Identification and expression of acetylcholinesterase in Octopus vulgaris arm development and regeneration: a conserved role for ACHE?

Acetylcholinesterase (ACHE) is a glycoprotein with a key role in terminating synaptic transmission in cho- linergic neurons of both vertebrates and invertebrates. ACHE is also involved in the regulation of cell growth and morpho- genesis during embryogenesis and regeneration acting through its non-cholinergic sites. The mollusk Octopus vulgaris provides a powerful model for investigating the mechanisms underlying tissue morphogenesis due to its high regenerative power. Here, we performed a comparative inves- tigation of arm morphogenesis during adult arm regeneration and embryonic arm development which may provide insights on the conserved ACHE pathways. In this study, we cloned and characterized O. vulgaris ACHE, finding a single highlyconserved ACHE hydrophobic variant, characterized by pro- totypical catalytic sites and a putative consensus region for a glycosylphosphatidylinositol (GPI)-anchor attachment at the COOH-terminus. We then show that its expression level is correlated to the stage of morphogenesis in both adult and embryonic arm. In particular, ACHE is localized in typical neuronal sites when adult-like arm morphology is established and in differentiating cell locations during the early stages of arm morphogenesis. This possibility is also supported by the presence in the ACHE sequence and model structure of both cholinergic and non-cholinergic sites. This study provides insights into ACHE conserved roles during processes of arm morphogenesis. In addition, our modeling study offers a solid basis for predicting the interaction of the ACHE domains with pharmacological blockers for in vivo investigations. We there- fore suggest ACHE as a target for the regulation of tissue morphogenesis.