The Rhizarian amoeba Filoreta ramosa develops a neuron-like arborized network using conserved cytoskeletal mechanisms

Cells must spatially differentiate to organize their organelles, maintain function, and interact with their environment efficiently. One type of spatial differentiation used throughout eukaryotes is branched morphology, as seen in neuronal arbors and fungal hyphae. However, the mechanisms driving branched morphogenesis remain undefined in most lineages. The Rhizaria are a eukaryotic lineage including numerous amoebae with branched network-forming pseudopodia called reticulopodia. Our Rhizarian isolate, Filoreta ramosa, develops an intricately branched network covering multiple centimeters in surface area. We investigated the development of its arborized morphology, focusing on cytoskeletal structure and organelle transport. Through live imaging, immunofluorescence, and drug perturbations, we show that conserved cytoskeletal proteins drive branching and development in a manner that mirrors the cytoskeleton of neuronal arbors, despite an estimated 1.2 billion years of evolutionary distance. Additionally, we demonstrate that its dynamic morphology is interdependent on branched microtubule arrays that facilitate rapid organelle transport, while actin-filled pseudopods enable nutrient uptake, new branch formation, and intercellular interactions. These findings suggest an ancient, shared strategy for long-distance spatial organization in arborizing cell types.