Figure 5. Differential expression patterns of the lin-4 and let-7 family members in the developing vulva and anchor cell.

Animals carrying mir∷gfp fusion constructs for lin-4, the lin-4 homologue, mir-237, let-7, and the let-7 family members, mir-84 and mir-48 were analyzed for expression in the vulval precursor cells (VPCs), P3.p-P8.p, and in the anchor cell of the somatic gonad (white arrows) at third larval (L3) stage. A schematic diagram of the spatial expression patterns for the lin-4 and let-7 family members during vulva development at the L3 stages is shown to the right. The morphogenic signal, LIN-3, secreted by the anchor cell (AC) induces the closest vulva precursor cell, P6.p, to adopt the 1° cell fate and the two adjacent VPCs, P5.p and P7.p, to adopt the 2° cell fates. 1° and 2° cells will later differentiate into the mature vulva (V). VPCs that are not induced by the anchor cell (P3.p, P4.p, and P8.p) will take on non-vulval 3° cell fates, fuse with the hyp 7 cell, and become part of the outlaying epidermis (E). Our mir∷gfp fusion studies for lin-4 (blue), let-7 (blue), mir-237 (green), mir-84 (green), and mir-48 (red) showed unique and partially overlapping expression patterns in both the anchor cell of the somatic gonad and the VPCs, indicating that these miRNAs may play an important role during cell fate specification and vulva formation. The (*) indicates that mir-84 shows dynamic expression in the VPCs and by the very late L3 stage, mir-84 expression was noted exclusively in the P5.p, P6.p, and P7.p cells (Johnson et al., 2005). Note that Pn.p cells depicted in panels for lin-4, let-7, and mir-48 have undergone one cell division.