SEMINAR: OI Seminar Series - Maja Adamska

Title: Simple bodies of calcaronean sponges are products of complex developmental toolkits

Abstract: Evolution of animal body plans, and genomic changes that are underlying the morphological changes, are key biological problems. From cnidarians to humans, bodies are patterned by a conserved developmental toolkit composed of signaling pathways and transcription factors. Sponges are evolutionarily ancient animals, representing an intermediate step between colonial protists and “true” animals (eumetazoans). While their embryonic development is comparable to eumetazoans, the apparently amorphous adult bodies of majority of sponge species seem to bear no similarity to eumetazoan bodies. Recently, genome of the siliceous sponge Amphimedon queenslandica revealed representatives of majority of eumetazoan developmental gene classes, with large eumetazoan gene families generally represented by fewer members. This fulfilled expectation that the developmental toolkits of ancient and simple animals are significantly less complex than these of later evolved, complex eumetazoans. We have now sequenced genomes and transcriptomes of two calcaronean sponges, distantly related tosiliceous sponges, and with different body plans: Sycon ciliatum with radially symmetrical, columnar body, and a single exhalant opening at the apical end, and Leucosolenia complicata, composed of multiple branching tubes. Analysis of the developmental toolkit demonstrated that multiple gene families are significantly larger than in Amphimedon and comparable in size to the eumetazoan ones. We are now taking advantage of the simplicity of the body plan of Sycon in order to identify genes involved in body plan patterning, especially in axial patterning of the adult. We are taking two complementary approaches: candidate (testing expression of genes involved in axial patterning in the eumetazoans) and unbiased (RNA-seq based identification of genes with differential expression along the adult axis). The candidate approach reveals that Wnt genes and antennapedia class homeobox transcription factors are involved in axialpatterning of both larvae and adults. In addition, the unbiased approach identified TGF-beta pathway as important in adult axial patterning. The usage of developmental genes demonstrates unexpected similarity in body plan patterning between sponges and eumetazoans, especially cnidarians, revealing homology of their body plans and shedding new light on animal evolution.

Bio: Maja Adamska studied biology, with special interest in embryology and evolutionary biology, at the Jagiellonian University in Krakow, Poland. To obtain training in modern developmental biology, she moved to Germany to work with Eva Bober and Thomas Braun on function of homeobox genes in inner ear development, using a variety of vertebrate models from medaka fish to mice in her PhD project. During postdoctoral work at the University of Michigan in Miriam Meisler’s laboratory she followed complex crosses of mouse mutants to reveal genetic interactions involved in limb patterning. At this time, she became convinced that origin of complex developmental toolkits and processes is as exciting as their current function, so in the next step she joined Bernie Degnan’s group at theUniversity of Queensland to analyze developmental signaling pathways in thefirst sequenced sponge, Amphimedon queenslandica. This work revealed surprising similarities in patterning of sponge and higher animal embryos. Since 2007 she is a group leader at the Sars International Centre for Marine Molecular Biology in Bergen, Norway. Her group is using calcaronean sponges to gain insight into the evolutionary origin of a variety of key developmental processes, including germ line formation and axial patterning of embryos and adults. Genome and transcriptome sequencing of Sycon ciliatum, the major lab model species, revealed unexpected complexity of its developmental toolkit, and prompted sequencing of several other species to address animal genome evolution.