scholarly journals Regulation of HoxA expression in developing and regenerating axolotl limbs

Development ◽  
1995 ◽  
Vol 121 (6) ◽  
pp. 1731-1741 ◽  
Author(s):  
D.M. Gardiner ◽  
B. Blumberg ◽  
Y. Komine ◽  
S.V. Bryant
Keyword(s):  
Pattern Formation ◽  
Limb Development ◽  
Expression Patterns ◽  
Homeobox Genes ◽  
Proximal Region ◽  
Expression Domain ◽  
Distal Limb ◽  
Limb Buds ◽  
Blastema Formation ◽  
Hox Code

Homeobox genes are important in the regulation of outgrowth and pattern formation during limb development. It is likely that homeobox genes play an equally important role during limb regeneration. We have isolated and identified 17 different homeobox-containing genes expressed by cells of regenerating axolotl limbs. Of these, nearly half of the clones represent genes belonging to the HoxA complex, which are thought to be involved in pattern formation along the proximal-distal limb axis. In this paper we report on the expression patterns of two 5′ members of this complex, HoxA13 and HoxA9. These genes are expressed in cells of developing limb buds and regenerating blastemas. The pattern of expression in developing axolotl limb buds is comparable to that in mouse and chick limb buds; the expression domain of HoxA13 is more distally restricted than that of HoxA9. As in developing mouse and chick limbs, HoxA13 likely functions in the specification of distal limb structures, and HoxA9 in the specification of more proximal structures. In contrast, during regeneration, HoxA13 and HoxA9 do not follow the rule of spatial colinearity observed in developing limbs. Instead, both genes are initially expressed in the same population of stump cells, giving them a distal Hox code regardless of the level of amputation. In addition, both are reexpressed within 24 hours after amputation, suggesting that reexpression may be synchronous rather than temporally colinear. Treatment with retinoic acid alters this Hox code to that of a more proximal region by the rapid and differential downregulation of HoxA13, at the same time that expression of HoxA9 is unaffected. HoxA reexpression occurs prior to blastema formation, 24–48 hours after amputation, and is an early molecular marker for dedifferentiation.

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.

Mouse Wnt genes exhibit discrete domains of expression in the early embryonic CNS and limb buds

Development ◽  
1993 ◽  
Vol 119 (1) ◽  
pp. 247-261 ◽  
Author(s):  
B.A. Parr ◽  
M.J. Shea ◽  
G. Vassileva ◽  
A.P. McMahon
Keyword(s):  
Limb Development ◽  
Expression Patterns ◽  
Limb Buds ◽  
Expression Studies ◽  
The Family ◽  
The Central Nervous System ◽  
Discrete Domains ◽  
Early Developmental ◽  
The Brain

Mutation and expression studies have implicated the Wnt gene family in early developmental decision making in vertebrates and flies. In a detailed comparative analysis, we have used in situ hybridization of 8.0- to 9.5-day mouse embryos to characterize expression of all ten published Wnt genes in the central nervous system (CNS) and limb buds. Seven of the family members show restricted expression patterns in the brain. At least three genes (Wnt-3, Wnt-3a, and Wnt-7b) exhibit sharp boundaries of expression in the forebrain that may predict subdivisions of the region later in development. In the spinal cord, Wnt-1, Wnt-3, and Wnt-3a are expressed dorsally, Wnt-5a, Wnt-7a, and Wnt-7b more ventrally, and Wnt-4 both dorsally and in the floor plate. In the forelimb primordia, Wnt-3, Wnt-4, Wnt-6 and Wnt-7b are expressed fairly uniformly throughout the limb ectoderm. Wnt-5a RNA is distributed in a proximal to distal gradient through the limb mesenchyme and ectoderm. Along the limb's dorsal-ventral axis, Wnt-5a is expressed in the ventral ectoderm and Wnt-7a in the dorsal ectoderm. We discuss the significance of these patterns of restricted and partially overlapping domains of expression with respect to the putative function of Wnt signalling in early CNS and limb development.

