The activation of the adenylyl cyclase A (ACA), which converts ATP into cAMP, is essential for relaying chemotactic signals in (Kriebel and Parent, 2004). program that allows them to chemotax and form an aggregate that will differentiate into a multicellular organism, thereby protecting them from harsh environmental conditions. In the early stages of differentiation, as the cells sense a gradient of the chemoattractant 3,5-cyclic adenosine monophosphate (cAMP), they polarize and migrate directionally in a head-to-tail fashion to form streams, which dramatically increase their recruitment range (McCann et al., 2010). The molecular mechanism that regulates streaming initiates when cAMP binds to the cAMP receptor 1 (cAR1) C a seven transmembrane G protein-coupled receptor (GPCR). Activation of the receptor leads to the dissociation of the heterotrimeric G proteins into – and -subunits, and the activation of downstream effectors that regulate cell polarity and directed motility. The activation of the adenylyl cyclase A (ACA), which converts ATP into cAMP, is essential for relaying chemotactic signals in (Kriebel and Parent, 2004). While some of the cAMP synthesized remains inside the cell to activate downstream PKA signaling, most of the cAMP is secreted and acts in a paracrine fashion to recruit neighboring cells (Manahan et al., 2004). Live-cell imaging of ACA has revealed that it resides in two distinct pools: one is restricted to the plasma membrane, and the other localizes on highly dynamic vesicles that coalesce at the back of polarized cells, and are shed during chemotaxis and streaming. We have shown that the enrichment of ACA at the back of cells is A-9758 essential for streaming, and proposed that the shedding of ACA-containing vesicles provides a compartment from which cAMP is secreted to act locally, leading to an environment where attractants can be sustained and delivered to neighboring cells (Kriebel et al., 2003, 2008). Interestingly, using fluorescence hybridization (FISH) we also showed that the ACA mRNA is asymmetrically distributed at the back of polarized cells (Das et al., 2017) and envisioned that localized ACA mRNA allows the local translation and accumulation of the ACA protein at the back of cells. We reasoned that in A-9758 starved, chemotaxis-competent cells, localized mRNA translation would provide an energy efficient means to localize proteins because mRNAs can be translated multiple times at their destination. Furthermore, on-site translation of localized mRNA would bypass the requirements for signals to be targeted to the nucleus to initiate transcription, mRNA export, cytoplasmic translation and the subsequent targeting of the protein to the proper cellular site (Buxbaum et al., 2015). In fact, mRNA localization is an evolutionary conserved gene expression regulation mechanism that underlies multiple cellular functions among different organisms (Jung et al., 2014). For example, the preferential accumulation of Ash1 mRNA in daughter cells in the budding yeast controls mating type switching (Long et al., 1997). Localization of Nanos mRNA at the posterior pole of the embryo during embryogenesis controls embryonic polarity (Gavis and Lehmann, 1992). Finally, the local translation of -actin mRNA, which localizes to growth cones and axons, is thought to modulate synaptic plasticity that dictates learning and memory formation in the brain (Bassell et al., 1998; Buxbaum et al., 2014; Kaplan et al., 1992), and it has been shown that localized translation is a key determinant of protein localization to protrusions (Mardakheh et al., 2015). Chemotaxis-competent cells are highly motile, reaching speeds of 20?m/min, and frequently reorganizing their shape and subcellular compartments as they navigate complex chemotactic gradients (Artemenko et al., 2014). The FISH technique could not provide the high spatio-temporal dynamics required to adequately assess ACA mRNA localization during chemotaxis. However, recent A-9758 advances in live-cell mRNA imaging have provided an unprecedented view of mRNA dynamics in a variety of systems. ITSN2 In particular, the.