Lipid levels during prenatal brain development impact autism

In a groundbreaking York University study, researchers have found that abnormal levels of lipid molecules in the brain can affect the interaction between two key neural pathways in early prenatal brain development, which can trigger autism. And, environmental causes such as exposure to chemicals in some cosmetics and common over-the-counter medication can affect the levels of these lipids, according to the researchers.

“We have found that the abnormal level of a lipid molecule called Prostaglandin E2 in the brain can affect the function of Wnt proteins. It is important because this can change the course of early embryonic development,” explains Professor Dorota Crawford in the Faculty of Health and a member of the York Autism Alliance Research Group.

This is the first time research shows evidence for cross-talk between PGE2 and Wnt signalling in neuronal stem cells, according to the peer reviewed study published at Cell Communication and Signaling.

Lead researcher and York U doctoral student Christine Wong adds, “Using real-time imaging microscopy, we determined that higher levels of PGE2 can change Wnt-dependent behaviour of neural stem cells by increasing cell migration or proliferation. As a result, this could affect how the brain is organized and wired.  Moreover, we found that an elevated level of PGE2 can increase expression of Wnt-regulated genes — Ctnnb1, Ptgs2, Ccnd1, and Mmp9. “Interestingly, all these genes have been previously implicated in various autism studies.”

Autism is considered to be the primary disorder of brain development with symptoms ranging from mild to severe and including repetitive behaviour, deficits in social interaction, and impaired language. It is four times more prevalent in boys than in girls and the incidence continues to rise. The US Center for Disease Control and Prevention (CDC) data from 2010 estimates that 1 in 68 children now has autism.

“The statistics are alarming. It’s 30 per cent higher than the previous estimate of 1 in 88 children, up from only two years earlier. Perhaps we can no longer attribute this rise in autism incidence to better diagnostic tools or awareness of autism,” notes Crawford. “It’s even more apparent from the recent literature that the environment might have a greater impact on vulnerable genes, particularly in pregnancy. Our study provides some molecular evidence that the environment likely disrupts certain events occurring in early brain development and contributes to autism.”

According to Crawford, genes don’t undergo significant changes in evolution, so even though genetic factors are the main cause, environmental factors such as insufficient dietary supplementations of fatty acids, exposures to infections, various chemicals or drugs can change gene expression and contribute to autism.

Muscle paralysis eased by light-sensitive stem cells

A genetic tweak can make light work of some nervous disorders. Using flashes of light to stimulate modified neurons can restore movement to paralysed muscles. A study demonstrating this, carried out in mice, lays the path for using such “optogenetic” approaches to treat nerve disorders ranging from spinal cord injury to epilepsy and motor neuron disease.

Optogenetics has been hailed as one of the most significant recent developments in neuroscience. It involves genetically modifying neurons so they produce a light-sensitive protein, which makes them “fire”, sending an electrical signal, when exposed to light.

So far optogenetics has mainly been used to explore how the brain works, but some groups are exploring using it as therapy. One stumbling block has been fears about irreversibly genetically manipulating the brain.

In the latest study, a team led by Linda Greensmith of University College London altered mouse stem cells in the lab before transplanting them into nerves in the leg – this means they would be easier to remove if something went wrong.

"It’s a very exciting approach that has a lot of potential," says Ziv Williams of Harvard Medical School in Boston.

Muscles in action

Greensmith’s team inserted an algal gene that codes for a light-responsive protein into mouse embryonic stem cells. They then added signalling molecules to make the stem cells develop into motor neurons, the cells that carry signals to and from the spinal cord to the rest of the body. They implanted these into the sciatic nerve – which runs from the spinal cord to the lower limbs – of mice whose original nerves had been cut.

After waiting five weeks for the implanted neurons to integrate with the muscle, Greensmith’s team anaesthetised the mice, cut open their skin and shone pulses of blue light on the nerve. The leg muscles contracted in response. “We were surprised at how well this worked,” says Greensmith.

Most current approaches being investigated to help people who are paralysed involve electrically stimulating their nerves or muscles. But this can be painful because they may still have working pain neurons. Plus, the electricity makes the muscles contract too forcefully, making them tire quickly.

Using the optogenetic approach, however, allows the muscle fibres to be stimulated more gently, because the light level can be increased with each pulse. “It gives a very smooth contraction,” says Greensmith.

Breathing restoration

To make the technique practical for use in people, the researchers are developing a light-emitting diode in the form of a cuff that would go around the nerve, which could be connected to a miniature battery pack under the skin.

They are also trying to develop an alternative to using embryonic stem cells, as these would require the recipient to take drugs to stop their immune system attacking the transplanted neurons. Instead the team is working with induced pluripotent stem cells, cells that have been reprogrammed to behave like embryonic stem cells, but can be made from a small sample of the intended recipient’s own skin.

The team’s first goal is to help people with motor neuron disease who lose the ability to control their breathing muscles. “Walking involves contracting about 40 different muscles in complex sequences,” says Greensmith. “Breathing is very simple – one muscle contracts and relaxes.”

