Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A big surprise: Young nerve cells can rewind their developmental clocks

02.01.2004


Scientists have identified a gene in the cerebral cortex that apparently controls the developmental clock of embryonic nerve cells, a finding that could open another door to tissue replacement therapy in the central nervous system. In a new study, the researchers found that they could rewind the clock in young cortical cells in mice by eliminating a gene called Foxg1. The finding could potentially form the basis of a new method to push progenitor cells in the brain to generate a far wider array of tissue than is now possible.



The study, led by researchers at NYU School of Medicine, is published in the January 2, 2004 issue of Science magazine.

"What we found was a complete surprise," says Gordon Fishell, Ph.D., Associate Professor in the Department of Cell Biology at New York University School of Medicine. "No one had believed that it was possible to push back the birth date of a cortical neuron. There is this central tenet governing the process of brain development, which says that late progenitor cells [forerunners of mature cell types] cannot give rise to cell types produced earlier in development," he explains.


"Consequently, while some populations of stem cells exist in the adult brain, these cells are restricted to producing only a subset of cell types," notes Dr. Fishell. "If one’s goal is to produce cells for replacement therapy, some method must be found to turn back the clock and allow adult stem cells to give rise to the wide variety of cells made during normal brain development."

Eseng Lai, Ph.D., of Merck & Co. and one of the study’s co-authors, cloned the Foxg1 gene while he was working at Memorial Sloan-Kettering Cancer Center in New York. He also did seminal work in the late 1990s showing that when the gene is eliminated in embryonic mice, the brain’s cerebral hemispheres barely develop. Subsequent work demonstrated that the gene played a role in the early phases of cortical development.

The cerebral cortex is massively folded gray matter incorporating billions of neurons. Despite its complexity, the cortex comprises six orderly layers of cortical cells that are laid down during development at a precise time and in a precise sequence. In the study, the researchers asked which cortical cell types embryonic mice lacking Foxg1 can generate. Carina Hanashima, Ph.D., a postdoctoral fellow in Dr. Fishell’s laboratory who had previously worked with Dr. Lai, conducted a series of experiments that made the analysis possible.

The progenitor cells for the cortex are born in a zone deep in the brain, and migrate to their assigned layer, depending on the time they are born. So a cortical cell’s identity is based on the date of its birth. The first cortical cells to be born populate layer 1, the most superficial layer, which is made up of special Cajal-Retzius (CR) cells. The next cells born migrate to the innermost layer, layer 6. Subsequent layers pile up above layer 6 (between layers 6 and 1), and in descending numerical order from 5 to 2. Each layer has a specific type of neuron associated with it.

The researchers looked at the cortical layers in embryonic mice at a time in their development when layers 1, 6, and 5, would normally have already been formed. In mice lacking the Foxg1 gene, the researchers found that only layer 1, which is made up of CR cells, was present, and these cells were abundant. The absence of other cell types implicated the gene in producing later-born cortical cell types.

One of the ways the scientists were able to identify CR cells was by the expression of a protein called reelin, which plays a vital role in building the developing brain and is only present in CR cells. Mice lacking the protein stumble around so much that they were named "reelers." The cortical layers in these mice are scrambled. In recent years, reelin deficiencies have been linked to such human disorders as schizophrenia and epilepsy.

In subsequent experiments, the researchers asked how the overproduction of CR cells occurs. They used a clever biochemical manipulation that served as a kind of genetic stop watch, allowing them to temporarily turn off the Foxg1 gene in late progenitor cells, after the normal birth date of CR cells had passed. In this way, they observed that cortical cells destined to become layer 5 became CR cells instead. Apparently, the gene orchestrates the program responsible for ensuring that the cortical layers of the cerebral cortex are laid down in a precise sequence. When the gene is inactivated or turned off, the program seems to revert to its earliest stage.

The researchers do not know how late in the game they can play their genetic tricks. If they turn off the Foxg1 gene at a later time in development, such as when cortical layers 2 or 3 are forming, will progenitor neuronal cells still become CR cells? Are there other genes that control the developmental clock? If such genes exist, it may be possible to turn these genes off in adult neural stem cells, and thereby generate a far broader array of tissue than otherwise possible. "I would say that the chances of this happening are very remote," says Dr. Fishell, "but then again, I never thought that the clock could have been turned back in neuronal progenitor cells."

The authors of the study are Gordon Fishell and Carina Hanashima of NYU School of Medicine; Eseng Lai of Merck; Suzanne Li of Memorial Sloan-Kettering Cancer Center; and Lijian Shen of Weill Medical College of Cornell University.

Pamela McDonnell | EurekAlert!
Further information:
http://www.med.nyu.edu/

More articles from Studies and Analyses:

nachricht Statistical method developed at TU Dresden allows the detection of higher order dependencies
07.02.2020 | Technische Universität Dresden

nachricht Novel study underscores microbial individuality
13.12.2019 | Bigelow Laboratory for Ocean Sciences

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A step towards controlling spin-dependent petahertz electronics by material defects

The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.

Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

Im Focus: Skyrmions like it hot: Spin structures are controllable even at high temperatures

Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices

The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...

Im Focus: Making the internet more energy efficient through systemic optimization

Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.

Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.

Im Focus: New synthesis methods enhance 3D chemical space for drug discovery

After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.

"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

 
Latest News

Journey to the center of Mars

20.02.2020 | Physics and Astronomy

Laser writing enables practical flat optics and data storage in glass

20.02.2020 | Physics and Astronomy

New graphene-based metasurface capable of independent amplitude and phase control of light

20.02.2020 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>