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• W2604449757 abstract "•JNK controls Mixer cell reprogramming through Polycomb downregulation•HOX genes spatially regulate cell mixing at segment boundaries•Abdominal-A acts as a pro-mixing factor•Abdominal-B is a prevalent, negative regulator of cell mixing In segmented tissues, anterior and posterior compartments represent independent morphogenetic domains, which are made of distinct lineages separated by boundaries. During dorsal closure of the Drosophila embryo, specific “mixer cells” (MCs) are reprogrammed in a JNK-dependent manner to express the posterior determinant engrailed (en) and cross the segment boundary. Here, we show that JNK signaling induces de novo expression of en in the MCs through repression of Polycomb (Pc) and release of the en locus from the silencing PcG bodies. Whereas reprogramming occurs in MCs from all thoracic and abdominal segments, cell mixing is restricted to the central abdominal region. We demonstrate that this spatial control of MC remodeling depends on the antagonist activity of the Hox genes abdominal-A and Abdominal-B. Together, these results reveal an essential JNK/en/Pc/Hox gene regulatory network important in controlling both the plasticity of segment boundaries and developmental reprogramming. In segmented tissues, anterior and posterior compartments represent independent morphogenetic domains, which are made of distinct lineages separated by boundaries. During dorsal closure of the Drosophila embryo, specific “mixer cells” (MCs) are reprogrammed in a JNK-dependent manner to express the posterior determinant engrailed (en) and cross the segment boundary. Here, we show that JNK signaling induces de novo expression of en in the MCs through repression of Polycomb (Pc) and release of the en locus from the silencing PcG bodies. Whereas reprogramming occurs in MCs from all thoracic and abdominal segments, cell mixing is restricted to the central abdominal region. We demonstrate that this spatial control of MC remodeling depends on the antagonist activity of the Hox genes abdominal-A and Abdominal-B. Together, these results reveal an essential JNK/en/Pc/Hox gene regulatory network important in controlling both the plasticity of segment boundaries and developmental reprogramming. During normal development, progenitor cells differentiate into specific cell types through a robust and essentially irreversible process. Nevertheless, some cells can retain plasticity, and, in some rare situations, they can change their identity and become reprogrammed into a different cell type. Fate switching can occur through an intermediate progenitor or pluripotent stage. In contrast, during transdifferentiation, cells are reprogrammed to acquire a new cell fate without reversion to a pluripotent state (Graf and Enver, 2009Graf T. Enver T. Forcing cells to change lineages.Nature. 2009; 462: 587-594Crossref PubMed Scopus (665) Google Scholar). Transdifferentiation is mostly induced upon in vitro manipulations and during regeneration (Graf, 2011Graf T. Historical origins of transdifferentiation and reprogramming.Cell Stem Cell. 2011; 9: 504-516Abstract Full Text Full Text PDF PubMed Scopus (147) Google Scholar, for a historical review); however, more recent studies indicate that transdifferentiation can also occur in normal development (Gettings and Noselli, 2011Gettings M. Noselli S. Mixer Cell formation during dorsal closure: a new developmental model of JNK-dependent natural cell reprogramming in Drosophila.Fly (Austin). 2011; 5: 327-332Crossref PubMed Scopus (2) Google Scholar, Gettings et al., 2010Gettings M. Serman F. Rousset R. Bagnerini P. Almeida L. Noselli S. JNK signalling controls remodelling of the segment boundary through cell reprogramming during Drosophila morphogenesis.PLoS Biol. 2010; 8: e1000390Crossref PubMed Scopus (37) Google Scholar, Jarriault et al., 2008Jarriault S. Schwab Y. Greenwald I. A Caenorhabditis elegans model for epithelial-neuronal transdifferentiation.Proc. Natl. Acad. Sci. USA. 2008; 105: 3790-3795Crossref PubMed Scopus (76) Google Scholar, Jung et al., 1999Jung J. Zheng M. Goldfarb M. Zaret K.S. Initiation of mammalian liver development from endoderm by fibroblast growth factors.Science. 