It has been convincingly shown that peptides play important roles in the regulation and maintenance of a variety of tissues and organs in living animals. However, little is known concerning the potential role of peptides as signaling molecules in developmental processes. In Hydra, there is circumstantial evidence that small diffusible molecules act as morphogens in the regulation of patterning processes. In order to view the entire spectrum of peptide signaling molecules, we initiated a project aiming at the systematic identification of (...) peptide signaling molecules in Hydra. In this review, we describe three peptide signaling molecules and one family of peptides that function as signaling molecules in the processes of axial pattern formation and neuron differentiation in Hydra. These peptides are produced by epithelial cells and are therefore termed “epitheliopeptides”. We discuss the importance of epitheliopeptides in developmental processes within a subset of hydrozoans. (shrink)

Understanding aging and how it affects an organism's lifespan is a fundamental problem in biology. A hallmark of aging is stem cell senescence, the decline of functionality, and number of somatic stem cells, resulting in an impaired regenerative capacity and reduced tissue function. In addition, aging is characterized by profound remodeling of the immune system and a quantitative decline of adequate immune responses, a phenomenon referred to as immune‐senescence. Yet, what is causing stem cell and immune‐senescence? This review discusses experimental (...) studies of potentially immortal Hydra which have made contributions to answering this question. Hydra transcription factor FoxO has been shown to modulate both stem cell proliferation and innate immunity, lending strong support to a role of FoxO as critical rate‐of‐aging regulator from Hydra to human. Constructing a model of how FoxO responds to diverse environmental factors provides a framework for how stem cell factors might contribute to aging. (shrink)