scholarly journals A positional information gradient of sonic hedgehog is required for flight feather formation in avian wings

2019 ◽  
Author(s):  
Lara Busby ◽  
Cristina Aceituno ◽  
Caitlin McQueen ◽  
Constance A. Rich ◽  
Maria A. Ros ◽  
...  
Keyword(s):  
Sonic Hedgehog ◽  
Limb Development ◽  
Positional Information ◽  
Embryonic Chick ◽  
Flight Feather ◽  
Avian Flight ◽  
Theropod Dinosaurs ◽  
Wing Bud ◽  
Tissue Recombination ◽  
Recombination Experiments

Flight is a triumph of evolution that enabled the radiation and success of birds. A crucial step was the development of forelimb flight feathers that may have evolved for courtship or territorial displays in ancestral theropod dinosaurs. Classical tissue recombination experiments performed in the chick embryo provide evidence that signals operating during early limb development specify the position and identity of feathers. Here we show that a positional information gradient of Sonic hedgehog (Shh) signalling in the embryonic chick wing bud specifies the pattern of adult flight feathers in a defined spatial and temporal sequence that reflects their different identities. We reveal that the Shh signalling gradient is interpreted into specific patterns of flight feather-associated gene expression. Our data suggests that flight feather evolution involved the co-option of the pre-existing digit patterning mechanism and therefore uncovers an embryonic process that played a fundamental step in the evolution of avian flight.

Relationship between retinoic acid and sonic hedgehog, two polarizing signals in the chick wing bud

Development ◽  
1994 ◽  
Vol 120 (11) ◽  
pp. 3267-3274 ◽  
Author(s):  
J. Helms ◽  
C. Thaller ◽  
G. Eichele
Keyword(s):  
Retinoic Acid ◽  
Sonic Hedgehog ◽  
Positional Information ◽  
Limb Bud ◽  
Dependent Manner ◽  
All Trans Retinoic Acid ◽  
Wing Bud ◽  
Zone Of Polarizing Activity ◽  
Dose Dependent

Local application of all-trans-retinoic acid (RA) to the anterior margin of chick limb buds results in pattern duplications reminescent of those that develop after grafting cells from the zone of polarizing activity (ZPA). RA may act directly by conferring positional information to limb bud cells, or it may act indirectly by creating a polarizing region in the tissue distal to the RA source. Here we demonstrate that tissue distal to an RA-releasing bead acquires polarizing activity in a dose-dependent manner. Treatments with pharmacological (beads soaked in 330 micrograms/ml) and physiological (beads soaked in 10 micrograms/ml) doses of RA are equally capable of inducing digit pattern duplication. Additionally, both treatments induce sonic hedgehog (shh; also known as vertebrate hedgehog-1, vhh-1), a putative ZPA morphogen and Hoxd-11, a gene induced by the polarizing signal. However, tissue transplantation assays reveal that pharmacological, but not physiological, doses create a polarizing region. This differential response could be explained if physiological doses induced less shh than pharmacological doses. However, our in situ hybridization analyses demonstrate that both treatments result in similar amounts of mRNA encoding this candidate ZPA morphogen. We outline a model describing the apparently disparate effects of pharmacologic and physiological doses RA on limb bud tissue.

The preliminary characterization of mitogens secreted by embryonic chick wing bud tissues in vitro

Development ◽  
1986 ◽  
Vol 93 (1) ◽  
pp. 257-265
Author(s):  
K. M. Bell
Keyword(s):  
Growth Factors ◽  
Limb Development ◽  
Rat Kidney ◽  
Active Regions ◽  
Limb Bud ◽  
Embryonic Chick ◽  
Bovine Endothelial Cells ◽  
Normal Rat ◽  
Wing Bud

