No XND-1 antibody staining was visible in <28-cell stage embryos; it was first detected in the cytoplasm and nucleus of P4. Chromatin association of XND-1 is readily apparent at this stage. This early embryo expression is consistent with mRNA expression data that indicated
xnd-1 mRNA is maternally deposited and preferentially enriched in P4 (NEXTDB;
http://nematode.lab.nig.ac.jp). We note that the in situ data suggests that
xnd-1 mRNAs are found in all embryonic blastomeres, raising the possibility that post-transcriptional mechanisms repress
xnd-1 both in the early embryo and in later, somatic blastomeres. Just prior to the division of P4, XND-1 localization became predominantly nuclear and remained chromatin-associated for the remainder of development and into the adult. No somatic expression was observed with the transgenes or by immunostaining, confirming our prior conclusion from genetic studies that
xnd-1 function appears limited to the germ line (Wagner et al., 2010). Wild-type embryos showed XND-1 expression in P4 and its daughters, Z2 and Z3.