Dual control exerted by dopamine in blood-progenitor cell cycle regulation in Drosophila

In Drosophila, definitive hematopoiesis occurs in a specialized organ termed "lymph gland", where multi-potent stem-like blood progenitor cells reside and their homeostasis is central to growth of this organ. Recent findings have implicated a reliance on neurotransmitters in progenitor development and function however, our understanding of these molecules is still limited. Here, we extend our analysis and show that blood-progenitors are self-sufficient in synthesizing dopamine, a well-established neurotransmitter and have modules for its sensing through receptor and uptake via, transporter. Modulating their expression in progenitor cells affects lymph gland growth. Progenitor cell cycle analysis revealed an unexpected requirement for intracellular dopamine in the progression of early progenitors from S to G2 phase of the cell cycle, while activation of dopamine-receptor later in development regulated progression from G2 to entry into mitosis. The dual capacity in which dopamine operates, both intra-cellular and extra-cellular, controls lymph gland growth. These data highlight a novel and non-canonical use of dopamine as a proliferative cue by the myeloid-progenitor system and reveals a functional requirement for intracellular dopamine in cell-cycle progression.