Slower protein breakdown in human cells may underlie developmental tempo differences

Researchers compared the degradation rates of about 4,000 shared proteins in human and mouse cells, finding a general tendency for human proteins to persist longer. This proteome-wide slowdown, beyond a previously identified single gene, may help explain why human embryos develop more slowly than those of mice. The findings were published in Developmental Cell.

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The study tracked the lifespan of roughly 4,000 proteins present in both human and mouse cells, measuring how quickly each was broken down. Across this large set, human proteins consistently showed greater stability, lasting longer before degradation than their mouse equivalents. This pattern points to a broad, systemic difference in cellular maintenance rather than an isolated quirk of one or two molecules.

Earlier work had flagged a single gene tied to species-specific developmental pacing. The new results suggest that this timing difference is far more widespread, involving thousands of proteins. A general