Neuromuscular development in the emerging scyphozoan model system, : implications for the evolution of cnidarian nervous systems.

The scyphozoan is an emerging cnidarian model system for studying regeneration, animal-algae symbiotic relationships, and various aspects of evolutionary biology including the early emergence of animal nervous systems. has a life cycle similar to other scyphozoans, which includes the alternation between a sessile, asexual form (polyp) and a sexually reproducing stage, the medusa. The transition between the two forms is called strobilation, where the polyp releases a miniature medusa, the iconic ephyra, that subsequently develops into the adult medusa.

A mosaic of conserved and novel modes of gene expression and morphogenesis in mesoderm and muscle formation of a larval bivalve.

Unlabelled: The mesoderm gives rise to several key morphological features of bilaterian animals including endoskeletal elements and the musculature. A number of regulatory genes involved in mesoderm and/or muscle formation (e.g.

Midbody-Localized Aquaporin Mediates Intercellular Lumen Expansion During Early Cleavage of an Invasive Freshwater Bivalve.

Intercellular lumen formation is a crucial aspect of animal development and physiology that involves a complex interplay between the molecular and physical properties of the constituent cells. Embryos of the invasive freshwater mussel are ideal models for studying this process due to the large intercellular cavities that readily form during blastomere cleavage. Using this system, we show that recruitment of the transmembrane water channel protein aquaporin exclusively to the midbody of intercellular cytokinetic bridges is critical for lumenogenesis.

HES and Mox genes are expressed during early mesoderm formation in a mollusk with putative ancestral features.

The mesoderm is considered the youngest of the three germ layers. Although its morphogenesis has been studied in some metazoans, the molecular components underlying this process remain obscure for numerous phyla including the highly diverse Mollusca. Here, expression of Hairy and enhancer of split (HES), Mox, and myosin heavy chain (MHC) was investigated in Acanthochitona fascicularis, a representative of Polyplacophora with putative ancestral molluscan features.

Ecdysis-related neuropeptide expression and metamorphosis in a non-ecdysozoan bilaterian.

Ecdysis-related neuropeptides (ERNs), including eclosion hormone, crustacean cardioactive peptide, myoinhibitory peptide, bursicon alpha, and bursicon beta regulate molting in insects and crustaceans. Recent evidence further revealed that ERNs likely play an ancestral role in invertebrate life cycle transitions, but their tempo-spatial expression patterns have not been investigated outside Arthropoda. Using RNA-seq and in situ hybridization, we show that ERNs are broadly expressed in the developing nervous system of a mollusk, the polyplacophoran Acanthochitona fascicularis.

Ancestral Role of Ecdysis-Related Neuropeptides in Animal Life Cycle Transitions.

Ecdysis or molting evolved ∼535 mya in Ecdysozoa, the most diverse and species-rich animal superphylum. A cascade of ecdysis-related neuropeptides (ERNs) controls the innate behavioral programs required for cuticle shedding in some ecdysozoan lineages (e.g.

The quagga mussel genome and the evolution of freshwater tolerance.

Freshwater dreissenid mussels evolved from marine ancestors during the Miocene ∼30 million years ago and today include some of the most successful and destructive invasive species of freshwater environments. Here, we sequenced the genome of the quagga mussel Dreissena rostriformis to identify adaptations involved in embryonic osmoregulation. We provide evidence that a lophotrochozoan-specific aquaporin water channel, a vacuolar ATPase subunit and a sodium/hydrogen exchanger are involved in osmoregulation throughout early cleavage, during which time large intercellular fluid-filled 'cleavage cavities' repeatedly form, coalesce and collapse, expelling excess water to the exterior.

Correction to: Roles of Retinoic Acid Signaling in Shaping the Neuronal Architecture of the Developing Amphioxus Nervous System.

The original version of this article unfortunately contained a mistake. The Fig. 7 sub-panel "f" was missing in the figure of the online first proofs of this article.

Retinoic acid signaling and neurogenic niche regulation in the developing peripheral nervous system of the cephalochordate amphioxus.

The retinoic acid (RA) signaling pathway regulates axial patterning and neurogenesis in the developing central nervous system (CNS) of chordates, but little is known about its roles during peripheral nervous system (PNS) formation and about how these roles might have evolved. This study assesses the requirement of RA signaling for establishing a functional PNS in the cephalochordate amphioxus, the best available stand-in for the ancestral chordate condition. Pharmacological manipulation of RA signaling levels during embryogenesis reduces the ability of amphioxus larvae to respond to sensory stimulation and alters the number and distribution of ectodermal sensory neurons (ESNs) in a stage- and context-dependent manner.

The origin of dopaminergic systems in chordate brains: insights from amphioxus.

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.

Roles of Retinoic Acid Signaling in Shaping the Neuronal Architecture of the Developing Amphioxus Nervous System.

The morphogen retinoic acid (RA) patterns vertebrate nervous systems and drives neurogenesis, but how these functions evolved remains elusive. Here, we show that RA signaling plays stage- and tissue-specific roles during the formation of neural cell populations with serotonin, dopamine, and GABA neurotransmitter phenotypes in amphioxus, a proxy for the ancestral chordate. Our data suggest that RA signaling restricts the specification of dopamine-containing cells in the ectoderm and of GABA neurons in the neural tube, probably by regulating Hox1 and Hox3 gene expression, respectively.

A developmental study of serotonin-immunoreactive neurons in the embryonic brain of the marbled crayfish and the migratory locust: evidence for a homologous protocerebral group of neurons.

It is well established that the brains of adult malacostracan crustaceans and winged insects display distinct homologies down to the level of single neuropils such as the central complex and the optic neuropils. We wanted to know if developing insect and crustacean brains also share similarities and therefore have explored how neurotransmitter systems arise during arthropod embryogenesis. Previously, Sintoni et al.

Retinoic acid signaling in spinal cord development.

Retinoic acid (RA) is an important signaling molecule mediating intercellular communication through vertebrate development. Here, we present and discuss recent information on the roles of the RA signaling pathway in spinal cord development. RA is an important player in the patterning and definition of the spinal cord territory from very early stages of development, even before the appearance of the neural plate and further serves a role in the patterning of the spinal cord both along the dorsoventral and anteroposterior axes, particularly in the promotion of neuronal differentiation.