Genome editing in the unicellular holozoan Capsaspora owczarzaki suggests a premetazoan role for the Hippo pathway in multicellular morphogenesis

Abstract

Animal development is mediated by a surprisingly small set of canonical signaling pathways such as Wnt, Hedgehog, TGF-beta, Notch, and Hippo pathways. Although once thought to be present only in animals, recent genome sequencing has revealed components of these pathways in the closest unicellular relatives of animals. These findings raise questions about the ancestral functions of these developmental pathways and their potential role in the emergence of animal multicellularity. Here, we provide the first functional characterization of any of these developmental pathways in unicellular organisms by developing techniques for genetic manipulation in Capsaspora owczarzaki, a close unicellular relative of animals that displays aggregative multicellularity. We then use these tools to characterize the Capsaspora ortholog of the Hippo signaling nuclear effector YAP/TAZ/Yorkie (coYki), a key regulator of tissue size in animals. In contrast to what might be expected based on studies in animals, we show that coYki is dispensable for cell proliferation but regulates cytoskeletal dynamics and the three-dimensional (3D) shape of multicellular structures. We further demonstrate that the cytoskeletal abnormalities of individual coYki mutant cells underlie the abnormal 3D shape of coYki mutant aggregates. Taken together, these findings implicate an ancestral role for the Hippo pathway in cytoskeletal dynamics and multicellular morphogenesis predating the origin of animal multicellularity, which was co-opted during evolution to regulate cell proliferation.

Chemical factors induce aggregative multicellularity in a close unicellular relative of animals

“…The first chemical factors that we found necessary for Capsaspora aggregation are calcium ions (corroborated by recent work from Phillips et al, (61)). Calcium ions are similarly required for the aggregation of D. discoideum, yeasts and sponge cells.…”

Host lipids regulate multicellular behavior of a predator of a human pathogen

“…al (2022). 26 Briefly, on the first day, 3*10 5 cells in exponential growth phase were seeded in 800 µL onto sterile 12 mm circular glass coverslips in a well of a 24-well plate and allowed to settle overnight. On the second day, the growth medium was removed and replaced with transfection medium (Scheider's Drosophila Medium with 10% (v/v) FBS, supplemented with 25 µg/mL ampicillin) and allowed to incubate for 10 minutes.…”

“…11,12 Due to its disease relevance, Biomphalaria snails have been well studied in the laboratory for decades. [13][14][15][16][17] More recently, Capsaspora has also become an emerging experimental model with substantial "omic" resources [18][19][20][21][22][23] and molecular tools available, [24][25][26][27] making this snail-amoeba symbiosis ideally suited for deeper analysis as a model system. More significantly, Capsaspora can readily adhere to and kill schistosomes while they are sporocysts (the intramolluscan growth stage) in vitro.…”

The premetazoan ancestry of the synaptic toolkit and appearance of first neurons

“…As functional techniques in these organisms expand [74][75][76][77], it is becoming possible to truly understand the role of these factors beyond predictions based on homology. The same applies for the expanded sampling of extant lineages of animals.…”

“…Consistent with this, TRP channels, often associated with ciliary signaling [ 69–71 ], localized to the cilia of Chlamydomonas have been shown to function in mating behavior [ 72 ] as well as mechanosensation [ 73 ]. Technical limitations on functional studies of these channels and signaling molecules in non-animal holozoans (ichthyosporea, pluriformea, filasterea, and choanoflagellatea) are lessening [ 74–77 ], making it an exciting time to better understand how organized the sensory components of these structures may have been in the first animals.…”