1999; 284: 1998-2003Crossref PubMed Scopus (607) Google Scholar, Red-Horse et al., 2010Red-Horse K. Ueno H. Weissman I.L. Krasnow M.A. Coronary arteries form by developmental reprogramming of venous cells.Nature. 2010; 464: 549-553Crossref PubMed Scopus (395) Google Scholar, Shen et al., 2000Shen C.N. Slack J.M. Tosh D. Molecular basis of transdifferentiation of pancreas to liver.Nat. Cell Biol. 2000; 2: 879-887Crossref PubMed Scopus (359) Google Scholar, Sprecher and Desplan, 2008Sprecher S.G. Desplan C. Switch of rhodopsin expression in terminally differentiated Drosophila sensory neurons.Nature. 2008; 454: 533-537Crossref PubMed Scopus (85) Google Scholar, Tursun, 2012Tursun B. Cellular reprogramming processes in Drosophila and C. elegans.Curr. Opin. Genet. Dev. 2012; 22: 475-484Crossref PubMed Scopus (3) Google Scholar), raising the question of its function in non-pathological conditions. We have recently shown that in vivo transdifferentiation occurs during dorsal closure in Drosophila embryos (Gettings et al., 2010Gettings M. Serman F. Rousset R. Bagnerini P. Almeida L. Noselli S. JNK signalling controls remodelling of the segment boundary through cell reprogramming during Drosophila morphogenesis.PLoS Biol. 2010; 8: e1000390Crossref PubMed Scopus (37) Google Scholar). Dorsal closure is characterized by the dorsal migration of the two lateral ectodermal sheets and their fusion at the midline in order to seal the embryo (Agnès and Noselli, 1999Agnès F. Noselli S. [Dorsal closure in Drosophila. A genetic model for wound healing?].C. R. Acad. Sci. III. 1999; 322: 5-13Crossref PubMed Scopus (15) Google Scholar, Noselli, 1998Noselli S. JNK signaling and morphogenesis in Drosophila.Trends Genet. 1998; 14: 33-38Abstract Full Text PDF PubMed Scopus (143) Google Scholar, Young et al., 1993Young P.E. Richman A.M. Ketchum A.S. Kiehart D.P. Morphogenesis in Drosophila requires nonmuscle myosin heavy chain function.Genes Dev. 1993; 7: 29-41Crossref PubMed Scopus (349) Google Scholar). The JNK signaling pathway is activated in the most dorsal row of ectodermal cells, called the “leading edge” (LE), and is essential for the process (Glise et al., 1995Glise B. Bourbon H. Noselli S. hemipterous encodes a novel Drosophila MAP kinase kinase, required for epithelial cell sheet movement.Cell. 1995; 83: 451-461Abstract Full Text PDF PubMed Scopus (288) Google Scholar). Our recent work showed that some specific cells of the central abdominal region of the LE, named “mixer cells” (MCs), can cross the segment boundary by moving from the anterior to the adjacent, posterior compartment. This surprising mixing behavior goes against the compartmental boundary rule restricting cell exchanges from compartments made of separate lineages (DiNardo et al., 1988DiNardo S. Sher E. Heemskerk-Jongens J. Kassis J.A. O’Farrell P.H. Two-tiered regulation of spatially patterned engrailed gene expression during Drosophila embryogenesis.Nature. 1988; 332: 604-609Crossref PubMed Scopus (271) Google Scholar, Larsen et al., 2003Larsen C.W. Hirst E. Alexandre C. Vincent J.P. Segment boundary formation in Drosophila embryos.Development. 