MitoTag mouse-based analysis of cell type-specific mitochondrial diversity in vivo
Laura Trovó1,3*, Caroline Fecher1,3*, Stephan Müller1,3, Nicolas Snaidero1 , Jennifer Wettmarshausen4, Oscar Ortiz5, Sylvia Heink1, Ralf Kühn5, Thomas Korn1,2, Wolfgang Wurst1,2,5,, Stefan Lichtenthaler1,2,3, Fabiana Perocchi2,4,5 & Thomas Misgeld1,2,3
1Technical University of Munich, 2Munich Cluster for Systems Neurology, 3DZNE, 4LMU Gene Center Munich, 5Helmholtz Zentrum München
Mitochondria serve bioenergetic needs, as well as many other cellular functions. While mitochondria show diverse morphologies and dynamics in different tissues and cell types, very little is known about the underlying molecular diversity and the mechanisms that regulate it.
To study this, we isolated cell type-specific mitochondria from their in vivo context using a new reporter mouse, in which mitochondria are tagged with an outer mitochondrial membrane-GFP in a Cre-dependent manner. Furthermore, we optimized immune-capture of functional GFP-tagged mitochondria with little cross-contamination from non-tagged mitochondria.
The CNS is the most complex tissue in our body and heavily depends on mitochondrial functions, using this organelle in a wide variety of cellular contexts. Thus, as a proof-of-principle, we isolated cell-type specific mitochondria from the adult cerebellum, a CNS tissue composed of numerous well-characterized neuronal and glial cell types that serve a wide variety of computational and metabolic functions - and explored mitochondrial diversity using proteomic profiling. Our results show substantial molecular diversity between mitochondria isolated from glial (astrocytes) and neuronal cell types (Purkinje and granule cells) with many mitochondrial proteins being highly enriched in a cell type-specific manner.
These data allowed us to predict a preference for fatty acid oxidation in astrocytic mitochondria, which we could corroborate using oxygen consumption measurements on isolated cell-type specific mitochondria. On the molecular level, we identified Rmdn3/PTPIP51 as a Purkinje cell-enriched protein, and could show - using knockout tissue - that this tether controls mitochondria-ER contact proximity specifically in Purkinje cells.
Our findings demonstrate the power of our approach, which in the future will allow exploring the diversity of cell type-specific mitochondrial signaling and metabolic pathways across many tissues in development, aging and disease.