreover, although there were some variations in the patterns between the 10 knappers, the toolmaking and language patterns within each individual were very closely aligned—suggesting, the team concludes, that the same brain areas recruited in both tasks.
The results, Uomini and Meyer argue, support earlier hypotheses that language and toolmaking coevolved, perhaps beginning as early as 1.75 million years ago. This doesn’t necessarily mean that early humans were talking in the same rapid-fire way that we do today, Uomini points out, but that “the circuits for both activities were there early on.”
Stout calls the new study “exciting work” that provides “one more piece of evidence supporting a link between stone-tool making and language evolution.” Yet a number of questions remain, he says, such as whether the correlation is between the motor skills involved in making tools and in making the sounds of speech, or whether toolmaking and language share higher cognitive functions such as those used in symbolic behavior.
That question is critical, some researchers say, because the knappers in this study and the ones that Stout conducted probably used a technique known as the Late Acheulean, dating from about 500,000 years ago, which put a much greater emphasis on symmetry and aesthetic considerations than did the earliest Acheulean, dating from 1.75 million years ago. “There is an enormous difference” between these varieties of Acheulean toolmaking, says Michael Petraglia, an archaeologist at the University of Oxford in the United Kingdom, who adds that “future experimental studies should thus examine the range of techniques and methods used.”
Thus the new work is “consistent with the hypothesis” of coevolution between language and toolmaking, “but not proof of it,” says Michael Corballis, a psychologist at the University of Auckland in New Zealand. “It is possible that language itself emerged much later, but was built on circuits established during the Acheulean” period.
Thomas Wynn, an archaeologist at the University of Colorado, Colorado Springs, is even more cautious about the results. He thinks that the fTCD technique, which measures blood flow to large areas of the cerebral cortex but does not have as high a resolution as fMRI or PET, “is a crude measure, even for brain imaging techniques.” As a result, Wynn says, he is “far from convinced” that the study has anything new to say about language evolution.
Monogamy’s Boost to Human Evolution
“Monogamy is a problem,” said Dieter Lukas of the University of Cambridge in a telephone news conference this week. As Dr. Lukas explained to reporters, he and other biologists consider monogamy an evolutionary puzzle.
In 9 percent of all mammal species, males and females will share a common territory for more than one breeding season, and in some cases bond for life. This is a problem — a scientific one — because male mammals could theoretically have more offspring by giving up on monogamy and mating with lots of females.
In a new study, Dr. Lukas and his colleague Tim Clutton-Brock suggest that monogamy evolves when females spread out, making it hard for a male to travel around and fend off competing males.
On the same day, Kit Opie of University College London and his colleagues published a similar study on primates, which are especially monogamous — males and females bond in over a quarter of primate species. The London scientists came to a different conclusion: that the threat of infanticide leads males to stick with only one female, protecting her from other males.
Even with the scientific problem far from resolved, research like this inevitably turns us into narcissists. It’s all well and good to understand why the gray-handed night monkey became monogamous. But we want to know: What does this say about men and women?
As with all things concerning the human heart, it’s complicated.
“The human mating system is extremely flexible,” Bernard Chapais of the University of Montreal wrote in a recent review in Evolutionary Anthropology. Only 17 percent of human cultures are strictly monogamous. The vast majority of human societies embrace a mix of marriage types, with some people practicing monogamy and others polygamy. (Most people in these cultures are in monogamous marriages, though.)
There are even some societies where a woman may marry several men. And some men and women have secret relationships that last for years while they’re married to other people, a kind of dual monogamy. Same-sex marriages acknowledge commitments that in many cases existed long before they won legal recognition.
Each species faces its own special challenges — the climate where it lives, or the food it depends on, or the predators that stalk it — and certain conditions may favor monogamy despite its drawbacks. One source of clues to the origin of human mating lies in our closest relatives, chimpanzees and bonobos. They live in large groups where the females mate with lots of males when they’re ovulating. Male chimpanzees will fight with each other for the chance to mate, and they’ve evolved to produce extra sperm to increase their chances that they get to father a female’s young.
Our own ancestors split off from the ancestors of chimpanzees about seven million years ago. Fossils may offer us some clues to how our mating systems evolved after that parting of ways. The hormone levels that course through monogamous primates are different from those of other species, possibly because the males aren’t in constant battle for females.
That difference in hormones influences how primates grow in some remarkable ways. For example, the ratio of their finger lengths is different.
In 2011, Emma Nelson of the University of Liverpool and her colleagues looked at the finger bones of ancient hominid fossils. From what they found, they concluded that hominids 4.4 million years ago mated with many females. By about 3.5 million years ago, however, the finger-length ratio indicated that hominids had shifted more toward monogamy.
Our lineage never evolved to be strictly monogamous. But even in polygamous relationships, individual men and women formed long-term bonds — a far cry from the arrangement in chimpanzees.
While the two new studies published last week disagree about the force driving the evolution of monogamy, they do agree on something important. “Once monogamy has evolved, then male care is far more likely,” Dr. Opie said.
Once a monogamous primate father starts to stick around, he has the opportunity to raise the odds that his offspring will survive. He can carry them, groom their fur and protect them from attacks.
In our own lineage, however, fathers went further. They had evolved the ability to hunt and scavenge meat, and they were supplying some of that food to their children. “They may have gone beyond what is normal for monogamous primates,” said Dr. Opie.
The extra supply of protein and calories that human children started to receive is widely considered a watershed moment in our evolution. It could explain why we have brains far bigger than other mammals.