Embryonic chick wing bud tissues secrete diffusible mitogens when cultured in vitro (Bell & McLachlan, 1985). These molecules may play an important role in limb development since media conditioned by morphogenetically active regions of the wing bud possess greater mitogenic activity than media conditioned by non-morphogenetic regions. These studies show that while the chick-derived growth factors were mitogenic for mouse-derived NIH 3T3,10T1/2 and NR6 cells and chick limb bud cells, they did not stimulate DNA synthesis in 3B11, PC13 END, normal rat kidney or bovine endothelial cells. Furthermore, the effects of the chick-derived mitogens were synergistically enhanced by insulin and PGF2α but remained unaffected by ECDGF, EGF, FGF and MSA. These findings indicate that embryonic chick limb bud cells synthesize and secrete growth factors which resemble in function other well-characterized growth factors and in particular PDGF.

scholarly journals Sonic hedgehog specifies flight feather positional information in avian wings

Development ◽  
2020 ◽  
Vol 147 (9) ◽  
pp. dev188821
Author(s):  
Lara Busby ◽  
Cristina Aceituno ◽  
Caitlin McQueen ◽  
Constance A. Rich ◽  
Maria A. Ros ◽  
...  
Keyword(s):  
Sonic Hedgehog ◽  
Positional Information ◽  
Flight Feather

scholarly journals Manifestation of the Limb Prepattern: Limb Development in the Absence of Sonic Hedgehog Function

2001 ◽  
Vol 236 (2) ◽  
pp. 421-435 ◽  
Author(s):  
Chin Chiang ◽  
Ying Litingtung ◽  
Matthew P. Harris ◽  
B.Kay Simandl ◽  
Yina Li ◽  
...  
Keyword(s):  
Sonic Hedgehog ◽  
Limb Development

Limb deformity proteins: role in mesodermal induction of the apical ectodermal ridge

Development ◽  
1997 ◽  
Vol 124 (1) ◽  
pp. 133-139 ◽  
Author(s):  
J. Kuhlman ◽  
L. Niswander
Keyword(s):  
Sonic Hedgehog ◽  
Limb Development ◽  
Apical Ectodermal Ridge ◽  
Primary Defect ◽  
Limb Deformity ◽  
Normal Morphology ◽  
Fibroblast Growth Factor 8 ◽  
Skeletal Pattern ◽  
Two Phases ◽  
And Function

During early limb development, distal tip ectoderm is induced by the underlying mesenchyme to form the apical ectodermal ridge. Subsequent limb growth and patterning depend on reciprocal signaling between the mesenchyme and ridge. Mice that are homozygous for mutations at the limb deformity (ld) locus do not form a proper ridge and the anteroposterior axis of the limb is shortened. Skeletal analyses reveal shortened limbs that involve loss and fusion of distal bones and digits, defects in both anteroposterior and proximodistal patterning. Using molecular markers and mouse-chick chimeras we examined the ridge-mesenchymal interactions to determine the origin of the ld patterning defects. In the ld ridge, fibroblast growth factor 8 (Fgf8) RNA is decreased and Fgf4 RNA is not detected. In the ld mesenchyme, Sonic hedgehog (Shh), Evx1 and Wnt5a expression is decreased. In chimeras between ld ectoderm and wild-type mesenchyme, a ridge of normal morphology and function is restored, Fgf8 and Shh are expressed normally, Fgf4 is induced and a normal skeletal pattern arises. These results suggest that the ld mesenchyme is unable to induce the formation of a completely functional ridge. This primary defect causes a disruption of ridge function and subsequently leads to the patterning defects observed in ld limbs. We propose a model in which ridge induction requires at least two phases: an early competence phase, which includes induction of Fgf8 expression, and a later differentiation phase in which Fgf4 is induced and a morphological ridge is formed. Ld proteins appear to act during the differentiation phase.

