The night of Tanabata (Star Festival) on July 7th. A heat map of metabolic reactions in each tissue of C. elegans, derived from single-cell transcriptome analysis, illuminates the surface of the sea. And the metabolic networks of each tissue drawn based on the heat map decorate the night sky like constellations floating in the Milky Way. For drawing this image, we referred to Yilmaz et al. (2020) Mol. Syst. Biol. 16:e9649, DOI: 10.15252/msb.20209649.
The heat map: Adapted from Figure 3(C) of © Yilmaz et al. (2020) Mol. Syst. Biol. 16:e9649, DOI: 10.15252/msb.20209649. Licensed under CC BY 4.0.
Even in the same mammal, the time it takes for development is very different between humans and mice. The period of the segmentation clock in humans is about 5 hours, whereas that in mice is about 2 hours. The key regulator of the segmentation clock is the transcription factor HES7, whose expression level periodically increases or decreases by self-repression. Experiments in which human and mouse HES7 loci were swapped showed that differences in the speeds of intracellular biochemical reactions, such as gene expression and protein degradation, between species, rather than the sequences of HES7 loci themselves, produce the period difference. This finding suggests that the period difference of the segmentation clock may also be related to the difference in time scales in development between elephants and mice. We thank Dr. Miki Ebisuya (EMBL Barcelona) for her advice.