Emma R Andersson

Genetically engineered mice are the current state of the art for understanding gene function, lineage tracing studies, and more. However, these mouse models entail by-production of mice of the wrong genotype, and can require complex breeding schemes or treatment of animals with chemicals. To circumvent these issues and reduce mouse usage, my lab has been pushing in utero injection beyond the state of the art to directly in utero engineer mouse models, without the need of dedicated genetic mouse strains or chemicals.In utero injection allows precise control over the number of manipulated mice, reducing the production of unwanted mice by 50-99%. My lab has shown that in utero injection into the amniotic fluid of mice at embryonic day 7.5 can manipulate up to 99% of brain cells, providing a new and highly efficient method to study gene function in the nervous system. We and others have used this approach to study neural lineages.Now, we aim to (1) refine the injections with robotics and artificial intelligence (to shorten injection times and improve reproducibility, reducing mouse usage further), and (2) adapt in utero injections to target mesoderm, and its derivatives such as heart, muscle and kidneys. To understand mesoderm targeting and development, we will perform single cell barcode lineage tracing from our transduced mice.This project can dramatically reduce the ethical costs of animal research in multiple fields, while providing new fundamental insights.

During embryonic liver development, developing nerves innervate both biliary cells and the vasculature. Biliary cells undergo tubulogenesis to form ducts, but the signals initiating tubulogenesis are unknown. We discovered that in a human bile duct tubulogenesis disorder, Alagille syndrome (ALGS, caused by JAG1 mutation), and in a mouse model we developed for ALGS, intrahepatic nerves are missing. In other organ systems, innervation can drive tubulogenesis.We hypothesize that innervation regulates bile duct tubulogenesis. We will map spatiotemporal liver innervation versus bile duct tubulogenesis using whole mount immunofluorescence of wild type and ALGS mouse embryos and whole livers from embryonic to postnatal stages. To test the function of nerves in regulating bile duct development, we will interfere with liver innervation in wild type mice using neurotoxins in utero, or neonatal vagatomy, and assess bile duct tubulogenesis. By adapting our technology NEPTUNE, we will map innervation with barcode labelling, and perform gain and loss of function studies of neurotransmitter pathways in vivo. Finally, we will re-express Jag1 in neural, biliary or mesenchymal cells to test which of these rescues bile duct morphogenesis in ALGS mice. Bringing together tools from neuroscience, hepatology and developmental biology, we will determine the neural circuits and mechanisms contributing to liver development.

How stem cells decide to develop into specific cell types, such as nerve or liver cells, is not known today. Nor how mature cells retain their identity through life, but in some cases they are transformed into other cell types in response to bodily injury or illness. Researchers at Karolinska Institutet will now investigate this. The group has developed a new technology to investigate stem cell development and ability to change. It will be used to understand developmental principles in two structures in mouse embryos. In the neural plate, which develops to the brain and the peripheral nervous system, and in the liver, which develops to the liver and immune system. By comparing different organs, it is possible to draw conclusions about the development of cell types with a fixed identity in the adult state, such as nerve cells, and the development of more plastic cells, such as liver cells. Creates the family tree of the cells The technology is based on labeling stem cells with fluorescent signals and biological barcodes that give each cell a unique ID number. With them, the stem cells can be traced during development. With RNA sequencing, it is possible to read the barcodes and cell IDs of individual cells, and in this way define the family trees of the mature cell types. The project group combines expertise in developmental biology, neuroscience, liver biology, immunology and physiology. - By connecting fields that are traditionally studied individually, we create a basis for unexpected discoveries about the principles that govern the identity and plasticity of the cells in our bodies, says Emma Andersson, researcher at the Department of Cell and Molecular Biology, Karolinska Institutet. The knowledge can be used in regenerative medicine, which is about repairing damaged tissue, and leading to new ways of attacking cells with abnormal developmental potential in cancer. Text Sara Nilsson Photo by Stefan Zimmerman Photo stem cells with fluorescent signals Katrin Mangold