Role of the chicken homeobox-containing genes GHox-4.6 and GHox-8 in the specification of positional identities during the development of normal and polydactylous chick limb buds

Development ◽  
1992 ◽  
Vol 115 (2) ◽  
pp. 629-637 ◽  
Author(s):  
C.N. Coelho ◽  
W.B. Upholt ◽  
R.A. Kosher
Keyword(s):  
Limb Development ◽  
Ectopic Expression ◽  
Limb Bud ◽  
Chick Embryos ◽  
Limb Buds ◽  
Hox Gene ◽  
Wing Bud ◽  
Coated Bead ◽  
Experimentally Induced

During early stages of normal chick limb development, the homeobox-containing (HOX) gene GHox-4.6 is expressed throughout the posterior mesoderm of the wing bud from which most of the skeletal elements including the digits will develop, whereas GHox-8 is expressed in the anterior limb bud mesoderm which will not give rise to skeletal elements. In the present study, we have examined the expression of GHox-4.6 and GHox-8 in the wing buds of two polydactylous mutant chick embryos, diplopodia-5 and talpid2, from which supernumerary digits develop from anterior limb mesoderm, and have also examined the expression of these genes in response to polarizing zone grafts and retinoic acid-coated bead implants which induce the formation of supernumerary digits from anterior limb mesoderm. We have found that the formation of supernumerary digits from the anterior mesoderm in mutant and experimentally induced polydactylous limb buds is preceded by the ectopic expression of GHox-4.6 in the anterior mesoderm and the coincident suppression of GHox-8 expression in the anterior mesoderm. These observations suggest that the anterior mesoderm of the polydactylous limb buds is “posteriorized” and support the suggestion that GHox-8 and GHox-4.6, respectively, are involved in specifying the anterior non-skeletal and posterior digit-forming regions of the limb bud. Although the anterior mesodermal domain of GHox-8 expression is severely impaired in the mutant and experimentally induced polydactylous limb buds, this gene is expressed by the prolonged, thickened apical ectodermal ridges of the polydactylous limb buds that extend along the distal anterior as well as the distal posterior mesoderm.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoregulation of Shh expression and Shh induction of cell death suggest a mechanism for modulating polarising activity during chick limb development

Development ◽  
2000 ◽  
Vol 127 (22) ◽  
pp. 4811-4823 ◽  
Author(s):  
J.J. Sanz-Ezquerro ◽  
C. Tickle
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Sonic Hedgehog ◽  
Limb Development ◽  
Retroviral Vector ◽  
Cellular Mechanism ◽  
Limb Bud ◽  
Drug Induced ◽  
Signalling Molecule ◽  
Vertebrate Limb

The polarising region expresses the signalling molecule sonic hedgehog (Shh), and is an embryonic signalling centre essential for outgrowth and patterning of the vertebrate limb. Previous work has suggested that there is a buffering mechanism that regulates polarising activity. Little is known about how the number of Shh-expressing cells is controlled but, paradoxically, the polarising region appears to overlap with the posterior necrotic zone, a region of programmed cell death. We have investigated how Shh expression and cell death respond when levels of polarising activity are altered, and show an autoregulatory effect of Shh on Shh expression and that Shh affects cell death in the posterior necrotic zone. When we increased Shh signalling, by grafting polarising region cells or applying Shh protein beads, this led to a reduction in the endogenous Shh domain and an increase in posterior cell death. In contrast, cells in other necrotic regions of the limb bud, including the interdigital areas, were rescued from death by Shh protein. Application of Shh protein to late limb buds also caused alterations in digit morphogenesis. When we reduced the number of Shh-expressing cells in the polarising region by surgery or drug-induced killing, this led to an expansion of the Shh domain and a decrease in the number of dead cells. Furthermore, direct prevention of cell death using a retroviral vector expressing Bcl2 led to an increase in Shh expression. Finally, we provide evidence that the fate of some of the Shh-expressing cells in the polarising region is to undergo apoptosis and contribute to the posterior necrotic zone during normal limb development. Taken together, these results show that there is a buffering system that regulates the number of Shh-expressing cells and thus polarising activity during limb development. They also suggest that cell death induced by Shh could be the cellular mechanism involved. Such an autoregulatory process based on cell death could represent a general way for regulating patterning signals in embryos.

