Specific guidance of motor axons to duplicated muscles in the developing amniote limb

Development ◽  
1988 ◽  
Vol 103 (1) ◽  
pp. 97-110 ◽  
Author(s):  
R.V. Stirling ◽  
D. Summerbell
Keyword(s):  
Axon Guidance ◽  
Retrograde Transport ◽  
Positional Information ◽  
Limb Bud ◽  
Horse Radish Peroxidase ◽  
Change Position ◽  
Zone Of Polarizing Activity ◽  
Limb Pattern ◽  
Positional Value ◽  
Significant Support

The effect of alteration of limb pattern upon motor axon guidance has been investigated in chick embryos. Following grafting of the zone of polarizing activity (ZPA) into the anterior margin of the early limb bud, limbs develop with forearms duplicated about the anteroposterior axis. The position of motoneurones innervating the duplicated posterior forearm extensor EMU was mapped by retrograde transport of horse radish peroxidase (HRP). The motor pool labelled from injection into the anteriorly duplicated EMU muscle is consistently similar to that supplying the posterior EMU muscle on the unoperated side of the embryo. In those cases where the axons are well filled, their trajectories from the injection site are observed to change position within the radial nerve to specifically innervate the duplicated muscle. The axons modify their trajectories proximal to the level of limb duplication in a region where there is no change in the pattern of overt differentiation of the limb cells. This suggests that axons may use a cell's positional value to navigate and provides significant support for the theory of positional information.

Interaction between the proximo-distal and antero-posterior co-ordinates of positional value during the specification of positional information in the early development of the chick limb-bud

Development ◽  
1974 ◽  
Vol 32 (1) ◽  
pp. 227-237
Author(s):  
Dennis Summerbell
Keyword(s):  
Early Development ◽  
Anterior Margin ◽  
Positional Information ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Anteroposterior Axis ◽  
Zone Of Polarizing Activity ◽  
Positional Value ◽  
Special Region

The experiments examine the extent of reduplication of skeletal parts across the anteroposterior axis, following the transplantation of a zone of polarizing activity (ZPA) to the anterior margin of the limb-bud at successively later stages. Previous studies have suggested that the function of the apical ectodermal ridge (AER) is to maintain cells in a special region at the distal tip (the progress zone) labile, with respect to their positional value along the proximo-distal axis. Similarly, the results of these experiments demonstrate that cells in the progress zone are able to change their antero-posterior positional value under the influence of the grafted ZPA, while cells at more proximal levels remain unaffected. In turn, the ZPA may effect the activity of the AER and hence the progress zone.

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.

Effects of biochemical inhibitors on positional signalling in the chick limb bud

Development ◽  
1981 ◽  
Vol 62 (1) ◽  
pp. 203-216
Author(s):  
Lawrence S. Honig ◽  
J. C. Smith ◽  
Amata Hornbruch ◽  
L. Wolpert
Keyword(s):  
Dna Synthesis ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
Positional Information ◽  
Limb Bud ◽  
Limb Buds ◽  
Protein And Rna Synthesis ◽  
Zone Of Polarizing Activity ◽  
Rna And Dna Synthesis ◽  
Rna And Dna

In 3- to 4-day embryonic chick limb buds, a region at the posterior margin of the limb, the zone of polarizing activity, appears to be responsible for signalling positional information along the anteroposterior axis. Our experiments were designed to test which biosynthetic processes are required for polarizing activity. We have treated polarizing regions with biochemical inhibitors, and then assayed their abilities to induce limb reduplications when grafted into anterior sites on host limb buds, and also measured their capacities for protein, RNA, and DNA synthesis. DNA synthesis, and possibly oxidative phosphorylation, do not seem to be required for polarizing activity. But, glycolysis and protein and RNA synthesis are necessary, although not sufficient, for polarizing region activity. Activity seems particularly sensitive to inhibitors (actinomycin D and α-amanitin) of RNA synthesis.

