Reiterative pattern of
            sonic hedgehog
            expression in the catshark dentition reveals a phylogenetic template for jawed vertebrates

For a dentition representing the most basal extant gnathostomes, that of the shark can provide us with key insights into the evolution of vertebrate dentitions. To detail the pattern of odontogenesis, we have profiled the expression of sonic hedgehog , a key regulator of tooth induction. We find in the catshark ( Scyliorhinus canicula ) that intense shh expression first occurs in a bilaterally symmetrical pattern restricted to broad regions in each half of the dentition in the embryo jaw. As in the mouse, there follows a changing temporal pattern of shh spatial restriction corresponding to epithelial bands of left and right dental fields, but also a subfield for symphyseal teeth. Then, intense shh expression is restricted to loci coincident with a temporal series of teeth in iterative jaw positions. The developmental expression of shh reveals previously undetected timing within epithelial stages of tooth formation. Each locus at alternate, even then odd, jaw positions establishes precise sequential timing for successive replacement within each tooth family. Shh appears first in the central cusp, iteratively along the jaw, then reiteratively within each tooth for secondary cusps. This progressive, sequential restriction of shh is shared by toothed gnathostomes and conserved through 500 million years of evolution.

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Early Palaeozoic dentine and patterned scales in the embryonic catshark tail

Biology Letters ◽

10.1098/rsbl.2007.0502 ◽

2007 ◽

Vol 4 (1) ◽

pp. 87-90 ◽

Cited By ~ 14

Author(s):

Zerina Johanson ◽

Mikiko Tanaka ◽

Natalie Chaplin ◽

Moya Smith

Keyword(s):

Scale Development ◽

Sonic Hedgehog ◽

The Body ◽

Iterative Sequence ◽

Histological Structure ◽

Scyliorhinus Canicula ◽

Pulp Cavity ◽

Early Palaeozoic ◽

Hedgehog Signal ◽

Modular Nature

Regular scale patterning, restricted to the caudalmost tail and organized into two opposing rows on each side of the tail, is observed in few chondrichthyans. These evenly spaced scales, in dorsal and ventral rows, develop in an iterative sequence from the caudal tip, either side of the notochord. They are subsequently lost as a scattered pattern of placoid scales develops on the body and fins. An identical organized pattern is observed in tail scales of Scyliorhinus canicula (catshark), where the expression of sonic hedgehog signal is restricted to the epithelium of developing scales and remains localized to the scale pocket. Regulation of iterative scale position by sonic hedgehog is deeply conserved in vertebrate phylogeny. These scales also reveal an archaic histological structure of a dentine type found in the oldest known shark scales from the Ordovician and Silurian. This combination of regulated pattern and ancient dentine occurs only in the tail, representing the primary scalation. Scattered body scales in elasmobranchs such as S. canicula originate secondarily from differently regulated development, one with typical orthodentine around a central pulp cavity. These observations emphasize the modular nature of chondrichthyan scale development and illustrate previously undetected variation as an atavism in extant chondrichthyan dentine.

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Spatial and temporal pattern for the dentition in the Australian lungfish revealed with sonic hedgehog expression profile

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2008.1364 ◽

2008 ◽

Vol 276 (1657) ◽

pp. 623-631 ◽

Cited By ~ 9

Author(s):

Moya M Smith ◽

Masataka Okabe ◽

Jean Joss

Keyword(s):

Sonic Hedgehog ◽

Temporal Order ◽

Developmental Process ◽

Cichlid Fish ◽

Sister Group ◽

Treatment Results ◽

Lower Jaw ◽

Left And Right ◽

Jaw Position ◽

Australian Lungfish

We report a temporal order of tooth addition in the Australian lungfish where timing of tooth induction is sequential in the same pattern as osteichthyans along the lower jaw. The order of tooth initiation in Neoceratodus starts from the midline tooth, together with left and right ones at jaw position 2, followed by 3 and then 1. This is the pattern order for dentary teeth of several teleosts and what we propose represents a stereotypic initiation pattern shared with all osteichthyans, including the living sister group to all tetrapods, the Australian lungfish. This is contrary to previous opinions that the lungfish dentition is otherwise derived and uniquely different. Sonic hedgehog ( shh ) expression is intensely focused on tooth positions at different times corresponding with their initiation order. This deployment of shh is required for lungfish tooth induction, as cyclopamine treatment results in complete loss of these teeth when applied before they develop. The temporal sequence of tooth initiation is possibly regulated by shh and is know to be required for dentition pattern in other osteichthyans, including cichlid fish and snakes. This reflects a shared developmental process with jawed vertebrates at the level of the tooth module but differs with the lack of replacement teeth.

