By reprogramming skin cells from Parkinson's disease patients with a known genetic mutation,
researchers at the
Salk Institute for Biological Studies have identified damage to neural stem cells as a powerful player in the disease. The findings, reported online October 17th in
Nature, may lead to new ways to diagnose and treat the disease.
The
scientists found that a common mutation to a gene that produce the
enzyme LRRK2, which is responsible for both familial and sporadic cases
of Parkinson's disease, deforms the membrane surrounding the nucleus of a
neural stem cell. Damaging the nuclear architecture leads to
destruction of these powerful cells, as well as their decreased ability
to spawn functional neurons, such as the ones that respond to dopamine.
The
researchers checked their laboratory findings with brain samples from
Parkinson's disease patients and found the same nuclear envelope
impairment.
 |
The Salk researchers found that a common genetic mutation
involved in
Parkinson's disease deforms the membranes
(green) surrounding the nuclei
(blue) of neural stem cells.
The discovery may lead to new ways to
diagnose and treat the disease. |
"This discovery helps explain how Parkinson's
disease, which has been traditionally associated with loss of neurons
that produce dopamine and subsequent motor impairment, could lead to
locomotor dysfunction and other common non-motor manifestations, such as
depression and anxiety," says
Juan Carlos Izpisua Belmonte, a professor in Salk's
Gene Expression Laboratory,
who led the research team. "Similarly, current clinical trials explore
the possibility of neural stem cell transplantation to compensate for
dopamine deficits. Our work provides the platform for similar trials by
using patient-specific corrected cells. It identifies degeneration of
the nucleus as a previously unknown player in Parkinson's."
Although
the researchers say that they don't yet know whether these nuclear
aberrations cause Parkinson's disease or are a consequence of it, they
say the discovery could offer clues about potential new therapeutic
approaches.
For example, they were able to use targeted
gene-editing technologies to correct the mutation in patient's nuclear
stem cells. This genetic correction repaired the disorganization of the
nuclear envelope, and improved overall survival and functioning of the
neural stem cells.
They were also able to chemically inhibit
damage to the nucleus, producing the same results seen with genetic
correction. "This opens the door for drug treatment of Parkinson's
disease patients who have this genetic mutation," says Belmonte.
The
new finding may also help clinicians better diagnose this form of
Parkinson's disease, he adds. "Due to the striking appearance in patient
samples, nuclear deformation parameters could add to the pool of
diagnostic features for Parkinson's disease," he says.
The
research team, which included scientists from China, Spain, and the
University of California, San Diego, and Scripps Research Institute,
made their discoveries using human induced pluripotent stem cells
(iPSCs). These cells are similar to natural stem cells, such as
embryonic stem cells, except that they are derived from adult cells.
While generation of these cells has raised expectations within the
biomedical community due to their transplant potential - the idea that
they could morph into tissue that needs to be replaced - they also
provide exceptional research opportunities, says Belmonte.
"We
can model disease using these cells in ways that are not possible using
traditional research methods, such as established cell lines, primary
cultures and animal models," he says.
In this study, the
researchers used skin fibroblast cells taken from Parkinson's disease
patients who have the LRRK2 mutation, and they reprogrammed them to iPSC
stem cells and developed them into neural stem cells.
Then, by
using an approach to model what happens when these neural stem cells
aged, they found that older Parkinson disease neural stem cells
increasingly displayed deformed nuclear envelopes and nuclear
architecture. "This means that, over time, the LRRK2 mutation affects
the nucleus of neural stem cells, hampering both their survival and
their ability to produce neurons," Belmonte says.
"It is the
first time to our knowledge that human neural stem cells have been shown
to be affected during Parkinson's pathology due to aberrant LRRK2," he
says. "Before development of these reprogramming technologies, studies
on human neural stem cells were elusive because they needed to be
isolated directly from the brain."
Belmonte speculates that the
dysfunctional neural stem cell pools that result from the LRRK2 mutation
might contribute to other health issues associated with this form of
Parkinson's disease, such as depression, anxiety and the inability to
detect smells.
Finally, the study shows that these reprogramming
technologies are very useful for modeling disease as well as
dysfunction caused by aging, Belmonte says.
source: http://www.newswise.com/articles/salk-scientists-pinpoint-key-player-in-parkinson-s-disease-neuron-loss