Ancient homeobox gene loss and the evolution of chordate brain and pharynx development: deductions from amphioxus gene expression

Homeobox genes encode a large superclass of transcription factors with widespread roles in animal development. Within chordates there are over 100 homeobox genes in the invertebrate cephalochordate amphioxus and over 200 in humans. Set against this general trend of increasing gene number in vertebrate evolution, some ancient homeobox genes that were present in the last common ancestor of chordates have been lost from vertebrates. Here, we describe the embryonic expression of four amphioxus descendants of these genes—AmphiNedxa, AmphiNedxb, AmphiMsxlx and AmphiNKx7. All four genes are expressed with a striking asymmetry about the left–right axis in the pharyngeal region of neurula embryos, mirroring the pronounced asymmetry of amphioxus embryogenesis. AmphiMsxlx and AmphiNKx7 are also transiently expressed in an anterior neural tube region destined to become the cerebral vesicle. These findings suggest significant rewiring of developmental gene regulatory networks occurred during chordate evolution, coincident with homeobox gene loss. We propose that loss of otherwise widely conserved genes is possible when these genes function in a confined role in development that is subsequently lost or significantly modified during evolution. In the case of these homeobox genes, we propose that this has occurred in relation to the evolution of the chordate pharynx and brain

Mouse Retinal Development: a Dark Horse Model for Systems Biology Research

The developing retina is an excellent model to study cellular fate determination and differentiation in the context of a complex tissue. Over the last decade, many basic principles and key genes that underlie these processes have been experimentally identified. In this review, we construct network models to summarize known gene interactions that underlie determination and fundamentally affect differentiation of each retinal cell type. These networks can act as a scaffold to assemble subsequent discoveries. In addition, these summary networks provide a rational segue to systems biology approaches necessary to understand the many events leading to appropriate cellular determination and differentiation in the developing retina and other complex tissues

Conserved and divergent functions of Drosophila atonal , amphibian, and mammalian Ath5 genes

Insect and vertebrate eyes differ in their formation, cellular composition, neural connectivity, and visual function. Despite this diversity, Drosophila atonal and its vertebrate Ortholog in the eye, Ath5 , each regulate determination of the first retinal neuron class—R8 photo-receptors and retinal ganglion cells (RGCs)—in their respective organisms. We have performed a cross-species functional comparison of these genes. In ato 1 mutant Drosophila , ectopic Xenopus Ath5 ( Xath5 ) rescues photoreceptor cell development comparably with atonal . In contrast, mouse Ath5 ( Math5 ) induces formation of very few ommatidia, and most of these lack R8 cells. In the developing frog eye, ectopic atonal , like Xath5 , promotes the differentiation RGCs. Despite strong conservation of atonal , Xath5 , and Math5 structure and shared function, other factors must contribute to the species specificity of retinal neuron determination. These observations suggest that the atonal family may occupy a position in a gene hierarchy where differences in gene regulation or function can be correlated with evolutionary diversity of eye development.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72909/1/j.1525-142X.2003.03058.x.pd

A Three Dimensional FEM-Simulation of the Selective Laser Sintering Process with Locally Refined Meshes and Non-Constant Thermal Conductivity

Mechanical Engineerin

Gunshot wounds in parenchymatous organs: the morphology mainly depends on the physical properties of the affected tissues.

In contrast to gunshot wounds in skin and bone, the medico-legal literature pays little attention to the appearance of bullet penetration sites in abdominal organs. It was only in 1983 that Metter and Schulz published an article entitled "Morphological features of gunshot wounds in the liver and spleen." According to their observations, the organs in question showed stellate tears at the bullet penetration sites resembling skin wounds from contact shots to body regions having a bony support. The study presented simulated the real conditions by means of test shots to composite models consisting of porcine organs embedded in ballistic gelatin. The ammunition used was pistol cartridges 9 mm Luger with full metal jacket round nose bullets. The shots were video-documented with a high-speed camera in order to record the bullet's travel through the target. In addition, the composite models fired at underwent CT examinations followed by a macroscopic assessment of the organs. The study confirmed the findings of Metter and Schulz with regard to the star-like appearance of gunshot wounds in the liver and spleen. Likewise, the kidney showed radiating tears originating from the bullet path, whereas the wound track in pulmonary tissue was tube-shaped and lacked additional cracks. The varying wound patterns in parenchymatous organs can reasonably be explained as a consequence of the respective viscoelastic tissue properties

