“…Axons from different circuits and cell types are intermingled, and isolation techniques that lack genetic targeting likely mask neuronal class specific features. Several genetically encoded proteomics strategies have been developed to profile cell-type-specific proteomes in the mouse brain, including metabolic labeling ( Alvarez-Castelao et al, 2017 ; Krogager et al, 2018 ) and proximity labeling strategies ( Dumrongprechachan et al, 2021 ; Hobson et al, 2022 ; Rayaprolu et al, 2021 ; Spence et al, 2019 ; Uezu et al, 2016 ). We and others have previously shown that APEX-based proximity labeling in the acute brain sections is highly efficient and robust, providing sufficient material with both cell-type and subcellular compartment specificity such that there is no need for tissue dissociation, biochemical fractionation, or subject pooling ( Dumrongprechachan et al, 2021 ; Hobson et al, 2022 ).…”