First Look At How Astrocyctes Function In Humans

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Pretty much everything happening in the brain would fail without astrocytes. These star-shaped glial cells are known to have a critical role in synapse creation, nervous tissue repair, and the formation of the blood-brain barrier. But while we have decades of data in mice about these nervous system support cells, how relevant those experiments are to human biology (and the success of potential therapies) has been an open question.

In Neuron on December 10, Stanford researchers present the first functional and molecular comparison of human and mouse astrocytes, and while 85%-90% of the genes are similar, human astrocytes have unique genes and respond differently to neurotransmitters, particularly glutamate. This presumably means that, at the adult stage, human astrocytes, in contrast to mouse astrocytes, are better at detecting neuroactivity and adjusting their functions in response.

“We are only beginning to understand the unique properties of human astrocytes,” says first author Ye Zhang, a postdoctoral scholar in Stanford University School of Medicine’s Department of Neurobiology. “We found hundreds of genes expressed exclusively by human astrocytes, and future studies will likely reveal additional biological differences. Potentially, this work will help us recognize the role of these cells in biological disorders.”

Astrocyctes (1)
Author Ye Zhang

The study of human astrocytes has faced issues related to access (samples of living tissue must be obtained from brain cancer or epilepsy surgeries or fetal tissue) and purification (breaking apart astrocytes away from other cells often killed them and many experiments ended in failure). Zhang, co-first author and graduate student Steven Sloan, and their faculty mentor, senior author and professor Ben Barres, overcame the technical challenges by developing an antibody-driven protocol that isolates astrocytes and keeps them alive in culture.

This method also allowed the researchers to compare astrocytes in healthy tissue versus those coming from people with glioblastoma or epilepsy. It’s known from mouse studies that astrocytes become highly reactive in these diseases, but what this means remains unclear. Genes that produce both positive and negative effects are expressed during these active periods, and through this study, some of the good and bad genes in humans are beginning to be parsed out. The next step is to screen for drugs that can promote or quell the expression of specific genes.

Another surprising discovery was that astrocytes come in two distinct stages (progenitor and mature) and that early-stage astrocytes and brain cancer closely resemble one another. This brings up the possibility that brain cancer cells that originate from glial cells can be forced into a mature state and thus unable to divide. The authors note that this finding could not have been made without the use of fetal tissue.

Astrocyctes

“Such knowledge could not have been obtained without access to fetal tissue,” Zhang says. “We can’t guess the biology of human brains and neurodevelopmental disorders just by studying mouse brains.”

With their new method, Zhang and her colleagues hope to soon begin looking at the unique properties of human astrocyte cells in a range of disease types, including Alzheimer’s, ALS, stroke, injury, autism, and schizophrenia.

The report, “Purification and characterization of progenitor and mature human astrocytes reveals transcriptional and functional differences with mouse” was published in the journal Cell.

By Bruce Goldman

Possible new law of nature on the way

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The world of physics is excited about strong but early evidence about the behavior of muons, paricles identical to electrons only 200x more massive (heavier), which once born take 2.2 microseconds to decay into an electron, and which spin like tops. In a new, extremely precise measurement, they were made to wobble using magnetic fields but they unexpectedly wobbled quite significantly faster than the Standard Model suggests they would. They might spin so fast due to an unknown force caused by an unknown particle, and this is what is so exciting.

“We found that a muon … is not in agreement with our current best theory of physics at the subatomic level, and … it potentially points to a future with new laws, new particles and new forces in physics which we haven’t seen to date,” said Professor Mark Lancaster at U of Manchester.

“The main goal of the experiment is to make the measurement and compare with the theory, and if they disagree then it’s telling us that there’s something in nature which is not in the theory,” explained James Mott at Fermilab.

The four known forces of nature (gravity, electricity, two nuclear forces: strong and weak interactions) have left scientists without an answer for some observed phenomena, such as the speed at which galaxies spin (faster than the best model suggests). Therefore, they continue to search for glitches in their already-tight models which might point them things they don’t yet know about.

The most recent work was done at Fermilab (Muon g-2 experiment), but a similar experiment was already done earlier at the Large Hadron Collider. These tools accelerate particles in large rings at close to the speed of light.

The evidence needs more tests for greater certainty, particularly to rule out the possibility of a systematic error, and particularly with a new, independent experiment, but physicists will be chasing this line of experiment eagerly.

“This is outstanding confirmation of experimental technique, and very, very suggestive of the possibility of new physics,” noted scientist David Hertzon of U of Washington.

By the editors

#AnomalousMagneticDipoleMomentOfTheMuon #QuantumElectrodynamics

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People in Kachin state demonstrate against China

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YANGON, Myanmar – The people in the Pharkant area of Kachin state demonstrated against China this week, drawing a cross on the Chinese flag and burning a picture of Myanmar’s military leader Min Aung Hlaing.

“China stands with the military leader,” shouted the demonstrators.

By Htay Win
Photo credit Aye Yarwaddy

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Myanmar military council arrests the artist Zarganar

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YANGON, Myanmar – The artist Zarganar was arrested by the Myanmar military council from his home in Tarmwe township, Yangon this morning.

Zarganar is not only a director but also a comedian famous for political jokes since the 1988 democratic revolution.

Zarganar was arrested by the Myanmar military many times before 2010.

By Htay Win
Photo credit Zarganar page

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Kayin IDPs struggle to get for food

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YANGON, Myanmar – Kayin internally displaced people are desperate for food, clothing and shelter, hiding in the forest from the air strikes of the Myanmar military.

The IDPs fled to neighboring Thailand, but Thai government turned them back. However, Wednesday morning the Thai government opened Maeseli jetty in Maehaungsaung district to sending rations and medicines over the border to Kayin state, according to a Thai media.

By Htay Win

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Twenty Myanmar celebrities charged with incitement

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YANGON, Myanmar -They were charged under the country’s media law with inciting government employees to join the popular civil disobedience movement (CDM) through social media.

Celebrities took part in the NLD election campaigns and are thought to have played a large part in influencing the public, particularly Myanmar’s youth, to vote for Aung San Suu Kyi.

By Htay Win
Photo credit Myanmar celebrity

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