Lehrende in der interprofessionellen Bildung: Ein Vorschlag zur Terminologie

Different terms (e.g., interprofessional, multiprofessional, interdisciplinary) are used in interprofessional education and collaboration without sufficient differentiation or precision in regard to meaning. In recent years academic publications in English and German have contributed to clarifying this issue. However, there are no definitions internationally or in the German-speaking countries (Germany, Austria, Switzerland) specifically referring to the people engaged in teaching interprofessional education. Teaching in interprofessional education has evolved from the traditional role of expert to one of mentor or facilitator. It is also evident that those who teach play a central role in the success of interprofessional courses. While many different designations are used to refer to interprofessional teachers in the relevant literature and in the language of daily use, a uniform and adequate terminology should be used to refer to such teaching staff. Based on literature reviews, this commentary seeks to propose terms for teaching staff active in the area of interprofessional education and thus provide a basis for discussion in the German-speaking countries. Taking the results of the literature analysis and the roles of teachers in interprofessional settings into consideration, we propose that the English term "IP facilitator" (IP for interprofessional) should also be used in the German-speaking world and "facilitateur IP" in the French-speaking world. A French translation is included in attachment 1 to enable broader discussion in Switzerland.Im Bereich der interprofessionellen Bildung und Zusammenarbeit werden verschiedene Begrifflichkeiten (z.B. interprofessionell, multiprofessionell, interdisziplinär) mitunter wenig trennscharf oder nicht sinngemäß verwendet. In den letzten Jahren haben hier einschlägige Diskussionsbeiträge zur weiteren Klärung in englischsprachigen Publikationen als auch im deutschsprachigen Raum beigetragen. Jedoch finden sich keine internationalen oder gar auf den DACH-Raum (Deutschland, Österreich, Schweiz) bezogenen terminologischen Klärungen zur Benennung der Lehrenden im Bereich der IPE (interprofessional education, IPE). Die Charakteristik von Lehrenden im Bereich der IPE verändert sich von der traditionellen Expert*innenrolle hin zur Rolle von Lernbegleitenden. Zudem ist evident, dass Lehrende eine zentrale Rolle zum Gelingen von interprofessionellen Lehr-/Lernveranstaltungen beitragen. In der einschlägigen Literatur und im alltäglichen Sprachgebrauch finden sich viele verschiedene Bezeichnungen für interprofessionell Lehrende. Daher sollte eine einheitliche und adäquate Benennung dieser Lehrenden erfolgen. Auf Basis von Literaturrecherchen möchte der vorliegende Kommentar Vorschläge zur Bezeichnung von Lehrenden im Feld der IPE und folglich eine Diskussionsgrundlage für den DACH-Raum liefern. Unter Berücksichtigung der vorgenommenen Literaturanalyse und dem damit einhergehenden Verständnis sowie den Rollen von Lehrenden in IPE-Settings, wird die englische Bezeichnung "IP facilitator" (IP für interprofessionell) auch für den deutschsprachigen Raum bzw. "facilitateur IP" für den französischsprachigen Raum vorgeschlagen. Im Anhang 1 des Artikels wurde eine französischsprachige Übersetzung des Beitrags angefügt, um so eine breitere Diskussion in der Schweiz zu ermöglichen

Conservation of Pax-6 in a lower chordate, the ascidian Phallusia mammillata

The Pax-6 genes of vertebrates and invertebrates encode transcription factors with both a paired domain and a homeodomain. They are expressed in the developing eye and in the central nervous system. Loss-of-function mutations in mammals and in flies result in a reduction or absence of eyes and targeted expression of the Drosophila and the mouse Pax-6 genes induces ectopic eye structures in Drosophila. These findings lead to the proposal that the morphogenesis of the different types of eyes is controlled by a Pax-6-dependent genetic pathway and that the various eye types are of monophyletic origin. We have isolated a Pax-6 homologous gene from the ascidian Phallusia mammillata, because ascidians occupy an important position in early chordate evolution. Furthermore, the Phallusia larva has a simple photosensitive ocellus. Phallusia Pax-6 shares extensive sequence identity and conserved genomic organization with the known Pax-6 genes of vertebrates and invertebrates. Expression of Phallusia Pax-6 is first detected at late gastrula stages in distinct regions of the developing neural plate. At the tailbud stage, it is expressed in the spinal cord and the brain vesicle, where the sensory organs (ocellus and otolith) form, suggesting an important function in their development. Ectopic expression of the ascidian Pax-6 gene in Drosophila leads to the induction of supernumerary eyes indicating a highly conserved gene regulatory function for Pax-6 genes