Rivera-Rodriguez, E. J. | Search bioRxiv

bioRxiv2021

Bantam regulates the adult sleep circuit in Drosophila

Sleep is a highly conserved feature of animal life characterized by dramatic changes in behavior, neural physiology and gene expression. The gene regulatory factors responsible for these sleep-dependent changes remain largely unknown. microRNAs are post-transcriptional modulators of gene expression which have been implicated in sleep regulation. Our previous screen identified 25 sleep-regulating microRNAs in Drosophila melanogaster, including the developmental regulator bantam (ban). Here we show that ban promotes early nighttime sleep through a population of glutamatergic neurons- the {gamma}5{beta}'2a/{beta}'2mp/{beta}'2mp_bilateral Mushroom Body Output Neurons (MBONs). We found that knockdown of ban in these neurons led to a reduction in early night sleep. The {gamma}5{beta}'2a/{beta}'2mp/{beta}'2mp_bilateral MBONs were previously shown to be wake-promoting, suggesting that ban acts to inhibit these neurons. GCaMP calcium imaging revealed that bantam inhibits the neural activity of the {gamma}5{beta}'2a/{beta}'2mp/{beta}'2mp_bilateral MBONs during the night but not the day. Blocking synaptic transmission in the {gamma}5{beta}'2a/{beta}'2mp/{beta}'2mp_bilateral MBONs rescued the effect of ban knockdown on sleep. Together these results suggest that ban promotes night sleep via the inhibition of the {gamma}5{beta}'2a/{beta}'2mp/{beta}'2mp_bilateral MBONs. RNAseq further revealed that bantam negatively regulates the wake-promoting mRNAs Kelch and CCHamide-2 receptor in the {gamma}5{beta}'2a/{beta}'2mp/{beta}'2mp_bilateral MBONs. These experiments establish bantam as an active regulator of sleep and neural activity within the fly brain.

neuroscience↗

bioRxiv2020

Regulation of olfactory associative memory by the circadian clock output signal Pigment-dispersing factor (PDF)

Dissociation between the output of the circadian clock and external environmental cues is a major cause of human cognitive dysfunction. While the effects of ablation of the molecular clock on memory have been studied in many systems, little has been done to test the role of specific clock circuit output signals. To address this gap, we examined the effects of mutation of Pigment-dispersing factor (Pdf) and its receptor, Pdfr on associative memory in male and female Drosophila. Loss of PDF signaling significantly decreases the ability to form associative memory. Appetitive short-term memory (STM), which in wildtype is time-of-day (TOD)-independent, is decreased across the day by mutation of Pdf or Pdfr, but more substantially in the morning than in the evening. This defect is due to PDFR expression in adult neurons outside the core clock circuit and the mushroom body Kenyon cells. The acquisition of a TOD difference in mutants implies the existence of multiple oscillators that act to normalize memory formation across the day for appetitive processes. Interestingly, aversive STM requires PDF but not PDFR, suggesting that there are valence-specific pathways downstream of PDF that regulate memory formation. These data argue that the circadian clock uses circuit-specific and molecularly diverse output pathways to enhance the ability of animals to optimize responses to changing conditions. SIGNIFICANCE STATEMENTFrom humans to invertebrates, cognitive processes are influenced by organisms internal circadian clocks, the pace of which is linked to the solar cycle. Disruption of this link is increasingly common (e.g. jetlag, social jetlag disorders) and causes cognitive impairments that are costly and long-lasting. A detailed understanding of how the internal clock regulates cognition is critical for the development of therapeutic methods. Here, we show for the first time that olfactory associative memory in Drosophila requires signaling by Pigment-dispersing factor (PDF), a neuromodulatory signaling peptide produced only by circadian clock circuit neurons. We also find a novel role for the clock circuit in stabilizing appetitive sucrose/odor memory across the day.

neuroscience↗