{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"1cd33b99f404390ff195a4658345de43bf022587dca6759e265247123a4bb9de","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5034f4455b4d02cd0e7339af787f63f5949f8522cae25e5bc828dbc70a1a0a90","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"40ec10965894e496b207e3ee6d7cd67668f077764ae6705c9a4a61f7491ea528","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"bio.biological-clocks.segmentation-clock-tempo","kind":"phenomenon","literature_status":"partially-resolved","n":"2","parents":[],"plain":"The genetic oscillator that times backbone segments has a period of roughly 2 to 3 hours in mouse and about 5 hours in human cells grown in a dish. Which single cellular property slows every step of the clock by the same factor is not established.","posed_since":"2020","precise":"For the Hes7 oscillator in presomitic mesoderm (period approximately $2.5\\,\\mathrm{h}$ in mouse and $5\\,\\mathrm{h}$ in human stem-cell-derived tissue), Matsuda and co-workers (2020) showed that protein degradation rates and expression delays scale together with the period, and Diaz-Cuadros and co-workers (2023) linked the period to mass-specific metabolic rate and the NAD+/NADH ratio. Identify the global variable that sets all these rates proportionally and give a model that predicts the clock period of at least four species from independent measurements of that variable.","problem_ref":"5034f4455b4d02cd0e7339af787f63f5949f8522cae25e5bc828dbc70a1a0a90","references":"","settled_by":"Measurements of the candidate global variable and of the clock period in stem-cell-derived presomitic mesoderm from several species, plus perturbations of that variable that shift the period by the predicted amount.","status_note":"Matsuda and co-workers (Science 2020, doi 10.1126/science.aba7668) and Diaz-Cuadros and co-workers (Nature 2023, doi 10.1038/s41586-022-05574-4) tied the period to reaction speeds and metabolism; what controls the global rate remains open.","title":"What sets the species-specific period of the segmentation 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