The GSTA4 gene restored vision in aged mice, suggesting that aging's 'program' and 'damage' may be a single mechanism

The GSTA4 gene restored vision in aged mice, suggesting that aging's 'program' and 'damage' may be a single mechanism

Aging researcher Pyotr Lidsky and evolutionary biologist Alexander Wolf spent nearly twenty-four hours debating on X whether aging is a program or an accumulation of damage. An analysis of their exchange, published on October 4, found an answer in a preprint on the GSTA4 gene, which restored vision in aged mice: in this mechanism, program and damage turn out to be links in a single causal chain.

On September 27, Lidsky wrote on X that he believes in a genetic program of aging: if no disease is considered to be caused by damage, aging should not be treated as an exception. Wolf pushed back. According to his theory, cancer is driven by DNA mutations, and mutations are a form of damage. In his model, aging is a side effect of cancer defense: to keep cells with dangerous mutations from becoming tumors, the body forces them into dormancy or destroys them, and the buildup of such cells gradually wears tissues down.

On October 4, the aging-focused account HackAging.ai analyzed this debate and read in full the paper that Lidsky himself had dismissed in his thread with a single phrase, 'a specific molecular mechanism,' without reading further. The same laboratory that in 2020 first restored vision in mice using the OSK genes has now, with David Sinclair among the authors, published a preprint on the retinal pigment epithelium (RPE), a layer of cells that nourishes the eye's photoreceptors and is the first to deteriorate with age. Three cell-reprogramming genes (Oct4, Sox2, and Klf4, collectively known as OSK) restored vision in aged mice to the level of three-month-olds within eight weeks.

To identify the protective mechanism, the authors screened the genes activated by OSK in the retina and found one without which the effect disappears: GSTA4, an enzyme that breaks down a toxic lipid peroxidation product that accumulates in the retina with age. GSTA4 alone improved vision in aged mice and reduced the retinal molecular age by nearly half, without the side effects of prolonged OSK expression. According to the mSALT database developed by biologist Vadim Gladyshev, GSTA4 is among the genes most strongly associated with mouse longevity: its expression increases under caloric restriction, growth hormone deficiency, and rapamycin treatment.

This already serves as a counterexample to Lidsky's position: a single activated gene reverses damage. But the authors went further and proposed a mechanism that connects both theories. The regulation of GSTA4 by OSK recapitulates its regulation in the early embryo: the gene is active at early stages and is silenced by mid-gestation. This is an instance of antagonistic pleiotropy, a principle proposed by biologist George Williams (1957): the same trait can benefit an organism early in life and harm it in old age. The authors write:

"Beyond confirming the antagonistic pleiotropy model, our finding helps unite the epigenetic information theory of aging with the mitochondrial free-radical theory of aging."

The damage theory has a long and complicated history. Of the several dozen mouse lines with altered antioxidant defenses, most showed no difference in lifespan. Mitochondria-targeted catalase is one of the few exceptions that did extend mouse lifespan, and mice lacking the Sod1 gene lived shorter lives, though mostly because of liver cancer, a confounding factor that makes it difficult to link antioxidant deficiency to the rate of aging.

The effect has been verified in the retina. Whether sustained GSTA4 activity extends the lifespan of a whole mouse is a separate experiment that the authors did not conduct. The outcome of this debate over terminology determines where effort and money are directed: treating aging as damage by boosting enzymes like GSTA4 and clearing damaged cells, or treating it as a program by resetting it with switches like OSK. The GSTA4 finding shows that interventions can be tested now, without waiting for the debate to be settled.