The unc-33::gfp reporter is expressed in dividing neuroblasts at pre-comma embryonic stages. unc-33::gfp expression can be observed outside the nervous system in two amphid socket cells and weakly in non-neuronal pharyngeal cells.
A short gcy-33 promoter fragment is expressed in the BAG sensory neurons ( Yu et al., 1997 ), here was observed that an extended gcy-33::GFP reporter gene fusion was expressed in BAG, URX, AQR, and PQR neurons.
Using a fosmid-based reporter in which the ceh-33 locus is tagged with gfp, we found that the CEH-33 protein shows no expression in the nervous system within or outside the pharynx at any developmental stage. The only observed expression was in a subset of head muscle cells.
GLB-33 is exclusively expressed in the nervous system. The GLB-33 protein was present in a large number of neurons in the head and tail region, the nerve ring, the ventral and dorsal nerve cord, and several lateral nerve cords. However, despite its wide expression in the nervous system, GLB-33 did not seem to be expressed in any of the amphid, cephalic, labial, or phasmid sensory neurons; the typical expression pattern for these neurons was not observed, nor was any overlap seen between GFP-expression and DiI-staining, a compound that selectively stained several amphid and phasmid neurons. This indicates that GLB- 33 is expressed in motor- or interneurons, which are involved in locomotory behaviour or information processing, and not in neurons that sense environmental cues.
Unexpectedly, str-33 was not expressed in HSNs or VC neurons, which are directly involved in egg-laying behavior. However, it was detected in ALM and PLM mechanosensory neurons and head neurons.