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Fig. 9 Post-transcriptional regulatory interactions with the hox clusters. A) Schematic representation of miR-10 and target gene expression in the Zebrafish hindbrain. MiR-10 is expressed posterior from the rhombomere 6/7 boundary. The target genes HoxB1a and HoxB3a are expressed in a strong domain (dark colour) anterior in the anterior hindbrain and in a weaker domain (light colour) in the area where they overlap with miR-10. HoxB1a shows a gap in expression in r5 and 6, possibly due to stronger transcriptional repression. B) Schematic representation of the post-transcriptional relations within the hox clusters. MiR-196 is known to represses HoxB8, HoxC8, HoxD8 and HoxA7 and we have identified HoxB1a and HoxB3a as targets for miR-10. The emerging view is that the microRNAs in the hox clusters target more anterior genes in their close proximity. C) Polycistronic transcripts identified from the EST database show inclusion of miR-196 paralogues and HoxB8 and HoxC8 target genes on the same primary transcripts.