RNA Seq analysis following RNAi perturbation of Hox genes in flatworm

Hox genes are highly conserved transcription factors renowned for their roles in the segmental patterning of the embryonic anterior-posterior (A/P) axis1. Emerging evidence for Hox gene expression and function in postnatally derived structures has fueled interest in their additional roles beyond embryogenesis2,3. We report novel functions for Hox genes in A/P directed adult tissue segmentation and transverse fission behavior underlying asexual reproduction in the planaria, Schmidtea mediterranea. Silencing of each of the 13 planarian Hox family members revealed 5 Hox genes required for asexual reproduction. Amongst these, silencing of hox3 genes resulted in supernumerary segments, while silencing of post2b eliminated segmentation altogether. The opposing roles of hox3 and post2b in segmentation are paralleled in the regulation of fission behavior. Silencing of hox3 increases the frequency of fission behavior initiation, while silencing of post2b eliminates fission behavior entirely. Furthermore, we identified a network of downstream effector genes mediating Hox gene regulation of asexual reproduction, thereby providing insight into their respective mechanisms of action. In summation, our study identifies roles for planarian Hox genes as mediators of adult tissue segmentation and behavior, as well as providing the first lines of evidence that Hox genes function post-embryonically to regulate asexual reproduction. RNA profiling by RNA Seq of unc22 Control or Hox gene RNAi animals in quadruplicate.