Posts tagged nervous system
Articles and news from the latest research reports.
Tracking Fruit Flies to Understand the Function of the Nervous System
Researchers at the Freie Universität Berlin, Germany and the Center for Genomic Regulation (CRG) in Barcelona, Spain have designed open source software that allows tracking the position of Drosophila fruit flies as well as their larvae during behavioral experiments.
Dr. Matthieu Louis, the head of the Spanish team explains: “Until we developed these tools, many researchers relied on expensive commercial hardware and software to study the behavior of larvae and adult flies. Now, virtually anybody can do this kind of research. The value of the software we are proposing is that they are written in a simple programming language, which facilitates their adaptation to new experimental paradigms” Inexpensive, ubiquitous digital cameras, such as webcams are sufficient to capture the movements of the animals and the open source software packages both for the evaluation the video feeds for tracking as well as for later data analysis are available for free (http://buridan.sourceforge.net).
"Apart from ruining your glass of expensive red wine, Drosophila is a central model organism to study, amongst other problems, how brains work. By carefully watching whether flies turn left or right, we aim at understanding how humans make decisions” explained Dr. Alejandro Gomez-Marin, first author in the Spanish team.
Ion selectivity in neuronal signaling channels evolved twice in animals
July 26, 2012
Excitation of neurons depends on the selected influx of certain ions, namely sodium, calcium and potassium through specific channels. Obviously, these channels were crucial for the evolution of nervous systems in animals. How such channels could have evolved their selectivity has been a puzzle until now. Yehu Moran and Ulrich Technau from the University of Vienna together with Scientists from Tel Aviv University and the Woods Hole Oceanographic Institution (USA) have now revealed that voltage-gated sodium channels, which are responsible for neuronal signaling in the nerves of animals, evolved twice in higher and lower animals. These results were published in Cell Reports.
Close-up of nervous system of a transgenic polyp of the sea anemone Nematostella vectensis, in which a red fluorescent reporter gene (mCherry) is driven by the regulatory sequence of the neuronal ELAV gene. The picture shows the diffuse structure of the nervous system, but also reveals the accumulation of longitudinal axonal tracts along the eight gastric tissue folds (mesenteries). Credit: Copyright: U. Technau
The opening and closing of ion channels enable flow of ions that constitute the electrical signaling in all nervous systems. Every thought we have or every move we make is the result of the highly accurate opening and closing of numerous ion channels. Whereas the channels of most lower animals and their unicellular relatives cannot discern between sodium and calcium ions, those of higher animals are highly specific for sodium, a characteristic that is important for fast and accurate signaling in complex nervous system.
Surprising results in sea anemones and jellyfish
However, the researchers found that a group of basal animals with simple nerve nets including sea anemones and jellyfish also possess voltage-gated sodium channels, which differ from those found in higher animals, yet show the same selectivity for sodium. Since cnidarians separated from the rest of the animals more than 600 million years ago, these findings suggest that the channels of both cnidarians and higher animals originated independently twice, from ancient non-selective channels which also transmit calcium.
Since many other processes of internal cell signaling are highly dependent on calcium ions, the use of non-selective ion channels in neurons would accidently trigger various signaling systems inside the cells and will cause damage. The evolution of selectivity for sodium ions is therefore considered as an important step in the evolution of nervous systems with fast transmission. This study shows that different parts of the channel changed in a convergent manner during the evolution of cnidarians and higher animals in order to perform the same task, namely to select for sodium ions.
This demonstrates that important components for the functional nervous systems evolved twice in basal and higher animals, which suggests that more complex nervous systems that rely on such ion-selective channels could have also evolved twice independently.
Source: PHYS.ORG
Mechanism Prevents Alterations in Neuronal Production During Embryonic Development
ScienceDaily (June 26, 2012) — Scientists from the University of Barcelona (UB) in collaboration with a multidisciplinary team from the Spanish National Research Council (CSIC) has discovered a mechanism that prevents alterations in neurogenesis, the process of neuronal formation, during the development of the nervous system in vertebrates. The study, published in the journal Development, relates these distortions to the natural presence of a molecule that inhibits the neuronal formation at the regions adjacent to the tissue suitable for neurogenesis.
Left: altered neurogenic wavefront in the absence of Delta. Right: normal neurogenic wavefront. (Credit: Image courtesy of Universidad de Barcelona)
Through a theoretical and computational analysis of the retina, scientists have found that lateral inhibition, a process that regulates the generation of neurons in the central nervous system, undergoes alterations at the neurogenic wavefront (i.e. the edge between the regions that generate neurons and the adjacent areas, where neurogenesis has not yet begun).
"The study shows that the absence of the Delta molecule at the adjacent regions reduces the robustness of the neurogenic process, often resulting in an increased production of neurons or in the presence of morphological alterations of the wavefront. These alterations could be catastrophic for the proper development of the nervous system," explains José María Frade, researcher from the CSIC, at the Cajal Institute.
Lateral inhibition during embryonic development aims to control the amount of neurons that are formed. It consists in cells that inhibit other neighbouring cells, promoting neuronal differentiation. “Neuronal precursor cells expressing high levels of Delta induce inhibitory signals in neighbouring cells. These inhibitory signals reduce the capacity of these cells to express Delta itself and, in turn, facilitate the differentiation of the high Delta-expressing precursors. Thus, the massive generation of neurons is avoided and the orderly production of different types of neurons necessary for brain function is facilitated,” explains researcher from the CSIC Saúl Ares, who works at the Spanish National Biotechnology Centre.
