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International Journal of Developmental Biology

Matteo Bozzo, Jiri Pergner, Zbynek Kozmik, Iryna Kozmikova
Cephalochordates, commonly called amphioxus or lancelets, are widely regarded as a useful proxy for the chordate ancestor. In recent decades, expression patterns of important developmental genes have been used extensively to infer homologies between cephalochordate and vertebrate embryos. Such comparisons provided important insight into cephalochordate biology and the origin of vertebrate traits. Most of the developmental expression data are collected using whole-mount in situ hybridization that allows the distributions of specific transcripts to be detected in fixed embryos...
2017: International Journal of Developmental Biology
Chaofan Xing, Guang Li, Xian Liu, Xi Deng, Yiquan Wang
Amphioxus is a good proxy for studying the evolution and development of mechanisms during the invertebrate to vertebrate transition. However, one of the major limitations of amphioxus as a model organism is the lack of well-developed technical approaches. Promoters of genes encoding heat shock proteins are useful tools for gene function studies. In the present study, we tested heat shock temperatures on 4-cell, 128-cell, late blastula, mid-gastrula and late gastrula amphioxus embryos and optimized the heat shock conditions...
2017: International Journal of Developmental Biology
João E Carvalho, François Lahaye, Michael Schubert
Cephalochordates, commonly known as amphioxus or lancelets, are small, marine animals that can be found in coastal habitats of temperate, subtropical, and tropical waters. Together with vertebrates and tunicates, the cephalochordates belong to the chordate phylum, whose members are characterized by a number of conserved morphological features, such as a dorsal nerve cord, a notochord, a pharynx, a segmented musculature as well as a post-anal tail. Due to their basal position within the phylum, cephalochordates have become essential models for studying the evolutionary origin and diversification of vertebrates...
2017: International Journal of Developmental Biology
Chrysoula N Pantzartzi, Jiri Pergner, Iryna Kozmikova, Zbynek Kozmik
Light detection in animals is predominantly based on the photopigment composed of a protein moiety, the opsin, and the chromophore retinal. Animal opsins originated very early in metazoan evolution from within the G-Protein Coupled Receptor (GPCR) gene superfamily and diversified into several distinct branches prior to the cnidarian-bilaterian split. The origin of opsin diversity, opsin classification and interfamily relationships have been the matter of long-standing debate. Comparative studies of opsins from various Metazoa provide key insight into the evolutionary history of opsins and the visual perception in animals...
2017: International Journal of Developmental Biology
Elisabeth Zieger, Thurston C Lacalli, Mario Pestarino, Michael Schubert, Simona Candiani
The basic anatomy of the central nervous system (CNS) is well conserved within the vertebrates and differs in significant ways from that of non-vertebrate chordates. Of the latter, amphioxus is of special interest, being the best available stand-in for the basal chordate condition. Immunohistochemical and gene expression studies on the developing CNS of amphioxus embryos and larvae are now sufficiently advanced that we can begin to assign specific neurotransmitter phenotypes to neurons identified by transmission electron microscopy (TEM), and then compare the distribution of cell types to that in vertebrate brains...
2017: International Journal of Developmental Biology
João E Carvalho, François Lahaye, Jenifer C Croce, Michael Schubert
During development, morphogens, such as retinoic acid (RA), act as mediators of intercellular communication systems to control patterning and cell fate specification processes. In vertebrates, the tightly regulated production and degradation of RA creates an anterior-posterior (A-P) morphogen gradient that is required for regional patterning of the embryo. RA catabolism in particular, mediated by members of the cytochrome P450 subfamily 26 (CYP26), has been highlighted as a key regulatory component for the formation of this gradient...
