Biology subjects

Leise, T. L.

Publications and source records attributed to Leise, T. L..

3 recordsLinked to original sources

bioRxiv2021

Cell-type specific circadian bioluminescence rhythms recorded from Dbp reporter mice reveal circadian oscillator misalignment

Circadian rhythms are endogenously generated physiological and molecular rhythms with a cycle length of about 24 h. Bioluminescent reporters have been exceptionally useful for studying circadian rhythms in numerous species. Here, we report development of a reporter mouse generated by modification of a widely expressed and highly rhythmic gene encoding D-site albumin promoter binding protein (Dbp). In this line of mice, firefly luciferase is expressed from the Dbp locus in a Cre-recombinase-dependent manner, allowing assessment of bioluminescence rhythms in specific cellular populations. A mouse line in which luciferase expression was Cre-independent was also generated. The Dbp reporter alleles do not alter Dbp gene expression rhythms in liver or circadian locomotor activity rhythms. In vivo and ex vivo studies show the utility of the reporter alleles for monitoring rhythmicity. Our studies reveal cell-type specific characteristics of rhythms among neuronal populations within the suprachiasmatic nuclei ex vivo. In vivo studies show Dbp-driven bioluminescence rhythms in the liver of Albumin-Cre;DbpKI/+ "liver reporter" mice. After a shift of the lighting schedule, locomotor activity achieved the proper phase relationship with the new lighting cycle more rapidly than hepatic bioluminescence did. As previously shown, restricting food access to the daytime altered the phase of hepatic rhythmicity. Our model allowed assessment of the rate of recovery from misalignment once animals were provided with food ad libitum. These studies confirm the previously demonstrated circadian misalignment following environmental perturbations and reveal the utility of this model for minimally invasive, longitudinal monitoring of rhythmicity from specific mouse tissues.

physiology↗

bioRxiv2020

Methods for detecting PER2::LUCIFERASE bioluminescence rhythms in freely moving mice

Circadian rhythms are driven by daily oscillations of gene expression. An important tool for studying cellular and tissue rhythms is the use of a gene reporter, such as bioluminescence from the reporter gene luciferase controlled by a rhythmically expressed gene of interest. Here we describe methods that allow measurement of bioluminescence from a freely-moving mouse housed in a standard cage. Using a LumiCycle In Vivo (Actimetrics), we determined conditions that allow detection of circadian rhythms of bioluminescence from the PER2 reporter, PER2::LUC, in freely behaving mice. We tested delivery of D-luciferin via a subcutaneous minipump and in the drinking water. Further, we demonstrate that a synthetic luciferase substrate, CycLuc1, can support circadian rhythms of bioluminescence, even when delivered at a lower concentration than D-luciferin. We share our analysis scripts and suggestions for further improvements in this method. This approach will be straightforward to apply to mice with tissue-specific reporters, allowing insights into responses of specific peripheral clocks to perturbations such as environmental or pharmacological manipulations.

systems biology↗

bioRxiv2020

Weekend light shifts evoke persistent Drosophila circadian neural network desynchrony

Billions of people subject themselves to phase-shifting light signals on a weekly basis by remaining active later at night and sleeping in later on weekends relative to weekday for up to a 3hr weekend light shift (WLS). Unnatural light signals disrupt circadian rhythms and physiology and behavior. Real-time light responses of mammalian suprachiasmatic nucleus are unmeasurable at single cell resolution. We compared Drosophila whole-circadian circuit responses between unshifted daytime/nighttime schedule and a 3hr WLS schedule at the single-cell resolution in cultured adult Drosophila brains using real-time bioluminescence imaging of the PERIOD protein for 11 days to determine how light shifts alter biological clock entrainment and stability. We find that circadian circuits show highly synchronous oscillations across all major circadian neuronal subgroups in unshifted light schedules. In contrast, circadian circuits exposed to a WLS schedule show significantly dampened oscillator synchrony and rhythmicity in most circadian neurons during, and after exposure. The WLS schedule first desynchronizes lateral ventral neuron (LNv) oscillations and the LNv are the last to resynchronize upon returning to a simulated weekday schedule. Surprisingly, one circadian subgroup, the dorsal neuron group-3 (DN3s), robustly increase their within-group synchrony in response to WLS exposure. Intact adult flies exposed to the WLS schedule show post-WLS transient defects in sleep stability, learning, and memory. Our findings suggest that WLS schedules disrupt circuit-wide circadian neuronal oscillator synchrony for much of the week, thus leading to observed behavioral defects in sleep, learning, and memory. Significance StatementThe circadian clock controls numerous aspects of daily animal physiology, metabolism and behavior. Shift work in humans is harmful. Our understanding of circadian circuit-level oscillations stem from ex vivo imaging of mammalian suprachiasmatic nucleus (SCN) brain slices. However, our knowledge is limited to investigations without direct interrogation of phase-shifting light signals. We measured circuit-level circadian responses to a WLS protocol in light sensitive ex vivo Drosophila whole-brain preparation and find robust sub-circuit-specific oscillator desynchrony/resynchrony responses to light. These circuit-level behaviors correspond to our observed functional defects in learning and memory, and sleep pattern disruption in vivo. Our results reflect that WLS cause circadian-circuit desynchronization and correlate with disrupted cognitive and sleep performance.

neuroscience↗