The Organizer

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Evolution of the organizer and the chordate body plan

Evolution of the organizer and the chordate body plan

organizer. Their evidence indicates that as gastrulation begins, the involuted part of the organizer interacts with the part still on the surface, enabling the head and trunk-tail organizers to differentiate from one another. This is at a time when the Nieuwkoop center has supposedly ceased activity (Boterenbrood and Nieuwkoop, 1973). Evidence in Xenopus also favors a secondary induction of some aspect of the trunk-tail organizer. As mentioned above, the Xenopus organizer, in contrast to that of urodeles, has distinct parts at the start of gastrulation, which is defined as the time of bottle cell formation. However, Xenopus differs from urodeles in relevant ways. It begins gastrulation internally at least an hour before bottle cells form, and its mesoderm is internal even before gastrulation (Nieuwkoop and Florschütz, 1950). The final patterning of the Xenopus organizer via intra-organizer interactions may occur before the blastopore lip appears. The separability of the final steps of organizer formation may be revealed by embryos deficient in FGF signaling because of a dominant negative FGF receptor (Amaya et al., 1991). In these embryos the head organizer forms successfully but the trunk tail organizer does not (or does not persist). Stewart and Gerhart (1991; Gerhart et al., 1991) showed that an animal cap from an organizer- less embryo, when grafted onto the vegetal base of a normal embryo at the late blastula stage, can still form chordamesoderm and a trunk- tail organizer in large amounts. This result suggests that the head organizer part of the organizer, and/or the deep endodermal part, can induce the trunk-tail organizer after the Nieuwkoop center has lost activity. Finally, Domingo and Keller (1995) have shown in normal embryos that non-organizer cells can be grafted into the trunk-tail organizer at the mid or late gastrula stage, and they are still induced to behaviors of trunk-tail organizer cells. A spreading trunk-tail induction seems to continue into these advanced stages. Thus, it may be that the Nieuwkoop center induces the head organizer region in the ventral band of the marginal zone, which later induces the trunk tail organizer in nearby mesoderm of the dorsal band. It remains to be clarified whether all properties of the trunk-tail organizer require this secondary interaction or just a subset, such as the posteriorization/ convergent-extension activities of the trunk-tail organizer.

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Formation and maintenance of the organizer among the vertebrates

Formation and maintenance of the organizer among the vertebrates

Grafts of the middle of the primitive streak or a source of Vg1/Wnt into different positions in a host embryo revealed that organizer- forming potential declines towards the periphery of the embryo and in the vicinity of Hensen’s node itself (Joubin and Stern, 1999), suggesting the existence of inhibitors released from these regions which would impose spatial constraints to the response to organizer inducing signals. Molecules that may mediate these inhibitory activi- ties include members of the BMP gene family: BMP4 and BMP7, which are expressed at the edges of the area pellucida, and ADMP, which is expressed in the node itself. This working model accounts for the regeneration of a new organizer after removal of the node: after ablation, cells lateral to the node are released from the inhibitory effect of ADMP and are induced to become organizer by Vg1 and Wnt activity. It also raises a paradox of why during normal development cells outside the organizer region are affected by ADMP, whereas the organizer cells themselves which produce ADMP are immune. This is a problem raised with many genetic cascades involving feedback inhibitors expressed at sites of highest signaling activity. Interest- ingly, ADMP is one of the last organizer genes to be expressed by

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The organizer concept and modern embryology: Anglo American perspectives

