All eight applicants for this award met the criteria specified in the selection regulations—"early-career researchers who conduct active research and are strongly expected to make future progress and development"—making the selection process a high-level one. As a result of detailed deliberations regarding the applicants' research content, research achievements, and future potential, the following two individuals (in Japanese syllabary order) were decided to be recommended to the Board of Directors.

Selection Committee for the Zoological Society of Japan Awards and Other Honors
Committee Chairperson Takahiro Asami

2015 Zoological Society of Japan Award for Encouragement of Research

Shin Sato
Okayama University, Research Core for Interdisciplinary Sciences, Associate Professor
Research topic: Study on neural factors in limb regeneration

Reasons for the Recommendation

Member Shin Sato has consistently and energetically pursued research on the molecular mechanisms of vertebrate organ regeneration, focusing on amphibian limbs. His research on tissue regeneration such as bone, tendon, and muscle during limb regeneration, as well as his research on the regenerative capacity of muscle satellite cells, is particularly noteworthy. His research achievements regarding neurotrophic factors in limb regeneration are prominent; using a unique amphibian supernumerary limb induction experimental model system, Member Sato revealed that FGF and BMP are the essential neurosecretory factors for amphibian limb regeneration. The identification of the neurotrophic factors that trigger limb regeneration is a critically important discovery for inducing limb regeneration in animals that cannot regenerate limbs, such as mammals. Member Sato's research, which has elucidated classically interesting phenomena in organ regeneration at the molecular level, is highly commendable, and further development in the future is greatly anticipated.

Winner Summary

Urodeles can regenerate lost limbs to their original state. This is a single sentence of an introduction I have written hundreds of times over. I no longer feel any sense of strangeness about it, but when I say this sentence to children, it is not uncommon to draw out their sparkling interest along with a sense of wonder I had long since forgotten. I am convinced that this is simply because it is an "interesting" phenomenon, even to a childlike heart. Believing that I have been given a golden opportunity to publicize a phenomenon interesting enough to compensate for the immaturity of our research, I would like to introduce a part of limb regeneration research in amphibians.

Newts and Mexican salamanders (commonly known as axolotls) have an exceptionally high capacity for organ regeneration. Even when extensive damage is inflicted on their limbs, tail, gills, heart, brain, and other body parts, they can regenerate structures that function just as they did originally. Of course, such an ability is not observed in humans or similar animals. In the regenerative process of animals capable of regeneration, a specialized structure called a blastema can be observed. Conversely, animals incapable of regeneration cannot induce a blastema after injury. In other words, the presence or absence of the ability to form a blastema following injury can be considered a matter directly linked to the presence or absence of regenerative capacity. It has been reported since ancient times that "nerves" play a crucial role in inducing this blastema. In amphibian limb regeneration, if the nerves are removed prior to amputation, blastema formation does not occur, and a repair of the severed site similar to (though not the same as) that in regeneration-incompetent humans takes place. These experimental results have suggested that some substance is released from the nerves, converting a simple repair response into a blastema induction response. Therefore, identifying the neural factors is a crucial key to understanding the high organ regeneration capacity possessed by regeneration-competent animals.

