The embryonic nervous system is a hollow tube consisting of elongated neural progenitor cells, which extend from the inner to the outer surface of the tube. In a section inside the tube called the ventricular zone (VZ), these cells divide and produce immature neurons that migrate outwards. This involves well-characterized movements that are coupled to cell division. After a cell divides at the inner-most VZ region, the nuclei migrate to the outer region, where they synthesize new DNA before returning.
Figure 1: Cell nuclei of brain cells accumulate at the outer surface of the ventricular zone when the cell cycle is blocked. Copyright : 2011 Yoichi Kosodo et al.
To determine how the direction of movement is coupled to the cell division cycle, Yoichi Kosodo and colleagues in Matsuzaki's group at RIKEN Center for Developmental Biology labeled nuclei in the embryonic mouse brain with green fluorescent protein. This enabled them to not only track their movements in cultured brain slices using a video-imaging system, but also correlate their positions with phases of the cell cycle. They found that outward nuclear migration involves back and forth ‘ratcheting’ motions and occurs more slowly than inward migration.
Importantly, they discovered that blocking the cell cycle before DNA synthesis caused nuclei to accumulate at the outer VZ surface (Fig.1), and reduced outward migration. Nuclei migrating back inwards normally crowd out those just finished dividing, thus pushing them away from the inner VZ surface.
Examining their results further, the researchers computationally modeled nuclear migration, and incorporated fluorescent magnetic beads into the inner VZ surface. They observed the beads moving away from the inner VZ surface, and remaining at its outer region.
The researchers also showed that inward migration is closely linked to microtubule reorganization orchestrated by a protein called Tpx2, which is initially expressed in the nuclei of progenitors before moving to the mitotic spindle. This separates newly duplicated chromosomes. Translocation of Tpx2 to the cell region nearest the inner VZ surface promotes migration of the nucleus in that direction by microtubule re-organization. Reducing Tpx2 activity lowered the velocity of inward migration, but introducing the human Tpx2 gene into the cells lacking Tpx2 restored normal speed.
The researchers conclude that two mechanisms maintain brain structure during development. One couples cell migration to the cell cycle, and occurs independently of other cells, with Tpx2 providing an active driving force; and the other involves interactions between the nuclei in the VZ.
The corresponding author for this highlight is based at the Laboratory for Cell Asymmetry, RIKEN Center for Developmental Biology
 Kosodo, Y., Suetsugu, T., Suda, M., Mimori-Kiyosue, Y., Toida, K., Baba, S. A., Kimura, A. & Matsuzaki, F. Regulation of interkinetic nuclear migration by cell cycle-coupled active and passive mechanisms in the developing brain. The EMBO Journal 30, 1690–1704 (2011).
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