mRNA-tagging isolates neural specific transcripts. (a) The mRNA-tagging strategy for profiling gene expression in the C. elegans nervous system. A pan-neural promoter drives expression of FLAG-tagged poly-A binding protein (F25B3.3::FLAG-PAB-1) in neurons (black). Native PAB-1 is ubiquitously expressed in all cells (gray). Neural-specific transcripts are isolated by coimmunoprecipitation with anti-FLAG antibodies (artwork courtesy of Erik Jorgensen). (b) Immunostaining detects FLAG::PAB-1 expression in neurons in head and tail ganglia (red arrows), ventral nerve cord motor neurons (red arrowheads), and touch neurons (white arrow). Lateral view of L2 larvae. Anterior to left. (c) Close-up view of posterior ventral cord (boxed area in (b)), showing anti-FLAG staining (red) in cytoplasm surrounding motor neuron nuclei (for example, AS9, DD5, and so on) stained with DAPI (blue). Note that hypodermal blast cells (P9p and P10p) do not show anti-FLAG staining. Anterior is left, ventral is down. Scale bars = 10 μm.