Brains are hungry organs, demanding 20 times more calories than a similar piece of muscle. Only with a steady supply of energy-rich meat, Dr. Okie suggests, were we able to evolve big brains — and all the mental capacities that come with it.
Because of monogamy, Dr. Opie said, “This could be how humans were able to push through a ceiling in terms of brain size.”
Did Neandertals have language?
A recent study suggests that Neandertals shared speech and language with modern humans
Fast-accumulating data seem to indicate that our close cousins, the Neandertals, were much more similar to us than imagined even a decade ago. But did they have anything like modern speech and language? And if so, what are the implications for understanding present-day linguistic diversity? The Max Planck Institute for Psycholinguistics in Nijmegen researchers Dan Dediu and Stephen C. Levinson argue in their paper in Frontiers in Language Sciences that modern language and speech can be traced back to the last common ancestor we shared with the Neandertals roughly half a million years ago.
The Neandertals have fascinated both the academic world and the general public ever since their discovery almost 200 years ago. Initially thought to be subhuman brutes incapable of anything but the most primitive of grunts, they were a successful form of humanity inhabiting vast swathes of western Eurasia for several hundreds of thousands of years, during harsh ages and milder interglacial periods. We knew that they were our closest cousins, sharing a common ancestor with us around half a million years ago (probably Homo heidelbergensis), but it was unclear what their cognitive capacities were like, or why modern humans succeeded in replacing them after thousands of years of cohabitation. Recently, due to new palaeoanthropological and archaeological discoveries and the reassessment of older data, but especially to the availability of ancient DNA, we have started to realise that their fate was much more intertwined with ours and that, far from being slow brutes, their cognitive capacities and culture were comparable to ours.
Dediu and Levinson review all these strands of literature and argue that essentially modern language and speech are an ancient feature of our lineage dating back at least to the most recent ancestor we shared with the Neandertals and the Denisovans (another form of humanity known mostly from their genome). Their interpretation of the intrinsically ambiguous and scant evidence goes against the scenario usually assumed by most language scientists, namely that of a sudden and recent emergence of modernity, presumably due to a single – or very few – genetic mutations. This pushes back the origins of modern language by a factor of 10 from the often-cited 50 or so thousand years, to around a million years ago – somewhere between the origins of our genus, Homo, some 1.8 million years ago, and the emergence of Homo heidelbergensis. This reassessment of the evidence goes against a saltationist scenario where a single catastrophic mutation in a single individual would suddenly give rise to language, and suggests that a gradual accumulation of biological and cultural innovations is much more plausible.
Interestingly, given that we know from the archaeological record and recent genetic data that the modern humans spreading out of Africa interacted both genetically and culturally with the Neandertals and Denisovans, then just as our bodies carry around some of their genes, maybe our languages preserve traces of their languages too. This would mean that at least some of the observed linguistic diversity is due to these ancient encounters, an idea testable by comparing the structural properties of the African and non-African languages, and by detailed computer simulations of language spread.
New insight into the human genome through the lens of evolution
By comparing the human genome to the genomes of 34 other mammals, Australian scientists have described an unexpectedly high proportion of functional elements conserved through evolution.
Less than 1.5% of the human genome is devoted to conventional genes, that is, encodes for proteins. The rest has been considered to be largely junk. However, while other studies have shown that around 5-8% of the genome is conserved at the level of DNA sequence, indicating that it is functional, the new study shows that in addition much more, possibly up to 30%, is also conserved at the level of RNA structure.
DNA is a biological blueprint that must be copied into another form before it can be actualised. Through a process known as ‘transcription’, DNA is copied into RNA, some of which ‘encodes’ the proteins that carry out the biological tasks within our cells. Most RNA molecules do not code for protein, but instead perform regulatory functions, such as determining the ways in which genes are expressed.
Like infinitesimally small Lego blocks, the nucleic acids that make up RNA connect to each other in very specific ways, which force RNA molecules to twist and loop into a variety of complicated 3D structures.
Dr Martin Smith and Professor John Mattick, from Sydney’s Garvan Institute of Medical Research, devised a method for predicting these complex RNA structures – more accurate than those used in the past – and applied it to the genomes of 35 different mammals, including bats, mice, pigs, cows, dolphins and humans. At the same time, they matched mutations found in the genomes with consistent RNA structures, inferring conserved function. Their findings are published in Nucleic Acids Research, now online.
“Genomes accumulate mutations over time, some of which don’t change the structure of associated RNAs. If the sequence changes during evolution, yet the RNA structure stays the same, then the principles of natural selection suggest that the structure is functional and is required for the organism,” explained Dr Martin Smith.
“Our hypothesis is that structures conserved in RNA are like a common template for regulating gene expression in mammals – and that this could even be extrapolated to vertebrates and less complex organisms.”
“We believe that RNA structures probably operate in a similar way to proteins, which are composed of structural domains that assemble together to give the protein a function.”
“We suspect that many RNA structures recruit specific molecules, such as proteins or other RNAs, helping these recruited elements to bond with each other. That’s the general hypothesis at the moment – that non-coding RNAs serve as scaffolds, tethering various complexes together, especially those that control genome organization and expression during development.”
“We know that many RNA transcripts are associated with diseases and developmental conditions, and that they are differentially expressed in distinct cells.”
“Our structural predictions can serve as an annotative tool to help researchers understand the function of these RNA transcripts.”
“That is the first step – the next is to describe the structures in more detail, figure out exactly what they do in the cell, then work out how they relate to our normal development and to disease.”
(Source: garvan.org.au)