Cholecystokinin neurons in mouse suprachiasmatic nucleus regulate the robustness of circadian clock.

The suprachiasmatic nucleus (SCN) can generate robust circadian behaviors in mammals under different environments, but the underlying neural mechanisms remained unclear. Here, we showed that the activities of cholecystokinin (CCK) neurons in the mouse SCN preceded the onset of behavioral activities under different photoperiods. CCK-neuron-deficient mice displayed shortened free-running periods, failed to compress their activities under a long photoperiod, and developed rapid splitting or became arrhythmic under constant light. Furthermore, unlike vasoactive intestinal polypeptide (VIP) neurons, CCK neurons are not directly light sensitive, but their activation can elicit phase advance and counter light-induced phase delay mediated by VIP neurons. Under long photoperiods, the impact of CCK neurons on SCN dominates over that of VIP neurons. Finally, we found that the slow-responding CCK neurons control the rate of recovery during jet lag. Together, our results demonstrated that SCN CCK neurons are crucial for the robustness and plasticity of the mammalian circadian clock.

Proteomic and metabolomic profiling reveals the involvement of apoptosis in meat quality characteristics of ovine M. longissimus from different callipyge genotypes.

Proteome and metabolome changes in muscles from callipyge mutation (+/C) and non-callipyge phenotype (+/+, C/+, and C/C) lambs were profiled to provide insight into the biochemical changes affecting meat quality attributes. M. longissimus thoracis from lambs with all four possible callipyge genotype (n = 4, C/+, C/C, +/C, and +/+) were collected after 3d aging and analyzed using mass-spectrometry based platforms. Among identified proteomes, cytochrome c (pro-apoptotic protein) was detected with significantly lower abundances in +/C. Anti-apoptotic HSP70, BAG3, and PARK7 were over-abundant in +/C, which could result in delayed apoptosis and possibly attributed to tougher meat in callipyge lambs. Eight glycolysis enzymes were overabundant in +/C lambs, whereas 3 enzymes involved in TCA cycle were overabundant in non-callipyge ones (C/C and/or C/+). Twenty-five metabolites were affected by genotypes (P < .05), including metabolic co-factors, polyphenols, and AA/short peptides. Our omics results provided insightful information for revealing the differences in biochemical attributes caused by callipyge mutation.