Int. J. Dev. Biol. 62: 311 - 318 (2018)

https://doi.org/10.1387/ijdb.180092ct

Vol 62, Issue 4-5

Real time dynamics of β-catenin expression during Hydra development, regeneration and Wnt signalling activation

Developmental Expression Pattern | Published: 5 June 2018

Roberta Iachetta¹, Alfredo Ambrosone^1,#, Alexander Klimovich², Jörg Wittlieb², Giada Onorato¹, Alessia Candeo³, Cosimo D’Andrea^3,5, Daniela Intartaglia^1,##, Nunzia Scotti⁶, Martina Blasio¹, Angela Tino¹, Andrea Bassi^3,4 and Claudia Tortiglione*^,1

¹Istituto di Scienze Applicate e Sistemi Intelligenti “E.Caianiello”, Consiglio Nazionale delle Ricerche, Pozzuoli, Italy, ²Zoological Institute, Christian-Albrechts-University of Kiel, Kiel, Germany, ³Dipartimento di Fisica, Politecnico di Milano, Milano, Italy, ⁴Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Milano, Italy, ⁵Center for Nano Science and Technology, Italian Institute of Technology, Milano, Italy and ⁶Istituto di Bioscienze e Biorisorse, Consiglio Nazionale delle ricerche, Portici, Italy

Abstract

Understanding the dynamic cellular behaviours driving morphogenesis and regeneration is a long-standing challenge in biology. Live imaging, together with genetically encoded reporters, may provide the necessary tool to address this issue, permitting the in vivo monitoring of the spatial and temporal expression dynamics of a gene of interest during a variety of developmental processes. Canonical Wnt/β-catenin signalling controls a plethora of cellular activities during development, regeneration and adulthood throughout the animal kingdom. Several reporters have been produced in animal models to reveal sites of active Wnt signalling. In order to monitor in vivo Wnt/β-catenin signalling activity in the freshwater polyp Hydra vulgaris, we generated a β-cat-eGFP transgenic Hydra, in which eGFP is driven by the Hydra β-catenin promoter. We characterized the expression dynamics during budding, regeneration and chemical activation of the Wnt/β-cat signalling pathway using light sheet fluorescence microscopy. Live imaging of the β-cat-eGFP lines recapitulated the previously reported endogenous expression pattern of β-catenin and revealed the dynamic appearance of novel sites of Wnt/β-catenin signalling, that earlier evaded detection by mean of in situ hybridization. By combining the Wnt activity read-out efficiency of the β-catenin promoter with advanced imaging, we have created a novel model system to monitor in real time the activity of Hydra β-cat regulatory sequences in vivo, and open the path to reveal β-catenin modulation in many other physiological contexts.

Keywords

Hydra, live imaging, Wnt, β-catenin reporter, light sheet fluorescence microscopy