The organizer concept and modern embryology: Anglo American perspectives

The scientific process is a historical one in the obvious sense that each new step is built up on the basis of knowledge and understand- ing already achieved. Much of this step-wise progression is logical and systematic - even mechanical and routine - and limited choices are involved. As part of the ongoing, forward-directedness of the process past data is, ideally, generalised and consolidated into laws, new concepts, general principles, applications, or rules of thumb, etc. In such a process, details of older data and historical origins are essentially edited out and ultimately forgotten. As we have seen above, there is a constant imperative to supercede, to modernize and to seek novelty. On the other hand concepts, theories or models - much more than detailed data - often retain their importance as explanatory building blocks over long periods (relatively invariant biological concepts like homology, adaptation, selection, gene, cell differentiation, species are examples). Embryology has, in the way described in this paper, been relatively unsuccessful in establishing a stable, generally agreed set of foundational explanatory concepts. (The few enduring generalisations such as “regulation” or “harmoni- ous equipotential systems” are largely “descriptive” in kind, in the sense that they imply no specific explanations or mechanisms). And yet embryology is unusually dependent on its central concepts. It was the un-met need for an explanatory framework that made the introduction of PI possible. The organizer and PI concepts provided attempted encapsulations of the ways in which embryos were to be understood. Moreover they each determined the directions and priorities of research programmes. It is particularly at the level of concepts - precisely because, compared to raw data, they are complex and slow to evolve - that historical forces are most relevant. It is at these most basic levels of scientific thought and progression that the potentially distorting effects of history are likely to be most potent. So, I have focused specifically on ways in which historical considerations may have been real and significant contributors to the evolution of concepts in this subject.

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Contribution of the Belgian school of embryology to the concept of neural induction by the organizer

Contribution of the Belgian school of embryology to the concept of neural induction by the organizer

Albert BRACHET, founder of the Brussels School of embryology, conducted delicate experiments in which he selectively destroyed zones of the grey crescent with heated needles. This allowed him to observe, in 1923, that the median region of the grey crescent of the blastula is a area of spontaneous differentiation and that this «primary self-differentiation centre» organizes the axial organs in anurans. It is thus fair to say that A. BRACHET contributed significantly to the emergence of the organizer concept. Albert DALCQ and Jean PASTEELS, successors of A. BRACHET, trying to solve the problem of the organizer’s determination, proposed their famous quantitative theory of embryonic development resulting in the concept of morphogenetic potential, which increases with the CV concentration, a combination of a cortical constituent C and a vegetal substance V. Jean BRACHET, the younger son of A. BRACHET and one of the founding father of molecular biology and embryology, was soon convinced that the organizer owes its inducing power to a chemical substance. Being the first to suggest the role of RNA in protein synthesis, he first imagined that RNA could be the active substance in induction but became convinced afterwards that the inducer must have a proteic nature. His interest in the molecular aspects of induction stimulated research that was to make chemical embryology molecular.

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Introducing the Spemann Mangold organizer: experiments and insights that generated a key concept in developmental biology

Introducing the Spemann Mangold organizer: experiments and insights that generated a key concept in developmental biology

manuscript to be published jointly. (3) Most importantly, Spemann (as outlined above) had developed all by himself the conceptual approach as well as the techniques required. Early in 1921, he actually had predicted two possible outcomes of the chimeric experi- ment, one of them - as mentioned above - the induction of neural plate by the archenteron roof. Notwithstanding Spemann’s conceptual contributions, Hilde got her Ph.D. with nearly the best marks (Fig. 12). With these facts and judgements, a fair attribution of merit to each author of the organizer paper would credit Spemann with Fig. 10. Hilde Mangold´s Lab notes on the famous heteroplastic lip transplantation (Um. 132) and her own slide boxes labelled “Mangold” by the curator of the Embryological Collection of the Hubrecht Laboratory (Utrecht/The Netherlands). Hilde’s name does not appear in the register! Obviously the slides and the corresponding files were considered part of Otto Mangold’s work donated to the collection. (Courtesy Embryological Collection / Gesineke Bangma, Hubrecht Laboratory, Utrecht/NL).

