mir-237, was not expressed in the seam cells until eL3, which mirrored the up-regulation of this gene at this stage by northern blot.
mir-237, was detected two stages earlier at L1 in the somatic gonad progenitor cells, Z1 and Z4. This result differs from our northern blot data, which showed that miR-237 RNA was first detected at L2 (Expr3739). We believe that the
mir-237::gfp expression at the L1 stage is accurate, and since
mir-237 is only expressed in the Z1 and Z4 cells at this stage, miR-237 RNA is below the levels of detection by northern blot analysis. Once the Z1 and Z4 somatic gonad derivatives expand at L2, miR-237 RNA can be seen by northern blot. By the L3 stage, and persisting into the adult,
mir-237 was expressed in the developing gonad, including the anchor cell, a subset of unidentified uterine cells, and the distal tip cells. The up-regulation of
mir-237 expression in animals carrying the
mir-237::gfp construct at the L3 stage in a variety of tissues, such as the gonad and the hypodermis, mirrors the increased miR-237 RNA levels observed at L3 by northern blot analysis. In addition, mir- 237 and mir- 84, were both expressed in the anchor cell and in the VPCs except P6.p at the mL3 stage. It is interesting to note that expression of
mir-237,
mir-84, and
mir-48 was absent in the P6.p cell during the mid- to late L3 stage, and expression of
mir-237 and
mir-84 but not
mir-48 was present in the anchor cell.