Mutations in mouse Aristaless-like4 cause Strong's luxoid polydactyly

Development ◽  
1998 ◽  
Vol 125 (14) ◽  
pp. 2711-2721 ◽  
Author(s):  
S. Qu ◽  
S.C. Tucker ◽  
J.S. Ehrlich ◽  
J.M. Levorse ◽  
L.A. Flaherty ◽  
...  
Keyword(s):  
Limb Development ◽  
Evolutionary Biology ◽  
Biochemical Characterization ◽  
Limb Bud ◽  
Critical Threshold ◽  
Homeodomain Protein ◽  
Loss Of Function ◽  
Posterior Aspect ◽  
Vertebrate Limb Development ◽  
Zone Of Polarizing Activity

Mutations that affect vertebrate limb development provide insight into pattern formation, evolutionary biology and human birth defects. Patterning of the limb axes depends on several interacting signaling centers; one of these, the zone of polarizing activity (ZPA), comprises a group of mesenchymal cells along the posterior aspect of the limb bud that express sonic hedgehog (Shh) and plays a key role in patterning the anterior-posterior (AP) axis. The mechanisms by which the ZPA and Shh expression are confined to the posterior aspect of the limb bud mesenchyme are not well understood. The polydactylous mouse mutant Strong's luxoid (lst) exhibits an ectopic anterior ZPA and expression of Shh that results in the formation of extra anterior digits. Here we describe a new chlorambucil-induced deletion allele, lstAlb, that uncovers the lst locus. Integration of the lst genetic and physical maps suggested the mouse Aristaless-like4 (Alx4) gene, which encodes a paired-type homeodomain protein that plays a role in limb patterning, as a strong molecular candidate for the Strong's luxoid gene. In genetic crosses, the three lst mutant alleles fail to complement an Alx4 gene-targeted allele. Molecular and biochemical characterization of the three lst alleles reveal mutations of the Alx4 gene that result in loss of function. Alx4 haploinsufficiency and the importance of strain-specific modifiers leading to polydactyly are indicative of a critical threshold requirement for Alx4 in a genetic program operating to restrict polarizing activity and Shh expression in the anterior mesenchyme of the limb bud, and suggest that mutations in Alx4 may also underlie human polydactyly.

A quantitative analysis of the effect of excision of the AER from the chick limb-bud

Development ◽  
1974 ◽  
Vol 32 (3) ◽  
pp. 651-660
Author(s):  
Dennis Summerbell
Keyword(s):  
Quantitative Analysis ◽  
Quantitative Method ◽  
Continuous Process ◽  
Apical Ectodermal Ridge ◽  
Rate Of Change ◽  
Limb Bud ◽  
Zone Model ◽  
Gradual Change ◽  
Analysis Of Results ◽  
Positional Value

The effect of removal of the apical ectodermal ridge from the early chick limb-bud is re-examined using a new quantitative method of analysis of results. The concept of the proximo-distal sequence of laying down of parts is confirmed and evidence is presented thatthis proceeds as a continuous process, there being a gradual change in the level specified from one cell to another at a more distal level. The results are then interpreted in terms of the ‘progress zone’ model to show that they are both consistent with the model and that they provide an assay for one of its parameters, the rate of change of positional value with time at the tip.

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.

The mesenchymal factor, FGF10, initiates and maintains the outgrowth of the chick limb bud through interaction with FGF8, an apical ectodermal factor

Development ◽  
1997 ◽  
Vol 124 (11) ◽  
pp. 2235-2244 ◽  
Author(s):  
H. Ohuchi ◽  
T. Nakagawa ◽  
A. Yamamoto ◽  
A. Araga ◽  
T. Ohata ◽  
...  
Keyword(s):  
Sonic Hedgehog ◽  
Limb Bud ◽  
Fibroblast Growth ◽  
Lateral Plate Mesoderm ◽  
Lateral Plate ◽  
Bud Formation ◽  
Limb Mesenchyme ◽  
Vertebrate Limb ◽  
Fgf10 Expression ◽  
Zone Of Polarizing Activity

Vertebrate limb formation has been known to be initiated by a factor(s) secreted from the lateral plate mesoderm. In this report, we provide evidence that a member of the fibroblast growth factor (FGF) family, FGF10, emanates from the prospective limb mesoderm to serve as an endogenous initiator for limb bud formation. Fgf10 expression in the prospective limb mesenchyme precedes Fgf8 expression in the nascent apical ectoderm. Ectopic application of FGF10 to the chick embryonic flank can induce Fgf8 expression in the adjacent ectoderm, resulting in the formation of an additional complete limb. Expression of Fgf10 persists in the mesenchyme of the established limb bud and appears to interact with Fgf8 in the apical ectoderm and Sonic hedgehog in the zone of polarizing activity. These results suggest that FGF10 is a key mesenchymal factor involved in the initial budding as well as the continuous outgrowth of vertebrate limbs.