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Nodal signaling and the zebrafish organizer

Nodal signaling and the zebrafish organizer

The results described above reveal essential roles for Nodal signaling and Boz in the formation of dorsal mesoderm. It is striking that the neural tube forms despite the absence of the shield and mesendodermal derivatives in these mutants. This result suggests that despite abnormal development of the organizer region and the lack of axial mesoderm, neuralizing activity is still present in the affected embryos. This apparent paradox parallels the results of embryological studies, which show that the shield and its derivatives are not required to form a neural tube (Shih and Fraser, 1996; Driever et al., 1997). Extirpation of the shield produces cyclopic embryos lacking notochord and prechordal plate, but the neural tube forms, although it lacks floor plate and other ventral cell types. These results indicate that organizing activities are not restricted to the shield. In molecular terms, these results imply that molecules with neural inducing activity must also be expressed outside the shield or before shield formation and in the absence of Boz and Nodal-related signals. Consistent with this, Nodal-related signals are not required for chordin expression (Gritsman et al., 1999; Sirotkin et al., 2000a), which is expressed in a broad dorsal domain that includes not only presumptive axial and paraxial mesoderm, but also presumptive dorsal ectoderm (Miller-Bertoglio et al., 1997; Schulte-Merker et al., 1997). Double mutants for boz and sqt have reduced chordin expression and are ventralized, but still form neural structures. Moreover, the neural tube of boz;sqt;cyc triple mutants is greatly reduced, but not absent, revealing the existence of pathways not requiring Boz and Nodal signals that can activate neural inducing molecules (Shimizu et al., 2000; Sirotkin et al., 2000a).

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Organizer and axes formation as a self organizing process

Organizer and axes formation as a self organizing process

Axes formation in higher organisms is proposed to proceed by a chain of pattern forming reactions in which the following elemen- tary steps play a major role: (i) Organizing regions (including poles and signaling centers) are represented by local concentration maxima of substances, and are generated by local self-enhance- ment and long-range inhibition. (ii) A second organizing region can be generated at a position displaced from the first, if the first system induces the second at long-range and/or low concentrations, while excluding it at short-range and high concentrations. Minute asymmetries are sufficient for a predictable orientation of the resulting pattern. In the absence of such asymmetries, the choice of orientation will be random. Such a coupling of two centers ensures a specific polarity and is proposed to generate the dorsal side eccentric to the animal-vegetal axis and the markers for the left side to one side of the midline. (iii) Zones surrounding hot spots can be generated if the organizing region activates at long-range feedback loops that are locally exclusive. The mesoderm in the amphibian marginal zone can be generated in this way. The selective activation of genes in developmental pathways requires similar components: competing feedback loops. However, for pathway selection the competition must be more local. (iv) A concentration-dependent selection of developmental pathways can be achieved by stepwise and irreversible transitions from the activation of one default gene to genes higher in a hierarchy. This stepping through stops when the gene activation matches the local morphogen concentration. If the genes are part of competing feedback loops, particular genes become active in sharply sepa- rated zones since, close to the threshold, a minute increase of the signal can cause a complete transition into another pathway. The Spemann-Mangold organizer proper with its anterior-posterior subdivision can form in this way, utilizing (as suggested by others) a gradient generated by the Nieuwkoop center. (v) A hot spot can be converted to a hot stripe if the spot induces the stripe, and the stripe, in turn, induces a shift of the spot. An apparent movement of the organizer leaves behind a single band of activated cells. The midline system is proposed to form in this way. (vi) Tissue far from an organizer can lose the competence to perform the pattern forming reaction by a feedback of the organizing regions on the surrounding tissue. This mechanism suppresses spontaneous onsets of the pattern forming reaction at ectopic positions.

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A study of Xlim1 function in the Spemann Mangold organizer

