Comparative cellular and molecular approaches to epithelial morphogenesis in insects
Final Report Abstract
Our primary goal was to investigate how conserved, or not, epithelial tissue morphogenesis is across species, developmental stages, and scales of biological organization – from genetic regulation to the whole-organism phenotype. We used the extraembryonic (EE) epithelia of insects, the amnion and serosa, as an excellent and inherently comparative research model on tissue dynamics, focusing on the flour beetle Tribolium castaneum and the milkweed bug Oncopeltus fasciatus. Tissue-specific, fluorescent live cell imaging and RNA interference were key experimental techniques, encompassing long-term, high-throughput, and high spatiotemporal resolution approaches to characterize events from early formation of the EE tissues through to late EE withdrawal during embryonic dorsal closure. Key emergent principles from investigation of candidate genes during early development (focusing on Dorsocross (Doc) and folded gastrulation (fog)) were that the same regulatory factors are redeployed repeatedly, with species- and tissuespecific roles. For example, Tc-Doc has dynamic expression that straddles the amnion-serosa border, and it is involved in BMP-signaling feedback loops for activation in the serosa and inhibition in the amnion to promote the progression of early EE morphogenesis. In contrast, in Drosophila BMP activity is solely upstream of a nonmorphogenesis EE role of Doc. In late development, we identified fundamentally different cellular processes in the amnion as it prepares for EE rupture: apoptosis in Oncopeltus compared to morphological specialization and apposition to the serosa in Tribolium. In the latter context, this delimits a specific rupture competence zone. Our working model is that the amnion thus initiates EE rupture while the highly contractile serosa drives subsequent withdrawal of the EE tissues from the embryo. Throughout these events, we find a complex interplay of dynamic adhesion between the serosa and amnion, which both supports and requires inter-tissue coordination. Fate map alterations and other experiments further allowed us to probe the morphogenetic potential of each tissue alone. This approach revealed novel strategies in an amnion capable of compensatory morphogenetic activity to achieve dorsal closure. However, assessments of cell shape change and rates of tissue contraction and reorganization indicate that full function of both EE tissues ensures robust development. Altogether, our research outcomes have furthered understanding on tissue morphogenesis across species and a range of specific molecular, cellular, and tissue contexts during embryogenesis. The nuance and complexities that we have identified enrich general perspectives on morphogenesis as an integrated developmental event and have led to a number of testable hypotheses and new research avenues.
Publications
- 2012. Development: Making waves for segments (Perspective). Science 336: 306-307
Roth, R., Panfilio, K.A.
(See online at https://doi.org/10.1126/science.1222242) - 2013. Development: Getting into the groove, or evolving off the rails? (Dispatch). Curr. Biol. 23: R1101-R1103
Panfilio, K.A., Roth, S.
(See online at https://doi.org/10.1016/j.cub.2013.10.073) - 2013. High plasticity in epithelial morphogenesis during insect dorsal closure. Biol. Open 2: 1108-1118
Panfilio, K.A., Oberhofer, G., Roth, S.
(See online at https://doi.org/10.1242/bio.20136072) - 2014. Visualizing late insect embryogenesis: Extraembryonic and mesodermal enhancer trap expression in the beetle Tribolium castaneum. PLoS ONE 9(7): e103967
Koelzer, S., Kölsch, Y., Panfilio, K.A.
(See online at https://doi.org/10.1371/journal.pone.0103967) - 2015. Evolution of epithelial morphogenesis: Phenotypic integration across multiple levels of biological organization. Front. Genet. 6: 303
Horn, T., Hilbrant, M. Panfilio, K.A.
(See online at https://doi.org/10.3389/fgene.2015.00303) - 2015. The iBeetle large scale RNAi screen reveals novel gene functions for insect development and physiology. Nat. Commun. 6: 7822
Schmitt-Engel, C., (31 additional authors, including Panfilio, K.A.), Bucher, G.
(See online at https://doi.org/10.1038/ncomms8822) - 2016. Novel functions for Dorsocross in epithelial morphogenesis in the beetle Tribolium castaneum. Development 143(16): 3002- 3011
Horn, T., Panfilio, K.A.
(See online at https://doi.org/10.1242/dev.133280) - 2016. The beetle amnion and serosa functionally interact as apposed epithelia. eLife 5: e13834
Hilbrant, M., Horn, T., Koelzer, S., Panfilio, K.A.
(See online at https://doi.org/10.7554/eLife.13834) - 2017. Characterizing multiple roles of pannier during embryogenesis, as revealed with an augmented fluorescent live imaging toolkit, in the beetle Tribolium castaneum. Ph.D. Thesis. Universität zu Köln, Mathematisch- Naturwissenschaftliche Fakultät
Seibert, J.
- 2019. Fog signaling has diverse roles in epithelial morphogenesis in insects. eLife 8: e47346
Benton, M.A., Frey, N., Nunes da Fonseca, R., von Levetzow, C., Stappert, D., Hakeemi, M.S., Conrads, K., Pechmann, M., Panfilio K.A., Lynch, J.A., Roth, S.
(See online at https://doi.org/10.7554/eLife.47346) - 2020. Enhanced genome assembly and a new official gene set for Tribolium castaneum - from a draft to a reference genome. BMC Genomics 21: 47
Herndon, N., (42 additional authors, including Gurska, D., Horn, T., Seibert, J., Vargas Jentzsch, I.M., Panfilio, K.A.), Bucher, G
(See online at https://doi.org/10.1186/s12864-019-6394-6)