They plan to test the restoration of breathing ability in pigs, and are developing a pacemaker that could repeatedly illuminate the phrenic nerve in the chest, which controls the diaphragm.

Other groups are exploring different therapeutic applications of optogenetics, including treatments for epilepsy and Parkinson’s disease

(Image caption: In this microscope photo of motor neurons created in the laboratory of Su-Chun Zhang, green marks the nucleus and red marks the nerve fibers. Zhang and co-workers at the Waisman Center have identified a misregulation of protein in the nucleus as the likely first step in the pathology of ALS. Credit: Hong Chen, Su-Chun Zhang/Waisman Center)

Study helps unravel the tangled origin of ALS

By studying nerve cells that originated in patients with a severe neurological disease, a University of Wisconsin-Madison researcher has pinpointed an error in protein formation that could be the root of amyotrophic lateral sclerosis.

Also called Lou Gehrig’s disease, ALS causes paralysis and death. According to the ALS Association, as many as 30,000 Americans are living with ALS.

After a genetic mutation was discovered in a small group of ALS patients, scientists transferred that gene to animals and began to search for drugs that might treat those animals. But that approach has yet to work, says Su-Chun Zhang, a neuroscientist at the Waisman Center at UW-Madison, who is senior author of the new report, published April 3 in the journal Cell Stem Cell.

Zhang has been using a different approach — studying diseased human cells in lab dishes. Those cells, called motor neurons, direct muscles to contract and are the site of failure in ALS.

About 10 years ago, Zhang was the first in the world to grow motor neurons from human embryonic stem cells. More recently, he updated that approach by transforming skin cells into iPS (induced pluripotent stem) cells that were transformed, in turn, into motor neurons.

IPS cells can be used as “disease models,” as they carry many of the same traits as their donor. Zhang says the iPS approach offers a key advantage over the genetic approach, which “can only study the results of a known disease-causing gene. With iPS, you can take a cell from any patient, and grow up motor neurons that have ALS. That offers a new way to look at the basic disease pathology.”

In the new report, Zhang, Waisman scientist Hong Chen, and colleagues have pointed a finger at proteins that build a transport structure inside the motor neurons. Called neurofilament, this structure moves chemicals and cellular subunits to the far reaches of the nerve cell. The cargo needing movement includes neurotransmitters, which signal the muscles, and mitochondria, which process energy.

Motor neurons that control foot muscles are about three feet long, so neurotransmitters must be moved a yard from their origin in the cell body to the location where they can signal the muscles, Zhang says. A patient lacking this connection becomes paralyzed; tellingly, the first sign of ALS is often paralysis in the feet and legs.

Scientists have known for some time that in ALS, “tangles” along the nerve’s projections, formed of misshapen protein, block the passage along the nerve fibers, eventually causing the nerve fiber to malfunction and die. The core of the new discovery is the source of these tangles: a shortage of one of the three proteins in the neurofilament.

The neurofilament combines structural and functional roles, Zhang says. “Like the studs, joists and rafters of a house, the neurofilament is the backbone of the cell, but it’s constantly changing. These proteins need to be shipped from the cell body, where they are produced, to the most distant part, and then be shipped back for recycling. If the proteins cannot form correctly and be transported easily, they form tangles that cause a cascade of problems.”

Finding neurofilament tangles in an autopsy of an ALS patient “will not tell you how they happen, when or why they happen,” Zhang says. But with millions of cells — all carrying the human disease — to work with, Zhang’s research group discovered the source of the tangles in the protein subunits that compose the neurofilaments. “Our discovery here is that the disease ALS is caused by misregulation of one step in the production of the neurofilament,” he says.

Beyond ALS, Zhang says “very similar tangles” appear in Alzheimer’s and Parkinson’s diseases. “We got really excited at the idea that when you study ALS, you may be looking at the root of many neurodegenerative disorders.”

While working with motor neurons sourced in stem cells from patients, Zhang says he and his colleagues saw “quite an amazing thing. The motor neurons we reprogrammed from patient skin cells were relatively young, and we found that the misregulation happens very early, which means it is the most likely cause of this disease. Nobody knew this before, but we think if you can target this early step in pathology, you can potentially rescue the nerve cell.”

In the experiment just reported, Zhang found a way to rescue the neural cells living in his lab dishes. When his group “edited” the gene that directs formation of the deficient protein, “suddenly the cells looked normal,” Zhang says.

Already, he reports, scientists at the Small Molecule Screening and Synthesis Facility at UW-Madison are looking for a way to rescue diseased motor neurons. These neurons are made by the millions from stem cells using techniques that Zhang has perfected over the years.

Zhang says “libraries” of candidate drugs, each containing a thousand or more compounds, are being tested. “This is exciting. We can put this into action right away. The basic research is now starting to pay off. With a disease like this, there is no time to waste.”

