mom-2 has previously been reported to be widely expressed along the anteroposterior axis of developing larvae, with expression in body wall muscle cells, ventral cord neurons, intestinal cells and seam cells (Gleason et al., 2006). By contrast, we found that mom- 2 shows a restricted expression pattern, with
mom-2 transcripts localizing only to the germ cell precursors Z2 and Z3, their descendants and a few unidentified cells in the tail.
mom-2 expression in the germ cells continued throughout larval development, whereas the tail expression reached a maximum at the mid-L1 stage and disappeared before the L1 to L2 molt. In addition, one or two
mom-2 transcripts were occasionally detected in posterior seam cells in early L1 larvae. Consistent with the early embryonic function of
mom-2 (Thorpe et al., 1997), we found that
mom-2 transcripts were already present in the zygote. At the four-cell stage,
mom-2 transcripts were enriched in the P2 blastomere. During later stages of embryonic development, mom- 2 transcripts were restricted to the posterior, with expression remaining in the tail and in the region of the Z2 and Z3 germ line precursors in comma stage embryos.