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The developmental expression of foxl2 in the dogfish Scyliorhinus canicula

Gene Expression Patterns ◽

10.1016/j.modgep.2007.05.003 ◽

2007 ◽

Vol 7 (7) ◽

pp. 793-797 ◽

Cited By ~ 13

Author(s):

Karl R. Wotton ◽

Kathryn E.M. French ◽

Sebastian M. Shimeld

Keyword(s):

Developmental Expression ◽

Scyliorhinus Canicula

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Decision letter for "Differential expression of five prosomatostatin genes in the central nervous system of the catshark Scyliorhinus canicula"

10.1002/cne.24898/v1/decision1 ◽

2019 ◽

Keyword(s):

Central Nervous System ◽

Nervous System ◽

Differential Expression ◽

Scyliorhinus Canicula ◽

The Central Nervous System

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The three-dimensional structure of frozen-hydrated left- and right-handed forms of bacterial flagellar filaments from an identical serotype

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143110 ◽

1986 ◽

Vol 44 ◽

pp. 298-299

Author(s):

S. Trachtenberg ◽

D. J. DeRosier

Keyword(s):

Ionic Strength ◽

Basal Body ◽

Three Dimensional ◽

Dimensional Structure ◽

Protein Species ◽

Liquid Environment ◽

Bacterial Flagellum ◽

Left And Right ◽

Rotary Motor ◽

Helical Parameters

The bacterial cell is propelled through the liquid environment by means of one or more rotating flagella. The bacterial flagellum is composed of a basal body (rotary motor), hook (universal coupler), and filament (propellor). The filament is a rigid helical assembly of only one protein species — flagellin. The filament can adopt different morphologies and change, reversibly, its helical parameters (pitch and hand) as a function of mechanical stress and chemical changes (pH, ionic strength) in the environment.

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Advantages of Complementary Stereo Images as Viewed with the Low-Temperature Field-Emission SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100131206 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1314-1315

Author(s):

William P. Wergin ◽

Eric F. Erbe

Keyword(s):

Fold Increase ◽

Horizontal Displacement ◽

Three Dimensions ◽

Stereo Image ◽

Stereo Pair ◽

Sem Micrograph ◽

Left And Right ◽

The Common ◽

The Brain ◽

Pair Analysis

The eye-brain complex allows those of us with normal vision to perceive and evaluate our surroundings in three-dimensions (3-D). The principle factor that makes this possible is parallax - the horizontal displacement of objects that results from the independent views that the left and right eyes detect and simultaneously transmit to the brain for superimposition. The common SEM micrograph is a 2-D representation of a 3-D specimen. Depriving the brain of the 3-D view can lead to erroneous conclusions about the relative sizes, positions and convergence of structures within a specimen. In addition, Walter has suggested that the stereo image contains information equivalent to a two-fold increase in magnification over that found in a 2-D image. Because of these factors, stereo pair analysis should be routinely employed when studying specimens.Imaging complementary faces of a fractured specimen is a second method by which the topography of a specimen can be more accurately evaluated.

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Histological evaluation of cochlear hair cell damage from noise-induced hearing loss in chinchillas

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100159217 ◽

1990 ◽

Vol 48 (3) ◽

pp. 332-333

Author(s):

R.V. Harrison ◽

R.J. Mount ◽

P. White ◽

N. Fukushima

Keyword(s):

Hair Cell ◽

Evoked Potential ◽

Cell Damage ◽

Acoustic Trauma ◽

Histological Evaluation ◽

Cell Integrity ◽

Functional Changes ◽

Cochlear Hair Cell ◽

Left And Right ◽

Contralateral Ear

In studies which attempt to define the influence of various factors on recovery of hair cell integrity after acoustic trauma, an experimental and a control ear which initially have equal degrees of damage are required. With in a group of animals receiving an identical level of acoustic trauma there is more symmetry between the ears of each individual, in respect to function, than between animals. Figure 1 illustrates this, left and right cochlear evoked potential (CAP) audiograms are shown for two chinchillas receiving identical trauma. For this reason the contralateral ear is used as control.To compliment such functional evaluations we have devised a scoring system, based on the condition of hair cell stereocilia as revealed by scanning electron microscopy, which permits total stereociliar damage to be expressed numerically. This quantification permits correlation of the degree of structural pathology with functional changes. In this paper wereport experiments to verify the symmetry of stereociliar integrity between two ears, both for normal (non-exposed) animals and chinchillas in which each ear has received identical noise trauma.

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The crystallography characteristic of (Mn,Fe)S single crystal

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177623 ◽

1990 ◽

Vol 48 (4) ◽

pp. 898-899

Author(s):

Jiang Xishan

Keyword(s):

Single Crystal ◽

Cast Steel ◽

Point Group ◽

Central Area ◽

Hexagonal Crystal ◽

Growth Step ◽

Left And Right ◽

Relationship Of ◽

Fcc Structure ◽

New Discovery

This paper reports the growth step pattern and morphology at equilibrium and growth states of (Mn,Fe)S single crystal on the wall of micro-voids in ZG25 cast steel by using scanning electron microscope. Seldom report was presented on the growth morphology and steppattern of (Mn,Fe)S single crystal.Fig.1 shows the front half of the polyhedron of(Mn,Fe)S single crystal,its central area being the square crystal plane,the two pairs of hexagons symmetrically located in the high and low, the left and right with a certain, angle to the square crystal plane.According to the symmetrical relationship of crystal, it was defined that the (Mn,Fe)S single crystal at equilibrium state is tetrakaidecahedron consisted of eight hexagonal crystal planes and six square crystal planes. The macroscopic symmetry elements of the tetrakaidecahedron correpond to Oh—n3m symmetry class of fcc structure,in which the hexagonal crystal planes are the { 111 } crystal planes group,square crystal plaits are the { 100 } crystal planes group. This new discovery of the (Mn,Fe)S single crystal provides a typical example of the point group of Oh—n3m.

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