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The liver makes transthyretin as a transport protein, moving thyroid hormone and vitamin A around the body. It normally travels as a group of four joined together. If that group comes apart, the individual pieces misfold and clump into deposits that damage nerves and heart muscle. Because people who make very little transthyretin seem to do fine, switching the gene off is a reasonable treatment strategy.
TTR, at 18q12.1, encodes transthyretin, a homotetrameric transport protein for thyroxine and retinol-binding protein. Destabilising variants — over 130 are known, V30M and V122I among the most common — promote tetramer dissociation and amyloid fibril formation. Since circulating transthyretin is almost entirely hepatic and low levels appear well tolerated, hepatic knockout is a rational one-time strategy, pursued by in vivo CRISPR alongside approved stabilisers and RNA silencers.
Sources
- MedlinePlus Genetics, U.S. National Library of Medicine
TTR gene ↗