Using transcriptional reporters of the five Wnt ligands [cis-regulatory elements of the Wnt ligands placed upstream of a nuclear GFP (Gleason et al., 2006)], we observed that three Wnt ligands (CWN-1, CWN-2 and MOM-2) are expressed in the embryo at the time of the terminal division of the SMDD/AIY mother cell. We could not detect expression of the two remaining Wnt ligands (LIN-44 and EGL-20) at that time but start seeing expression at later stages, during elongation, in the posterior end of the embryo. Interestingly, at the time of the terminal division of the SMDD/AIY mother cell,
cwn-1,
cwn-2 and
mom-2 are transcribed at a higher level in the posterior region of the embryo than in the anterior region. These observations are consistent with an analysis of the transcription pattern of Wnt ligands by fluorescent in situ hybridization (Harterink et al., 2011).
cwn-1,
cwn-2 and
mom-2 are transcribed in several tissues:
cwn-1 (posterior muscle),
cwn-2 ( posterior neuronal progenitors, posterior epidermis, intestine and posterior muscle) and
mom-2 (posterior epidermis and muscle). Their zygotic expression starts during gastrulation and remains during embryonic elongation.