Elife. 2019 Apr 26;8:e42015. doi: 10.7554/eLife.42015. | PubMed

Dayan J Li^1,2,3,4, Conor L McMann^1,2,3, Peter W Reddien^1,2,3

1. Whitehead Institute for Biomedical Research, Cambridge, United States.
2. Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.
3. Howard Hughes Medical Institute, Chevy Chase, United States.
4. Harvard/MIT MD-PhD Program, Harvard Medical School, Boston, United States.

Abstract

Positional information is fundamental to animal regeneration and tissue turnover. In planarians, muscle cells express signaling molecules to promote positional identity. At the ends of the anterior-posterior (AP) axis, positional identity is determined by anterior and posterior poles, which are putative organizers. We identified a gene, nr4A, that is required for anterior- and posterior-pole localization to axis extremes. nr4A encodes a nuclear receptor expressed predominantly in planarian muscle, including strongly at AP-axis ends and the poles. nr4A RNAi causes patterning gene expression domains to retract from head and tail tips, and ectopic anterior and posterior anatomy (e.g., eyes) to iteratively appear more internally. Our study reveals a novel patterning phenotype, in which pattern-organizing cells (poles) shift from their normal locations (axis extremes), triggering abnormal tissue pattern that fails to reach equilibrium. We propose that nr4A promotes pattern at planarian AP axis ends through restriction of patterning gene expression domains.

Presented by Dayan Li

Also mentioned in this talk--Curr Biol. 2017 Mar 6;27(5):733-742:
[Landmarks in Existing Tissue at Wounds Are Utilized to Generate Pattern in Regenerating Tissue.][1] [1]: https://www.ncbi.nlm.nih.gov/pubmed/28216315