2003; 130: 5625-5635Crossref PubMed Scopus (83) Google Scholar). The way MCs break the rule is by de novo expression of the posterior determinant engrailed (en), thus allowing them to switch their identity from anterior cells to posterior cells. We have shown that this reprogramming event depends on JNK signaling as loss of JNK activity blocks en expression and mixing altogether (Gettings et al., 2010Gettings M. Serman F. Rousset R. Bagnerini P. Almeida L. Noselli S. JNK signalling controls remodelling of the segment boundary through cell reprogramming during Drosophila morphogenesis.PLoS Biol. 2010; 8: e1000390Crossref PubMed Scopus (37) Google Scholar). Cell mixing, therefore, represents an interesting model to analyze cell compartmentalization and cell reprogramming/plasticity in vivo. However, how JNK regulates en de novo expression and why cell mixing is restricted to the central part of the embryo remain open questions. The Trithorax-group (trxG) and Polycomb-group (PcG) proteins form complexes with transcription factors to regulate the chromatin state and transcription (Geisler and Paro, 2015Geisler S.J. Paro R. Trithorax and Polycomb group-dependent regulation: a tale of opposing activities.Development. 2015; 142: 2876-2887Crossref PubMed Scopus (99) Google Scholar, Schuettengruber et al., 2007Schuettengruber B. Chourrout D. Vervoort M. Leblanc B. Cavalli G. Genome regulation by polycomb and trithorax proteins.Cell. 2007; 128: 735-745Abstract Full Text Full Text PDF PubMed Scopus (1122) Google Scholar). PcG proteins form two multimeric complexes (PRC1 and PRC2) that act on chromatin compaction and methylation (Bantignies and Cavalli, 2011Bantignies F. Cavalli G. Polycomb group proteins: repression in 3D.Trends Genet. 2011; 27: 454-464Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar). They bind to specific DNA sequences called PREs (PcG-responsive elements), forming nuclear aggregates named “PcG bodies,” in which target genes are silenced (Saurin et al., 1998Saurin A.J. Shiels C. Williamson J. Satijn D.P. Otte A.P. Sheer D. Freemont P.S. The human polycomb group complex associates with pericentromeric heterochromatin to form a novel nuclear domain.J. Cell Biol. 1998; 142: 887-898Crossref PubMed Scopus (235) Google Scholar). Classical PcG target genes are the Homeotic (Hox) genes, known to specify the segment identity along the anterior-posterior (A-P) axis (Bantignies and Cavalli, 2006Bantignies F. Cavalli G. Cellular memory and dynamic regulation of polycomb group proteins.Curr. Opin. Cell Biol. 2006; 18: 275-283Crossref PubMed Scopus (113) Google Scholar). Several studies showed that PcG proteins maintain the repressed state of Hox genes outside their domain of expression, allowing a precise pattern of expression along the A-P axis (Lewis, 1978Lewis E.B. A gene complex controlling segmentation in Drosophila.Nature. 1978; 276: 565-570Crossref PubMed Scopus (2589) Google Scholar, Soshnikova and Duboule, 2009Soshnikova N. Duboule D. Epigenetic temporal control of mouse Hox genes in vivo.Science. 2009; 324: 1320-1323Crossref PubMed Scopus (192) Google Scholar). Interestingly, the en locus contains PREs that are bound by PcG to repress its expression (DeVido et al., 2008DeVido S.K. Kwon D. Brown J.L. Kassis J.A. The role of Polycomb-group response elements in regulation of engrailed transcription in Drosophila.Development. 2008; 135: 669-676Crossref PubMed Scopus (42) Google Scholar, Schuettengruber et al., 2009Schuettengruber B. Ganapathi M. Leblanc B. Portoso M. Jaschek R. Tolhuis B. van Lohuizen M. Tanay A. Cavalli G. Functional anatomy of polycomb and trithorax chromatin landscapes in Drosophila embryos.PLoS Biol. 2009; 7: e13Crossref PubMed Scopus (249) Google Scholar), thus raising the possibility that PcG could control en in the context of cell mixing during dorsal closure. In this work, we decipher the genetic program leading to MC transdifferentiation and their pattern of mixing along the A-P axis. We show that JNK signaling represses en association to PcG bodies in the nucleus of MCs, thus controlling their transdifferentiation. We further analyzed the contribution of the Polycomb (Pc) gene in MC formation by looking at the role of its target genes abdominal-A (abdA) and Abdominal-B (AbdB). We show that abdA is a pro-mixing factor essential for mixing in abdominal segments A1–A5 and that AbdB behaves as a strong repressor posteriorly, thus identifying the Hox genes abdA and AbdB as essential factors in MC patterning along the A-P axis. Our results identify