Evidence that preaxial polydactyly in the Doublefoot mutant is due to ectopic Indian Hedgehog signaling

Development ◽  
1998 ◽  
Vol 125 (16) ◽  
pp. 3123-3132 ◽  
Author(s):  
Y. Yang ◽  
P. Guillot ◽  
Y. Boyd ◽  
M.F. Lyon ◽  
A.P. McMahon
Keyword(s):  
Hedgehog Signaling ◽  
Interspecific Backcross ◽  
Limb Bud ◽  
Chromosome 1 ◽  
Indian Hedgehog ◽  
Posterior Limb ◽  
Preaxial Polydactyly ◽  
Ectopic Activation ◽  
Zone Of Polarizing Activity ◽  
Anterior Posterior

Patterning of the vertebrate limb along the anterior-posterior axis is controlled by the zone of polarizing activity (ZPA) located at the posterior limb margin. One of the vertebrate Hh family members, Shh, has been shown to be able to mediate the function of the ZPA. Several naturally occurring mouse mutations with the phenotype of preaxial polydactyly exhibit ectopic Shh expression at the anterior limb margin. In this study, we report the molecular characterization of a spontaneous mouse mutation, Doublefoot (Dbf). Dbf is a dominant mutation which maps to chromosome 1. Heterozygous and homozygous embryos display a severe polydactyly with 6 to 8 digits on each limb. We show here that Shh is expressed normally in Dbf mutants. In contrast, a second Hh family member, Indian hedgehog (Ihh) which maps close to Dbf, is ectopically expressed in the distal limb bud. Ectopic Ihh expression in the distal and anterior limb bud results in the ectopic activation of several genes associated with anterior-posterior and proximal-distal patterning (Fgf4, Hoxd13, Bmp2). In addition, specific components in the Hedgehog pathway are either ectopically activated (Ptc, Ptc-2, Gli1) or repressed (Gli2). We propose that misexpression of Ihh, and not a novel Smoothened ligand as recently suggested (Hayes et al., 1998), is responsible for the Dbf phenotype. We consider that Ihh has a similar activity to Shh when expressed in the early Shh-responsive limb bud. To determine whether Dbf maps to the Ihh locus, which is also on chromosome 1, we performed an interspecific backcross. These results demonstrate that Dbf and Ihh are genetically separated by approximately 1.3 centimorgans, suggesting that Dbf mutation may cause an exceptionally long-range disruption of Ihh regulation. Although this leads to ectopic activation of Ihh, normal expression of Ihh in the cartilaginous elements is retained.

Control of growth related to pattern specification in chick wing-bud mesenchyme

Development ◽  
1981 ◽  
Vol 65 (Supplement) ◽  
pp. 169-185
Author(s):  
Jonathan Cooke ◽  
Dennis Summerbell
Keyword(s):  
Mitotic Index ◽  
Packing Density ◽  
Limb Development ◽  
Limb Mesenchyme ◽  
Wing Bud ◽  
Zone Of Polarizing Activity ◽  
Pattern Specification ◽  
Limb Pattern

The distribution of raised mitotic index, and the co-incidence of this with lowered cell packing density, has been studied across the anteroposterior dimension of the terminal 500 μm of chick wing buds following various numbers of hours signalling from an anteriorly grafted extra Zone of Polarizing Activity (ZPA). The results show propagation of the situation that causes these correlated phenomena, from graft-host interface essentially right across the limb mesenchyme, frequently within 8 h. This contrasts with the much slower and more local succession of changes in position memory, for differentiation of a duplicated limb pattern, that also occurs in mesenchyme relatively close to the graft after this operation. The results are discussed, in relation to current ideas about the control of pattern during limb development.

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