Early development of the vertebral column

The segmental organization of the vertebrate body is most obviously visible in the vertebral column, which consists of a series of vertebral bones and interconnecting joints and ligaments. During embryo genesis, the vertebral column derives from the somites, which are the primary segments of the embryonic paraxial mesoderm. Anatomical, cellular and molecular aspects of vertebral column development have been of interest to developmental biologists for more than 150 years. This review briefly summarizes the present knowledge on early steps of vertebral column development in amniotes, starting from sclerotome formation and leading to the establishment of the anatomical bauplan of the spine composed of vertebral bodies, vertebral arches, intervertebral discs and ribs, and their specific axial identities along the body axis. (C) 2015 Elsevier Ltd. All rights reserved

Development of the amniote ventrolateral body wall

In vertebrates, the trunk consists of the musculoskeletal structures of the back and the ventrolateral body wall, which together enclose the internal organs of the circulatory, digestive, respiratory and urogenital systems. This review gives an overview on the development of the thoracic and abdominal wall during amniote embryogenesis. Specifically, I briefly summarize relevant historical concepts and the present knowledge on the early embryonic development of ribs, sternum, intercostal muscles and abdominal muscles with respect to anatomical bauplan, origin and specification of precursor cells, initial steps of pattern formation, and cellular and molecular regulation of morphogenesis

Signaling filopodia in vertebrate embryonic development

Next to classical diffusion-based models, filopodia-like cellular protrusions have been proposed to mediate long range signaling events and morphogen gradient formation during communication between distant cells. An increasing wealth of data indicates that in spite of variable characteristics of signaling filopodia in different biological contexts, they represent a paradigm of intercellular crosstalk which is presently being unraveled in a growing literature. Here, we summarize recent advances in investigating the morphology, cellular basis and function of signaling filopodia, with focus on their role during embryonic development in vertebrates

Chick muscle development

Striated muscle is the most abundant tissue in the body of vertebrates and it forms, together with the skeleton, the locomotory system required both for movement and the creation of the specific body shape of a species. Research on the embryonic development of muscles has a long tradition both in classical embryology and in molecular developmental biology. While the gene networks regulating muscle development have been discovered mostly in the mouse through genetics, our knowledge on cell lineages, muscle morphogenesis and tissue interactions regulating their formation is to a large extent based on the use of the avian model. This review highlights present knowledge of the development of skeletal muscle in vertebrate embryos. Special focus will be placed on the contributions from chicken and quail embryo model systems

Foramina in plesiosaur cervical centra indicate a specialized vascular system

The sauropterygian clade Plesiosauria arose in the Late Triassic and survived to the very end of the Cretaceous. A long, flexible neck with over 35 cervicals (the highest number of cervicals in any tetrapod clade) is a synapomorphy of Pistosauroidea, the clade that contains Plesiosauria. Basal plesiosaurians retain this very long neck but greatly reduce neck flexibility. In addition, plesiosaurian cervicals have large, paired, and highly symmetrical foramina on the ventral side of the centrum, traditionally termed subcentral foramina, and on the floor of the neural canal. We found that these dorsal and the ventral foramina are connected by a canal that extends across the center of ossification of the vertebral centrum. We posit that these foramina are not for nutrient transfer to the vertebral centrum but that they are the osteological correlates of a highly paedomorphic vascular system in the neck of plesiosaurs. This is the retention of intersegmental arteries within the vertebral centrum that are usually obliterated during sclerotome re-segmentation in early embryonic development. The foramina and canals are a rare osteological correlate of the non-cranial vascular (arterial) system in fossil reptiles. The adaptive value of the retention of the intersegmental arteries may be improved oxygen transport during deep diving and thermoregulation. These features may have been important in the global dispersal of plesiosaurians

Signaling filopodia in avian embryogenesis: formation and function

In vertebrates and invertebrates specialized cellular protrusions, called signaling filopodia or cytonemes, play an important role in cell-cell communication by carrying receptors and ligands to distant cells to activate various signaling pathways. In the chicken embryo, signaling filopodia were described in limb bud mesenchyme and in somite epithelia. The formation of signaling filopodia depends on the activity of Rho GTPases and reorganization of the cytoskeleton. Here, we give a short overview on the present knowledge on avian signaling filopodia and discuss the molecular basis of cytoskeletal rearrangements leading to filopodia formation

Communication between distant epithelial cells by filopodia-like protrusions during embryonic development

Long-range intercellular communication is essential for the regulation of embryonic development. Apart from simple diffusion, various modes of signal transfer have been described in the literature. Here, we describe a novel type of cellular extensions found in epithelial cells of the somites in chicken embryos. These filopodia-like protrusions span the subectodermal space overlying the dorsal surface of the somites and contact the ectoderm. We show that these protrusions are actin-and tubulin-positive and require Rac1 for their formation. The presence of glycophosphatidylinositol-anchored proteins and net retrograde trafficking of the transmembrane Wnt-receptor Frizzled-7 along the protrusions indicate their role in signal transport and distribution. Taken together, our data suggest a role of filopodia-like protrusions in mediating signaling events between distant epithelial cells during embryonic development