a gene regulatory network involving JNK, Pc, en, and Hox genes that is important for developmental reprogramming and cell remodeling during tissue morphogenesis. MCs are integral components of the LE. They are anterior cells with groove-cell identity that are located at the segment boundary (Gettings et al., 2010Gettings M. Serman F. Rousset R. Bagnerini P. Almeida L. Noselli S. JNK signalling controls remodelling of the segment boundary through cell reprogramming during Drosophila morphogenesis.PLoS Biol. 2010; 8: e1000390Crossref PubMed Scopus (37) Google Scholar) (Figure 1A). By using the odd-skipped (odd) Gal4 driver (Mulinari and Häcker, 2009Mulinari S. Häcker U. Hedgehog, but not Odd skipped, induces segmental grooves in the Drosophila epidermis.Development. 2009; 136: 3875-3880Crossref PubMed Scopus (4) Google Scholar), which is specific to groove cells, we could clearly identify the MCs as GFP-positive cells invading the adjacent, GFP-negative, posterior compartment at the end of dorsal closure (Figures 1B and 1C). As previously shown (Gettings et al., 2010Gettings M. Serman F. Rousset R. Bagnerini P. Almeida L. Noselli S. JNK signalling controls remodelling of the segment boundary through cell reprogramming during Drosophila morphogenesis.PLoS Biol. 2010; 8: e1000390Crossref PubMed Scopus (37) Google Scholar), mixing only takes place in the central segments from A1 to A5 (Figure 1C), with MCs expressing en de novo (Figures 1D and 1E). We further analyzed the extent of reprogramming by looking at en expression in all potential MCs (i.e., all groove cells of the LE from T1 to A8). We observed that, in addition to regular MCs (A1–A5), en is also expressed in all other potential MCs from thoracic T1–T3 and abdominal A6–A7 segments (Figure 1F). These observations thus identify two populations of MCs: while both express en de novo, some undergo mixing (in segments A1–A5), while others do not (T1–T3; A6–A7). These results further indicate that MC reprogramming, although necessary as previously shown (Gettings et al., 2010Gettings M. Serman F. Rousset R. Bagnerini P. Almeida L. Noselli S. JNK signalling controls remodelling of the segment boundary through cell reprogramming during Drosophila morphogenesis.PLoS Biol. 2010; 8: e1000390Crossref PubMed Scopus (37) Google Scholar), is not sufficient to induce subsequent mixing. The activity of the JNK pathway in the whole anterior compartment is essential for MC reprogramming and mixing (Gettings et al., 2010Gettings M. Serman F. Rousset R. Bagnerini P. Almeida L. Noselli S. JNK signalling controls remodelling of the segment boundary through cell reprogramming during Drosophila morphogenesis.PLoS Biol. 2010; 8: e1000390Crossref PubMed Scopus (37) Google Scholar). However, it remains unclear whether JNK activity is required and sufficient in the MC itself. To address this question, we used the oddGal4-GFP line to manipulate JNK activity specifically in MCs. Inactivating JNK signaling leads to a complete absence of reprogramming and mixing. Indeed, no mixing was observed when blocking JNK activity through overexpression either of puckered (puc), a negative regulator of JNK (Figures 2A and 2B ), or of a dominant-negative form of the JNK/basket gene (bskDN; Figure S1). Consistently, no en expression was detected in these conditions (Figures 2C and 2D). In contrast, hyper-activation of JNK signaling by overexpressing JNKK/hemipterous (hep) led to an excessive number of MCs (four to five instead of two; Figures 2E, 2F, 2I, and 2J). Of note, JNK over-activation did not lead to ectopic MCs outside the A1–A5 domain, indicating that only these central segments are competent for mixing (Figures 2F and 2J). Like genuine MCs, the extra MCs also accumulate the posterior determinant En (Figures 2G and 2H). These results show that JNK activity is specifically required in the MCs from all segments to allow their reprogramming through en de novo expression. However, the spatial restriction of mixing indicates that MC reprogramming is necessary but not sufficient for cell remodeling and that additional activities are required to determine the full MC phenotype. The JNK signaling pathway is known to downregulate the expression of Pc during transdetermination of the regenerating imaginal discs (Lee et al., 2005Lee N. Maurange C. Ringrose L. Paro R. Suppression of Polycomb group proteins by JNK signalling induces transdetermination in Drosophila imaginal discs.Nature. 