Figure 1. The conserved miR-51 family is widely expressed throughout development in C. elegans. (A) The miR-51 is highly conserved. Its origin predates the origin of Bilateria. Bases 2-8 ('seed region') are highlighted. (B) Genomic location of miR-51 family genes in the C. elegans genome. Mutant alleles shown in boldface type.
mir-54,
mir-55, and
mir-56 are likely expressed from the same transcript. Not drawn to scale. (C-J) GFP fluorescence and DIC/Nomarski imaging of animals carrying promoter::gfp fusion transgenes.
mir-51::gfp is expressed in anterior ventral cells (C and D, Z-projection; 10 um), and
mir-52::gfp is ubiquitously expressed in the soma (E and F).
mir-53::gfp is also ubiquitously expressed, but expression is weak in the gut and in anterior pharyngeal cells (G and H), and
mir-54-56::gfp is very weakly expressed in anterior ventral cells (I and J, gain adjusted, Z-projection; 10 um). Germline expression cannot be assessed using these reporters due to possible transgene silencing. Coelomocyte expression may represent uptake of GFP exported from other cells. Developmental stage: embryos at 1.5-fold stage. Scale bar: 20 um. (K) Summary of miR-51 family expression patterns as assessed by GFP expression in transgenes in embryos and/or larvae. (L) Northern blotting confirms the absence of miR-51 family miRNAs in
mir-51 family mutants. A total of 20 ug total RNA extracted from mixed-stage animals was used for each lane. Two blots were probed and stripped three times in the following order: (i) miR-51, miR-52, miR-54; (ii) miR-53, miR-56, miR-55. The probe for miR-54 was not specific and is not shown, but probes for miR-55 and miR-56 confirmed the absence of the miR-54-56 cluster in nDf58 mutants. miR-52 is detected by the miR-53 probe (compare lanes 4 and 7) because these two miRNAs differ by only one nucleotide. However, miR-53 is not detected by the miR-52 probe at the same exposure, likely because miR-53 is expressed at a lower level than miR-52.