New hope for treating ALS

Patient stem cells help identify common problem, leading to clinical trials

Harvard stem cell scientists have discovered that a recently approved medication for epilepsy might be a meaningful treatment for amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, a uniformly fatal neurodegenerative disorder. The researchers are now collaborating with Massachusetts General Hospital (MGH) to design an initial clinical trial testing the safety of the treatment in ALS patients.

The investigators all caution that a great deal of work needs to be done to assure the safety and efficacy of the treatment in ALS patients before physicians should start offering it.

The work, laid out in two related advance online publications in April by Cell Stem Cell and Cell Reports, is the long-term fruit of studies by Harvard Stem Cell Institute (HSCI) principal faculty member Kevin Eggan, who in a 2008 Science paper first raised the possibility of using ALS patient-derived stem cells to better understand the disease and identify therapeutic targets for new drugs.

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Team finds a better way to grow motor neurons from stem cells

Researchers report they can generate human motor neurons from stem cells much more quickly and efficiently than previous methods allowed. The finding, described in Nature Communications, will aid efforts to model human motor neuron development, and to understand and treat spinal cord injuries and motor neuron diseases such as amyotrophic lateral sclerosis (ALS).

The new method involves adding critical signaling molecules to precursor cells a few days earlier than previous methods specified. This increases the proportion of healthy motor neurons derived from stem cells (from 30 to 70 percent) and cuts in half the time required to do so.

“We would argue that whatever happens in the human body is going to be quite efficient, quite rapid,” said University of Illinois cell and developmental biology professor Fei Wang, who led the study with visiting scholar Qiuhao Qu and materials science and engineering professor Jianjun Cheng. “Previous approaches took 40 to 50 days, and then the efficiency was very low – 20 to 30 percent. So it’s unlikely that those methods recreate human motor neuron development.”

Qu’s method produced a much larger population of mature, functional motor neurons in 20 days.

The new approach will allow scientists to induce mature human motor neuron development in cell culture, and to identify the factors that are vital to that process, Wang said.

Stem cells are unique in that they can adopt the shape and function of a variety of cell types. Generating neurons from stem cells (either embryonic stem cells or those “induced” to revert back to an embryo-like state) requires adding signaling molecules to the cells at critical moments in their development.

Wang and other colleagues previously discovered a molecule (called compound C) that converts stem cells into “neural progenitor cells,” an early stage in the cells’ development into neurons. But further coaxing these cells to become motor neurons presented unusual challenges.

Previous studies added two important signaling molecules at Day 6 (six days after exposure to compound C), but with limited success in generating motor neurons. In the new study, Qu discovered that adding the signaling molecules at Day 3 worked much better: The neural progenitor cells quickly and efficiently differentiated into motor neurons.

This indicates that Day 3 represents a previously unrecognized neural progenitor cell stage, Wang said.

The new approach has immediate applications in the lab. Watching how stem cells (derived from ALS patients’ own skin cells, for example) develop into motor neurons will offer new insights into disease processes, and any method that improves the speed and efficiency of generating the motor neurons will aid scientists. The cells can also be used to screen for drugs to treat motor neuron diseases, and may one day be used therapeutically to restore lost function.

“To have a rapid, efficient way to generate motor neurons will undoubtedly be crucial to studying – and potentially also treating – spinal cord injuries and diseases like ALS,” Wang said.

First comprehensive atlas of human gene activity released

A large international consortium of researchers has produced the first comprehensive, detailed map of the way genes work across the major cells and tissues of the human body. The findings describe the complex networks that govern gene activity, and the new information could play a crucial role in identifying the genes involved with disease.

“Now, for the first time, we are able to pinpoint the regions of the genome that can be active in a disease and in normal activity, whether it’s in a brain cell, the skin, in blood stem cells or in hair follicles,” said Winston Hide, associate professor of bioinformatics and computational biology at Harvard School of Public Health (HSPH) and one of the core authors of the main paper in Nature. “This is a major advance that will greatly increase our ability to understand the causes of disease across the body.”

The research is outlined in a series of papers published March 27, 2014, two in the journal Nature and 16 in other scholarly journals. The work is the result of years of concerted effort among 250 experts from more than 20 countries as part of FANTOM 5 (Functional Annotation of the Mammalian Genome). The FANTOM project, led by the Japanese institution RIKEN, is aimed at building a complete library of human genes.

Researchers studied human and mouse cells using a new technology called Cap Analysis of Gene Expression (CAGE), developed at RIKEN, to discover how 95% of all human genes are switched on and off. These “switches”—called “promoters” and “enhancers”—are the regions of DNA that manage gene activity. The researchers mapped the activity of 180,000 promoters and 44,000 enhancers across a wide range of human cell types and tissues and, in most cases, found they were linked with specific cell types.

“We now have the ability to narrow down the genes involved in particular diseases based on the tissue cell or organ in which they work,” said Hide. “This new atlas points us to the exact locations to look for the key genetic variants that might map to a disease.”