Time filter

Source Type

Cincinnati, Ohio, United States

In experiments on the fruit fly model organism Drosophila melanogaster, Heidelberg University biologists gained new insight into how feeding behaviour is encoded and controlled. The research team led by Prof. Dr. Ingrid Lohmann of the Centre for Organismal Studies (COS) studied the function of a special developmental gene of the Hox gene family. This gene is essential for maintaining a motor unit in the fly's head that consists of a muscle and the stimulating neurons that enable the fly to feed. If the function of the Hox gene was damaged or defective, the unit was not or only partially developed and the animals starved. The results of the research were published in the journal Cell Reports. "Animals interact with their environment based on stereotypical movement patterns, such as those performed during running, breathing or feeding," explains Prof. Lohmann, who directs the Developmental Biology research group at the Centre for Organismal Studies. "We have known for some time that a family of regulatory genes known as Hox genes is essential for establishing coordinated movement patterns. But until now we did not understand the molecular underpinnings of feeding behaviour." Using Drosophila melanogaster, Prof. Lohmann's team was able to demonstrate that a specific Hox gene, known as Deformed, controls the establishment of the feeding motor unit not only during the development of the embryo. It is also responsible for maintaining its function in later phases of life, which was revealed when the researchers deactivated Deformed after embryogenesis when the motor unit was successfully formed. Yet the typical movement patterns were lost anyway. The team was able to attribute the loss to major changes at the junctions, or synapses, between the neuron and the muscle. "Our studies show that Hox genes have a protective function in neurons. As soon as this protection is gone, the neurons degenerate, like we observe in neurodegenerative diseases such as Alzheimer's and Parkinson's," explains Prof. Lohmann. Future studies will be devoted to elucidate how Hox genes perform this protective function at the molecular level. The research project was funded by the German Research Foundation. More information: Jana Friedrich et al. Hox Function Is Required for the Development and Maintenance of the Drosophila Feeding Motor Unit, Cell Reports (2016). DOI: 10.1016/j.celrep.2015.12.077

A team of Yale scientists led by Scott Holley of the Department of Molecular, Cellular, and Developmental Biology illustrate the key role played by the cell adhesion molecule cadherin in formation of segments called somites, which become the vertebrae and musculature. In an image taken from a developing zebrafish, the sawtooth pattern of the cadherin protein within the somites can been seen on both sides of the notochord, which together with the somite will form the vertebral column. In fish, somites form the flakes of flesh in a fish fillet. But if these structures do not form properly in fish or humans, the result can be defects of the vertebrae such as scoliosis. The research was published online Feb. 4 in the journal Current Biology. More information: Patrick McMillen et al. A Sawtooth Pattern of Cadherin 2 Stability Mechanically Regulates Somite Morphogenesis, Current Biology (2016). DOI: 10.1016/j.cub.2015.12.055

Until now, however, exactly how that happens has been somewhat of a scientific mystery. New research conducted by UC Santa Barbara neuroscientists has deciphered some of the earliest changes that occur before stems cells transform into neurons and other cell types. Working with human embryonic stems cells in petri dishes, postdoctoral fellow Jiwon Jang discovered a new pathway that plays a key role in cell differentiation. The findings appear in the journal Cell. "Jiwon's discovery is very important because it gives us a fundamental understanding of the way stem cells work and the way they begin to undergo differentiation," said senior author Kenneth S. Kosik, the Harriman Professor of Neuroscience Research in UCSB's Department of Molecular, Cellular, and Developmental Biology. "It's a very fundamental piece of knowledge that had been missing in the field." When stem cells begin to differentiate, they form precursors: neuroectoderms that have the potential to become brain cells, such as neurons; or mesendoderms, which ultimately become cells that comprise organs, muscles, blood and bone. Jang discovered a number of steps along what he and Kosik labeled the PAN (Primary cilium, Autophagy Nrf2) axis. This newly identified pathway appears to determine a stem cell's final form. "The PAN axis is a very important player in cell fate decisions," explained Jang. "G1 lengthening induces cilia protrusion and the longer those cellular antennae are exposed, the more signals they can pick up." For some time, scientists have known about Gap 1 (G1), the first of four phases in the cell cycle, but they weren't clear about its role in stem cell differentiation. Jang's research demonstrates that in stem cells destined to become neurons, the lengthening phase of G1 triggers other actions that cause stem cells to morph into neuroectoderms. During this elongated G1 interval, cells develop primary cilia, antennalike protrusions capable of sensing their environment. The cilia activate the cells' trash disposal system in a process known as autophagy. Another important factor is Nrf2, which monitors cells for dangerous molecules such as free radicals—a particularly important job for healthy cell formation. "Nrf2 is like a guardian to the cell and makes sure the cell is functioning properly," said Kosik, co-director of the campus's Neuroscience Research Institute. "Nrf2 levels are very high in stem cells because stem cells are the future. Without Nrf2 watching out for the integrity of the genome, future progeny are in trouble." Jang's work showed that levels of Nrf2 begin to decline during the elongated G1 interval. This is significant, Kosik noted, because Nrf2 doesn't usually diminish until the cell has already started to differentiate. "We thought that, under the same conditions if the cells are identical, that both would differentiate the same way, but that is not what we found," Jang said. "Cell fate is controlled by G1 lengthening, which extends cilia's exposure to signals from their environment. That is one cool concept." Explore further: Scientists find a groovy way to influence specialization of stem cells

