The dorsoventral polarity of the presumptive limb is determined by signals produced by the somites and by the lateral somatopleure

Development ◽  
1997 ◽  
Vol 124 (8) ◽  
pp. 1453-1463 ◽  
Author(s):  
J.L. Michaud ◽  
F. Lapointe ◽  
N.M. Le Douarin
Keyword(s):  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Limb Buds ◽  
Dorsoventral Axis ◽  
Morphogenetic Movements ◽  
Dorsoventral Polarity ◽  
Ventral Aspect ◽  
Dorsal Aspect ◽  
Wing Bud ◽  
Two Sides

When it first appears at stage HH16, the wing bud is already polarized along the dorsoventral axis. To study the mechanisms leading to the establishment of its dorsoventral polarity, we decided to focus our attention on an earlier stage (HH13). Using the quail-chick chimera system, we first show that the presumptive wing mesoderm occupies the medial half of the somatopleure at the level of somites 15–20. The corresponding ectodermal area, however, will only give rise to the apical ectodermal ridge. The rest of the limb bud ectoderm originates from the ectoderm overlying the paraxial and the intermediate mesoderms for its dorsal aspect and the lateral somatopleural mesoderm for its ventral aspect. We next used five experimental paradigms to show that the dorsoventral polarity of the presumptive limb is determined by its environment. Thus, presumptive limb regions flanked on two sides by rows of somites give rise to bidorsal limb buds, indicating that the somites produce a dorsalizing factor. In addition, insertion of filters laterally to the presumptive limb region also results in bidorsal limb buds, suggesting that the lateral somatopleure produces a ventralizing factor. We propose a model in which the polarizing activity of these two signals is mediated by the morphogenetic movements of the presumptive dorsal and ventral ectoderms, which carry the dorsoventral information over the limb bud mesenchyme.

Initial limb budding is independent of apical ectodermal ridge activity; evidence from a limbless mutant

Development ◽  
1988 ◽  
Vol 104 (3) ◽  
pp. 361-367 ◽  
Author(s):  
J.L. Carrington ◽  
J.F. Fallon
Keyword(s):  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Limb Buds ◽  
Initial Formation ◽  
Bud Formation ◽  
Wing Bud

Outgrowth of normal chick limb bud mesoderm is dependent on the presence of a specialized epithelium called the apical ectodermal ridge. This ectodermal ridge is induced by the mesoderm at about the time of limb bud formation. The limbless mutation in the chick affects apical ectodermal ridge formation in the limb buds of homozygotes. The initial formation of the limb bud appears to be unaffected by the mutation but no ridge develops and further outgrowth, which is normally dependent on the ridge, does not take place. As a result, limbless chicks develop without limbs. In the present study, which utilized a pre-limb-bud recombinant technique, limbless mesoderm induced an apical ectodermal ridge in grafted normal flank ectoderm. However, at stages when normal flank ectoderm is capable of responding to ridge induction, limbless flank ectoderm did not form a ridge or promote outgrowth of a limb in response to normal presumptive wing bud mesoderm. We conclude from this that the limbless mutation affects the ability of the ectoderm to form a ridge. In addition, because the limbless ectoderm has no morphological ridge and no apparent ridge activity (i.e. it does not stabilize limb elements in stage-18 limb bud mesoderm), the limbless mutant demonstrates that the initial formation of the limb bud is independent of apical ectodermal ridge activity.

Myogenic cell movement in the developing avian limb bud in presence and absence of the apical ectodermal ridge (AER)

Development ◽  
1984 ◽  
Vol 80 (1) ◽  
pp. 105-125
Author(s):  
Madeleine Gumpel-Pinot ◽  
D. A. Ede ◽  
O. P. Flint
Keyword(s):  
Cell Migration ◽  
Cell Movement ◽  
Host Tissue ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Myogenic Cell ◽  
Myogenic Cells ◽  
Apical Direction ◽  
Wing Bud ◽  
Presence And Absence

