From First Principles
From First Principles

The Yak Mutation That Could Help Repair the Brain (EP 56)

September 7, 2026

AI Summary

5 min read

The Yak Mutation That Could Help Repair the Brain

Multiple sclerosis affects roughly 2.8 million people worldwide. For most of them, the disease is a slow, relentless war of attrition—their own immune system attacking the protective wrapping around their nerve cells. Today's best treatments can slow that immune assault, but they cannot reverse damage already done. Nerve damage has been notoriously a one-way street. But a paper published in Neuron on May 20, 2026, suggests a possible path toward rewinding that damage, and the inspiration comes from an unlikely source: the genomes of animals living on the Tibetan plateau.

What Myelin Does and Why Its Loss Matters

In a healthy nervous system, nerve fibers called axons are wrapped in a myelin sheath. This is analogous to insulation around copper wire. The membrane of a neuron is naturally leaky—ions want to flow across it. Without insulation, an electrical signal would decay before traveling far. Myelin solves this by concentrating the places where ions can enter and exit the cell to specific gaps called nodes of Ranvier. The signal jumps from node to node in a mechanism called saltatory conduction, dramatically increasing speed and efficiency.

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What you'll learn

  • 1 (00:01) **The Core Problem** - The episode introduces the challenge of finding a molecule small enough to cross the blood-brain barrier but specific enough to only activate the gamma receptor of stem cells, avoiding catastrophic side effects elsewhere in the body.
  • 2 (01:03) **Episode Roadmap** - The hosts outline the plan to cover a new paper from Neuron (May 2026) that tackles brain disease by looking at genetic adaptations in high-altitude Tibetan animals.
  • 3 (02:28) **The Scope of the Problem** - MS affects 2.8 million people worldwide, and current treatments can only slow the immune assault, not fix the damage.
  • 4 (04:58) **The Detective Work Begins** - The hosts explain the method of the paper, which starts with a large question about how a Yak adapts to the Tibetan plateau and hones in on the molecular mechanism.
  • 5 (08:58) **What is Myelin?** - The hosts explain the basics of the nervous system and the myelin sheath, using an analogy of electrical wiring and insulation.
  • 6 (17:50) **The Oligodendrocyte** - The hosts introduce the oligodendrocyte, the cell responsible for creating the myelin sheath.
  • 7 (22:53) **The Discovery of MS** - The hosts explain how Jean-Martin Charcot discovered MS in 1868 by correlating patient symptoms with plaques in the brain's white matter during autopsies.

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Show Notes

What can a yak living thousands of meters above sea level teach us about repairing the human brain?

In Episode 56 of From First Principles, Lester Nare and Krishna Choudhary break down a new Neuron paper that traces an evolutionary adaptation found in high-altitude animals to a previously hidden pathway involved in building and repairing myelin.

Summary

  • What myelin actually does and why losing it disrupts neural communication
  • How multiple sclerosis damages myelin and why the brain’s natural repair process eventually fails
  • Why oligodendrocyte precursor cells can remain present in damaged tissue without successfully rebuilding myelin
  • Why current therapies are better at slowing further damage than restoring what has already been lost
  • The challenge of getting drugs across the blood-brain barrier while maintaining target specificity
  • How evolutionary pharmacology has previously produced medicines from adaptations found in snakes and Gila monsters
  • The RETSAT Q247R variant identified in animals adapted to the hypoxic environment of the Tibetan Plateau
  • How researchers engineered the high-altitude variant into mice and tested its effect on myelin
  • The surprising discovery that neurons — rather than the myelin-producing cells themselves — generate the key repair signal
  • How RETSAT increases ATDR, which neurons convert into ATDRA
  • How ATDRA activates RXR-γ in oligodendrocyte precursor cells and promotes their differentiation
  • How administration of ATDR promoted remyelination across multiple preclinical models
  • Why the result is scientifically promising but still far from a proven human treatment

Featured Paper

A gain-of-function Retsat variant from high-altitude adaptation promotes myelination via a neuronal dihydroretinoic acid-RXR-γ pathway
Neuron, 2026
DOI: 10.1016/j.neuron.2026.01.013


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