To identify the "regeneration-inducing factor" released from nerves that governs the induction of limb blastema, an experimental system distinct from conventional ones was established, centered around Dr. Endo of the current Aichi Gakuin University (Endo et al., 2004,Dev. Biol.). Based on the resulting phenotype, this experimental system is called the "supernumerary limb insertion model" (Figure 1). Although the details are omitted, using the supernumerary limb insertion model allows us to narrow down the tissues (organs) required for limb regeneration induction to just two—nerves and skin—out of the numerous tissues that make up a limb. By minimizing the target, we can reduce the complexity of the analysis without having to deal with multiple tissues. Damage to the skin alone results only in skin repair. However, by providing nerves in addition to skin damage, it is possible to convert the skin repair response into a limb regeneration response (Satoh et al., 2008, Developmental Growth and Differentiation.）Using this experimental system, we searched for factors capable of converting skin repair into a regenerative response in place of nerves. First, we decided to clarify the relationship between nerves and damaged skin occurring during the regeneration initiation phase, and to estimate neurotrophic factors based on its characteristics. Induction of regeneration-specific epithelium through contact between nerves and the epithelium in the early initiation phase of regeneration (Satoh et al., 2008, Dev. Biol.) and its characteristics (Satohet al., 2012, Dev. Biol.), and the formation of a regeneration-specific microenvironment conceivable from that (Makanae et al., 2012, Anat. Rec.) clarified many of the early-occurring events (see HP achievements section). Proceeding along the hypothesis of the putative regeneration-specific environment, we were able to identify FGF2 and FGF8, which are expressed in nerves and contribute to blastema induction (Satoh et al., 2011, Dev. Biol.). However, it was also revealed that the input of FGF2 + FGF8 in addition to skin damage alone cannot induce complete regeneration. Aiming to induce complete regeneration, as research progressed, we discovered that the three factors BMP2 (or BMP7) + FGF2 + FGF8 can cause the formation of excess limbs from skin damage (Makanae et al., 2013, 2014, Dev. Biol.). We have also confirmed that these factors are expressed in nerves. In the future, we believe we can confirm them as neural factors by conditionally knocking out their functions specifically in nerves, but this will likely take some time given the difficulties of genetic modification technology in tailed amphibians. At the very least, we believe that these discoveries have fulfilled the objective of identifying a "regeneration-inducing substance" capable of substituting for nerves.

Following the identification of the regeneration-inducing substances, two major developments can be envisioned: one is to clarify the details of the signaling cascades utilized by BMP and FGF. The other is application to other animals with the aim of targeting humans. Regarding application to other animals, we have already confirmed that the aforementioned "regeneration-inducing substances" are effective not only in the axolotl, but also in newts and African clawed frogs (Makanae et al., 2014, Dev. Biol.,Satoh et al., 2015, Developmental Growth and Differentiation.). Therefore, we believe this suggests our findings are not merely regeneration-inducing factors in a single species, but possess the versatility to be applied to a diverse range of animals. Moving forward, we plan to expand our research with a view toward applications in various animals, including humans.

Can the unregenerate state be lifted if blastema induction is achieved? Personally, this sweet illusion has been thoroughly crushed by research on limb regeneration in the African clawed frog (Xenopus laevis). Xenopus possesses a regenerative capacity that might be described as semi-regenerative. For details, please refer to books such as "Limb Formation Mechanisms" (ISBN4-901493-37-X). Following limb amputation, adult Xenopus exhibit an incomplete regenerative response, as shown in Figure 2-B2. During this sequence of regenerative processes, a blastema is formed and is innervated. This suggests that in Xenopus as well, there is regulation by neural factors identical or very similar to those in the Mexican axolotl. In fact, research using supernumerary limb models has confirmed a similar regulatory mechanism and factor expression (Mitogawa et al., 2014, Reg., Satoh et al., 2015, Developmental Growth and Differentiation.This is thought to be caused by morphogenesis defects that occur subsequent to blastema induction in Xenopus limb regeneration (Fig. 2-B2). In other words, this suggests that even if blastema formation occurs, an additional layer of regulation must be considered in order to correctly regenerate the morphology. Improving morphogenesis defects in Xenopus limb regeneration has been one of my consistent research objectives since my student days. Recently, while expanding my research from the identification of the aforementioned regeneration-inducing factors, I feel I have finally grasped a breakthrough for improving morphological abnormalities in Xenopus limb regeneration (Fig. 2-B3). By achieving both blastema formation and the subsequent correct morphogenesis in Xenopus, I hope to get closer to the "delusion" of limb regeneration in regeneration-incompetent animals.

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Hiroaki Nakano
Associate Professor, Shimoda Marine Research Center, University of Tsukuba
Research topic: Evolutionary developmental studies on the life history of non-model marine animals

Reasons for the Recommendation

Member Hiroaki Nakano has conducted ecological surveys and collection of diverse marine animals, established the rearing of animals occupying evolutionarily important positions among them, and elucidated their developmental processes, thereby contributing to the understanding of evolution and the expansion of the research scope of zoology. In particular, his research on the early development of sea lilies, which retain the most ancestral traits among echinoderms, yielded important findings supporting the hypothesis that the ancestors of echinoderms and hemichordates possessed a dipleurula-type larva. He established methods for the stable collection and rearing of Xenoturbellida, which had been scarcely studied since their description in 1949, and reported their developmental process for the first time in the world. Xenoturbellida, possessing the simplest morphology among deuterostome subgroups, are expected to contribute to the understanding of deuterostome evolution. Furthermore, he established collection and rearing methods for Placozoa, which had been scarcely studied since they were reported in 1883. Placozoa are the simplest among extant free-living animals, and if their development can be observed, it is expected to contribute to the study of the evolution of ancestral animals. Member Nakano's past research is extremely important for zoology, and great future developments are expected.