A study of Xlim1 function in the Spemann Mangold organizer

of view. We showed that inhibitory forms of Lim1 do not suppress the expression of Siamois, which appears to be the earliest zygotic gene involved in axis formation, and which is normally expressed prior to Xlim1 (Lemaire et al., 1995). In contrast, inhibitory forms of Lim1, in agreement with the fact that Lim1 is normally required for organizer gene expression, suppress axis induction by Siamois. Less anticipated was the observation that Lim1 is also required downstream of organizer factors whose expression is regulated by this gene. These factors, such as Chordin and Frzb, serve to limit or prevent ventralizing activities of BMP and Wnt acting during gastrulation (Jones et al., 1996). We show here that these dorsal factors can induce the ectopic expression of Xlim1 during gastrulation, thereby suggesting the existence of a positive feedback between these genes, in order to enhance the dorsal expression program. Consistent with this idea, axis development is prevented when inhibitory forms of Lim1 are expressed during gastrulation under the control of the cytomegalovirus promoter (data not shown). Thus, our data indicate that Lim1 is a central regulator, required at two critical steps during early development: First, during the short period of organizer establishment where it participates in the activation of early genes. Second, during the phase where the organizer functions to antagonize ventralizing activities and to allocate dorsal fates. It will be interesting to determine whether Lim1 targets are the same during both phases, which would indicate that this factor is required for initiation and maintenance of organizer gene expression. Alternatively, Lim1 could activate a different set of targets at different times, arguing for a sequential progression towards the acquisition of anterior dorsal fates. Interestingly, the second view is supported by recent observa- tions made in Lim1 mutant mice. Using chimeric mice and explant recombination, Shawlot and colleagues (1999) put forward a double assurance model whereby Lim1 is required in different tissues at different developmental stages in order to impart anterior identity to the embryo. However, targets of Lim1 activity

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E-Organizer System For Department

E-Organizer System For Department

As we know, we all need to have a good activity organizing which make our daily activity be more planned and schedulable. Many sources can be used such as a device or planning resources. And because of that, there is also organizer or planner that comes in software version. There are many type of the organizer such as Home Organizer, Money Organizer, Meeting organizer, and so on. In this project will aim at developing an e-organizer which scope only at Computer department at FKEKK. It is focused to facilitate meeting, appointments, update event or information to every staff of the departments, allows staff to upload and download important document and also provide an e-forum to discussion session. The system will probably use PHP as a web base, MySQL for database, Jscript, html as programming language, and Apache as a web server.

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The isthmic organizer and brain regionalization

The isthmic organizer and brain regionalization

ABSTRACT Distinct neural identities are acquired through progressive restriction of developmental potential under the influence of local environmental signals. Evidence for the localization of such morphogenetic signals at specific locations of the developing neural primordium has suggested the concept of “secondary organizer regions”, which regulate the identity and regional polarity of neighboring neuroepithelial areas one step further. In recent years, the most studied secondary organizer has been the isthmic organizer, which is localized at the hind-midbrain transition and controls anterior hindbrain and midbrain regionalization. Otx2 and Gbx2 expression is fundamental for positioning the organizer and for the establishment of molecular interactions that induce Fgf8 expression and then, stabilize the autoregulative loop of En1, Wnt1 and Pax2 expression. Temporo- spatial patterns of such gene expressions are necessary for the correct development of the organizer which, by a planar mechanism of induction, controls the normal development of the rostral hindbrain from r2 to the midbrain-diencephalic boundary. Fgf8 appears as the active diffusible molecule for isthmic morphogenetic activity and has been suggested to be the morphogenetic effector in other inductive activities revealed in other neuroepithelial regions.

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Handbook for the Palm III Organizer

Handbook for the Palm III Organizer

The first time you synchronize your data, you need to enter user information on both the organizer and Palm Desktop software. After you enter this information and synchronize, the HotSync Manager recognizes your organizer and doesn’t ask for this information again. If you are a System Administrator preparing several organizers for a group of users, you may want to create a user profile. See “Creating a user profile” in Chapter 6 before performing the following steps. Important: You must perform your first HotSync operation with a

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Handbook for the Palm V Organizer

Handbook for the Palm V Organizer

The first time you synchronize your data, you need to enter user information on both the organizer and Palm Desktop software. After you enter this information and synchronize, the HotSync Manager recognizes your organizer and doesn’t ask for this information again. If you are a System Administrator preparing several connected organizers for a group of users, you may want to create a user profile. See “Creating a user profile” in Chapter 6 before performing the following steps.