Previous theoretical studies suggested that the lateral inhibition process can be altered at the neurogenic edges. “However, the importance of this inhibition process had not been appropriately acknowledged. Our study demonstrates the relevance of Delta expression ahead of the neurogenic wavefront, provides predictions and explains developmental alterations resulting from the absence of Delta. It also represents a breakthrough in the theoretical field because it formulates a front propagation mechanism based on self-regulatory mechanisms,” points out Marta Ibañes, researcher from the UB.
According to researchers, this study provides a new concept that will attract the attention of neurobiologists who work both in the development of the nervous system and in several pathologies derived from neuronal development.
Source: Science Daily
Clues to Nervous System Evolution Found in Nerve-Less Sponge
ScienceDaily (June 18, 2012) — UC Santa Barbara scientists turned to the simple sponge to find clues about the evolution of the complex nervous system and found that, but for a mechanism that coordinates the expression of genes that lead to the formation of neural synapses, sponges and the rest of the animal world may not be so distant after all. Their findings, titled “Functionalization of a protosynaptic gene expression network,” are published in the Proceedings of the National Academy of Sciences.
The genes of Amphimedon queenslandica, a marine sponge native to the Great Barrier Reef, Australia, have been fully sequenced, allowing the researchers to monitor gene expression for signs of neural development. (Credit: UCSB)
"If you’re interested in finding the truly ancient origins of the nervous system itself, we know where to look," said Kenneth Kosik, Harriman Professor of Neuroscience Research in the Department of Molecular, Cellular & Developmental Biology, and co-director of UCSB’s Neuroscience Research Institute.
That place, said Kosik, is the evolutionary period of time when virtually the rest of the animal kingdom branched off from a common ancestor it shared with sponges, the oldest known animal group with living representatives. Something must have happened to spur the evolution of the nervous system, a characteristic shared by creatures as simple as jellyfish and hydra to complex humans, according to Kosik.
A previous sequencing of the genome of the Amphimedon queenslandica — a sponge that lives in Australia’s Great Barrier Reef — showed that it contained the same genes that lead to the formation of synapses, the highly specialized characteristic component of the nervous system that sends chemical and electrical signals between cells. Synapses are like microprocessors, said Kosik explaining that they carry out many sophisticated functions: They send and receive signals, and they also change behaviors with interaction — a property called “plasticity.”
"Specifically, we were hoping to understand why the marine sponge, despite having almost all the genes necessary to build a neuronal synapse, does not have any neurons at all," said the paper’s first author, UCSB postdoctoral researcher Cecilia Conaco, from the UCSB Department of Molecular, Cellular, and Developmental Biology (MCDB) and Neuroscience Research Institute (NRI). "In the bigger scheme of things, we were hoping to gain an understanding of the various factors that contribute to the evolution of these complex cellular machines."
This time the scientists, including Danielle Bassett, from the Department of Physics and the Sage Center for the Study of the Mind, and Hongjun Zhou and Mary Luz Arcila, from NRI and MCDB, examined the sponge’s RNA (ribonucleic acid), a macromolecule that controls gene expression. They followed the activity of the genes that encode for the proteins in a synapse throughout the different stages of the sponge’s development.
"We found a lot of them turning on and off, as if they were doing something," said Kosik. However, compared to the same genes in other animals, which are expressed in unison, suggesting a coordinated effort to make a synapse, the ones in sponges were not coordinated.
"It was as if the synapse gene network was not wired together yet," said Kosik. The critical step in the evolution of the nervous system as we know it, he said, was not the invention of a gene that created the synapse, but the regulation of preexisting genes that were somehow coordinated to express simultaneously, a mechanism that took hold in the rest of the animal kingdom.
The work isn’t over, said Kosik. Plans for future research include a deeper look at some of the steps that lead to the formation of the synapse; and a study of the changes in nervous systems after they began to evolve.
"Is the human brain just a lot more of the same stuff, or has it changed in a qualitative way?" he asked.
Source: Science Daily
The Importance Of Nervous System Structure And Neural Wiring Evolution
Article Date: 24 Feb 2012 - 8:00 PST
A new study, in this week’s online edition of the Proceedings of the National Academy of Sciences , shows an incredible degree of biological diversity in a surprising location, i.e. in a single neural connection in the body wall of flies. The finding opens up a new spectrum of interesting questions regarding the importance of the nervous system structure and the evolution of neural wiring.
Geneticist Barry Ganetzky, Steenbock Professor of Biological Sciences at the University of Wisconsin-Madison declared:
”We know almost nothing about the evolution of the nervous system, although we know it has to happen - behaviors change, complexity changes, there is the addition of new neurons, formation of different synaptic connections.”
The finding proves even more astounding given that Ganetzky and his graduate student Megan Campbell discovered the unexpected diversity in a location very familiar to scientists, i.e. the neuromuscular junction 4 (NMJ4), the location where a single motor neuron contacts a particular muscle in the fly body wall to drive its activity. The synapses where neurons link to their neuronal or muscular targets have a complex structural form, looking like miniature trees decorated with tiny bulbs that are the nerve terminals (synaptic boutons).