Through a new study researchers have shown how fetus are able to work out the biological timing even when their own biological clocks are still under development.
As per the study published in the open-access journal PLOS Biology during fetal development, before the biological clock starts ticking on its own, genes within the fetus’s developing clock respond to rhythmic behavior in the mother.
The suprachiasmatic nuclei (SCN), structures within the hypothalamus, are the master timekeepers for the body. Rhythmic activity of genes in SCN cells in turn governs the activity of many other genes both locally and elsewhere in the body, ultimately influencing a wide variety of circadian rhythmic behavior, including feeding and sleeping. But that rhythmic gene activity begins in earnest relatively late in fetal development, raising the question of whether maternal influences entrain gene activity within the SCN prior to birth.
To explore that question, the authors compared the pattern of gene activity in SCN tissue from fetuses developing within pregnant rats kept in the dark, under two sets of conditions. Control rats had intact SCNs and free access to food, while lesioned rats had their SCNs disrupted but their access to food was limited to eight hours per day, to impose a circadian rhythm in their activity that their SCNs could no longer sustain.
They found that, within SCNs of both sets of fetuses, there was a very small set of genes whose timing pattern differed between the two groups, and a much larger set whose activity oscillated in sync with each other. Many of these latter genes could be assigned to two major processes—neuronal development and neuronal function, likely reflecting in the first case the ongoing development of the SCN as it wires itself up for mature function, and in the second case the earliest manifestation of that function.