Lox1, an Antennapedia-class homeobox gene, is expressed during leech gangliogenesis in both transient and stable central neurons.

The leech homeobox gene Lox1 contains a homeodomain homologous to those of Sex combs reduced and Antennapedia of Drosophila, and to homeodomains of the vertebrate Hox groups 5 and 6. Lox1 expression was detected during late gangliogenesis in 15-20 pairs of central neurons repeated in most segments, suggesting that Lox1 may play a role in the differentiation of these cells. The monoclonal antibody Laz1-1 identified two pairs of Lox1-expressing neurons as the Bipolar cells and the L1 neurons. The L1 neurons were detected late in gangliogenesis and became stable neurons. The Bipolar cells appeared very early in gangliogenesis, extended processes in the longitudinal connective nerves, and then degenerated, suggesting that they play a role in establishing the longitudinal tracts of the central nerve cord.