Fragments of quail wing bud containing myogenic cells of somitic origin and fragments of quail sphlanchopleural tissue were introduced into the interior of the wing bud of fowl embryo hosts. No movement of graft into host tissue occurred in the control, but myogenic cells from the quail wing bud fragments underwent long migrations in an apical direction to become incorporated in the developing musculature of the host. When the apical ectodermal ridge (AER), together with some subridge mesenchyme, was removed at the time of grafting, no such cell migration occurred. The capacity of grafted myogenic cells to migrate in the presence of AER persists to H.H. stage 25, when myogenesis has begun, but premyogenic cells in the somites, which normally migrate out into the early limb bud, do not migrate when somite fragments are grafted into the wing bud. Coelomic grafts of apical and proximal wing fragments showed that apical sections of quail wing buds become invaded by myogenic cells of the host, but grafts from proximal wing bud regions do not.

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)

Reduction of the rate of outgrowth, cell density, and cell division following removal of the apical ectodermal ridge of the chick limb-bud

Development ◽  
1977 ◽  
Vol 40 (1) ◽  
pp. 1-21
Author(s):  
Dennis Summerbell
Keyword(s):  
Cell Proliferation ◽  
Cell Death ◽  
Cell Division ◽  
Cell Density ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Short Term ◽  
Density Dependent ◽  
Wing Bud

Removal of the apical ectodermal ridge causes a reduction in the rate of outgrowth of the wing-bud and the loss of distal parts. More specifically it causes a short-term increase in cell density and cell death and a decrease in the rate of cell proliferation. The evidence supports the hypothesis of density-dependent control of cell division and suggests that there may also be a mechanism regulating skeletal length at the time of differentiation. An informal model is presented to explain the observations.

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.

In vitro studies on the morphogenesis and differentiation of the mesoderm subjacent to the apical ectodermal ridge of the embryonic chick limb-bud

Development ◽  
1979 ◽  
Vol 50 (1) ◽  
pp. 75-97
Author(s):  
Robert A. Kosher ◽  
Mary P. Savage ◽  
Sai-Chung Chan
Keyword(s):  
Organ Culture ◽  
Chondrogenic Differentiation ◽  
Mesenchymal Cells ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Embryonic Chick ◽  
Marked Contrast ◽  
Culture Cells ◽  
Wing Bud

It has been suggested that one of the major functions of the apical ectodermal ridge (AER) of the embryonic chick limb-bud is to maintain mesenchymal cells directly subjacent to it (i.e. cells extending 00·4–00·5 mm from the AER) in a labile, undifferentiated condition. We have attempted to directly test this hypothesis by subjecting the undifferentiated subridgemesoderm of stage-25 embryonic chick wing-buds to organ culture in the presence and absence of the AER and the ectoderm that normally surrounds the mesoderm dorsally and ventrally. During the period of culture, control explants comprised of the subridge mesoderm capped by the AER and surrounded by the dorsal/ventral ectoderm undergo progressivemorphogenesis characterized by polarized proximal to distal outgrowth and changes in the contour of the developing explant, and ultimately form a structure grossly resembling a normal distal wing-bud tip. In contrast, explants from which the AER and dorsal/ventral ectoderm have been removed (minus ectoderm explants) or from which just the AER has been removed (minus AER explants) form compact, rounded masses exhibiting no signs of morphogenesis. During the polarized proximal to distal outgrowth control explants undergo during the first 3 days of culture, as cells of the explant become located greater than 0·4– 0·5 mm from the AER, they concomitantly undergo a sequence of changes indicative of their differentiation into cartilage. However, those cells which remain 0·4–0·5 mm from the AER during this period retain the characteristics of non-specialized mesenchymal cells. In marked contrast to control explants, virtually all of the cells of minus ectoderm explants initiate chondrogenic differentiation during the first day of culture. Cells comprising the central core of minus AER explants also initiate chondrogenic differentiation during the first day of culture, but in contrast to minus ectoderm explants, non-chondrogenic tissue types form along the periphery of the explants subjacent to the dorsal/ventral ectoderm. These results indicate that the AER maintains cells directly subjacent to it in a labile, undifferentiated condition, and that when mesenchymal cells are freed from the AER's influence either artificially or as a result of normal polarized outgrowth, they are freed to commence cytodifferentiation. The results further suggest that the dorsal/ventral ectoderm may have an influence on the differentiation of the mesenchymal cells directly subjacent to it, once the cells have been removed from the influence of the AER.