Retinoic acid signaling is required during early chick limb development

Development ◽  
1996 ◽  
Vol 122 (5) ◽  
pp. 1385-1394 ◽  
Author(s):  
J.A. Helms ◽  
C.H. Kim ◽  
G. Eichele ◽  
C. Thaller
Keyword(s):  
Retinoic Acid ◽  
Limb Development ◽  
Acid Synthesis ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Retinoid Receptor ◽  
Limb Morphogenesis ◽  
Wing Bud ◽  
Zone Of Polarizing Activity

In the chick limb bud, the zone of polarizing activity controls limb patterning along the anteroposterior and proximodistal axes. Since retinoic acid can induce ectopic polarizing activity, we examined whether this molecule plays a role in the establishment of the endogenous zone of polarizing activity. Grafts of wing bud mesenchyme treated with physiologic doses of retinoic acid had weak polarizing activity but inclusion of a retinoic acid-exposed apical ectodermal ridge or of prospective wing bud ectoderm evoked strong polarizing activity. Likewise, polarizing activity of prospective wing mesenchyme was markedly enhanced by co-grafting either a retinoic acid-exposed apical ectodermal ridge or ectoderm from the wing region. This equivalence of ectoderm-mesenchyme interactions required for the establishment of polarizing activity in retinoic acid-treated wing buds and in prospective wing tissue, suggests a role of retinoic acid in the establishment of the zone of polarizing activity. We found that prospective wing bud tissue is a high-point of retinoic acid synthesis. Furthermore, retinoid receptor-specific antagonists blocked limb morphogenesis and down-regulated a polarizing signal, sonic hedgehog. Limb agenesis was reversed when antagonist-exposed wing buds were treated with retinoic acid. Our results demonstrate a role of retinoic acid in the establishment of the endogenous zone of polarizing activity.

dackel acts in the ectoderm of the zebrafish pectoral fin bud to maintain AER signaling

Development ◽  
2000 ◽  
Vol 127 (19) ◽  
pp. 4169-4178 ◽  
Author(s):  
H. Grandel ◽  
B.W. Draper ◽  
S. Schulte-Merker
Keyword(s):  
Transcription Factor ◽  
Growth Factor ◽  
Sonic Hedgehog ◽  
Limb Development ◽  
Induction Phase ◽  
Fibroblast Growth ◽  
Pectoral Fin ◽  
Vertebrate Limb ◽  
Fibroblast Growth Factor 10 ◽  
Vertebrate Limb Development

Classical embryological studies have implied the existence of an apical ectodermal maintenance factor (AEMF) that sustains signaling from the apical ectodermal ridge (AER) during vertebrate limb development. Recent evidence suggests that AEMF activity is composed of different signals involving both a sonic hedgehog (Shh) signal and a fibroblast growth factor 10 (Fgf10) signal from the mesenchyme. In this study we show that the product of the dackel (dak) gene is one of the components that acts in the epidermis of the zebrafish pectoral fin bud to maintain signaling from the apical fold, which is homologous to the AER of tetrapods. dak acts synergistically with Shh to induce fgf4 and fgf8 expression but independently of Shh in promoting apical fold morphogenesis. The failure of dak mutant fin buds to progress from the initial fin induction phase to the autonomous outgrowth phase causes loss of both AER and Shh activity, and subsequently results in a proximodistal truncation of the fin, similar to the result obtained by ridge ablation experiments in the chicken. Further analysis of the dak mutant phenotype indicates that the activity of the transcription factor engrailed 1 (En1) in the ventral non-ridge ectoderm also depends on a maintenance signal probably provided by the ridge. This result uncovers a new interaction between the AER and the dorsoventral organizer in the zebrafish pectoral fin bud.

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