Stories about: Parkinson’s disease

Maintaining mitochondria in neurons: A new lens for neurodegenerative disorders

cartoon of mitochondria being transported in neurons - part of mitostasis
In some neurons, mitochondria must travel several feet along an axon. (Elena Hartley illustration)

Tom Schwarz, PhD, is a neuroscientist at Boston Children’s Hospital’s F.M. Kirby Neurobiology Center, focusing on the cell biology of neurons. Tess Joosse is a biology major at Oberlin College. This article is condensed from a recent review article by Schwarz and Thomas Misgeld (Technical University of Munich).

Like all cells, the neurons of our nervous system depend on mitochondria to generate energy. Mitochondria need constant rejuvenation and turnover, and that’s especially true in neurons because of their high energy needs for signaling and “firing.” Mitochondria are especially abundant at presynaptic sites — the tips of axons that form synapses or junctions with other neurons and release neurotransmitters.

But the process of maintaining mitochondrial number and quality, known as mitostasis, also poses particular challenges in neurons. Increasingly, mitostasis is providing a helpful lens for understanding neurodegenerative disorders. Problems with mitostasis are implicated in Parkinson’s disease, Alzheimer’s disease, ALS, autism, stroke, multiple sclerosis, hypoxia and more.

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Immune cells “sculpt” brain circuits — by eating excess connections

The above movie shows an immune cell caught in the act of tending the brain—it’s just eaten away unnecessary connections, or synapses, between neurons.

That’s not something these cells, known as microglia, were previously thought to do. As immune cells, it was thought that their job was to rid the body of unwanted pathogens and debris, by engulfing and digesting them.

The involvement of microglia in the brain’s development has started to be recognized only recently. The latest research finds that microglia tune into the brain’s cues, akin to the way they survey their environment for invading microbes, and get rid of excess synapses the same way they’d dispatch these invaders—by eating them.

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Mitochondria running amok: Can we stop them from moving to treat Parkinson’s disease?

(Louisa Howard/Wikimedia Commons)

Mitochondria, as you may know, are the engines that power cells. They’re always in motion, supplying energy wherever it’s needed. In brain cells, mitochondria especially have to hoof it around, traveling out into the axons and dendrites to fuel the energy-intensive task of communicating with other cells.

But in at least one form of Parkinson’s disease, that movement becomes a problem: the genetic mutations causing the disease leave neurons unable to make the fidgety organelles hold still. Without this ability, the dopamine-producing neurons in the brain’s substantia nigra can’t safely dispose of mitochondria when they go bad, and the neurons die or become impaired.

“When damaged, mitochondria produce reactive oxygen species that are highly destructive, and can fuse with healthy mitochondria and contaminate them, too,” explains Tom Schwarz, of the F.M. Kirby Neurobiology Center at Children’s Hospital Boston, senior investigator on a study published in Cell today. “It’s the equivalent of an environmental disaster in the cell.”

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