Forebrain Architecture and Development in Cyclostomes, with Reference to the Early Morphology and Evolution of the Vertebrate Head.

The vertebrate head and brain are characterized by highly complex morphological patterns. The forebrain, the most anterior division of the brain, is subdivided into the diencephalon, hypothalamus, and telencephalon from the neuromeric subdivision into prosomeres. Importantly, the telencephalon contains the cerebral cortex, which plays a key role in higher order cognitive functions in humans.

Genetic Mechanism for the Cyclostome Cerebellar Neurons Reveals Early Evolution of the Vertebrate Cerebellum.

The vertebrate cerebellum arises at the dorsal part of rhombomere 1, induced by signals from the isthmic organizer. Two major cerebellar neuronal subtypes, granule cells (excitatory) and Purkinje cells (inhibitory), are generated from the anterior rhombic lip and the ventricular zone, respectively. This regionalization and the way it develops are shared in all extant jawed vertebrates (gnathostomes).

FGF- and SHH-based molecular signals regulate barbel and craniofacial development in catfish.

Background: Catfish (Siluriformes) are characterized by unique morphologies, including enlarged jaws with movable barbels and taste buds covering the entire body surface. Evolution of these characteristics was a crucial step in their adaptive radiation to freshwater environments. However, the developmental processes of the catfish craniofacial region and taste buds remain to be elucidated; moreover, little is known about the molecular mechanisms underlying the morphogenesis of these structures.

Atlas of the telencephalon based on cytoarchitecture, neurochemical markers, and gene expressions in Rhinogobius flumineus [Mizuno, 1960].

Gobiida is a basal subseries of percomorphs in teleost fishes, holding a useful position for comparisons with other orders of Percomorpha as well as other cohort of teleosts. Here, we describe a telencephalic atlas of a Gobiida species Rhinogobius flumineus (Mizuno, Memoirs of the College of Science, University of Kyoto, Series B: Biology, 1960; 27, 3), based on cytoarchitectural observations, combined with analyses of the distribution patterns of neurochemical markers and transcription factors. The telencephalon of R.

Egg structure and outline of embryonic development of the basal mantodean, Metallyticus splendidus Westwood, 1835 (Insecta, Mantodea, Metallyticidae).

The egg structure and outline of the embryonic development of Metallyticus splendidus of one of the basal Mantodea representatives, Metallyticidae, were described in the present study. The results obtained were compared with those from the previous studies, to reconstruct and discuss the groundplan of Mantodea and Dictyoptera. In M.

Expression patterns of Sema3A in developing amniote limbs: With reference to the diversification of peripheral nerve innervation.

Paired limbs were acquired in the ancestor of tetrapods and their morphology has been highly diversified in amniotes in relation to the adaptive radiation to the terrestrial environment. These morphological changes may have been induced by modification of the developmental program of the skeletal or muscular system. To complete limb modification, it is also important to change the neuronal framework, because the functions of the limbs rely on neural circuits that involve coordinated movement.

Evolutionary mechanisms that generate morphology and neural-circuit diversity of the cerebellum.

The cerebellum is derived from the dorsal part of the anterior-most hindbrain. The vertebrate cerebellum contains glutamatergic granule cells (GCs) and gamma-aminobutyric acid (GABA)ergic Purkinje cells (PCs). These cerebellar neurons are generated from neuronal progenitors or neural stem cells by mechanisms that are conserved among vertebrates.

Reconstructing the ancestral vertebrate brain.

Highly complicated morphologies and sophisticated functions of vertebrate brains have been established through evolution. However, the origin and early evolutionary history of the brain remain elusive, owing to lack of information regarding the brain architecture of extant and fossil species of jawless vertebrates (agnathans). Comparative analyses of the brain of less studied cyclostomes (only extant agnathan group, consisting of lampreys and hagfish) with the well-known sister group of jawed vertebrates (gnathostomes) are the only tools we have available to illustrate the ancestral architecture of the vertebrate brain.

Nervous system disruption and swimming abnormality in early-hatched pufferfish (Takifugu niphobles) larvae caused by pyrene is independent of aryl hydrocarbon receptors.

Pyrene, a member of the polycyclic aromatic hydrocarbons (PAHs), contributes to abnormality in the size of the brain and the swimming behavior of pufferfish (Takifugu niphobles) larvae. We hypothesized that the aryl hydrocarbon receptor (AHR) may mediate pyrene-induced toxic effects because AHR is assumed to be a candidate for the downstream target of PAHs in many cases. To identify the contribution of AHR on developing pufferfish, we performed exposure experiments using β-naphthoflavone, an agonist of AHR.

Evidence from cyclostomes for complex regionalization of the ancestral vertebrate brain.

The vertebrate brain is highly complex, but its evolutionary origin remains elusive. Because of the absence of certain developmental domains generally marked by the expression of regulatory genes, the embryonic brain of the lamprey, a jawless vertebrate, had been regarded as representing a less complex, ancestral state of the vertebrate brain. Specifically, the absence of a Hedgehog- and Nkx2.

The evolution of basal progenitors in the developing non-mammalian brain.

