Neuropeptides are highly represented in profiles of neural cells while transcripts highly enriched in body wall muscle are excluded. Line graphs display log base 10 of relative intensity values (experimental/reference) for selected genes on the C. elegans Affymetrix array (see Materials and methods). Vertical lines correspond to individual replicates for each experimental sample. Thus, trends in expression levels for a particular gene or sets of genes can be visualized across all datasets. EM, embryonic muscle; EP, embryonic pan-neural; LP, larval pan-neural; EA, embryonic A-class motor neuron; LA, larval A-class motor neuron. Horizontal lines are colored (see heat map at right) according to relative enrichment of a single LP replicate (vertical white line with arrowheads): enriched (red), blue (depleted) and yellow (no change). (a) The top-50 ranked genes from embryonic muscle show limited enrichment in neuronal datasets. One exception is acr-16, marked by the horizontal green line, which is highly enriched in the LP dataset. acr-16 encodes a nicotinic acetylcholine receptor that is expressed in both muscle cells and neurons [16,17]. (b) FRMFamide-like peptides (flp) are enriched in neurons. A majority (20/23) of the 23 defined flp transcripts is enriched in the LP dataset, whereas specific subsets of flp transcripts are enriched in other neuronal datasets (EP, EA, LA) but largely excluded from the muscle (EM) dataset. The horizontal green highlights flp-13, which is the most highly enriched flp transcript in the A-class motor neuron (EA, LA) datasets.