News Article | April 15, 2016
A sticky spaghetti and meatballs model may be sufficient to describe how the nucleus in each of our cells selectively allows the entrance and exit of certain molecules, while blocking others to protect genetic material and normal functions of the cell. That is the conclusion based on research by an international team of scientists, led by the London Centre for Nanotechnology and CIC biomaGUNE, and published in the journal eLife. Cells of humans, animals, and plants have a nucleus that contains most of their genetic material. For the appropriate use of this genetic material, it is essential that proteins and other molecules can only enter and exit the nucleus in a highly selective way, via channels in the protective membrane that surrounds the nucleus. Inside these tiny channels (nuclear pore complexes) reside specialized proteins (FG domains) that arrange similarly to sticky spaghetti, to act as a selective barrier. The molecules that cross the barrier can be thought of as meatballs. Some very particular meatballs are nuclear transport receptors, which shuttle rather freely into and out of the spaghetti-like FG domains, and enable other molecules to do so too. To study how these meatballs penetrate the channels, the scientists first made layers of FG domains of only 100,000th of a millimeter thick, and next measured how nuclear transport receptors bound to these layers. Since the results were highly similar for different FG domains and different nuclear transport receptors, the next step was to design a physical model that only included the features that were universal to all, namely that the FG domains behaved as rather sticky spaghetti interacting with the nuclear transport receptors as even stickier meatballs. This model was very successful in reproducing the experimental data. Moreover, and encouragingly, it is consistent with earlier, less quantitative work of the London team on the real channels. Given the enormous complexity of the biological structures and processes involved, it is remarkable that such a simple (polymer-physics) model applies. Its success implies that the basic mechanism underlying selective transport into and out of the cell nucleus could well be explained based on generic physical principles. Beside the London Centre for Nanotechnology and CIC biomaGUNE, the work included important contributions from the MRC Laboratory of Molecular Biology, Cambridge, the Max Planck Institute for Biophysical Chemistry in Germany, and the University of Osnabrück in Germany.
Romaniello R.,Neuropsychiatry and Neurorehabilitation Unit |
Arrigoni F.,Neuroimaging Unit |
Bassi M.T.,Laboratory of Molecular Biology |
Borgatti R.,Neuropsychiatry and Neurorehabilitation Unit
Brain and Development | Year: 2015
The tubulin gene family is mainly expressed in post-mitotic neurons during cortical development with a specific spatial and temporal expression pattern. Members of this family encode dimeric proteins consisting of two closely related subunits (α and β), representing the major constituents of microtubules. Tubulin genes play a crucial role in the mechanisms of the Central Nervous System development such as neuronal migration and axonal guidance (axon outgrowth and maintenance). Different mutations in α/β-tubulin genes (TUBA1A, TUBA8, TUBB2A, TUBB4A, TUBB2B, TUBB3, and TUBB) might alter the dynamic properties and functions of microtubules in several ways, effecting a reduction in the number of functional tubulin heterodimers and causing alterations in GTP binding and disruptions of the binding of other proteins to microtubules (motor proteins and other microtubule interacting proteins).In recent years an increasing number of brain malformations has been associated with mutations in tubulin genes: malformations of cortical development such as lissencephaly and various grades of gyral disorganization, focal or diffuse polymicrogyria and open or closed-lips schizencephaly as likely consequences of an altered neuronal migration process; abnormalities or agenesis of the midline commissural structures (anterior commissure, corpus callosum and fornix), hypoplasia of the oculomotor and optic nerves, dysmorphisms of the hind-brain as expression of axon guidance disorders. Dysmorphisms of the basal ganglia (fusion between the caudate nucleus and putamen with absence of the anterior limb of the internal capsule) and hippocampi were also observed. A rare form of leukoencephalopathy characterized by hypomyelination with atrophy of the basal ganglia an cerebellum (H-ABC) was also recently described. The present review, describing the structural and functional features of tubulin genes, aims to revise the main cerebral associated malformations and related clinical aspects, suggesting a genotype-phenotype correlation. © 2014 The Japanese Society of Child Neurology.
Kloosterman B.,Laboratory of Plant Breeding |
Kloosterman B.,Keygene NV |
Abelenda J.A.,CSIC - National Center for Biotechnology |
Gomez M.D.M.C.,Laboratory of Plant Breeding |
And 11 more authors.
