Inter-organ signals that regulate body size, physiology and developmental timing Identifying and characterizing physiologic mechanisms that regulate organ communication and function during development and adulthood is vital for understanding how many important human health problems arise and intensify during our lifetimes. This proposal outlines a research strategy to further characterize key signaling systems that regulate critical and conserved physiological processes. These include determining how a signaling network of three Drosophila Activin-like members of the TGF-beta superfamily coordinately control fundamental aspects of brain, muscle, and fatbody cellular function in response to environmental variables such as nutrition during development to maintain physiologic homeostasis and how neuroendocrine mechanisms regulate steroid production and release, also in response to various internal and external cues, to properly time developmental maturation. We will use a wide variety of modern biological investigative methods including genetic analysis, neuronal circuit and activity mapping, biochemistry, optical/EM imaging, metabolomics, temporal and tissue specific transcriptome characterization as well as chromatin immunoprecipitation experiments, to answer these questions. Impact on human health: The successful completion of these aims will provide novel insight into how an two very conserved inter-organ signaling networks parse out specific, as well as combinatorial control, over various fundamental cellular processes to produce a properly proportioned animal, that is optimized for survival in its particular ecological niche. It is expected that this knowledge will provide useful paradigms for understanding functional aspects of the more complex, but highly related vertebrate TGF-beta and neuroendocrine signaling systems, and will afford novel insights into molecular mechanisms that contribute to a number of human disorders including obesity, metabolic syndrome, muscle wasting, pubertal disorders and ageing.