[The Svedberg seminar]-The origins and functional evolution of amniote sex chromosomes
April 22, 2025 @ 15:15 – 16:15 CEST
Henrik Kaessmann
Professor of Evolutionary Genomics at Heidelberg , Germany
Bio
Dr. Henrik Kaessmann is Professor of Evolutionary Genomics at Heidelberg University. His research focuses on the molecular foundations of mammalian phenotypic evolution, leveraging various comparative and functional genomics approaches. After earning his Ph.D. at the Max Planck Institute for Evolutionary Anthropology, he conducted postdoctoral research at the University of Chicago as an EMBO Fellow. His interdisciplinary lab, which he initially established in Lausanne (Switzerland), has pioneered large-scale studies of gene expression changes and their phenotypic implications across various biological dimensions, including organs, species, developmental stages, gene expression layers, coding and noncoding gene types, splicing isoforms, and sexes. Prof. Kaessmann has published extensively in leading journals and has received numerous prestigious honors, including three ERC grants, EMBO membership, the Friedrich Miescher Award, and the Cloëtta Prize. Beyond his research, he teaches and mentors at Heidelberg University and maintains active collaborations with clinical researchers and major scientific institutions worldwide.
Collectively, Henrik Kaessmann’s transformative work has profoundly advanced our understanding of the molecular foundations of mammalian phenotypic evolution and the driving forces of natural selection. The remarkable scope of his lab‘s major findings demonstrates how large-scale genomics approaches can yield fundamental biological insights and test key hypotheses. Notably, his interdisciplinary research has had far-reaching impact beyond evolution and development, as evidenced by extensive citations across diverse fields. His findings, including the observation of functional divergence of many genes between humans and mice, and unique gene expression (i.e., transcriptome, epigenome, translatome) datasets spanning key organs and developmental stages in humans and various model and non-model species, have become indispensable resources for biomedical research in general. To maximize their impact, his team has created interactive public databases that ensure optimal usability for the scientific community.
The origins and functional evolution of amniote sex chromosomes
In our lab, we carry out large-scale studies of gene expression changes and their phenotypic implications across various biological dimensions (e.g., species, organs, developmental stages, gene expression layers, coding and noncoding gene types, splicing isoforms, and sexes). In this seminar, I will focus on our endeavors to unravel the origins of the different amniote sex chromosome systems, which emerged from ancestral sets of autosomes. We have, for example, unveiled the origins of the sex chromosomes of therian (i.e., placental and marsupial) and monotreme mammals, and those of birds and lizards. We then scrutinized the evolutionary and functional consequences of sex chromosome differentiations (i.e., the degeneration of Y or W chromosomes in males or females, respectively) and the associated selective forces. Overall, our work has illuminated the evolution of the specific gene contents on the respective sex chromosomes, the origins and consequences of male (meiotic) sex chromosome inactivation, and the forces and mechanisms underlying the evolution of the various amniote dosage compensation mechanisms, including the drivers underlying the emergence of the female X inactivation mechanism in therians. I will present published and unpublished highlights of our work
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