Winner Summary

I have worked on evolutionary-developmental research and studies on the phylogenetic evolution of metazoans through basic experiments, such as developing collection and rearing systems for rare marine animals with very little prior research, and observing early development.

Stalked crinoids are echinoderms named for their plant-like appearance at first glance. They are a critically important animal group for considering the evolution of echinoderms and deuterostomes from both phylogenetic and morphological perspectives. However, because almost all extant species are deep-sea dwellers, there has been virtually no research on living specimens, and since they were first collected in 1864, their developmental process had never been reported. Using Metacrinus rotundus, a species of stalked crinoid that can be collected near the coast at depths of about 100 meters, I succeeded for the first time in the world in observing the developmental process of stalked crinoids. This research revealed that stalked crinoids undergo a developmental process involving two types of larvae, suggesting that this developmental mode is ancestral for the phylum Echinodermata. Furthermore, this result provides support for the hypothesis that the ancestors of the coelomate deuterostomes (echinoderms and hemichordates) possessed a dipleurula-type larva.

Xenoturbellids are marine animals around 1 to 2 cm in size, featuring a bag-like structure where the epidermis simply encloses the digestive cavity. Lacking almost all major organs typically found in bilaterians—such as a central nervous system, reproductive organs, body cavity, and anus—their phylogenetic position remained a mystery for a long time due to this simple body plan. I participated in a large-scale molecular phylogenetic project on deuterostomes and reported that Xenoturbellids belong to a new phylum within deuterostomes, the phylum Xenacoelomorpha. Furthermore, although Xenoturbellids were first collected in 1878 and scientifically described in 1949, there had been no reports on their developmental process. I developed stable collection and long-term rearing methods for Xenoturbellids and succeeded in observing the world's first Xenoturbellid larvae. The larvae possess an extremely simple body plan, suggesting the possibility that the common ancestor of deuterostomes and all metazoans may have also possessed such a simple larva.

Placozoans are marine animals about 1 mm in diameter with an extremely simple body plan. Although they have a dorsoventral axis, they lack an anteroposterior axis, organs, tissues, nerve cells, and muscle cells, making them arguably the simplest in body plan among all extant free-living animals. Although adults were first reported in 1883, the developmental process after the cleavage stage has still not been reported. I developed a stable collection method and succeeded in collecting placozoans at all six sites investigated in Japan. Collection was also successful in winter, suggesting that placozoans inhabit various parts of Japan year-round. This also indicates the possibility that placozoans, previously thought to be tropical to subtropical, also inhabit temperate and subarctic waters around the world, including the North Pacific. Research using Japanese placozoans is expected to greatly advance the elucidation of many remaining mysteries, such as their developmental process.

Since 2013, I have been directing the JAMBIO Collaborative Survey of Marine Biota along the Japanese Coast. Together with researchers nationwide, I conduct surveys of coastal fauna and search for and collect marine animals whose research is not advanced. In 2015, I reported the discovery of about 50 undescribed species from Sagami Bay and its surrounding waters.

I have continued to study such consistently bizarre and minor marine animals. Through repeated fundamental experiments—such as developing collection and rearing methods and estimating breeding seasons—I have succeeded in observing the developmental processes of stalked crinoids and xenoturbellidans, which had remained a mystery for over 130 years. Moving forward, I intend to actively tackle fundamental experiments—such as exploring species that are phylogenetically and evolutionarily important yet understudied, developing collection and rearing methods, and observing developmental processes—in order to continuously make exciting, novel, and easily understandable discoveries that will have a significant impact on our understanding of the ancestors and evolutionary processes of metazoans.