2005; 438: 234-237Crossref PubMed Scopus (174) Google Scholar). Moreover, en possesses PRE sequences in its promoter region that can be bound by PcG proteins (DeVido et al., 2008DeVido S.K. Kwon D. Brown J.L. Kassis J.A. The role of Polycomb-group response elements in regulation of engrailed transcription in Drosophila.Development. 2008; 135: 669-676Crossref PubMed Scopus (42) Google Scholar, Schuettengruber et al., 2009Schuettengruber B. Ganapathi M. Leblanc B. Portoso M. Jaschek R. Tolhuis B. van Lohuizen M. Tanay A. Cavalli G. Functional anatomy of polycomb and trithorax chromatin landscapes in Drosophila embryos.PLoS Biol. 2009; 7: e13Crossref PubMed Scopus (249) Google Scholar). These observations raise the interesting hypothesis that reprogramming of the MCs could depend on JNK-dependent regulation of Pc binding to en DNA sequences. To test this possibility, we first used qRT-PCR to analyze the expression of the Pc gene in JNK loss- and gain-of-function embryos (Figure 3A). No significant change in Pc expression was detected in JNKK/hep mutant embryos (JNK-LOF) using this method, likely due to limited sensitivity resulting from the small number of JNK-activated cells in each embryo (approximately only 200 LE cells in total). However, over-activation of the JNK pathway in the whole ectoderm (69BGal4 > hepact; JNK-GOF) led to the strong reduction of Pc expression. This result suggests that JNK signaling downregulates expression of the Pc gene during dorsal closure, reminiscent of what is observed during imaginal disc regeneration (Lee et al., 2005Lee N. Maurange C. Ringrose L. Paro R. Suppression of Polycomb group proteins by JNK signalling induces transdetermination in Drosophila imaginal discs.Nature. 2005; 438: 234-237Crossref PubMed Scopus (174) Google Scholar). To further characterize en regulation in MCs, we next investigated the association between the en-PREs and the PcG bodies in the nuclei of MCs. To this goal, we used a technique coupling DNA-FISH (fluorescence in situ hybridization) to immunostaining to visualize the PcG bodies at the en locus (Bantignies and Cavalli, 2014Bantignies F. Cavalli G. Topological organization of Drosophila Hox genes using DNA fluorescent in situ hybridization.Methods Mol. Biol. 2014; 1196: 103-120Crossref PubMed Scopus (11) Google Scholar) (Figure 3B). The interaction between en-PREs and PcG bodies was evaluated by quantifying the overlap between the Pc and en-PRE probe signals. The Pc signal from MCs was compared to the one of their posterior and anterior neighbors at the LE. Results show that the overlap between the en locus and the Pc signal is lower in posterior cells (PCs, expressing en) than in anterior cells (ACs, not expressing en) (Figure 3C; Figure S2), indicating that dissociation of Pc from the en-PREs is responsible for en expression in PCs, as shown previously (DeVido et al., 2008DeVido S.K. Kwon D. Brown J.L. Kassis J.A. The role of Polycomb-group response elements in regulation of engrailed transcription in Drosophila.Development. 2008; 135: 669-676Crossref PubMed Scopus (42) Google Scholar, Moazed and O’Farrell, 1992Moazed D. O’Farrell P.H. Maintenance of the engrailed expression pattern by Polycomb group genes in Drosophila.Development. 