School of Psychology and Neuroscience, University of St Andrews, South Street, St Andrews, KY16 9JP, UK.
Department of Biological and Environmental Sciences, University of Gothenburg, Medicinaregatan 18A, 413 90, Gothenburg, Sweden.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2024 May;210(3):399-413. doi: 10.1007/s00359-023-01666-2. Epub 2023 Aug 17.
Maternal signals shape embryonic development, and in turn post-natal phenotypes. RNA deposition is one such method of maternal signalling and circadian rhythms are one trait thought to be maternally inherited, through this mechanism. These maternal circadian gene transcripts aid development of a functioning circadian system. There is increasing evidence that maternal signals can be modified, depending on prevailing environmental conditions to optimise offspring fitness. However, currently, it is unknown if maternal circadian gene transcripts, and consequently early embryonic gene transcription, are altered by maternal developmental conditions. Here, using avian mothers who experienced either pre-natal corticosterone exposure, and/or post-natal stress as juveniles we were able to determine the effects of the timing of stress on downstream circadian RNA deposition in offspring. We demonstrated that maternal developmental history does indeed affect transfer of offspring circadian genes, but the timing of stress was important. Avian mothers who experienced stress during the first 2 weeks of post-natal life increased maternally deposited transcript levels of two core circadian clock genes, BMAL1 and PER2. These differences in transcript levels were transient and disappeared at the point of embryonic genome transcription. Pre-natal maternal stress alone was found to elicit delayed changes in circadian gene expression. After activation of the embryonic genome, both BMAL1 and PER2 expression were significantly decreased. If both pre-natal and post-natal stress occurred, then initial maternal transcript levels of BMAL1 were significantly increased. Taken together, these results suggest that developmental stress differentially produces persistent transgenerational effects on offspring circadian genes.
母体信号塑造胚胎发育，进而影响出生后的表型。RNA 沉积是一种母体信号传递方式，而昼夜节律被认为是通过这种机制从母体遗传而来的一种特征。这些母体昼夜节律基因转录本有助于形成正常的昼夜节律系统。越来越多的证据表明，母体信号可以根据环境条件的变化进行修饰，以优化后代的适应能力。然而，目前尚不清楚母体昼夜节律基因转录本，以及由此产生的早期胚胎基因转录，是否会因母体发育条件而改变。在这里，我们使用经历过产前皮质酮暴露和/或青少年期产后应激的鸟类母亲，来确定应激时机对后代下游昼夜节律 RNA 沉积的影响。我们表明，母体发育史确实会影响后代昼夜节律基因的传递，但应激的时机很重要。在产后生活的前 2 周经历应激的鸟类母亲会增加两个核心昼夜节律钟基因 BMAL1 和 PER2 的母体沉积转录本水平。这些转录本水平的差异是短暂的，在胚胎基因组转录时消失。仅产前母体应激会导致昼夜基因表达延迟变化。胚胎基因组激活后，BMAL1 和 PER2 的表达均显著降低。如果产前和产后都有应激，那么 BMAL1 的初始母体转录本水平会显著增加。综上所述，这些结果表明，发育应激会对后代的昼夜节律基因产生持久的跨代影响。
