Organisms are adapted to their environment through their individual characteristics, like body size and body weight. Such complex traits are usually controlled by many genes.
One giant mouse weighs more than six 'mini-mice' of the same age. The biggest mice in the world evolved through targeted breeding over many generations. Scientists can use these animals to identify the genes responsible for body growth. Credit: Lutz Bunger, University of Edinburgh
As a result, individuals show tremendous variations and can also show subtle gradations. Researchers from the Max Planck Institute for Evolutionary Biology in Plön have now investigated how evolution alters such traits through selection. To do this, they examined the genomes of mouse lines that were selected independently of each other for extreme body size. They discovered that a number of genomic regions, or loci, have undergone changes in genes that underlie this genetically complex characteristic. They also discovered many new genes that play a role in the regulation of body weight, which can lead to obesity.
The Plön-based researchers obtained mouse lines that have been specifically selected for extreme body weight for 25 years. The mice, which have been bred for over 150 generations, belong to seven different strains and now weigh two to four times more than mice of normal weight. The Max Planck scientists were able to identify a total of 67 loci on the genome that had changed in the heavy mice. The different strains have become so similar in these regions as a result of the extreme artificial selection pressure, that the genomes of the heavier but unrelated animals were more similar at these loci than with their closely related sibling mouse strains of those with normal weight. This clearly indicates that these loci are involved in the regulation of body weight.
The discovered loci regulate, among other things, energy balance, metabolic processes and growth. The Gpr133 gene, which is expressed in the adrenal gland, is a novel gene and presumably controls body weight through the release of hormones. The second identified gene, Gpr10, which is active in the hypothalamus in the brain, was found to influence appetite and metabolic rates. Accordingly, the team has also identified genes for the regulation of fat cells and for taste and olfactory perception that can affect body weight. Moreover, many of the regions discovered coincide with loci on the human genome that influence body weight. "These genes probably also determine body weight in humans, because size and body weight are such tightly linked processes. This evolutionary connection serves as a nice confirmation," says Frank Chan from the Max Planck Institute for Evolutionary Biology.
Interestingly, the genome of mouse populations living in the wild on remote islands, shaped by natural selection, have also changed in similar ways to the animals bred in the laboratory. For example, on the Faroe Islands and St Kilda off the coast of Scotland, mice populations have evolved to be among the largest mice in the world. The researchers have found that island mice retained little variation specifically at the same genomic loci that changed in the heavy laboratory-bred animal strains. These telltale signs suggest that artificial selection in the laboratory changes the same loci in the genome as natural selection.
Thus, when complex characteristics must adapt to altered environmental conditions, selection affects many responsible genes simultaneously. These then change in parallel and contribute to varying extents to the organism's capacity for adaptation. In this way, the genetic basis of complex traits can be decoded through parallel selection.
Original article: Chan, Y. F. et al. Parallel selection mapping using artificially selected mice reveals body weight control loci.
Current Biology: Volume 22, Issue 9, 8 May 2012, Pages 794 doi:10.1016/j.cub.2012.03.011
Dr. Y. Frank Chan | EurekAlert!
Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden
The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy