Investigating Developing Diversity of Midbrain Dopaminergic Neurons

Alessandro Petese1, Franca Fries1, Nima Moradzadeh1, Ralf Stumm2, Sandra Blaess1

1 Neurodevelopmental Genetics, Institute of Reconstructive Neurobiology, University of Bonn School of Medicine & University Hospital Bonn, Bonn, Germany
2 Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich Schiller University Jena, Jena, Germany

Midbrain dopaminergic (mDA) neurons are located in three distinct anatomical regions, the substantia nigra pars compacta, the ventral tegmental area and the retrorubal field. mDA neurons are diverse in their projection targets, physiological properties and impact on behavior. However, little is known about how distinct dopaminergic subtypes are specified during embryogenesis. All mDA neurons are derived from a population of neuronal progenitors localized at the midline of the ventral midbrain. After cell-cycle exit, developing mDA neurons migrate towards their final destination and begin to express mDA neuron specific genes. Our goal is to explore how multiple mDA subtypes are generated at the neurogenesis stage. Here we aim to test whether a progressive competence restriction model could explain generation of mDA diversity. As mDA neurogenesis occurs over several days, different mDA neuronal subtypes might be generated in sequential waves. During development, Cxcr4 (CXC motif chemokine receptor 4) is transiently expressed in newly differentiated mDA neurons. Using an inducible genetic fate-mapping approach, we labelled cells of the Cxcr4 lineage between embryonic day (E)11.5 and E15.5, to distinguish cohorts of mDA neurons born at different developmental time points. The analysis in prenatal and adult mice indicated a progressive restricted population of mDA neurons, but also showed that the Cxcr4 lineage give rise to non-mDA cells. To specifically map Cxcr4-expressing mDA neurons and their projections, we are employing an intersectional genetic labelling strategy. We are now characterizing cell body localization and projection pattern of Cxcr4-lineage-mDA neurons fate-mapped at E11.5, E12.5 and E13.5.