Expression started at the end of gastrulation. At the 2-fold stage, about 60 cells in the head express
ast-1, most of them neurons, but also a few cells in the pharynx. A single cell in the retrovesicular ganglion expresses AST-1::YFP throughout development from the 1.5-fold stage onward. Using an
odr-2::CFP marker and checking for overlap in expression, this cell was identified as the AVG neuron. The ALN neurons in the tail weakly express AST-1::YFP in late embryo and early larval stages. Occasionally, a second pair of cells in the tail was seen based on cell body position most likely the rectV cells. Expression in the tail generally is weak and somewhat variable from animal to animal. In the L1 stage, AST-1::YFP coexpressed with
glr-1::CFP in AVA, AVD (weak
ast-1), AVE (weak
ast-1) RMDD and SMDD as well as AVG. AST-1::YFP expression decreases during larval development and is restricted to few neurons, which continue to express throughout the entire life cycle.