Apical ridge dependent and independent mesodermal domains of GHox-7 and GHox-8 expression in chick limb buds

Development ◽  
1992 ◽  
Vol 116 (3) ◽  
pp. 811-818 ◽  
Author(s):  
M.A. Ros ◽  
G. Lyons ◽  
R.A. Kosher ◽  
W.B. Upholt ◽  
C.N. Coelho ◽  
...  
Keyword(s):  
Pattern Formation ◽  
Limb Development ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Rapid Decline ◽  
Limb Buds ◽  
Limb Outgrowth ◽  
Removal Experiments ◽  
The Relationship

The homeobox-containing genes GHox-7 and GHox-8 have been proposed to play fundamental roles in limb development. The expression of GHox-8, by the apical ridge cells, and GHox-7, in the subridge mesoderm, suggests the involvement of these two genes in limb outgrowth and proximo-distal pattern formation. A straightforward way to test this is to remove the apical ridge. Here we report the relationship between the mesodermal expression of GHox-7 and GHox-8 and the apical ectodermal ridge in the chick limb bud. The data from ridge removal experiments indicate that there are at least two domains of GHox-7 expression in the apical limb bud mesoderm. The posterior subridge GHox-7 domain in the progress zone requires the influence of the apical ridge for continued expression, while the anterior GHox-7 domain continues expression after ridge removal. Posterior subridge mesoderm is exquisitely sensitive to the loss of the ridge in that GHox-7 expression by these cells is reduced in only two hours and undetectable by three hours after ridge removal. It would appear that one of the ways progress zone cells respond to the apical ridge signal is by expressing GHox-7. The loss of ridge influence whether by growth at the apex or by ridge removal is followed by an unusually rapid decline in detectable GHox-7 transcripts. Maintenance of GHox-8 expression by the anterior mesoderm appears to be independent of the presence of the apical ridge.(ABSTRACT TRUNCATED AT 250 WORDS)

Experiments on Anuran limb buds and their significance for principles of vertebrate limb development

Development ◽  
1981 ◽  
Vol 63 (1) ◽  
pp. 243-265
Author(s):  
M. Maden
Keyword(s):  
Limb Development ◽  
Rana Temporaria ◽  
Limb Bud ◽  
Limb Buds ◽  
Dorsoventral Axis ◽  
Vertebrate Limb ◽  
Vertebrate Limb Development ◽  
Supernumerary Limbs ◽  
Standard Set ◽  
And Inversion

A standard set of six experiments performed on the limb buds of two species of Anurans - Rana temporaria and Xenopus laevis -are described. The experiments are limb-bud amputation, distal to proximal shifts, proximal to distal shifts, inversion of the dorsoventral axis inversion of the anteroposterior axis and inversion of both axes. The results are compared to those previously reported for Urodeles and chicks to determine whether any principles of vertebrate limb development can be formulated. It appears that the proximodistal axis becomes increasingly mosaic from the Urodeles through Anurans to chicks. In the transverse axes however, there is much more uniformity of behaviour in the production of supernumerary limbs. The relation between the type of limb development (regulative or mosaic) and the subsequent regenerative powers of the adult limb is discussed.

