A stem cell zoo uncovers intracellular scaling of developmental tempo across mammals

Differential speeds in biochemical reactions have been proposed to be responsible for the differences in developmental tempo between mice and humans. However, the underlying mechanism controlling the spe-cies-specific kinetics remains to be determined. Using in vitro differentiation of pluripotent stem cells, we recapitulated the segmentation clocks of diverse mammalian species varying in body weight and taxa: marmoset, rabbit, cattle, and rhinoceros. Together with mousee and human, the segmentation clock periods of the six species did not scale with the animal body weight, but with the embryogenesis length. The biochemical kinetics of the core clock gene HES7 displayed clear scaling with the species-specific segmen-tation clock period. However, the cellular metabolic rates did not show an evident correlation. Instead, genes involving biochemical reactions showed an expression pattern that scales with the segmentation clock period. Altogether, our stem cell zoo uncovered general scaling laws governing species-specific develop-mental tempo.

Automated summary

By differentiating pluripotent stem cells in vitro, it was found that the segmentation clock period is not correlated with animal body weight, but with embryogenesis length. The biochemical kinetics of the core clock gene HES7 is correlated with the species-specific segmentation clock period, while cellular metabolic rates show no evident correlation. Instead, genes involving biochemical reactions show an expression pattern that scales with the segmentation clock period.