1992; 116: 805-810PubMed Google Scholar). Interestingly, MCs present an intermediate profile between anterior and posterior fates (Figure 3C; Figure S2), well reflecting the low level of en expression in the MCs compared to the strong expression seen in the PCs (Gettings et al., 2010Gettings M. Serman F. Rousset R. Bagnerini P. Almeida L. Noselli S. JNK signalling controls remodelling of the segment boundary through cell reprogramming during Drosophila morphogenesis.PLoS Biol. 2010; 8: e1000390Crossref PubMed Scopus (37) Google Scholar) (Figures 1E and 1F). We then tested the effect of JNK signaling on the en-PREs/Pc interaction. Over-activation of JNK has no detectable effect on the en-PREs/Pc association, consistent with the fact that JNK is already active in MCs (Figure 3C, MC JNK-GOF). In contrast, loss of JNK activity led to an increase of the en-PREs/Pc association, reaching the level of the signal observed in the AC (Figure 3C, MC JNK-LOF). In this JNK-LOF condition, the anterior, repressed fate of the MC is, therefore, maintained by a high level of en-PREs/Pc association. Together, these results suggest a two-repressor model (JNK represses Pc, which represses en; Figure 3D) in which MC reprogramming is due to a JNK-dependent relief of Pc inhibition at the en locus. The two-repressor model suggested earlier predicts that, in a Pc mutant embryo, one should observe ectopic en expression and mixing. As previously described (Pirrotta, 1997Pirrotta V. Chromatin-silencing mechanisms in Drosophila maintain patterns of gene expression.Trends Genet. 1997; 13: 314-318Abstract Full Text PDF PubMed Scopus (122) Google Scholar), and in agreement with our model, en expression expands in the anterior compartments of Pc mutants, especially in the lateral part of the embryo (Figures 4A and 4B ). We could also observe GFP-positive cells (i.e., most ACs) which express en, some of them being located in the LE and thus corresponding to putative MCs (Figures 4C and 4D). Although we observe ectopic en expression in the ectoderm (discussed earlier; Figures 4A–4D), we found that mixing does not occur in Pc embryos (Figures 4E and 4F), whose phenotype resembles that of JNK loss-of-function embryos (Figures 2A and 2B). What is the origin of this apparent discrepancy between the repressive role of Pc discussed earlier and the Pc phenotype? We first controlled that Pc was not affecting the overall JNK activity (Figure S3). We then tested the epistatic relationship between JNK and Pc, suggested by our two-repressor model (Figure 3D), by analyzing mixing in oddGal4-GFP > hepact embryos that are mutant for Pc (oddGal4-GFP > hepact; Pc/Pc). In these JNK gain-of-function embryos, the supernumerary MC phenotype is clearly suppressed by loss of Pc (Figures 4G and 4H; compare with Figures 2E and 2F), resembling simple Pc mutants (Figures 4E and 4F). These results indicate that Pc acts downstream of, or in parallel to, JNK. Therefore, while our results confirm a role of Pc on en repression downstream of JNK (Figures 3 and 4), the Pc phenotype (absence of cell mixing; Figures 4E and 4F) appears more complex. To reconcile our results, we hypothesize that, in addition to en, Pc must be controlling another essential factor for proper MC intercalation. As shown earlier (Figure 1), two different MC populations exist, with one population undergoing mixing (A1–A5 segments), while the other does not, despite expressing en (T1–T3 and A6–A7). Strikingly, the latter population resembles the MCs found in Pc mutants. These observations suggest a possible role of A-P cues to regulate the distribution of the different MC populations and explain the Pc mutant phenotype. Since Pc is known to regulate the Hox genes from the Bithorax complex (Lewis, 1978Lewis E.B. A gene complex controlling segmentation in Drosophila.Nature. 1978; 276: 565-570Crossref PubMed Scopus (2589) Google Scholar, Simon et al., 1993Simon J. Chiang A. Bender W. Shimell M.J. O’Connor M. Elements of the Drosophila bithorax complex that mediate repression by Polycomb group products.Dev. Biol. 1993; 158: 131-144Crossref PubMed Scopus (251) Google Scholar), we analyzed the expression profiles of abdA and AbdB. Whereas abdA is expressed from segments A1 to A7, AbdB expression gradually increases from A5 to the end of the embryo (Figures 5A–5D), as previously shown (Simon et al., 1992Simon J. Chiang A. Bender W. Ten different Polycomb group genes are required for spatial control of the abdA and AbdB homeotic products.Development. 