Fluorescent nanodiamond tracking reveals intraneuronal transport abnormalities induced by brain-disease-related genetic risk factors

Brain diseases such as autism and Alzheimer's disease (each inflicting >1% of the world population) involve a large network of genes displaying subtle changes in their expression. Abnormalities in intraneuronal transport have been linked to genetic risk factors found in patients, suggesting the relevance of measuring this key biological process. However, current techniques are not sensitive enough to detect minor abnormalities. Here we report a sensitive method to measure the changes in intraneuronal transport induced by brain-disease-related genetic risk factors using fluorescent nanodiamonds (FNDs). We show that the high brightness, photostability and absence of cytotoxicity allow FNDs to be tracked inside the branches of dissociated neurons with a spatial resolution of 12 nm and a temporal resolution of 50 ms. As proof of principle, we applied the FND tracking assay on two transgenic mouse lines that mimic the slight changes in protein concentration ( approximately 30%) found in the brains of patients. In both cases, we show that the FND assay is sufficiently sensitive to detect these changes

Analysis of integrin dynamics by fluorescence recovery after photobleaching

Cell migration is a complex cellular behavior that involves the controlled reorganization of the link between the actin cytoskeleton and the extracellular matrix. This mechanical connection is provided by transmembrane receptors of the integrin family. Integrins are heterodimeric receptors that undergo an allosteric switch when activated by external or intracellular signals, providing binding sites for ligands of the extracellular matrix and actin-associated cytoplasmic adapter proteins. Techniques such as fluorescence recovery after photobleaching (FRAP) are used to analyze the remodeling of green fluorescent protein (GFP)-tagged integrin receptors within focal adhesions, demonstrating that the dynamics of the remodeling of integrins in substrate adhesion sites is carefully regulated by extracellular ligands, cytoskeletal adapter proteins, and the actin cytoskeleton. FRAP analysis of GFP-tagged integrins is a tool that allows one to detect and dissect the internal dynamics of apparently immobile focal adhesions, allowing one to perceive the hierarchies and mechanisms of focal adhesion formation and dispersion