Nature | Year: 2013
Potato (Solanum tuberosum L.) originates from the Andes and evolved short-day-dependent tuber formation as a vegetative propagation strategy. Here we describe the identification of a central regulator underlying a major-effect quantitative trait locus for plant maturity and initiation of tuber development. We show that this gene belongs to the family of DOF (DNA-binding with one finger) transcription factors and regulates tuberization and plant life cycle length, by acting as a mediator between the circadian clock and the StSP6A mobile tuberization signal. We also show that natural allelic variants evade post-translational light regulation, allowing cultivation outside the geographical centre of origin of potato. Potato is a member of the Solanaceae family and is one of the world's most important food crops. This annual plant originates from the Andean regions of South America. Potato develops tubers from underground stems called stolons. Its equatorial origin makes potato essentially short-day dependent for tuberization and potato will not make tubers in the long-day conditions of spring and summer in the northern latitudes. When introduced in temperate zones, wild material will form tubers in the course of the autumnal shortening of day-length. Thus, one of the first selected traits in potato leading to a European potato type is likely to have been long-day acclimation for tuberization. Potato breeders can exploit the naturally occurring variation in tuberization onset and life cycle length, allowing varietal breeding for different latitudes, harvest times and markets. © 2013 Macmillan Publishers Limited. All rights reserved.
The study, by a team from the University of Leeds' Astbury Centre for Structural Molecular Biology and the John Innes Centre in Norwich, describes the structure of an empty version of Cowpea Mosaic Virus (CPMV) and the molecular 'glue' that allows the virus to build itself and encapsulate its genome. The findings, published in the journal Nature Communications and based on revolutionary new electron microscopy, may be a crucial step to eventually allowing scientists to build custom versions of the virus that can carry medicines into the body and target disease. Lead author Dr Neil Ranson, Associate Professor of Structural Molecular Biology at the University of Leeds, said: "To use Cowpea Mosaic Virus as a drug delivery vehicle, we need to understand how it puts itself together, and to do that we need to understand its structure in solution in very fine detail. "Just a couple of years ago, that was impossible because we simply couldn't see complex biological systems in the detail required. A new generation of electron microscopes, however, is revolutionising our ability to peer into the virus' inner workings and understand how we might make it work for us." The Nature Communications paper investigates vital steps to understanding how safe, plant-based virus-like particles could be created in the future. Dr Ranson said: "The aim of our project is to understand how the virus can put itself together from very simple building blocks. If we understand that properly, we may be able to efficiently make the virus package drugs, and then target them towards specific places or diseases in the human body, such as cancer cells. "Plant viruses are ideal for such work—they are a huge evolutionary distance from us. You can't catch plant viruses. Our paper shows the structure of the empty virus shell in unprecedented detail, including a part of the protein that is essential for assembly but has never been seen before. The virus-like particles, which were made by our collaborators at the John Innes Centre in Norwich, have no genome and therefore no ability to reproduce themselves or mutate," Dr Ranson said. "We are left with elegant, highly efficient and stable structures that have evolved to a level of perfection that it is currently impossible for man-made designs to rival, and these could be a major asset in developing targeted medicines. We could in the future change the sequences on their protein shells and retarget them at the diseases we want to hit." The paper is a product of a revolution in electron microscopy—dubbed the "resolution revolution"—that is transforming the level of detail at which structural biologists can work. It includes some of the most detailed electron microscope structures of protein complexes yet published, and these form the basis of a detailed analysis of how the CPMV virus builds itself. The researchers show how the virus constructs a highly symmetrical, protein shell from five-sided 'pentons' each built from five copies of a protein subunit. At the heart of the assembly process is a segment of a key protein—the C-terminus of the small coat protein subunit—that acts as a dab of molecular glue to hold the pentons together as the virus' outer structure is built. The C-terminus is also essential for the virus to package its genes, but it is cleaved from the virus when it has done its job. This has made it impossible to observe using other structural techniques such as x-ray crystallography. Dr Emma Hesketh, a University of Leeds Research Fellow and the first author of the paper in Nature Communications, said: "The basic unit is very simple, so the virus only needs a very small amount of information to make a large protein shell. Not only is it very efficient but CPMV is known for building a very stable structure that doesn't break down easily. We need that stability if these structures are going to survive drug manufacture and be introduced into the human body." "The new electron microscopes used in this study allowed us to see the segment in detail and understand its real role," Dr Hesketh said. The team used new-generation 300-kilovolt electron microscopes equipped with direct electron-detecting cameras at the Medical Research Council (MRC) Laboratory of Molecular Biology in Cambridge. The microscopes are capable of more than 130,000-times magnification. Two of the latest generation of this type of electron microscope are part of a £17 million investment in the new Astbury Biostructure Laboratory and are due to be installed at the University of Leeds next year. "This equipment is completely transforming the level of detail at which we can interact with molecules. The new microscopes have more power but are also more stable and have sensors that directly detect the electron beam, rather than indirectly detecting it with optical sensors as the previous generation did. "In practice, that means that, for the first time, we are looking in atomic detail at the individual amino acids in complex biological systems. This opens the way to manipulating those amino acids and intervening in the function of molecules with unprecedented precision." Explore further: Pliable plant virus, a major cause of crop damage, yields its secrets after 75+ years More information: E. Hesketh et al, 'Mechanisms of assembly and genome packaging in an RNA virus revealed by high-resolution cryo-EM' Nature Communications, 2015. DOI: 10.1038/ncomms10113