1992; 114: 493-505PubMed Google Scholar). Therefore, mixing specifically takes place in the abdA territory, where no or very weak expression of AbdB is detected, suggesting that abdA could be an important activator in the process while AbdB could be acting as an inhibitor. In the Pc mutant embryo, abdA expression expands anteriorly while being maintained in segments A1 to A7 (Figures 5E and 5F) (Simon et al., 1992Simon J. Chiang A. Bender W. Ten different Polycomb group genes are required for spatial control of the abdA and AbdB homeotic products.Development. 1992; 114: 493-505PubMed Google Scholar). Similarly, AbdB is ectopically expressed in the whole anterior of the Pc mutant (Figures 5G and 5H) (Simon et al., 1992Simon J. Chiang A. Bender W. Ten different Polycomb group genes are required for spatial control of the abdA and AbdB homeotic products.Development. 1992; 114: 493-505PubMed Google Scholar). Therefore, in Pc mutant embryos, both abdA and AbdB are co-expressed along the whole A-P axis, with AbdB ectopic expression possibly causing the absence of mixing in these embryos. To analyze the role of abdA and AbdB on mixing, we first examined the phenotype of loss-of-function mutants. Integration of the MCs was assessed by immunostaining against the groove-cell marker Enabled (Ena), a cytoskeleton protein overexpressed in odd-positive cells (the groove cells) and the LE (Gates et al., 2007Gates J. Mahaffey J.P. Rogers S.L. Emerson M. Rogers E.M. Sottile S.L. Van Vactor D. Gertler F.B. Peifer M. Enabled plays key roles in embryonic epithelial morphogenesis in Drosophila.Development. 2007; 134: 2027-2039Crossref PubMed Scopus (100) Google Scholar). At the end of dorsal closure, MCs can thus be identified as Ena-positive cells in the posterior compartments that also express En (Figures 6A–6C) (Gettings et al., 2010Gettings M. Serman F. Rousset R. Bagnerini P. Almeida L. Noselli S. JNK signalling controls remodelling of the segment boundary through cell reprogramming during Drosophila morphogenesis.PLoS Biol. 2010; 8: e1000390Crossref PubMed Scopus (37) Google Scholar). In abdA mutant embryos, mixing is strongly reduced (Figure 6D). Although MCs form correctly, with a normal en expression, they show incomplete mixing in the abdA mutant, with MCs staying attached to the groove (Figures 6E and 6F). These results indicate that, although abdA is not essential for MC transdifferentiation, it positively regulates MC integration into the posterior compartment, suggesting a role in the mixing process itself. In AbdB mutant embryos, mixing spreads posteriorly and can now be detected in segments A6 and A7 in 100% of the embryos, with MCs normally expressing en (Figures 6G–6I). Mixing is never observed in this region in wild-type (WT) embryos (Figures 1B, 1C, and 2J). These results indicate that AbdB is a major repressor of mixing and that abdA and AbdB have antagonistic functions. In segments where both abdA and AbdB are expressed (i.e., A6 and A7), mixing does not occur. This reveals that the negative action of AbdB is prevalent over abdA, reflecting the well-known posterior dominance of the Hox genes. In support of this view, co-expression of both Hox genes led to a strong reduction of mixing, like in the Pc mutant (Figure 6J). To further establish the role of abdA and AbdB in MCs, these genes were individually overexpressed in MCs using the oddGal4-GFP driver. AbdA overexpression is sufficient to induce ectopic mixing more anteriorly, as observed in the T1, T2, and T3 segments (Figures 6K–6M). In contrast, mixing is abolished in all segments upon AbdB overexpression (Figures 6N–6P). Similar results were obtained using the patched (ptc) Gal4-GFP