2017: International Journal of Developmental Biology
Simon C Dailey, Iryna Kozmikova, Ildikó M L Somorjai
A cluster of three Specificity Protein (Sp) genes (Sp1-4, Sp5 and Sp6-9) is thought to be ancestral in both chordates and the wider Eumetazoa. Sp5 and Sp6-9 gene groups are associated with embryonic growth zones, such as tailbuds, and are both Wnt/β-catenin signalling pathway members and targets. Currently, there are conflicting reports as to the number and identity of Sp genes in the cephalochordates, the sister group to the vertebrates and urochordates. We confirm the SP complement of Branchiostoma belcheri and Branchiostoma lanceolatum, as well as their genomic arrangement, protein domain structure and residue frequency...
2017: International Journal of Developmental Biology
Stephanie Bertrand, Yann Le Petillon, Ildikó M L Somorjai, Hector Escriva
During embryonic development, cells of metazoan embryos need to communicate in order to construct the correct bodyplan. To do so, they use several signals that usually act through interactions between ligands and receptors. Interestingly, only a few pathways are known to be fundamental during animal development, and they are usually found in all the major metazoan clades, raising the following question: how have evolution of the actors and of the functions of these pathways participated in the appearance of the current diversity of animal morphologies? The chordate lineage comprises vertebrates, their sister group the urochordates, and the cephalochordates (i...
2017: International Journal of Developmental Biology
Ildikó M L Somorjai
Regeneration is a variable trait in chordates, with some species capable of impressive abilities, and others of only wound healing with scarring. Regenerative capacity has been reported in the literature for 5 species from two cephalochordate genera, Branchiostoma and Asymmetron. Its cellular and molecular bases have been studied in some detail in only two species: tail regeneration in the European amphioxus B. lanceolatum; and oral cirrus regeneration in the Asian species B. japonicum. Gene expression analyses of germline formation and posterior elongation in cephalochordate embryos provide some insight into regulation of progenitor and stem cell function...
2017: International Journal of Developmental Biology
Nicholas D Holland
The history of studies on amphioxus kidney morphology is reviewed with special attention to four zoologists who made important early contributions. In 1884, Hatschek described a single anterior nephridial tubule in larval and adult amphioxus. Subsequently, in 1890, Weiss and Boveri independently found multiple branchial nephridia (morphologically similar to Hatschek's nephridium) associated with the pharyngeal gill slits. These initial discoveries set the stage for Goodrich to criticize Boveri repeatedly for the latter's contention that amphioxus nephridia develop from mesoderm and are connected to neighboring coeloms throughout the life history...
2017: International Journal of Developmental Biology
Jiri Pergner, Zbynek Kozmik
Studies on amphioxus, representing the most basal group of chordates, can give insights into the evolution of vertebrate traits. The present review of amphioxus research is focused on the physiology of light-guided behavior as well as on the fine structure, molecular biology, and electrophysiology of the nervous system, with special attention being given to the photoreceptive organs. The amphioxus visual system is especially interesting because four types of receptors are involved in light detection - dorsal ocelli and Joseph cells (both rhabdomeric photoreceptors) and the frontal eye and lamellar body (both ciliary photoreceptors)...
2017: International Journal of Developmental Biology
Beatriz Albuixech-Crespo, Carlos Herrera-Úbeda, Gemma Marfany, Manuel Irimia, Jordi Garcia-Fernàndez
The vertebrate brain is arguably the most complex anatomical and functional structure in nature. During embryonic development, the central nervous system (CNS) undergoes a series of morphogenetic processes that eventually obscure the major axes of the early neural plate to our perception. Notwithstanding this complexity, the "genoarchitecture" of the developing neural tube brings into light homologous regions between brains of different vertebrate species, acting as a molecular barcode of each particular domain...
2017: International Journal of Developmental Biology
Thurston Lacalli
Amphioxus is increasingly important as a model for ancestral chordates. Nevertheless, it is secondarily modified in various ways, especially in the larva, whose small size has resulted in a rescaling and repositioning of structures. This is especially pronounced in the head region, where the mouth opens asymmetrically on the left side, leading to speculation that the mouth is secondarily derived, e.g. from a gill slit, and is hence not homologous with mouths in other animals. The available evidence does not, in the author's view, support this interpretation...
