The Bmal1 gene plays a key role in controlling circadian rhythms. To better understand how the Bmal1 gene affects tumour growth and the response to anti-cancer drugs, we examined the effect of knockdown of Bmal1 by RNAi both in vitro and in vivo. Down-regulation of Bmal1 gene expression accelerated cell proliferation in vitro and promoted tumour growth in mice. Suppressing Bmal1 expression in murine colon cancer cells (C26) and fibroblast cells (L929) decreased apoptosis induced by Etoposid, reduced the distribution of cells in the G2/M phases treated by Docetaxel and decreased DNA damage induced by Cisplatin. Loss of Bmal1 reduced the expression of per1, per2, per3, wee1 and p53. The expression of p21 and c-myc was also altered in certain cell lines. However, Bmal1 deficiency increased the protein levels of cdc2, cyclin B1, cyclin D1 and cyclin E. Wee1 and cyclin A expression was minimally altered. Thus, the circadian clock gene Bmal1 plays a role in regulating tumour cell apoptosis, cell-cycle progression and DNA damage response and in homoeostasis regulation. Down-regulation of Bmal1 accelerates the development of tumours and may influence the response to anti-cancer drugs.

BackgroundAlthough feeding behavior and food habit are ecologically and economically important properties, little is known about formation and evolution of herbivory. Grass carp (Ctenopharyngodon idella) is an ecologically appealing model of vertebrate herbivore, widely cultivated in the world as edible fish or as biological control agents for aquatic weeds. Grass carp exhibits food habit transition from carnivory to herbivory during development. However, currently little is known about the genes regulating the unique food habit transition and the formation of herbivory, and how they could achieve higher growth rates on plant materials, which have a relatively poor nutritional quality.ResultsWe showed that grass carp fed with duckweed (modeling fish after food habit transition) had significantly higher relative length of gut than fish before food habit transition or those fed with chironomid larvae (fish without transition). Using transcriptome sequencing, we identified 10,184 differentially expressed genes between grass carp before and after transition in brain, liver and gut. By eliminating genes potentially involved in development (via comparing fish with or without food habit transition), we identified changes in expression of genes involved in cell proliferation and differentiation, appetite control, circadian rhythm, and digestion and metabolism between fish before and after food habit transition. Up-regulation of GHRb, Egfr, Fgf, Fgfbp1, Insra, Irs2, Jak, STAT, PKC, PI3K expression in fish fed with duckweed, consistent with faster gut growth, could promote the food habit transition. Grass carp after food habit transition had increased appetite signal in brain. Altered expressions of Per, Cry, Clock, Bmal2, Pdp, Dec and Fbxl3 might reset circadian phase of fish after food habit transition. Expression of genes involved in digestion and metabolism were significantly different between fish before and after the transition.ConclusionsWe suggest that the food habit transition from carnivory to herbivory in grass carp might be due to enhanced gut growth, increased appetite, resetting of circadian phase and enhanced digestion and metabolism. We also found extensive alternative splicing and novel transcript accompanying food habit transition. These differences together might account for the food habit transition and the formation of herbivory in grass carp.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1217-x) contains supplementary material, which is available to authorized users.

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