January 13, 2026

@michaelokun

When repeats break the brain: solving the polyglutamine puzzle. What is polyglutamine? Polyglutamine refers to an abnormally long stretch of the amino acid glutamine caused by repeated CAG DNA sequences that can disrupt how brain cells function and survive. Gonzalez and Zoghbi describe in a new paper in the Journal of Experimental Medicine (JEM) how polyglutamine diseases arise from a shared genetic mechanism, yet they unfold through a remarkably complex set of molecular events. Key Points: - Expanded CAG repeats lead to misfolded proteins that accumulate and interfere w/ essential cellular processes. - Toxicity emerges from a mix of gain of function and partial loss of normal protein roles across different brain cells. - Multiple downstream pathways converge including transcriptional control, energy balance, protein clearance and synaptic integrity. My take: This review reminds us that polyglutamine diseases are not driven by a single bad actor. They are 'systems failures.' Progress in this field will depend on matching therapies to the specific molecular stress points in each disease and for each vulnerable brain circuit. Here are 5 points that resonated w/ me: 1- These diseases share common biology, however affect very different brain regions. 2- Protein clumps may sometimes protect cells early on however can become harmful later. 3- Mitochondrial stress and energy failure appear frequently across conditions. 4- Somatic repeat expansion may worsen disease over time, especially in select neurons. 5-Future therapies will likely require a combination of approaches rather than a single fix. https://rupress.org/jem/article/223/1/e20241336/278392/Pathogenesis-of-polyglutamine-diseases-Piecing?searchresult=1 #ataxia #michaelokun #fixelinstitute