Smed-egfr-4 is required for planarian eye regeneration

• Published in: The International journal of developmental biology Vol. 63; no. 1-2; pp. 9 - 15
• Main Authors: Emili, Elena, Esteve Pallarès, Macià, Romero, Rafael, Cebrià, Francesc
• Format: Journal Article
• Language: English
• Published: Spain University of the Basque Country Press 2019
• Subjects: Animals; Bacterial Proteins - antagonists & inhibitors; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Cell Differentiation; Cells (biology); Differentiation; Epidermal growth factor; Epidermal growth factor receptors; ErbB Receptors - antagonists & inhibitors; ErbB Receptors - genetics; ErbB Receptors - metabolism; Eye - embryology; Fotoreceptors; Gene expression; Gene Expression Regulation, Developmental; Growth factors; Homology; Life span; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Photoreceptors; Planaria (Genus); Planarians - embryology; Planarians - genetics; Planarians - physiology; Planària (Gènere); Pluripotency; Progenitor cells; Regeneration; Ribonucleic acid; RNA; RNA, Small Interfering - genetics; RNA-mediated interference; Specifications; Stem cell transplantation; Stem cells; Stem Cells - cytology; Stem Cells - metabolism; Turbellaria
• ISSN: 0214-6282; 1696-3547
• DOI: 10.1387/ijdb.180361fc

Planarians are remarkable organisms that can regenerate their entire body from a tiny portion thereof. This capability is made possible by the persistence throughout the lifespan of these animals of a population of pluripotent stem cells known as neoblasts. Planarian neoblasts include both pluripotent stem cells and specialized lineage-committed progenitors that give rise to all mature cell types during regeneration and homeostatic cell turnover. However, little is known about the mechanisms that regulate neoblast differentiation. A recent study demonstrated that Smed-egfr-1, a homologue of the epidermal growth factor receptor (EGFR) family, is required for final differentiation, but not specification, of gut progenitor cells into mature cells. Given the expression by planarians of several EGFR homologues, it has been proposed that these homologues may have diverged functionally to regulate the differentiation of distinct cell types in these animals. In this study, we investigated the role of Smed-egfr-4 in eye regeneration. Compared with controls, animals in which this gene was silenced by RNA interference (RNAi) regenerated smaller eyes. Moreover, the numbers of both mature eye cell types, photoreceptor neurons and cells of the pigment cup, were significantly reduced in Smed-egfr-4(RNAi) animals. By contrast, these animals exhibited an increase in the numbers of eye progenitor cells expressing the specific markers Smed-ovo and Smed-sp6-9. These results suggest that Smed-egfr-4 is required not for the specification of eye progenitor cells but for their final differentiation, and support the view that in planarians the EGFR pathway might play a general role in regulating the differentiation of lineage-committed progenitors.