ALBERT

Description: Publication date: 20 November 2014 Source: Cell Reports, Volume 9, Issue 4 Author(s): Morgane Belle , David Godefroy , Chloé Dominici , Céline Heitz-Marchaland , Pavol Zelina , Farida Hellal , Frank Bradke , Alain Chédotal Clearing techniques have been developed to transparentize mouse brains, thereby preserving 3D structure, but their complexity has limited their use. Here, we show that immunolabeling of axonal tracts followed by optical clearing with solvents (3DISCO) and light-sheet microscopy reveals brain connectivity in mouse embryos and postnatal brains. We show that the Robo3 receptor is selectively expressed by medial habenula axons forming the fasciculus retroflexus (FR) and analyzed the development of this commissural tract in mutants of the Slit/Robo and DCC/Netrin pathways. Netrin-1 and DCC are required to attract FR axons to the midline, but the two mutants exhibit specific and heterogeneous axon guidance defects. Moreover, floor-plate-specific deletion of Slit ligands with a conditional Slit2 allele perturbs not only midline crossing by FR axons but also their anteroposterior distribution. In conclusion, this method represents a unique and powerful imaging tool to study axonal connectivity in mutant mice. Graphical abstract Teaser Clearing techniques have recently been developed to look at mouse brains, but they are complex and expensive. Belle et al. now describe a simple procedure that combines immunolabeling, solvent-based clearing, and light-sheet fluorescence microscopy. This technique allows large-scale screening of axon guidance defects and other developmental disorders in mutant mice.