Regulation of PDF neuropeptide production in the central nervous system
Authors: Jae Park 1; Gyunghee Lee 1; Siuk Yoo 2
Affiliations: 1) University of Tennessee; 2) Yeongnam University
Keywords: d. repressors/corepressors; b. neuropeptides
Pigment-dispersing hormone was first characterized in Crustaceans for its role in the daily rhythms of the retinal pigment dispersion. Insect gene encoding PDH-homolog, PDF, was first characterized in Drosophila. PDF is an important output factor for the maintenance of the circadian rhythms via synchronizing various clock-gene expressing neurons. Expression of PDF was found in the three distinct groups of neurons in the central nervous system; s-LNvs and l-LNvs in the brain lobe, and abdominal ganglionic neuron (PDFab). However, regulation of PDF production is not well understood. We have identified a cis-acting regulatory element (PRE) that is critical for the PDF transcription. We also identified NK2.1 homeodomain (HD) transcription factor, scarecrow (scro), as a binding factor to the PRE. Transgenic expression of wild-type scro eliminated PDF expression, while that of homeodomain-deficient scro failed to do so. A construct containing HD-alone also suppressed PDF expression, supporting that scro suppresses PDF expression via the interaction of HD with PRE in PDF-negative neurons. While loss-of-function mutations caused abnormal development of the optic lobes, ectopic expression of scro in different gal4 domains caused various developmental defects, such as rough eye phenotypes and extension of ventral nerve cord. We also observed that knockdown of disco-related (disco-r) gene suppressed PDF expression, raising the possibility of disco-r as a putative PDF transcription activator. To understand the maturational mechanisms of PDF precursor, we generated an antibody that is intended to detect only PDF-associated peptide. The antibody detected all endogenous cell bodies and axonal projections, suggesting that PDF maturation takes place in the vesicles while transporting to the axon terminals. This reagent will be used to study the genetic and molecular mechanisms of the maturational processes of PDF precursor in the clock neurons.