HLH-3::GFP was expressed in the I4 neuron shortly after its mother divided to generate I4; by contrast, the I4 sister, pm5, did not express this protein. Expression of HLH-3::GFP was also observed in multiple AB-derived neural precursors. The broad expression of HLH-3::GFP was mostly confined to embryos and was no longer detectable in the I4 neuron in newly hatched L1s, suggesting that hlh-3 functions primarily in early embryos to promote I4 specification.
HLH-2::GFP was expressed in the I4 neuron shortly after its generation but was absent from its sister cell, pm5. Also like HLH-3::GFP (Expr13297), HLH-2::GFP was broadly expressed in early embryos but was not detectable in most neurons, including I4 in newly hatched L1s, suggesting that hlh-2 most likely functions in early embryos to promote I4 specification.
Region I4 drove expression in the sex myoblasts through two cell divisions, as previously described by Wagmaister et al. (2006). Although expression was also reported in the Pn.p cells, it was not observed in this study, perhaps because I4 was not identical to the pJW5 region assayed by Wagmaister et al. (2006).
Expression of gur-3prom::gfp was detected in the I2 and I4 pharyngeal neurons, as well as in the AVD head neurons. Occasionally, weaker expression was observed in the PVC tail neurons.