P175
Intriguing differences in gene expression between the Morning and Evening
Cells of Drosophila
Katharine Abruzzi , Abigail Zadina , Evelyn Wiyanto , Michael Rosbash
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1Howard Hughes Medical Institute, Brandeis University, National Center for Behavioral Genomics, Waltham, MA, UNITED STATES
The central clock of Drosophila consists of two major groups of neurons: PDF-positive LNvs that control the
morning peak (morning cells; M-cells) and a group of evening cells (E-cells). We have recently refined this
group to 4 key LNds and the 5th small LNv, which have a major impact on all aspects of locomotor activity
as well as rhythmicity. To learn more about the molecular signatures of these M- and E-cells, we have used
deep sequencing to analyze the RNA population of two independent replicates of M- and E-cells collected at
6 timepoints throughout the day. The data were analyzed to identify cycling transcripts and differentially
expressed genes and isoforms. Both M-cells and E-cells have similar numbers of cycling transcripts (~300)
and interestingly, only ~10% of the transcripts (e.g., the core clock components) were found in both cell
types. Approximately 95% of these cycling transcripts are novel and were not found in previous deep
sequencing studies of the head transcriptome. For example, the TrpA1 channel was found to be cycling
specifically in E-cells. Differential expression of non-cycling transcripts also revealed differences between
these two neuronal subtypes. Approximately 400 genes are enriched in evening cells compared to morning
cells. Among these genes are interesting neuropeptides such as hug, the putative Drosophila homolog of
Neuromedian-U, a SCN-expressed circadian-controlled neuropeptide involved in mammalian feeding
behaviors. Conversely many M-cell specific genes (~200) were also identified. Preliminary evidence
indicates that they include an isoform of synaptotagmin beta that is not expressed in E-cells. Experiments
are underway to determine the role of these cell-specific cycling and constitutive transcripts in the circadian
clock and in Drosophila sleep.