WASHINGTON — This is your bedbug-size brain on drugs. Researchers at Johns Hopkins University in Baltimore are growing "mini-brains" — smaller than the period at the end of this sentence — that may contain enough human brain cells to be useful in studying drug addiction and other neurological diseases. The mini-brains, grown in a laboratory dish, could one day reduce the need for the use of laboratory animals to conduct this type of research or to test therapeutic drugs, the researchers said. Labs from around the world have been racing to grow these and other organoids — microscopic, yet primitively functional versions of livers, kidneys, hearts and brains grown from real human cells. The version of the mini-brain from Johns Hopkins represents an advance over others reported in the last three years, in that it is quickly reproducible and contains many types of brain cells that interact with each other, just like a real brain, the researchers said. The researchers, led by Dr. Thomas Hartung, director of the Johns Hopkins Center for Alternatives to Animal Testing, reported their progress on Feb. 13 at the annual meeting of the American Association for the Advancement of Science. [11 Body Parts Grown in the Lab] Hartung noted that the mini-brain cannot yet replace animal models in the study of neurological diseases. But he added that the concept, which until quite recently seemed years from maturity, may be realized in as little as 10 months. Growing organoids involves the use of cells called induced pluripotent stem (iPS) cells, a technology developed by Japanese researcher Shinya Yamanaka, who won the Nobel Prize in 2012 for that line of research. With iPS cell technology, scientists can theoretically turn back the clock in any type of mature cell — be it skin, muscle, bone, etc. — and bring it to a near-embryonic state. From there, cells can be coaxed into developing into any of a number of cell types, much in the same way that actual human embryonic cells develop into all the cell types that make up the human body. Several labs are growing mini-brains. The first researchers to accomplish this, in 2013, were Jüergen Knoblich of the Institute of Molecular Biotechnology in Vienna, Austria, and Madeline Lancaster of the MRC Laboratory of Molecular Biology in Cambridge, England. These researchers said they can grow globular mini-brains a few millimeters in diameter in about three months, and that these organoids may be ideal for the study of fetal brain development, including microcephaly, the incomplete brain growth seen in some infants that researchers say may be linked with the Zika virus. Hartung's group has taken a different approach to grow smaller mini-brains, about 350 microns (0.35 millimeters) across, but say their method has easier reproducibility, a greater diversity of brain cell types and takes less time — only 10 weeks. He described them as "Mini Coopers" in that they are small but identical, ideal for comparative studies, as opposed to the hand-crafted, custom-made "luxury cars" made in other labs. "This allows us not to compare different brains but to compare different drivers," Hartung said, referring to different experiments that could be performed on identical brain models. Hartung said his lab's mini-brains have a variety of glia cells (which support neurons) such as astrocytes and Schwann cells, as well as oligodendrocytes, which form the insulating myelin sheaths that enable nerve impulses — all in proportions similar to those found in the human brain. The mini-brains' three-dimensional structure and ability to carry neurotransmitters — chemical messengers such as dopamine that enable communication between neurons — provide a simple but relatively realistic platform to study what goes wrong in the brain in, say, drug addiction and how the problem can be remedied. Hartung said his group accomplishes this by starting with a type of adult skin cell called a fibroblast, inducing those cells back to the state of neural stem cells that give rise to all the cells of the brain and nervous system, and then growing them in a gently rolling, vibrating environment to create the 3D-ball structure. The lab has grown thousands of these mini-brains, each with about 20,000 cells. Missing for now in the mini-brain but present in a real brain, Hartung said, are immune cells, which come from a different line of stem cells. He said he hopes to incorporate these types of cells soon. Hartung said he may have a working mini-brain for laboratory experimentation by the end of 2016, which could be mailed to any laboratory in the world. [Top 3 Techniques for Creating Organs in the Lab] Once the mini-brain model is mature, "no one should have the excuse to still use animal models, which come with tremendous disadvantages for brain studies in particular," Hartung said. "While rodent models have been useful, we are not 150-lb. rats. And even though we are not balls of cells, either, you can often get much better information from these balls of cells than from rodents." Hartung added that upward of 95 percent of therapeutic drugs for neurological orders that look promising in rodent studies fail in humans because of the intrinsic brain differences between the species. The mini-brain model is well-suited for studying brain addiction, in that scientists can study how drugs can destroy glia cells. Such destruction leads to the death of neurons and poorer transmission of neural impulses, Hartung said. Hartung's group is investigating the possibility of using the mini-brain to study the effect of Zika virus on a developing brain. Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, Bad Medicine, appears regularly on Live Science. 10 Things You Didn't Know About the Brain 6 Foods That Are Good for Your Brain Copyright 2016 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.