TY - JOUR TI - Positional information specifies the site of organ regeneration and not tissue maintenance in planarians AU - Hill, Eric M AU - Petersen, Christian P A2 - Sánchez Alvarado, Alejandro VL - 7 PY - 2018 DA - 2018/03/16 SP - e33680 C1 - eLife 2018;7:e33680 DO - 10.7554/eLife.33680 UR - https://doi.org/10.7554/eLife.33680 AB - Most animals undergo homeostatic tissue maintenance, yet those capable of robust regeneration in adulthood use mechanisms significantly overlapping with homeostasis. Here we show in planarians that modulations to body-wide patterning systems shift the target site for eye regeneration while still enabling homeostasis of eyes outside this region. The uncoupling of homeostasis and regeneration, which can occur during normal positional rescaling after axis truncation, is not due to altered injury signaling or stem cell activity, nor specific to eye tissue. Rather, pre-existing tissues, which are misaligned with patterning factor expression domains, compete with properly located organs for incorporation of migratory progenitors. These observations suggest that patterning factors determine sites of organ regeneration but do not solely determine the location of tissue homeostasis. These properties provide candidate explanations for how regeneration integrates pre-existing tissues and how regenerative abilities could be lost in evolution or development without eliminating long-term tissue maintenance and repair. KW - Planaria KW - Regeneration KW - Homeostasis KW - progenitors KW - patterning KW - Wnt JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -