The spatial and temporal distribution of polarizing activity in the flank of the pre-limb-bud stages in the chick embryo

Development ◽  
1991 ◽  
Vol 111 (3) ◽  
pp. 725-731 ◽  
Author(s):  
A. Hornbruch ◽  
L. Wolpert
Keyword(s):  
Posterior Part ◽  
Temporal Distribution ◽  
Early Embryo ◽  
Limb Bud ◽  
Posterior Edge ◽  
Limb Buds ◽  
Avian Embryos ◽  
Low Levels ◽  
Clear Change ◽  
Somitic Mesoderm

The presence of polarizing activity in the limb buds of developing avian embryos determines the pattern of the anteroposterior axis of the limbs in the adult. Maps of the spatial distribution and the strength of the signal within limb buds of different stages are well documented. Polarizing activity can also be found in Hensen's node in the early embryo. We have mapped the distribution of polarizing activity as it emerges from Hensen's node and spreads into the flank tissue of the embryo. There is a clear change in the local pattern of expression of polarizing activity between stage 8 and 18. Almost no activity is measured for stages 8 and 9. More or less uniform levels of around 10% are spread along the flank lateral to the unsegmented somitic mesoderm from somite position 12 to 22 in stage 10 embryos. Some 6 to 8 h later at stage 12, there is a distinct peak of activity at somite position 18, the middle of the wing field. This peak increases at stages 13 to 15 and its position traverses to the posterior edge of the wing field. Full strength of activity is reached shortly before the onset of limb bud formation at stage 16 to 17. Stages 16 to 18 were investigated for polarizing activity in the wing and the leg field. Low levels of polarizing activity are present in the anterior leg field at stages 16 and 17 but have disappeared by stage 18 and all activity is confined to the posterior part of the leg bud.

The distribution of the polarizing zone (ZPA) in the legbud of the chick embryo.

Development ◽  
1985 ◽  
Vol 86 (1) ◽  
pp. 169-175
Author(s):  
J. Richard Hinchliffe ◽  
Anna Sansom
Keyword(s):  
Pattern Formation ◽  
Chick Embryo ◽  
High Activity ◽  
Posterior Margin ◽  
Posterior Part ◽  
Limb Bud ◽  
Limb Buds ◽  
Anteroposterior Axis ◽  
Low Activity

The stage-21 to 22 legbud polarizing zone (ZPA) was mapped by transplanting small blocks of posterior marginal mesenchyme preaxially into stage-20 to -22 chick wing buds and assessing the degree of duplication of the wing digital skeleton produced in the host. Blocks taken from the posterior flank, from the angle between posterior flank and the proximal base of the limb bud, and from the most anterior distal position chosen (under the AER), all had very low activity. Blocks taken from the posterior margin of the legbud, plus the next distal block under the posterior part of the AER, all had high activity. We consider that barrier and amputation results on wing and legbud, when interpreted in the light of maps of the ZPA in both limb buds, are consistent with the hypothesis that both leg and wing have their growth and anteroposterior axis of pattern formation controlled by the ZPA.

Coordinated expression of Hoxa-11 and Hoxa-13 during limb muscle patterning

Development ◽  
1998 ◽  
Vol 125 (7) ◽  
pp. 1325-1335 ◽  
Author(s):  
M. Yamamoto ◽  
Y. Gotoh ◽  
K. Tamura ◽  
M. Tanaka ◽  
A. Kawakami ◽  
...  
Keyword(s):  
Hox Genes ◽  
Anterior Part ◽  
Posterior Part ◽  
Precursor Cells ◽  
Limb Bud ◽  
Limb Muscle ◽  
Limb Buds ◽  
Muscle Precursor ◽  
Muscle Precursor Cells ◽  
Ventral Muscle

The limb muscle precursor cells migrate from the somites and congregate into the dorsal and ventral muscle masses in the limb bud. Complex muscle patterns are formed by successive splitting of the muscle masses and subsequent growth and differentiation in a region-specific manner. Hox genes, known as key regulator genes of cartilage pattern formation in the limb bud, were found to be expressed in the limb muscle precursor cells. We found that HOXA-11 protein was expressed in the premyoblasts in the limb bud, but not in the somitic cells or migrating premyogenic cells in the trunk at stage 18. By stage 24, HOXA-11 expression began to decrease from the posterior halves of the muscle masses. HOXA-13 was expressed strongly in the myoblasts of the posterior part in the dorsal/ventral muscle masses and weakly in a few myoblasts of the anterior part of the dorsal muscle mass. Transplantation of the lateral plate of the presumptive wing bud to the flank induced migration of premyoblasts from somites to the graft. Under these conditions, HOXA-11 expression was induced in the migrating premyoblasts in the ectopic limb buds. Application of retinoic acid at the anterior margin of the limb bud causes duplication of the autopodal cartilage and transformation of the radius to the ulna, and at the same time induces duplication of the muscle pattern along the anteroposterior axis. Under these conditions, HOXA-13 was also induced in the anterior region of the ventral muscles in the zeugopod. These results suggest that Hoxa-11 and Hoxa-13 expression in the migrating premyoblasts is under the control of the limb mesenchyme and the polarizing signal(s). In addition, these results indicate that these Hox genes are involved in muscle patterning in the limb buds.

Positional signalling by Hensen's node when grafted to the chick limb bud

Development ◽  
1986 ◽  
Vol 94 (1) ◽  
pp. 257-265
Author(s):  
Amata Hornbruch ◽  
Lewis Wolpert
Keyword(s):  
Anterior Margin ◽  
Early Embryo ◽  
Limb Bud ◽  
Stage 4 ◽  
The Future

Hensen's node from stage 4 to stage 10 shows polarizing activity when grafted to the anterior margin of the chick limb bud. It can specify additional digits though its action is somewhat attenuated when compared with the effect of a grafted polarizing region. At stage 10 the activity disappears from the node and is found both posterior to the node and in the future wing region of the flank. The ability of Hensen's node to generate a positional signal suggests that the signal in the limb and early embryo may be similar. The results support the view of the polarizing region as a discrete signalling region.

Conservation of Pitx1 expression during amphibian limb morphogenesis

2006 ◽  
Vol 84 (2) ◽  
pp. 257-262 ◽  
Author(s):  
W Y Chang ◽  
F KhosrowShahian ◽  
M Wolanski ◽  
R Marshall ◽  
W McCormick ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Xenopus Laevis ◽  
Expression Patterns ◽  
Limb Bud ◽  
Eleutherodactylus Coqui ◽  
Limb Buds ◽  
Homeodomain Transcription Factor ◽  
Limb Morphogenesis ◽  
Pelvic Limb

In contrast to the pattern of limb emergence in mammals, chicks, and the newt N. viridescens, embryos such as Xenopus laevis and Eleutherodactylus coqui initiate pelvic limb buds before they develop pectoral ones. We studied the expression of Pitx1 in X. laevis and E. coqui to determine if this paired-like homeodomain transcription factor directs differentiation specifically of the hindlimb, or if it directs the second pair of limbs to form, namely the forelimbs. We also undertook to determine if embryonic expression patterns were recapitulated during the regeneration of an amputated limb bud. Pitx1 is expressed in hindlimbs in both X. laevis and E. coqui, and expression is similar in both developing and regenerating limb buds. Expression in hindlimbs is restricted to regions of proliferating mesenchyme.Key words: regeneration, Xenopus laevis, limb bud, Pitx1 protein, specification.

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)

Extracellular matrix synthesis in the chick embryo lateral plate prior to and during limb outgrowth

Development ◽  
1980 ◽  
Vol 59 (1) ◽  
pp. 71-87
Author(s):  
Trent D. Stephens ◽  
N. S. Vasan ◽  
James W. Lash
Keyword(s):  
Extracellular Matrix ◽  
Chick Embryo ◽  
Molecular Basis ◽  
Limb Bud ◽  
Matrix Synthesis ◽  
Lateral Plate ◽  
Limb Buds ◽  
Cartilage Development ◽  
Limb Outgrowth ◽  
Lateral Plates

Little is known at the present time about the molecular basis and mechanisms of morphogenesis. The present study is an attempt to determine what influence the extracellular matrix has on the initial outgrowth of the limb bud. Stage -12 to -18 chick embryo lateral plates were examined in relation to proline and sulfate incorporation into collagen and proteoglycan. The flank and limbs incorporated the same amount of labeled proline and sulfate before stage 16. At stage 16 the flank began to incorporate more of both isotopes until at stage 18 there was twice as much incorporation into the flank as into the limbs. The flank and limbs contained the same type of collagen during the period examined. The limbs contained both large and small proteoglycans but the flank contained only small proteoglycans. These data suggest that the extracellular matrix in the flank and limb regions may play a role in limb outgrowth and that the limb buds at these stages may be more inclined toward cartilage development.

Sonic hedgehog is not required for polarising activity in the Doublefoot mutant mouse limb bud

Development ◽  
1998 ◽  
Vol 125 (3) ◽  
pp. 351-357 ◽  
Author(s):  
C. Hayes ◽  
J.M. Brown ◽  
M.F. Lyon ◽  
G.M. Morriss-Kay
Keyword(s):  
Gene Expression ◽  
Limb Development ◽  
Target Genes ◽  
Anterior Part ◽  
Expression Patterns ◽  
Ectopic Expression ◽  
Mutant Gene ◽  
Limb Bud ◽  
Active Constituent ◽  
Limb Buds

The mouse mutant Doublefoot (Dbf) shows preaxial polydactyly of all four limbs. We have analysed limb development in this mutant with respect to morphogenesis, gene expression patterns and ectopic polarising activity. The results reveal a gain-of-function mutation at a locus that mediates pattern formation in the developing limb. Shh expression is identical with that of wild-type embryos, i.e. there is no ectopic expression. However, mesenchyme from the anterior aspects of Dbf/+ mutant limb buds, when transplanted to the anterior side of chick wing buds, induces duplication of the distal skeletal elements. Mid-distal mesenchymal transplants from early, but not later, Dbf/+ limb buds are also able to induce duplication. This demonstration of polarising activity in the absence of Shh expression identifies the gene at the Dbf locus as a new genetic component of the Shh signalling pathway, which (at least in its mutated form) is able to activate signal transduction independently of Shh. The mutant gene product is sufficient to fulfil the signalling properties of Shh including upregulation of the direct Shh target genes Ptc and Gli, and induction of the downstream target genes Bmp2, Fgf4 and Hoxd13. The expression domains of all these genes extend from their normal posterior domains into the anterior part of the limb bud without being focused on a discrete ectopic site. These observations dissociate polarising activity from Shh gene expression in the Dbf/+ limb bud. We suggest that the product of the normal Dbf gene is a key active constituent of the polarising region, possibly acting in the extracellular compartment.

An atlas of notochord and somite morphogenesis in several anuran and urodelean amphibians

Development ◽  
1980 ◽  
Vol 59 (1) ◽  
pp. 223-247
Author(s):  
B. Woo Youn ◽  
R. E. Keller ◽  
G. M. Malacinski
Keyword(s):  
Posterior Part ◽  
Ambystoma Mexicanum ◽  
Electron Microscopic ◽  
Cross Sectional ◽  
Scanning Electron Microscopic ◽  
Somite Formation ◽  
Comparative Survey ◽  
Pleurodeles Waltlii ◽  
Lateral Mesoderm ◽  
Somitic Mesoderm

A scanning electron microscopic, comparative survey of notochord and somite formation including some details of change in cell morphology and arrangement, was made of selected stages of two species of anuran amphibians (Xenopus laevis and Rana pipiens) and two species of urodeles (Ambystoma mexicanum and Pleurodeles waltlii). The ectoderm or neural plate was removed from fixed embryos and the dorsal aspect of the developing notochord and somite mesoderm was photographed. Micrographs of comparable stages of all species were arranged together to form an atlas of notochord and somite formation. Similar morphogenetic events occur in the same sequence in the four species. Notochordal cells become distinguishable from paraxial mesodermal cells by shape, closeness of packing, and arrangement. Notochordal elongation is accompanied by a decrease in cross-sectional area and by cell rearrangement. Somitic mesoderm becomes distinguished from lateral mesoderm by a change in cell shape and orientation, followed by segmentation of somites. The schedule of somite formation was compared and related to the staging series for each species. The urodeles differ from the anurans in that the notochordal region in the early neurula stages is triangular, with the broadest part in the posterior region of the embryo. In anurans it is uniform in width. This difference may reflect differences in gastrulation and in the mechanism of elongation of the posterior part of the embryo in the neurula.

Correlation of wing-leg identity in ectopic FGF-induced chimeric limbs with the differential expression of chick Tbx5 and Tbx4

Development ◽  
1998 ◽  
Vol 125 (1) ◽  
pp. 51-60 ◽  
Author(s):  
H. Ohuchi ◽  
J. Takeuchi ◽  
H. Yoshioka ◽  
Y. Ishimaru ◽  
K. Ogura ◽  
...  
Keyword(s):  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Expression Patterns ◽  
Ectopic Expression ◽  
Limb Bud ◽  
Chick Embryos ◽  
Fibroblast Growth ◽  
Limb Buds ◽  
Specific Position

It has been reported that members of the fibroblast growth factor (FGF) family can induce additional limb formation in the flank of chick embryos. The phenotype of the ectopic limb depends on the somite level at which it forms: limbs in the anterior flank resemble wings, whereas those in the posterior flank resemble legs. Ectopic limbs located in the mid-flank appear chimeric, possessing characteristics of both wings and legs; feather buds are present in the anterior halves with scales and claws in the posterior halves. To study the mechanisms underlying the chimerism of these additional limbs, we cloned chick Tbx5 and Tbx4 to use as forelimb and hindlimb markers and examined their expression patterns in FGF-induced limb buds. We found that Tbx5 and Tbx4 were differentially expressed in the anterior and posterior halves of additional limb buds in the mid-flank, respectively, consistent with the chimeric patterns of the integument. A boundary of Tbx5/Tbx4 exists in all ectopic limbs, indicating that the additional limbs are essentially chimeric, although the degree of chimerism is dependent on the position. The boundary of Tbx5/Tbx4 expression is not fixed at a specific position within the interlimb region, but dependent upon where FGF was applied. Since the ectopic expression patterns of Tbx5/Tbx4 in the additional limbs are closely correlated with the patterns of their chimeric phenotypes, it is likely that Tbx5 and Tbx4 expression in the limb bud is involved in determination of the forelimb and hindlimb identities, respectively, in vertebrates.

Normal incorporation rates for precursors of collagen and mucopolysaccharide during expression of micromelia induced by 6-aminonicotinamide

Development ◽  
1974 ◽  
Vol 31 (2) ◽  
pp. 305-312
Author(s):  
Robert E. Seegmiller ◽  
Meredith N. Runner
Keyword(s):  
Core Protein ◽  
Limb Bud ◽  
Matrix Proteins ◽  
Synthesis Rate ◽  
Control Groups ◽  
In Ovo ◽  
Limb Buds ◽  
Radioactive Precursor ◽  
Hind Limbs ◽  
And Control

Further delineation of mechanisms by which 6-aminonicotinamide (6-AN) induces micromelia in the chick embryo was investigated by studies on rates of incorporation of thymidine, proline, glucosamine and sulfate as precursors to DNA, collagen and mucopolysaccharide, respectively. Twenty-four hours after in ovo administration of the vitamin antagonist, 6-AN, to day-4 chick embryos, hind limbs from experimental and control groups were excised and incubated for 1 h in medium containing 3 × 10−6m radioactive precursor. Molar incorporation of precursors into the TCA-precipitable fraction showed, in isolated limb buds, (a) that 6-AN enhanced incorporation of thymidine, (b) that 6-AN inhibited utilization of sulfate, and (c) that 6-AN did not significantly alter utilization of glucosamine and proline. Rates of incorporation of thymidine, glucosamine and proline indicate that 6-AN is not cytotoxic to the isolated limb bud. Enhanced incorporation of thymidine suggests expression of compensatory change 24 h after initial effects of 6-AN on DNA synthesis. Rate of incorporation of proline suggests that, under the influence of 6-AN, tropocollagen was synthesized in normal quantities by limb cells. Similarly, rate of incorporation of glucosamine suggests that under the influence of 6-AN normal amounts of hexosamine sugars were being attached to the nascent core-protein of chondroitin. Inhibition of sulfation and failure to complete the chondroitin sulfate molecule seem to account for 6-AN-induced micromelia. This suggests that sulfation depends upon specific NAD-dependent dehydrogenase reactions. As far as can be established by rates of incorporation of labeled precursors, 5-day limb buds, at 24 h after exposure to teratogenic levels of 6-AN, synthesize matrix proteins and hexosamine polysaccharides at normal rates.

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