Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists identify first gene in programmed axon degeneration

08.06.2012
Discovery provides evidence of new therapeutic target that could delay axon decay

Degeneration of the axon and synapse, the slender projection through which neurons transmit electrical impulses to neighboring cells, is a hallmark of some of the most crippling neurodegenerative and brain diseases such as amyotrophic lateral sclerosis (ALS), Huntington's disease and peripheral neuropathy.

Scientists have worked for decades to understand axonal degeneration and its relation to these diseases. Now, researchers at the University of Massachusetts Medical School are the first to describe a gene – dSarm/Sarm1 – responsible for actively promoting axon destruction after injury. The research, published today online by Science, provides evidence of an exciting new therapeutic target that could be used to delay or even stop axon decay.

"This discovery has the potential to have a profound impact on our understanding of neurodegenerative diseases, much like the discovery of apoptosis (programmed cell death) fundamentally changed our understanding of cancer," said Marc R. Freeman, PhD, associate professor of neurobiology at the University of Massachusetts Medical School and lead investigator on the study. "Identification of this gene allows us to start asking exciting new questions about the role of axon death in neurodegenerative diseases. For example, is it possible that these pathways are being inappropriately activated to cause premature axon death?"

For more than a century, scientists believed that injured axons severed from the neuron cell body passively wasted away due to a lack of nutrients. However, a mouse mutation identified in the early 1990s – called slow Wallerian degeneration (Wlds) – was able to suppress axon degeneration for weeks. This finding forced scientists to reassess Wallerian degeneration, the process through which an injured axon degenerates, as a passive process and consider the possibility that an active program of axon auto-destruction, akin to apoptotic death, was at work instead.

If Wallerian degeneration was an active process, hypothesized Dr. Freeman, a Howard Hughes Medical Institute Early Career Scientist, then it should be possible through forward genetic screens in Drosophila to identify mutants exhibiting Wlds-like axon protection. Freeman and colleagues screened more than 2,000 Drosophila mutants for ones that exhibited long-term survival of severed axons. Freeman says this was a heroic effort on the part of his colleagues. The screen took place over the next two and a half years, and involved seven students and post-docs in the Freeman lab—Jeannette M. Osterloh, A. Nicole Fox, PhD, Michelle A. Avery, PhD, Rachel Hackett, Mary A. Logan, PhD, Jennifer M. MacDonald, Jennifer S. Zeigenfuss—who performed the painstaking and labor-intensive experiments needed on each Drosophila mutant to identify flies that suppressed axonal degeneration after nerve injury.

Through these tests, they identified three mutants (out of the 2,000 screened) where severed axons survived for the lifespan of the fly. Next generation sequencing and chromosome deficiency mapping techniques were then used to isolate the single gene affected in all three – dSarm. These were loss-of-function alleles, meaning that Drosophila unable to produce the dSarm/Sarm1 molecule exhibited prolonged axon survival for as many as 30 days after injury. Freeman and colleagues went on to show that mice lacking Sarm1, the mammalian homolog of dSarm, also displayed remarkable preservation of injured axons. These findings provided the first direct evidence that Wallerian degeneration was driven by a conserved axonal death program and not a passive response to axon injury.

"For 20 years people have been looking for a gene whose normal function is to promote axon degeneration," said Osterloh, first author on the study. "Identification of the dSarm/Sarm1 gene has enormous therapeutic potential, for example as a knockdown target for patients suffering from diseases involving axonal loss."

The next step for Freeman and colleagues is to identify additional genes in the axon death pathway and investigate whether any have links with specific neurodegenerative diseases. "We're already working with scientists at UMMS to understand the role axon death plays in ALS and Huntington's disease," said Freeman. "We are very excited about the possibility that these findings could have broad therapeutic potential in many neurodegenerative diseases."

About the University of Massachusetts Medical School

The University of Massachusetts Medical School, one of the fastest growing academic health centers in the country, has built a reputation as a world-class research institution, consistently producing noteworthy advances in clinical and basic research. The Medical School attracts more than $270 million in research funding annually, 80 percent of which comes from federal funding sources. The mission of the Medical School is to advance the health and well-being of the people of the commonwealth and the world through pioneering education, research, public service and health care delivery with its clinical partner, UMass Memorial Health Care.

Jim Fessenden | EurekAlert!
Further information:
http://www.umassmed.edu

More articles from Life Sciences:

nachricht Scientists unlock ability to generate new sensory hair cells
22.02.2017 | Brigham and Women's Hospital

nachricht New insights into the information processing of motor neurons
22.02.2017 | Max Planck Florida Institute for Neuroscience

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Microhotplates for a smart gas sensor

22.02.2017 | Power and Electrical Engineering

Scientists unlock ability to generate new sensory hair cells

22.02.2017 | Life Sciences

Prediction: More gas-giants will be found orbiting Sun-like stars

22.02.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>