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Handbook for the Palm V Organizer

Handbook for the Palm V Organizer

The first time you synchronize your data, you need to enter user information on both the organizer and Palm Desktop software. After you enter this information and synchronize, the HotSync Manager recognizes your organizer and doesn’t ask for this information again. If you are a System Administrator preparing several connected organizers for a group of users, you may want to create a user profile. See “Creating a user profile” in Chapter 6 before performing the following steps.

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Handbook for the Palm VII Organizer

Handbook for the Palm VII Organizer

The first time you synchronize your data, you need to enter user information on both the organizer and Palm Desktop software. After you enter this information and synchronize, the HotSync Manager recognizes your organizer and doesn’t ask for this information again. If you are a System Administrator preparing organizers for a group of users, you may want to create a user profile. See “Creating a user profile” in Chapter 7 before performing the following steps. Important: You must perform your first HotSync operation with a

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Formation of the embryonic organizer is restricted by the competitive influences of Fgf signaling and the SoxB1 transcription factors

Formation of the embryonic organizer is restricted by the competitive influences of Fgf signaling and the SoxB1 transcription factors

We next investigated whether inhibition of SoxB1 function would be sufficient to elicit ectopic expression of the fgfs in the absence of any other additional dorsal or vegetal signals. For this, a dominant negative approach is preferable to a morpholino (MO) knockdown approach. Because of redundancy between different members of the SoxB1 family and maternal expression of at least one of the family members [11], [9], a phenotype is only seen in morpholino injected embryos at stages of development after organizer formation (as reported by Okuda et al. 2010 [11]) and no effect on the early expression of the fgfs was seen (data not shown). This suggest that there is sufficient maternal protein for at least one of the SoxB1 factors to mask any effects of blocking translation of the other factors. However, we have previously shown that a dominant negative Sox3 construct, in which the nuclear localization signals were mutated (hereafter referred to as dnSox3) interferes with the activity of all the SoxB1 factors (by inhibiting their nuclear localization), and was able to elicit ectopic expression of four organizer markers (boz, sqt, gsc and chd), an effect rescued by co-injection with any of the SoxB1 factors [9]. Here, we found that injection of the same dnSox3 construct also induced ectopic expression of both fgf3 and fgf8 at 4.5 hpf in a manner similar to the induction of other markers of organizer (Fig. 1M,N). This effect was more striking at 30% epiboly (approximately 5 hpf), a stage when endogenous fgf expression is more robust (Fig. 1O,P). One concern in using dominant-negative approaches is that the dnSox3 construct might not only block the function of the protein of interest, but might also generate unrelated neomorphic effects. However, in this case, like the effects on other markers of the organizer, this induction of fgf expression by dnSox3 was rescued by overexpression of sox3, sox19a or sox19b with the dnSox3 similarly negating the ability of any of the SoxB1 factors from repressing fgf expression and resulting in reversion to wild type fgf expression (see Fig. S2 in the supplementary material). This rescue experiment indicates that the effects of the dnSox3 described are via inhibiting SoxB1 function and are not neomorphic effects. Together these data indicate that the endogenous SoxB1 proteins repress the expression of fgf3 and fgf8 in the organizer and that interfering with this repression using

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Transcriptional Integration of Wnt and Nodal Signals in the Establishment of the Spemann Organizer

Transcriptional Integration of Wnt and Nodal Signals in the Establishment of the Spemann Organizer

