Supplementary Materials Supplemental Materials (PDF) JCB_201802113_sm. of Myc pathway during zebrafish retina regeneration, which could pave way for therapeutic intervention during mammalian retina regeneration. Graphical Abstract Open in a separate window Introduction Compared with mammals, vertebrates such as fishes and amphibians have robust regenerative potential, which has facilitated better understanding of molecular mechanisms during tissue regeneration (Gemberling et al., 2013; Goldman, 2014; Mokalled et al., 2016; Ail and Perron, 2017; Rabinowitz et al., 2017). The zebrafish is usually extensively used to study regeneration of complex tissues such as retinae. Unlike mammals, zebrafish Muller glia (MG) possess remarkable ability to reprogram themselves to produce MG-derived progenitor cells (MGPCs), irrespective of the injury paradigms (Powell et al., 2016), which are capable of regenerating the damaged retina (Fausett and Goldman, 2006; Ramachandran et al., 2010b). Zebrafish retina regeneration is possible through the orchestration of various growth factors (Russell, 2003; Wan et al., 2012; Zhao et al., 2014b; Gramage et al., 2015), cytokines (Wan et al., 2014; Zhao et al., 2014b), gene transcription factors (Ramachandran et al., 2010a, 2012; Thummel et al., 2010; Nelson et al., 2012; Wan et al., 2014), epigenome modifiers (Powell et al., 2012, 2013; Mitra et al., 2018), cell cycle regulators (Ramachandran et al., 2011, 2012; Luo et al., 2012), Sonic hedgehog signalingCinduced gene regulatory network (Kaur et al., 2018; Thomas et al., 2018), and differentiation factors (Munderloh et al., 2009) that are induced at the site of injury. Interestingly, mammalian MG exhibiting stem cell characteristics have been identified, which can be coaxed to grow and differentiate into retinal neurons to a limited extent (Ooto et al., 2004; Pollak et al., 2013; Ueki et al., 2015; Jorstad et al., 2017; Elsaeidi et al., 2018). Unraveling the complete cascade of gene regulatory network after zebrafish retina injury could help in deciphering the lack of efficient regeneration in mammals. With the increasing knowledge of pluripotency-inducing factors (PIFs) in cellular reprogramming (Yu et al., 2007; Maekawa et al., 2011), studies have been undertaken to unravel the roles of naturally induced PIFs during MG reprogramming, leading to MGPC induction and retina regeneration (Ramachandran et al., 2010a; Reyes-Aguirre and Lamas, 2016; Yao Fosfosal et al., 2016; Gorsuch et al., 2017). However, the roles of an important PIF, Myc, during retina regeneration largely remain unknown. The c-Myc has been well characterized because of its impact on diverse biological functions. These include cellular transformation, cell cycle progression, escaping of Fosfosal the cell cycle arrest, inhibiting cell differentiation, and apoptosis (Amati and Land, 1994; Cleveland and Packham, 1995; Packham et al., 1996; Liebermann and Hoffman, 1998). The participation of c-Myc in wound curing (Shi et al., 2015) and in addition after epithelial injury (Volckaert et al., 2013) is usually well documented. However, the functions of c-Myc with regards to regeneration are restricted to liver tissue of mice (Sobczak et al., 1989; Morello et al., 1990; Sanders et al., 2012) and rats (Arora et al., 2000), rat pancreas (Calvo et al., 1991), and limb (Lema?tre et al., 1992) with limited knowledge about its actual mechanistic involvement. The zebrafish has two Myc genes, namely and expression during MG reprogramming and induction of MGPCs. We show both the inductive and repressive functions played by Myc, enabling fine-tuned gene expression at the site of injury. Also, we mechanistically show the Mycb-influenced regulation of (expression was seen as early as 2 h of embryonic development, indicating its importance (Fig. S1 B). When their mRNA levels were examined after retinal injury by quantitative PCR (qPCR) and reverse transcription PCR (RT-PCR; Fig. 1, A and B), showed an early expression-peak compared with Fosfosal The mRNA in situ hybridization Fosfosal (ISH) of both and exhibited a panretinal expression pattern at 12 h post injury (hpi) that became restricted to the injury site by 2 d post injury (dpi; Fig. S1, C and D). The expression was seen in both GFP+ and adjacent cells of transgenic fish retina, in which MGPCs are marked with GFP upon injury (Fig. 1 C and Fig. S1 E; Fausett and Goldman, 2006). Both and were expressed in proliferating cell nuclear antigen (PCNA)+/EdU+ MGPCs and adjacent cells at 4C6 dpi (Fig. Efnb2 1, DCF; and Fig. S1, C.