The Akt signaling pathway is required for tissue maintenance and regeneration in planarians. Issue 1 (December 2016)

• Record Type: Journal Article
• Authors: Peiris, T.; Ramirez, Daniel; Barghouth, Paul; Oviedo, Néstor
• Is Part Of: BMC developmental biology. Volume 16:Issue 1(2016)
• Page Start: 1
• Page End: 15
• Publication Date: 2016-12
• Subjects: Planarians -- Regeneration -- Akt -- Stem cells; Developmental biology -- Periodicals; 571.8
• DOI: 10.1186/s12861-016-0107-z
• Languages: English
• ISSNs: 1471-213X

Abstract

Abstract Background Akt (PKB) is a serine threonine protein kinase downstream of the phosphoinositide 3-kinase (PI3K) pathway. In mammals, Akt is ubiquitously expressed and is associated with regulation of cellular proliferation, metabolism, cell growth and cell death. Akt has been widely studied for its central role in physiology and disease, in particular cancer where it has become an attractive pharmacological target. However, the mechanisms by which Akt signaling regulates stem cell behavior in the complexity of the whole body are poorly understood. Planarians are flatworms with large populations of stem cells capable of dividing to support adult tissue renewal and regeneration. The planarian orthologSmed-Akt is molecularly conserved providing unique opportunities to analyze the function of Akt during cellular turnover and repair of adult tissues. Results Our findings abrogatingSmed-Akt with RNA-interference in the planarianSchmidtea mediterranea led to a gradual decrease in stem cell (neoblasts) numbers. The reduced neoblast numbers largely affected the maintenance of adult tissues including the nervous and excretory systems and ciliated structures in the ventral epithelia, which impaired planarian locomotion. Downregulation ofSmed-Akt function also resulted in an increase of cell death throughout the animal. However, in response to amputation, levels of cell death were decreased and failed to localize near the injury site. Interestingly, the neoblast mitotic response was increased around the amputation area but the regenerative blastema failed to form. Conclusions We demonstrate Akt signaling is essential for organismal physiology and in late stages of the Akt phenotype the reduction in neoblast numbers may impair regeneration in planarians. Functional disruption ofSmed-Akt alters the balance between cell proliferation and cell death leading to systemic impairment of adult tissue renewal. Our results also reveal novel roles for Akt signaling during regeneration, specifically for the timely localization of cell death near the injury site. Thus, Akt signaling regulates neoblast biology and mediates in the distribution of injury-mediated cell death during tissue repair in planarians.