However, subsequent knockdown studies of Sia and Twn did not reflect this hypothesis. Knockdown of Sia and Twn by morpholino oligonucleotide resulted in a ventralized embryo lacking the anterior-most structures, the forebrain and midbrain, but dorsal structures, including the notochord, were still present (Ishibashi et al., 2008). In contrast, dorsal expression of Eng-Sia resulted in ventralized embryos, lacking both anterior and dorsal structures (Fan and Sokol, 1997; Kessler, 1997). This raises the possibility that Eng-Sia may repress genes that are normally not targets of Sia or Twn, or that knockdown of Sia and Twn in these studies was not complete. If Sia/Twn are indeed required for the formation of the fully functional organizer, then a partial knockdown of Sia/Twn activity may result in increasingly more severe anterior truncations, as organizer formation is restricted. However, if Sia/Twn are required only for the formation of the head organizer, increasing inhibition of Sia/Twn activity would only affect the anterior- most tissues of the head. Interestingly, the phenotype observed in Sia/Twn knockdown embryos is reminiscent of the phenotypes obtained when small regions of the organizer are extirpated from an embryo. As more organizer tissue is removed from the embryo, more anterior tissue is lost (Stewart and Gerhart, 1990), suggesting that incomplete knockdown of Sia/Twn may cause a partial defect in organizer formation and function. These observations offer two possibilities for the role of Sia/Twn in organizer formation. Sia and Twn could be necessary for formation of the entire, fully functional organizer, or could play a more limited role in the formation of the head organizer. Given these distinct possibilities, further work is required to determine the exact role of Sia and Twn in

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The Spemann Mangold organizer: the control of fate specification and morphogenetic rearrangements during gastrulation in Xenopus

The Spemann Mangold organizer: the control of fate specification and morphogenetic rearrangements during gastrulation in Xenopus

The organizer in Xenopus is established on the dorsal side of the embryo through the combinatorial action of the “dorsalizing” Wnt/ β -catenin signalling pathway and the “vegetal” TGF- β signalling cascade (Harland and Gerhart, 1997; Nieto, 1999). Both pathways are dependent on maternal cytoplasmic determinants that are localized in the vegetal hemisphere of the oocyte, which only displays animal-vegetal polarity. Radial symmetry in the uni- polarized egg is broken by fertilization, which elicits a displacement of cortically attached organelles from a vegetal position to the future dorsal side, in a process referred to as cortical rotation (see Moon and Kimelman, 1998). This translocation results in the cytoplasmic enrichment of the Wnt signal transducer β -catenin on the presumptive dorsal side of the dividing embryo (Moon and Kimelman, 1998). The dorsal accumulation of β -catenin protein could in part be the consequence of directed vectorial transport, along cortically aligned microtubules, of Dishevelled (Dsh), an- other upstream intracellular Wnt pathway component (Miller et al., 1999). Translocated Dsh antagonizes the activity of the constitu- tively active serine/threonine kinase glycogen synthase kinase-3 β (GSK-3 β ), which is part of a multimeric β -catenin destruction complex, which in addition contains Axin and the tumor suppressor Adenomatous Polyposis Coli (APC). This ubiquitous kinase com- plex, when active in the absence of Wnt signal transduction, phosphorylates β -catenin and thereby targets it for proteolytic degradation by the proteasome (Moon and Kimelman, 1998; Peifer and Polakis, 2000). Besides the Dsh-dependent inhibition of GSK- 3 β activity, the depletion of GSK-3 β protein on the dorsal side, by an as yet unknown mechanism, could also contribute to β -catenin stabilization (Dominguez and Green, 2000). Thus, the initial step leading to the induction of the Spemann-Mangold organizer, is the stabilization of β -catenin on the dorsal side. Cytosolic β -catenin translocates to the nucleus during cleavage stages, where it forms a heteromeric complex with the architectural HMG-box protein Tcf- 3, to transactivate post-mid blastula transition (MBT) the expres- sion of early zygotic target genes, such as Siamois and Twin. These homeodomain proteins in turn activate transcription of early Spemann-Mangold organizer genes in the dorsal marginal zone (Harland and Gerhart, 1997; Moon and Kimelman, 1998; Table 1). The activation of Spemann-Mangold organizer genes in the dorsal marginal zone is in addition dependent on the specification of the mesodermal germ layer. Nieuwkoop originally demonstrated that the mesodermal germ layer arises in the equator or marginal zone of

