Corals and sponges are morphologically simple organisms, playing key roles in the ecosystems they build and maintain, providing habitats for other species of animals, plants and microbes: branching stony corals are reef builders, while sponges concentrate nutrients dissolved and suspended in water, making them available for other organisms. Corals and sponges display huge regenerative capacity, which might be one of the keys to their enormous ecological success. Regenerative processes in sponges and corals are important from the ecological and evolutionary perspectives and might provide general insights into animal regeneration, with potential impact on regenerative medicine. Surprisingly, very little is known about cellular, and even less about molecular mechanisms underlying these processes. To fill this gap, my lab is investigating genetic and genomic basis of regeneration in the calcareous sponge Sycon capricorn, and the staghorn coral Acropora millepora.
In Sycon, regeneration from tissue slices is dependent on a combination of cell movement and transdifferentiation. The dissociated cells re-aggregate easily and within days form complex structures. Transcriptome sequencing combined with in situ hybridization revealed that the TGF-beta pathway is involved in the collective cell movement (as it has been shown for other animals), while taxonomically restricted, putative signalling proteins are involved in re-aggregation. Strikingly, expression of multiple genes is dramatically upregulated within minutes of dissociation. We are now investigating changes in chromatin landscape to identify elements responsible for this precise regulation. In Acropora, removed individual polyps are easily replaced by coral fragments growing in laboratory conditions. We used photography and time lapse videography to identify key milestones in wound healing and regeneration in this species. RNA-Seq and differential gene expression analysis were then used to identify genes and molecular pathways involved in wound healing and formation of polyps. Among the identified genes are many homologues of genes involved in regeneration of vertebrates, but there is also a large number of taxonomically restricted genes with unknown roles. Many – but not all – of the differentially expressed genes appear to also be involved in normal growth of A. millepora, blurring the line between growth and regeneration. This result supports the notion that regeneration mechanisms are, in their core, re-deployment of developmental mechanisms, especially in case of continuously growing organisms.
Bio: Maja Adamska studied biology in Krakow, Poland, and carried PhD work on function of homeobox genes in inner ear development in Braunschweig and Halle, Germany. During postdoctoral work at the University of Michigan she followed complex crosses of mouse mutants to reveal genetic interactions involved in limb patterning. At that time, she became convinced that the origin of complex developmental toolkits and processes is as exciting as their current function, so in her second postdoc at the University of Queensland she focused on analysis of developmental signalling pathways in the first sequenced sponge, Amphimedon queenslandica. This work revealed surprising similarities in patterning of sponge and higher animal embryos. Maja was a group leader from 2007-2015 at the Sars International Centre for Marine Molecular Biology in Bergen, Norway; in 2015 she became Senior Lecturer/Lab Leader and in 2017 ARC Future Fellow/Associate Professor in the Research School of Biology of the Australian National University. She is also a Chief Investigator and Program 3 co-leader in the ARC CoE for Coral Reef Studies. Her group uses calcareous sponges to gain insight into the evolutionary origin of a variety of key developmental processes, including segregation of germ layers and axial patterning of embryos and adults as well as regeneration mechanisms. Maja is also interested in major transitions in animal evolution, such as emergence of multicellularity and morphological complexity and their relationship to genomic complexity.