The IRI Life Sciences organizes symposia to connect scientist from Berlin with experts from all over the world and to provide a networking platform for junior researchers.
We are delighted to welcome David Garfield as Independent Junior Group Leader for “Evolutionary Biology” to the IRI Life Sciences and the Humboldt-Universität zu Berlin.
On March 23rd from 4-7 pm, David Garfield’s Inaugural Lecture will take place within the framework of a scientific symposium to which you are cordially invited.
Günter P. Wagner
Systems Biology Institute & Department of Ecology and Evolutionary Biology, Yale University
Cell Types and Cell Type Origination: the next frontier of Devo-Evo
Cells and cell types are the building blocks of animals, plants and other multicellular forms of life. The number of cell types is also a major determinant of body plan complexity, with about 6 cell types in the simplest free-living metazoan, Trichoplax adhaerens, and at least 500 cell types, but probably many more, in mammals. Hence the origin of novel cell types is a key event in the evolution of complex organisms. To investigate the origin of novel cell types, however, requires an, at least preliminary, model of what cell types are and how they are realized mechanistically. Recently an evolutionary cell type concept has been proposed building upon the intellectual framework of the evolutionary homology concept: a cell type is a group of developmentally individualized cells that are able to execute a cell differentiation program different from that of other cells in the body. A corollary of this characterization is that cell types are also able to evolve cell type specific phenotypes and functions, i.e. are units of phenotypic evolution. At the mechanistic level, it is proposed that the cell type specific gene expression is enabled through the formation of a cell type specific “core regulatory complex” (CoRC), that is a physical complex of transcription factor proteins that cooperatively regulate the expression of target genes. I will exemplify this approach cell type evolution with our research program on the evolution of the decidual stromal cell (DSC) of eutherian mammals. The DSC is part of the endometrial lining of the uterus that forms the maternal side of the fetal-maternal interface. It differentiates from endometrial stromal fibroblasts (ESF) and the DSC only exists in eutherians, but not in marsupials, where only ESF have been identified. We showed that decidual gene expression depends on changes to certain transcription factor proteins that occurred at the same time as the DSC originated in the stem lineage of eutherian mammals. We further show that opossum ESF are already progesterone responsive but undergo cell death rather than differentiation to DSC. I will propose a model, in which novel cell types originate from an ancestral plastic response that leads to an alternative gene regulatory state that becomes stabilized and reprogramed leading to a novel cell type.
Nadia B. Fröbisch
Museum für Naturkunde, Leibniz Institut für Evolutions- und Biodiversitätsforschung & Dept. of Biology, Humboldt-Universität zu Berlin
Amphibian evolution through deep time: fossils, genes, and regeneration
Salamanders are unique among four limbed vertebrates (tetrapods) in showing a reversed, so called preaxial patterning of skeletal limb elements. Moreover, they have an impressive regenerative capacity that is unique amongst tetrapods, including full limb and tail regeneration. Tetrapod limb development is considered a highly conservative process and it is therefore rather surprising that salamanders show such a striking deviation from this pattern. The evolution of these two pathways in tetrapod limb development and a possible evolutionary and/or mechanistic link between preaxial polarity in limb development with the capacity of regenerating the limbs remained elusive. Evidence from fossil record shows that preaxial polarity was present in a number of early tetrapod groups and is not derived for salamanders. Moreover, fossil evidence shows that salamander-like regenerative capacities in the limbs and tails is likely an ancient feature of tetrapods that evolved independently of patterns of limb development, providing a new evolutionary framework for studying vertebrate regeneration.
IRI Life Sciences, Humboldt-Universität zu Berlin
Genome-wide patterns of regulatory evolution in Drosophila (and why you should care)
Mutations affecting regulatory DNA play an important role in phenotypic evolution and contribute disproportionately to genetic variation in human disease susceptibility. Advances in DNA-sequencing technology have greatly improved our ability to survey this variation in natural populations, but our ability to interpret this variation has lagged behind: Unlike coding DNA, there is no clear ‘regulatory code’, and the functional impact of regulatory mutations is often complicated by complex interactions among DNA regulatory elements and regulatory proteins (e.g. transcription factors). Two sets of tools are thus required for understanding regulatory evolution. The first are experiments designed to identify and functionally interrogate the DNA regulatory elements that define developmental gene regulatory networks (GRNs). The second are models of DNA-sequence evolution that are designed to incorporate variation in the functional consequences of mutations within regulatory elements. In this talk, I will discuss my work on understanding regulatory evolution in Drosophila and how this research can help us to understand regulatory evolution more broadly. Through the coupling of evolutionary sequence analyses with functional annotation of the Drosophila non-coding genome, I will argue that evidence for positive selection is surprisingly common within regulatory DNA, including regulatory regions associated with highly-conserved developmental transcription factors. Interestingly, many of the patterns observed in Drosophila are also observed in other species, including humans, suggesting that deeply conserved, cell-type specific regulatory mechanisms play a role in shaping the evolution of regulatory DNA. I will conclude with a forward looking discussion of how new technologies, particularly single-cell techniques, can help us to extend these types of studies to taxonomically important, non-traditional model systems.
You are welcome to join the reception following the symposium.
Venue: Lecture Hall, Leonor Michaelis House (Building 18) on Campus Nord of the Humboldt-Universität zu Berlin. Please use the separate »Hörsaal« entrance at the rear of the building.