2017: International Journal of Developmental Biology
Gerhard Schlosser
Cranial placodes are an evolutionary novelty of vertebrates that give rise to many cranial sense organs and ganglia, as well as to the neurosecretory anterior pituitary. Although amphioxus does not have placodes, it shares with vertebrates several of the ectodermal patterning mechanisms and cell types that are important in placode development. Comparisons between amphioxus, vertebrates and other groups provide us with important insights into what the last common chordate ancestor probably looked like and allow us to propose a scenario for how placodes evolved by rewiring of gene regulatory networks...
2017: International Journal of Developmental Biology
Takayuki Onai, Noritaka Adachi, Shigeru Kuratani
The vertebrate head characteristically exhibits a complex pattern with sense organs, brain, paired eyes and jaw muscles, and the brain case is not found in other chordates. How the extant vertebrate head has evolved remains enigmatic. Historically, there have been two conflicting views on the origin of the vertebrate head, segmental and non-segmental views. According to the segmentalists, the vertebrate head is organized as a metameric structure composed of segments equivalent to those in the trunk; a metamere in the vertebrate head was assumed to consist of a somite, a branchial arch and a set of cranial nerves, considering that the head evolved from rostral segments of amphioxus-like ancestral vertebrates...
2017: International Journal of Developmental Biology
Vladimir Soukup
Extant bilaterally symmetrical animals usually show asymmetry in the arrangement of their inner organs. However, the exaggerated left-right (LR) asymmetry in amphioxus represents a true peculiarity among them. The amphioxus larva shows completely disparate fates of left and right body sides, so that organs associated with pharynx are either positioned exclusively on the left or on the right side. Moreover, segmented paraxial structures such as muscle blocks and their neuronal innervation show offset arrangement between the sides making it difficult to propose any explanation or adaptivity to larval and adult life...
2017: International Journal of Developmental Biology
Iryna Kozmikova, Jr-Kai Yu
How the embryonic body axis is generated is a fundamental question in developmental biology. The molecular mechanisms involved in this process have been the subject of intensive studies using traditional model organisms during the last few decades, and the results have provided crucial information for understanding the formation of animal body plans. In particular, studies exploring the molecular nature of Spemann's organizer have revealed the intricate interactions underlying several signaling pathways (namely the Wnt/β-catenin, Nodal and Bmp pathways) that pattern the dorsoventral (DV) axis in vertebrate embryos...
2017: International Journal of Developmental Biology
Kinya Yasui
Comparison of early development is a powerful approach to understand how spherical embryos set up the basis for body patterning. Localization of the germ plasm likely couples with the site of gastrulation in many animals including cnidarians. A center of single or complex Wnt signaling pathway(s) is also co-localized with germ plasm and plays a role primarily in antero-posterior patterning in most animals. In addition, a Nodal signaling center appears in deuterostomes perpendicular to Wnt signaling and governs dorso-ventral patterning...
2017: International Journal of Developmental Biology
Peter Holland
The cloning and embryonic expression analysis of an amphioxus Hox gene in 1992 marked the start of molecular analysis of cephalochordate development. Other papers quickly followed, including a description of the amphioxus Hox gene cluster in 1994, fuelling a resurgence of interest in a long-forgotten animal. I describe the academic background, laboratory experiments and field work leading to the earliest publications in amphioxus molecular developmental biology and explain their scientific impact. The story of amphioxus biology in the 1990s involved collaboration, team work, opportunistic meetings, serendipity, incredulous journal editors, stingrays, airport departure lounges and popcorn...
2017: International Journal of Developmental Biology
Nicholas D Holland, Linda Z Holland
Humans (at least a select few) have long known about the cephalochordate amphioxus, first as something to eat and later as a subject for scientific study. The rate of publication on these animals has waxed and waned several times. The first big surge, in the late nineteenth century, was stimulated by Darwin's evolutionary ideas and by Kowalevsky's embryologic findings suggesting that an amphioxus-like creature might have bridged the gap between the invertebrates and the vertebrates. Interest declined sharply in the early twentieth century and remained low for the next 50 years...
2017: International Journal of Developmental Biology
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