News Article
Site: www.biosciencetechnology.com

The first gene identified for graying hair has been discovered by an international UCL-led study, confirming graying has a genetic component and is not just environmental. Published in Nature Communications, the study analyzed a population of over 6,000 people with varied ancestry across Latin America to identify new genes associated with hair color, graying, density and shape, i.e. straight or curly. "We already know several genes involved in balding and hair colour but this is the first time a gene for graying has been identified in humans, as well as other genes influencing hair shape and density," said lead author, Dr Kaustubh Adhikari, UCL Cell & Developmental Biology. "It was only possible because we analyzed a diverse melting pot of people, which hasn't been done before on this scale. These findings have potential forensic and cosmetic applications as we increase our knowledge on how genes influence the way we look." The findings could help develop forensic DNA technologies that build visual profiles based on an individual's genetic makeup. Research in this field has previously used samples from people of European descent, but these new results could help forensic reconstructions in Latin America and East Asia. The gene identified for grey hair -- IRF4 -- is known to play a role in hair color but this is the first time it has been associated with the graying of hair. This gene is involved in regulating production and storage of melanin, the pigment that determines hair, skin and eye color. Hair graying is caused by an absence of melanin in hair so the scientists want to find out IRF4's role in this process. Understanding how IRF4 influences hair graying could help the development of new cosmetic applications that change the appearance of hair as it grows in the follicle by slowing or blocking the graying of hair. Professor Andres Ruiz-Linares, UCL Biosciences, who led the study, said: "We have found the first genetic association to hair graying, which could provide a good model to understand aspects of the biology of human aging. Understanding the mechanism of the IRF4 graying association could also be relevant for developing ways to delay hair greying." Another gene, PRSS53, which was found to influence hair curliness, was investigated by the University of Bradford's Centre for Skin Sciences as part of the study. "An enduring fascination of human evolution has been our peculiarly luxuriant scalp hair, and finding a new variation in the Protease Serine S1 family member 53 (PRSS53) gene provides an important insight into the genetic controls underpinning scalp hair shape and texture," explained Professor Desmond Tobin, University of Bradford. "The PRSS53 enzyme functions in the part of the hair follicle that shapes the growing hair fiber, and this new genetic variation, associated with straight hair in East Asians and Native Americans, supports the view that hair shape is a recent selection in the human family." The scientists found additional genes associated with hair including EDAR for beard thickness and hair shape; FOXL2 for eyebrow thickness and PAX3 for monobrow prevalence. "It has long been speculated that hair features could have been influenced by some form of selection, such as natural or sexual selection, and we found statistical evidence in the genome supporting that view," added Dr Adhikari. "The genes we have identified are unlikely to work in isolation to cause graying or straight hair, or thick eyebrows, but have a role to play along with many other factors yet to be identified." The team collected and analyzed DNA samples from 6,630 volunteers from the CANDELA cohort recruited in Brazil, Colombia, Chile, Mexico and Peru. After an initial screen, a sample size of 6,357 was used, at 45 percent male and 55 percent female. This group included individuals of mixed European (48 percent), Native American (46 percent) and African (6 percent) ancestry, giving a large variation in head hair appearance. Both men and women were assessed for hair shape, colour, balding and greying, but only men were tested for beard, monobrow and eyebrow thickness. Visual traits for each individual were compared to whole genome analysis results to identify the genes driving differences in appearance. These were then checked against existing databases of different populations to see if the differences made sense based on previous knowledge and were under selection.

