Identification of unc-55-regulated transcripts by cell-specific gene expression profiling. A, Experimental design. In wild-type L2 larvae, synaptic remodeling genes are expressed in DD motor neurons but not in VD motor neurons; in unc-55(e1170) larvae, synaptic remodeling genes are also expressed in VD motor neurons. B, Anti-FLAG staining of FLAG-tagged PAB-1 transgenic line, wdIs31[pttr-39::3xFLAG::PAB-1] is restricted to GABAergic motor neurons in L2 stage larvae (top); ventral cord motor neuron soma are stained with DAPI (bottom). Scale bar, 10 μm. C, The mRNA tagging method. Lysates are treated with anti-FLAG-coated beads to capture FLAG-tagged PAB-1 cross-linked to cell-specific mRNA. Immunoprecipitated mRNA is amplified and labeled for hybridization to a C. elegans Affymetrix GeneChip array (see Materials and Methods).