Altered expression of the chicken homeobox-containing genes GHox-7 and GHox-8 in the limb buds of limbless mutant chick embryos

Development ◽  
1991 ◽  
Vol 113 (4) ◽  
pp. 1487-1493 ◽  
Author(s):  
C.N. Coelho ◽  
K.M. Krabbenhoft ◽  
W.B. Upholt ◽  
J.F. Fallon ◽  
R.A. Kosher
Keyword(s):  
Proper Time ◽  
Blot Hybridization ◽  
Development Stage ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Chick Embryos ◽  
Dot Blot ◽  
Limb Buds ◽  
Altered Expression

It has been suggested that the reciprocal expression of the chicken homeobox-containing genes GHox-8 and GHox-7 by the apical ectodermal ridge and subjacent limb mesoderm might be involved in regulating the proximodistal outgrowth of the developing chick limb bud. In the present study the expression of GHox-7 and GHox-8 has been examined by in situ and dot blot hybridization in the developing limb buds of limbless mutant chick embryos. The limb buds of homozygous mutant limbless embryos form at the proper time in development (stage 17/18), but never develop an apical ectodermal ridge, fail to undergo normal elongation, and eventually degenerate. At stage 18, which is shortly following the formation of the limb bud, the expression of GHox-7 is considerably reduced (about 3-fold lower) in the mesoderm of limbless mutant limb buds compared to normal limb bud mesoderm. By stages 20 and 21, as the limb buds of limbless embryos cease outgrowth, GHox-7 expression in limbless mesoderm declines to very low levels, whereas GHox-7 expression increases in the mesoderm of normal limb buds which are undergoing outgrowth. In contrast to GHox-7, expression of GHox-8 in limbless mesoderm at stage 18 is quantitatively similar to its expression in normal limb bud mesoderm, and in limbless and normal mesoderm GHox-8 expression is highly localized in the anterior mesoderm of the limb bud. In normal limb buds, GHox-8 is also expressed in high amounts by the apical ectodermal ridge.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Formin isoforms are differentially expressed in the mouse embryo and are required for normal expression of fgf-4 and shh in the limb bud

Development ◽  
1995 ◽  
Vol 121 (10) ◽  
pp. 3151-3162 ◽  
Author(s):  
D.C. Chan ◽  
A. Wynshaw-Boris ◽  
P. Leder
Keyword(s):  
Limb Development ◽  
Expression Patterns ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Amino Terminus ◽  
Ureteric Bud ◽  
Mrna Isoforms ◽  
Distal Limb ◽  
Limb Buds ◽  
Developing Kidney

Mice homozygous for the recessive limb deformity (ld) mutation display both limb and renal defects. The limb defects, oligodactyly and syndactyly, have been traced to improper differentiation of the apical ectodermal ridge (AER) and shortening of the anteroposterior limb axis. The renal defects, usually aplasia, are thought to result from failure of ureteric bud outgrowth. Since the ld locus gives rise to multiple RNA isoforms encoding several different proteins (termed formins), we wished to understand their role in the formation of these organs. Therefore, we first examined the embryonic expression patterns of the four major ld mRNA isoforms. Isoforms I, II and III (all containing a basic amino terminus) are expressed in dorsal root ganglia, cranial ganglia and the developing kidney including the ureteric bud. Isoform IV (containing an acidic amino terminus) is expressed in the notochord, the somites, the apical ectodermal ridge (AER) of the limb bud and the developing kidney including the ureteric bud. Using a lacZ reporter assay in transgenic mice, we show that this differential expression of isoform IV results from distinct regulatory sequences upstream of its first exon. These expression patterns suggest that all four isoforms may be involved in ureteric bud outgrowth, while isoform IV may be involved in AER differentiation. To define further the developmental consequences of the ld limb defect, we analyzed the expression of a number of genes thought to play a role in limb development. Most significantly, we find that although the AERs of ld limb buds express several AER markers, they do not express detectable levels of fibroblast growth factor 4 (fgf-4), which has been proposed to be the AER signal to the mesoderm. Thus we conclude that one or more formins are necessary to initiate and/or maintain fgf-4 production in the distal limb. Since ld limbs form distal structures such as digits, we further conclude that while fgf-4 is capable of supporting distal limb outgrowth in manipulated limbs, it is not essential for distal outgrowth in normal limb development. In addition, ld limbs show a severe decrease in the expression of several mesodermal markers, including sonic hedgehog (shh), a marker for the polarizing region and Hoxd-12, a marker for posterior mesoderm. We propose that incomplete differentiation of the AER in ld limb buds leads to reduction of polarizing activity and defects along the anteroposterior axis.

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