A new genetic mutation that causes familial amyotrophic lateral sclerosis (ALS), a fatal neurological disorder also known as Lou Gehrig's Disease, has been identified by a team of scientists led by researchers at the University of Massachusetts Medical School (UMMS).
Mutations to the profilin (PFN1) gene, which is essential to the growth and development of nerve cell axons, is estimated to account for one to two percent of inherited ALS cases. The finding, described today in the online edition of Nature, points to defects in a neuron's cytoskeleton structure as a potential common feature among diverse ALS genes.
"This discovery identifies what may possibly be a common biological mechanism involved across familial ALS cases regardless of genetics," said John Landers, PhD, associate professor of neurology and senior author of the study. "We know of at least three other ALS genes, in addition to PFN1, that adversely impact axon growth. If indeed, this is part of the disease's mechanism, then it might also be a potential target for therapeutics."
Robert Brown, MD, DPhil, a co-author on the study and chair of neurology at UMass Medical School, said "Dr. Landers has done great work in defining this new pathway for motor neuron death. We are delighted to have identified the defects in families from the U.S., Israel and France that we have been investigating for several years. Our finding is particularly exciting because it may provide new insights into ALS treatment targets."
ALS is a progressive, neurodegenerative disorder affecting the motor neurons in the central nervous system. As motor neurons die, the brain's ability to send signals to the body's muscles is compromised. This leads to loss of voluntary muscle movement, paralysis and eventually respiratory failure. The cause of most cases of ALS is not known. Approximately 10 percent of cases are inherited. Though investigators at UMass Medical School and elsewhere have identified several genes shown to cause inherited or familial ALS, almost 50 percent of these cases have an unknown genetic cause.
The current Nature study details the discovery of the PFN1 gene mutation among two large ALS families. Both families were negative for known ALS-causing mutations and displayed familial relationships that suggested a dominant inheritance mode for the disease. For each family, two affected members with maximum genetic distance were selected for deep DNA sequencing. To identify an ALS-causing mutation, genetic variations between the family members were identified and screened against known databases of human genetic variation, such as the 1000 Genomes Project. This narrowed down the resulting number of candidate, ALS-causing mutations to two within the first family and three within the second. Interestingly, both families contained different mutations within the same gene – PFN1, the likely causative mutation. With additional screening, the team documented that in a total of 274 families sequenced, seven contained a mutation to the PFN1 gene, establishing it as a likely cause for ALS.
While it is not certain how the PFN1 mutation causes ALS, the cellular functions it controls within the motor neurons are responsible for regulation of a number of activities, including the growth and development of the axon, the slender projection through which neurons transmit electrical impulses to neighboring cells, such as muscle. When introduced into motor neuron cells, normal PFN1 protein was found diffused throughout the cytoplasm. Conversely, the mutant PFN1 observed in ALS patients was found to collect in dense aggregates, keeping it from functioning properly. Motor neurons producing mutated PFN1 showed markedly shorter axon outgrowth.
"The discovery that mutant PFN1 interferes with axon outgrowth was very exciting to us," said Claudia Fallini, PhD, a postdoctoral researcher at Emory University School of Medicine who collaborated with the UMass Medical School authors to investigate PFN1's functions in cultured motor neurons. "It suggests that alterations in actin dynamics may be an important mechanism at the basis of motor neuron degeneration."
"In healthy neurons, PFN1 acts almost like a railroad tie for fibrous filaments called actin, which make up the axon" said Landers. "PFN1 helps bind these filaments to each other, promoting outgrowth of the axon. Without properly functioning PFN1 these filaments can't come together. Here we show that mutant PFN1 may contribute to ALS pathogeneses by accumulating in these aggregates and altering the actin dynamics in a way that inhibits axon outgrowth."
Drs. Landers and Brown are members of the Neurotherapeutics Institute at the University of Massachusetts Medical School.
Grant support for this project was provided by the NIH/NINDS 1R01NS065847 JEL, 1R01NS050557 RHB, RC2-NS070-342 RHB, Project ALS and P2ALS, the Angel Fund for ALS Research, the Muscular Dystrophy Association MDA173851 WR and AriSLA co-financed with support of 5x1000 Healthcare research of the Ministry of Health EXOMEFALS NT, CG, VS, JEL. Support was also provided by an SMA Europe fellowship to CF.
About the University of Massachusetts Medical School
The University of Massachusetts Medical School 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 work of UMMS researcher Craig Mello, PhD, an investigator of the prestigious Howard Hughes Medical Institute (HHMI), and his colleague Andrew Fire, PhD, then of the Carnegie Institution of Washington, toward the discovery of RNA interference was awarded the 2006 Nobel Prize in Physiology or Medicine and has spawned a new and promising field of research, the global impact of which may prove astounding. UMMS is the academic partner of UMass Memorial Health Care, the largest health care provider in Central Massachusetts.
Jim Fessenden | EurekAlert!
Zap! Graphene is bad news for bacteria
23.05.2017 | Rice University
Discovery of an alga's 'dictionary of genes' could lead to advances in biofuels, medicine
23.05.2017 | University of California - Los Angeles
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
23.05.2017 | Physics and Astronomy
23.05.2017 | Life Sciences
23.05.2017 | Medical Engineering