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The avian organizer

The avian organizer

A transplanted PMZ is capable of inducing an ectopic primitive streak in epiblast tissue from an early pre-streak embryo lacking a PMZ of its own (Khaner and Eyal-Giladi, 1986; Khaner and Eyal- Giladi, 1989; Khaner, 1998). It could be demonstrated by cell labeling that PMZ cells do not take part in the formation of the axis they induce (Bachvarova et al., 1998). An important secreted protein in the PMZ is the TGF β related factor cVg1 (Seleiro et al., 1996; Shah et al., 1997). cVg1 secreting cells are able to promote the formation of a streak expressing organizer markers when transplanted to the epiblast of the marginal zone, but not of the central disc. The restriction to the marginal zone possibly correlates with the presence of nuclear β− catenin, and thus the activity of a Wnt pathway (Roeser et al., 1999). However, the activity of a Wnt factor is difficult to prove, since these proteins cannot be produced easily in soluble form. Some evidence for the role of a Wnt factor in avian axis induction, organizer induction and cooperation with cVg1 could be obtained applying cells producing the Wnt1 protein (Joubin and Stern, 1999). In order to understand the organizer inducing function of a Nieuwkoop center in zebrafish and Xenopus, it was of great help to identify the homeobox genes dharma/nieuwkoid (Koos and Ho, 1998; Yamanaka et al., 1998) and siamois (Lemaire et al., 1995),

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GREEN SUPPLY CHAIN EVENT ORGANIZER (GSCEO): STRATEGY EVENT ORGANIZER BUSINESS IN JAKARTA

GREEN SUPPLY CHAIN EVENT ORGANIZER (GSCEO): STRATEGY EVENT ORGANIZER BUSINESS IN JAKARTA

Indonesia currently together with other ASEAN members is preparing itself in order to welcome the era of ASEAN Economic Community (MEA) / AEC (ASEAN economic community). With the enactment of mea in the countries joined in the ASEAN countries, it will experience a change in the free flow of goods into the Asian countries, including investment, for example Indonesia received a visit from the king of Saudi Arabia salman bin abdulaziz al saud on the 1st until 9 March 2017 with the agenda to increase bilateral cooperation between the two countries. Furthermore, the visit of Italian president, Sergio Mattarella to Indonesia, bringing a business delegation of 30 people and of course will result in total contract worth approximately usd1,055 billion. From that background, what Indonesia needs to do is how Indonesia as part of the ASEAN community strives to prepare for the quality of self and exploit the 2015 MEA opportunities, and must enhance the capability to compete with other ASEAN member countries so that the fear of losing competitiveness in their own country the implementation of MEA 2015 did not happen (Ida Pujiani, 2014). One of them is in the field of event organizer or called event organizer (event management). The term event is an activity, while the organizer is defined as management, so the definition of event organizer is a management activity or event with the aim of arranging systematically, grouping and arranging so that the purpose and purpose of organizing activities can be done well.

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Formation of the head organizer in hydra involves the canonical Wnt pathway

Formation of the head organizer in hydra involves the canonical Wnt pathway

The canonical Wnt pathway is known to act as a positive feedback loop in Drosophila (Heslip et al., 1997). If it acted in a similar manner in hydra, it could be involved in maintaining the head organizer. The Wnt signal produced by the head organizer in the tip of the hypostome could stimulate neighboring cells just basal to the tip by blocking GSK-3 β and raising the nuclear level of β -catenin. In addition, HyPKC2, a hydra PKC homolog that is expressed in the apical half of the hypostome (Hassel et al., 1998), may augment this activity, as PKC is known to inhibit the activity of GSK-3 β (Goode et al., 1992). Subsequently HyWnt would be transcribed in the neighboring cells, completing the positive feedback loop. Hence, the Wnt positive feedback loop would be continuously active, which would maintain the head organizer in the context of the continuous displacement toward, and loss of tissue at, the apex of the hypostome. This would also be consistent with the continuous expression of HyWnt and HyTcf in the hypostome (Hobmayer et al., 2000).

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