The amplification of distinct neural stem/progenitor cell subtypes during embryogenesis is essential for the intricate brain structures present in various vertebrate species. For example, in both mammals and birds, proliferative neuronal progenitors transiently appear on the basal side of the ventricular zone of the telencephalon (basal progenitors), where they contribute to the enlargement of the neocortex and its homologous structures. In placental mammals, this proliferative cell population can be subdivided into several groups that include Tbr2(+) intermediate progenitors and basal radial glial cells (bRGs).

Involvement of Slit-Robo signaling in the development of the posterior commissure and concomitant swimming behavior in Xenopus laevis.

Introduction: During vertebrate development, the central nervous system (CNS) has stereotyped neuronal tracts (scaffolds) that include longitudinal and commissural axonal bundles, such as the medial longitudinal fascicle or the posterior commissure (PC). As these early tracts appear to guide later-developing neurons, they are thought to provide the basic framework of vertebrate neuronal circuitry. The proper construction of these neuronal circuits is thought to be a crucial step for eliciting coordinated behaviors, as these circuits transmit sensory information to the integrative center, which produces motor commands for the effective apparatus.

Expression patterns of Eph genes in the "dual visual development" of the lamprey and their significance in the evolution of vision in vertebrates.

Image-forming vision is crucial to animals for recognizing objects in their environment. In vertebrates, this type of vision is achieved with paired camera eyes and topographic projection of the optic nerve. Topographic projection is established by an orthogonal gradient of axon guidance molecules, such as Ephs.

A comparative examination of neural circuit and brain patterning between the lamprey and amphioxus reveals the evolutionary origin of the vertebrate visual center.

Vertebrates are equipped with so-called camera eyes, which provide them with image-forming vision. Vertebrate image-forming vision evolved independently from that of other animals and is regarded as a key innovation for enhancing predatory ability and ecological success. Evolutionary changes in the neural circuits, particularly the visual center, were central for the acquisition of image-forming vision.

Transient suppression of AHR activity in early red seabream embryos does not prevent the disruption of peripheral nerve projection by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

The toxicity of dioxins such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is mainly mediated by an aryl hydrocarbon receptor (AHR), which regulates the transcription of multiple target genes including cytochrome P450 1A (CYP1A). Our pervious study identified the presence of TCDD-induced defects of peripheral nerve projection in red seabream (Pagrus major) embryos. However, it remains unclear whether the TCDD-induced peripheral neurotoxicity is mediated by the AHR.

Pyrene induces a reduction in midbrain size and abnormal swimming behavior in early-hatched pufferfish larvae.

Spills of heavy oil (HO) have an adverse effect on marine life. We have demonstrated previously that exposure to HO by fertilized eggs of the pufferfish (Takifugu rubripes) induces neural disruption and behavioral abnormality in early-hatched larvae. Here, two kinds of polycyclic aromatic hydrocarbons, pyrene and phenanthrene, were selected to examine their toxic effects on larval behavior of another pufferfish species (T.

Reconstruction of ancestral brains: exploring the evolutionary process of encephalization in amniotes.

There is huge divergence in the size and complexity of vertebrate brains. Notably, mammals and birds have bigger brains than other vertebrates, largely because these animal groups established larger dorsal telencephali. Fossil evidence suggests that this anatomical trait could have evolved independently.

Saltatory evolution of the ectodermal neural cortex gene family at the vertebrate origin.

The ectodermal neural cortex (ENC) gene family, whose members are implicated in neurogenesis, is part of the kelch repeat superfamily. To date, ENC genes have been identified only in osteichthyans, although other kelch repeat-containing genes are prevalent throughout bilaterians. The lack of elaborate molecular phylogenetic analysis with exhaustive taxon sampling has obscured the possible link of the establishment of this gene family with vertebrate novelties.

Evolution of the regionalization and patterning of the vertebrate telencephalon: what can we learn from cyclostomes?

The telencephalon, the most anterior part of the vertebrate central nervous system (CNS), is a highly diversified region of the vertebrate body. Its evolutionary origin remains elusive, especially with regard to the ancestral state of its architecture as well as the origin of telencephalon-specific neuron subtypes. Cyclostomes (lampreys and hagfish), the sister group of the gnathostomes (jawed vertebrates), serve as valuable models for studying the evolution of the vertebrate CNS.

Reptiles: a new model for brain evo-devo research.

Vertebrate brains exhibit vast amounts of anatomical diversity. In particular, the elaborate and complex nervous system of amniotes is correlated with the size of their behavioral repertoire. However, the evolutionary mechanisms underlying species-specific brain morphogenesis remain elusive.

Toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on the peripheral nervous system of developing red seabream (Pagrus major).

We investigated 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced effects on the morphology of peripheral nervous system (PNS) in the developing red seabream (Pagrus major) embryos. The embryos at 10h post-fertilization (hpf) were treated with 0, 0.1, 0.

Inference of the protokaryotypes of amniotes and tetrapods and the evolutionary processes of microchromosomes from comparative gene mapping.

Comparative genome analysis of non-avian reptiles and amphibians provides important clues about the process of genome evolution in tetrapods. However, there is still only limited information available on the genome structures of these organisms. Consequently, the protokaryotypes of amniotes and tetrapods and the evolutionary processes of microchromosomes in tetrapods remain poorly understood.