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金沢大学理工学研究域物質化学系, A methylene group was introduced into the C–H bond of α-carbonyl aldonitrones by reaction with dimethylsulfoxonium methylide, producing one-carbon homologated C-methyl ketonitrones. This formal methylene insertion was applied to one-pot synthesis of quaternary C3-methyl isoxazolidines via successive 1,3-dipolar cycloaddition with alkenes bearing an electron withdrawing group.

The hatcing enzyme gene (HE) encodes a protease that is indispensable for the hatching process and is conserved during vertebrate evolution. During teleostean evolution, it is known that HE experienced a drastic transfiguration of gene structure, namely, losing all of its introns. However, these facts are contradiction with each other, since intron-less genes typically lose their original promoter because of duplication via mature mRNA, called retrocopy. Here, using a comparative genomic assay, we showed that HEs have changed their genomic location several times, with the evolutionary timings of these translocations being identical to those of intron-loss. We further showed that HEs maintain the promoter sequence upstream of them after translocation. Therefore, teleostean HEs are unique genes which have changed intra- (exon-intron) and extra-genomic structure (genomic loci) several times, although their indispensability for the reproductive process of hatching implies that HE genes are translocated by retrocopy with their promoter sequence.

The lung is an important organ for air breathing in tetrapods and originated well before the terrestrialization of vertebrates. Therefore, to better understand lung evolution, we investigated lung development in the extant basal actinopterygian fish Senegal bichir (Polypterus senegalus). First, we histologically confirmed that lung development in this species is very similar to that of tetrapods. We also found that the mesenchymal expression patterns of three genes that are known to play important roles in early lung development in tetrapods (Fgf10, Tbx4 and Tbx5) were quite similar to those of tetrapods. Moreover, we found a Tbx4 core lung mesenchyme-specific enhancer (C-LME) in the genomes of bichir and coelacanth (Latimeria chalumnae) and experimentally confirmed that these were functional in tetrapods. These findings provide the first molecular evidence that the developmental program for lung was already established in the common ancestor of actinopterygians and sarcopterygians.

Hatching gland cells (HGCs) originate from different germ layers between frogs and teleosts, although the hatching enzyme genes are orthologous. Teleostei HGCs differentiate in the mesoendodermal cells at the anterior end of the involved hypoblast layer (known as the polster) in late gastrula embryos. Conversely, frog HGCs differentiate in the epidermal cells at the neural plate border in early neurula embryos. To infer the transition in the developmental origin of HGCs, we studied two basal ray-finned fishes, bichir (Polypterus) and sturgeon. We observed expression patterns of their hatching enzyme (HE) and that of three transcription factors that are critical for HGC differentiation: KLF17 is common to both teleosts and frogs; whereas FoxA3 and Pax3 are specific to teleosts and frogs, respectively. We then inferred the transition in the developmental origin of HGCs. In sturgeon, the KLF17, FoxA3, and HE genes were expressed during the tailbud stage in the cell mass at the anterior region of the body axis, a region corresponding to the polster in teleost embryos. In contrast, the bichir was suggested to possess both teleost- and amphibian-type HGCs, i.e. the KLF17 and FoxA3 genes were expressed in the anterior cell mass corresponding to the polster, and the KLF17, Pax3 and HE genes were expressed in dorsal epidermal layer of the head. The change in developmental origin is thought to have occurred during the evolution of basal ray-finned fish, because bichir has two HGCs, while sturgeon only has the teleost-type.

The evolution of phenotypic traits is a key process in diversification of life. However, the mechanisms underlying the emergence of such evolutionary novelties are largely unknown. Here we address the origin of bulbus arteriosus (BA), an organ of evolutionary novelty seen in the teleost heart outflow tract (OFT), which sophisticates their circulatory system. The BA is a unique organ that is composed of smooth muscle while the OFTs in other vertebrates are composed of cardiac muscle. Here we reveal that the teleost-specific extracellular matrix (ECM) gene, elastin b, was generated by the teleost-specific whole-genome duplication and neofunctionalized to contribute to acquisition of the BA by regulating cell fate determination of cardiac precursor cells into smooth muscle. Furthermore, we show that the mechanotransducer yap is involved in this cell fate determination. Our findings reveal a mechanism of generating evolutionary novelty through alteration of cell fate determination by the ECM., The bulbus arteriosus is an organ unique to the heart of teleosts, composed of specialized smooth muscle. Here, the authors show that the gene elastin b, which regulates cell fate of cardiac precursor cells into smooth muscle, evolved after whole-genome duplication and neofunctionalization in teleosts.

Introduction Despite the great diversity in digit morphology reflecting the adaptation of tetrapods to their lifestyle, the number of digits in extant tetrapod species is conservatively stabilized at five or less, which is known as the pentadactyl constraint. Results We found that an anuran amphibian species, Xenopus tropicalis (western clawed frog), has a clawed protrusion anteroventral to digit I on the foot. To identify the nature of the anterior-most clawed protrusion, we examined its morphology, tissue composition, development, and gene expression. We demonstrated that the protrusion in the X. tropicalis hindlimb is the sixth digit, as is evident from anatomical features, development, and molecular marker expression. Conclusion Identification of the sixth digit in the X. tropicalis hindlimb strongly suggests that the prehallux in other Xenopus species with similar morphology and at the same position as the sixth digit is also a vestigial digit. We propose here that the prehallux seen in various species of amphibians generally represents a rudimentary sixth digit. Electronic supplementary material The online version of this article (doi:10.1186/s40851-015-0019-y) contains supplementary material, which is available to authorized users.