driver, which is expressed in the whole anterior compartment (Figure S4). These results confirm the loss-of-function data and indicate that abdA is a general positive regulator of mixing, while AbdB behaves as a strong prevalent repressor. The oddGal4 > abdA experiment indicates that abdA may promote mixing by acting in the MC itself or in the groove cell located more laterally. To distinguish between these two possibilities, abdA was overexpressed in the LE using the LE-Gal4 driver, leading to mixing in the T3 segment and thus showing that the action of abdA takes place specifically in the MC (Figures 6Q and 6R). We then analyzed the epistatic relationship between abdA and JNK signaling. Overexpression of abdA was not sufficient to induce mixing in JNK loss-of-function embryos (Figures 7A and 7B ; compare with oddGal4-GFP > puc embryos in Figures 2A and 2B), indicating that JNK-induced MC transdifferentiation is required for AbdA-dependent cell mixing. As a control, we have verified that AbdA itself is not capable of turning on en de novo expression (Figure S5). In contrast, abdA overexpression in the JNK gain-of-function condition induced ectopic mixing in the most anterior T2 and T3 compartments, as observed in embryos overexpressing abdA (Figures 7C and 7D; compare with Figure 6K). These results are consistent with the fact that the JNK gain of function does not change the en-PRE/Pc association, reflecting a fully activated pathway in WT embryos (Figure 3C). Therefore, JNK and abdA are both required to trigger cell mixing by regulating transdifferentiation of MCs and cell remodeling, respectively. Altogether, our results identify a gene regulatory network involving a two-tiered role of Pc, negatively regulating en expression and MC reprogramming on the one hand and positively activating mixing through abdA and AbdB gene regulation on the other hand. Interestingly, this model provides a solution to the paradoxical phenotype of the Pc mutant, in which mixing was not observed. In this condition, AbdA and AbdB are ectop" @default.
• W2604449757 created "2017-04-14" @default.
• W2604449757 creator A5021252944 @default.
• W2604449757 creator A5025223058 @default.
• W2604449757 creator A5048657353 @default.
• W2604449757 date "2017-04-01" @default.
• W2604449757 modified "2023-10-13" @default.
• W2604449757 title "Polycomb and Hox Genes Control JNK-Induced Remodeling of the Segment Boundary during Drosophila Morphogenesis" @default.
• W2604449757 cites W1587712169 @default.
• W2604449757 cites W1846532932 @default.
• W2604449757 cites W1855977133 @default.
• W2604449757 cites W1974484497 @default.
• W2604449757 cites W1979976641 @default.
• W2604449757 cites W1981566818 @default.
• W2604449757 cites W1986381098 @default.
• W2604449757 cites W1990478485 @default.
• W2604449757 cites W1990778876 @default.
• W2604449757 cites W1995771448 @default.
• W2604449757 cites W2000871658 @default.
• W2604449757 cites W2004598588 @default.
• W2604449757 cites W2006788765 @default.
• W2604449757 cites W2023915893 @default.
• W2604449757 cites W2026269751 @default.
• W2604449757 cites W2027703497 @default.
• W2604449757 cites W2030869439 @default.
• W2604449757 cites W2033791639 @default.
• W2604449757 cites W2039056680 @default.
• W2604449757 cites W2043622818 @default.
• W2604449757 cites W2048340555 @default.
• W2604449757 cites W2057734590 @default.
• W2604449757 cites W2062890130 @default.
• W2604449757 cites W2072818545 @default.
• W2604449757 cites W2073935204 @default.
• W2604449757 cites W2075794898 @default.
• W2604449757 cites W2078637309 @default.
• W2604449757 cites W2080933801 @default.
• W2604449757 cites W2088388005 @default.
• W2604449757 cites W2089049882 @default.
• W2604449757 cites W2089414860 @default.
• W2604449757 cites W2091151146 @default.
• W2604449757 cites W2094157761 @default.
• W2604449757 cites W2098204492 @default.
• W2604449757 cites W2109089699 @default.
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