News Article
Site: phys.org

But the nature, development and evolution of these staggeringly diverse decorations (of the more than 18,000 species of butterfly, almost all differ in their wing patterns) has also attracted the attention of scientists; although studied since antiquity, many butterfly secrets continue to be revealed, as this selection of research published in PLOS journals and other open access sources in the last 12 months shows. Butterfly wing patterning seems to serve many functions related to survival – camouflage, mimicry, mate recognition or warning signals. And because the benefits conferred by these depend in turn on the environment, location and other (equally evolvable) creatures such as predators or other butterflies, the forces underlying pattern evolution are complex, and the mechanisms by which they arise are fascinatingly elegant. A paper just published in PLOS Biology, for example, examines how the wing patterns of 17 species of Amazonian Heliconius butterflies have arisen. The answer, it seems, is that modular chunks of regulatory DNA that control the red colour "master gene" optix have been mixed and matched by mating between different species of butterfly, allowing complex combinations of red "dennis" patches (on forewings) and rays (on hindwings) to emerge in different species. This modularity should make the spread of common mimetic patterns easier, and facilitate innovation. Extreme subtlety of pattern variation is seen in species like Bicyclus anynana, which has different forms in the dry season and wet season to suit the different predators encountered (mostly vertebrates and invertebrates, respectively). The forewing bears eyespots in both forms, as the butterfly can choose when to flash these, but the hindwing is always on show, so while the wet-season form keeps these to ward off invertebrate predators, the dry-season form develops without hindwing eyespots, enhancing its camouflage. How do they do this? A recent PLOS Genetics paper shows that the temperature at which the larvae develop determines the levels of a hormone called 20-hydroxyecdysone, and it's the levels of this substance that determine whether the hingwings develop eyespots (take a look at the authors' own blog post for more detail). The colours of the scales on butterflies wings arise through two fundamentally distinct mechanisms – through the production of pigment (such as the ommochromes that impart the red colour to the Heliconious patches and rays above) and through nano-engineering of the structure of the scale to create photonic devices. It's the latter "structural colour" that confers the more striking iridescent visual effects seen in butterflies' wings. A recent paper in Scientific Reports set out to emulate the vivid blue colour of Morpho didius by making nanometre-scale Christmas tree-like arrays of polymer that resemble the real Morpho's scales. You can see the convincing results of the nano-mimicry in this picture. Researchers are also exploring how wings develop during pupation. 3D confocal microscopy in this PLOS ONE study shows that the flat cells that make up the larval wing precursor (the "imaginal disc") expand lengthwise during pupation to give an epithelial layer more than 100 microns deep. Further work by the same group, also in PLOS ONE, shows that the thickness of this epithelium seems to reflect the future wing patterning, such that eyespots correspond to noticeable bulges in the developing organ. The way in which the positions of multiple eyespots might be specified has been modeled mathematically in a further PLOS ONE paper, and a potential role for long-range waves of calcium ions is explored in this BMC Developmental Biology study. Although wing patterns often serve to reduce the chances of being eaten, predators' eyes aren't the only target audience for the butterflies' wings. A paper in Zoological Letters examines different pigmentary and structural colours in the wings of Papilio xunthus match the spectral properties of their own eyes, consistent with the colours being used to help them spot mates of the same species. Human eyes may also impact butterflies' survival; while species that appeal most to our aesthetic sense might previously have been depleted by the once-popular hobby of butterfly collecting, a PLOS ONE study showed that one aspect of their wing pattern – eyespots – increases the perceived attractiveness of a butterfly and has a positive influence influence on people's attitudes to their conservation. While this blog post has focused on the beauty of butterflies, we shouldn't forget that their distant cousins are also worth looking at. This PLOS ONE paper uses wing patterns of the basal moth genus Micropterix to show that the relationship between patterning and wing veins has remained almost unchanged in the tens of millions of years since they split from butterflies. The amazing blue of the real Morpho didius wing (above) and its nanofabricated doppleganger (below) doi: 10.1038/srep16637 Papilio xuthus‘ eyes are tuned to detect its wing colours (DOI: 10.1186/s40851-015-0015-2) Four species of primitive moth from the genus Micropterix (doi: 10.1371/journal.pone.0139972.g003) More information: Zoi Manesi et al. Butterfly Eyespots: Their Potential Influence on Aesthetic Preferences and Conservation Attitudes, PLOS ONE (2015). DOI: 10.1371/journal.pone.0141433 Doekele G Stavenga et al. Combined pigmentary and structural effects tune wing scale coloration to color vision in the swallowtail butterfly Papilio xuthus, Zoological Letters (2015). DOI: 10.1186/s40851-015-0015-2 Yoshikazu Ohno et al. Live Cell Imaging of Butterfly Pupal and Larval Wings In Vivo, PLOS ONE (2015). DOI: 10.1371/journal.pone.0128332

Discover hidden collaborations