The application of aqueous two-phase partition to the study of chick limb mesenchymal diversification

Development ◽  
1986 ◽  
Vol 94 (1) ◽  
pp. 267-275
Author(s):  
C. P. Cottrill ◽  
Paul T. Sharpe ◽  
Lewis Wolpert
Keyword(s):  
Pattern Formation ◽  
Limb Development ◽  
Developmental Stages ◽  
Proximal Region ◽  
Limb Bud ◽  
Cell Populations ◽  
Two Phase ◽  
Phase Partition ◽  
Surface Character ◽  
Two Phase Partition

A technique which identifies cells differing in surface character, aqueous two-phase partition using thin-layer countercurrent distribution (TLCCD), has been used to study differentiation and pattern formation in the developing chick limb bud. The TLCCD profiles of cell populations, derived from various regions of morphologically undifferentiated mesenchyme from three different stages of limb development, have been compared. At no stage, or location, has the population been found to be homogeneous. Cells from progress zones and more proximal regions could all be resolved into several populations. The populations from progress zones at three different developmental stages were qualitatively similar but differed in the proportions of cells in each. The most striking differences in cell populations were those obtained from the most proximal region of the limb, closest to the flank, which represents the developmentally most advanced region.

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.

Ghox 4.7: a chick homeobox gene expressed primarily in limb buds with limb-type differences in expression

Development ◽  
1991 ◽  
Vol 112 (3) ◽  
pp. 791-806 ◽  
Author(s):  
S. Mackem ◽  
K.A. Mahon
Keyword(s):  
Expression Patterns ◽  
Homeobox Genes ◽  
Homeobox Gene ◽  
Limb Bud ◽  
Limb Buds ◽  
Limb Morphogenesis ◽  
Degenerate Oligonucleotide ◽  
Polymerase Chain ◽  
Anterior Posterior

Homeobox genes play a key role in specifying the segmented body plan of Drosophila, and recent work suggests that at least several homeobox genes may play a regulatory role during vertebrate limb morphogenesis. We have used degenerate oligonucleotide primers from highly conserved domains in the homeobox motif to amplify homeobox gene segments from chick embryo limb bud cDNAs using the polymerase chain reaction. Expression of a large number of homeobox genes (at least 17) is detected using this approach. One of these genes contains a novel homeobox loosely related to the Drosophila Abdominal B class, and was further analyzed by determining its complete coding sequence and evaluating its expression during embryogenesis by in situ hybridization. Based on sequence and expression patterns, we have designated this gene as Ghox 4.7 and believe that it is the chick homologue of the murine Hox 4.7 gene (formerly Hox 5.6). Ghox 4.7 is expressed primarily in limb buds during development and shows a striking spatial restriction to the posterior zone of the limb bud, suggesting a role in specifying anterior-posterior pattern formation. In chick, this gene also displays differences in expression between wing and leg buds, raising the possibility that it may participate in specifying limb-type identity.

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)

scholarly journals SPC4, SPC6, and the novel protease SPC7 are coexpressed with bone morphogenetic proteins at distinct sites during embryogenesis.

1996 ◽  
Vol 134 (1) ◽  
pp. 181-191 ◽  
Author(s):  
D B Constam ◽  
M Calfon ◽  
E J Robertson
Keyword(s):  
Growth Factors ◽  
Bone Morphogenetic Proteins ◽  
Limb Development ◽  
Expression Patterns ◽  
Dorsal Surface ◽  
Mrna Levels ◽  
The Novel ◽  
Surface Ectoderm ◽  
Limb Buds ◽  
Dynamic Expression

In the present study, we screened for subtilisin-like proprotein convertases (SPCs) that potentially regulate the activation of known growth factors during embryonic development. We isolated a novel protease, SPC7, as well as several known SPCs. SPC7, like SPC1, is expressed ubiquitously throughout development. In contrast, SPC4 and SPC6 exhibit dynamic expression patterns. SPC4 transcripts were initially detected in the granulosa cells of secondary follicles. Shortly after implantation, SPC4 transcripts are localized to extraembryonic cell populations, and at later stages are detected in discrete tissues including the primitive gut, heart, neural tube, and limb buds. Within the limb buds, SPC4 mRNA is most abundant in the apical ectodermal ridge (AER). At later stages of limb development, SPC4 mRNA is strongly expressed in cartilage and in the interdigital mesenchyme. In contrast, high SPC6 mRNA levels are detected in somites, the dorsal surface ectoderm, and in vertebral cartilage primordia. In limb buds, SPC6 is strongly expressed in the AER, and at later stages in dorsal mesenchyme. A comparison of these expression patterns with those of several bone morphogenetic proteins (BMPs) indicates that processing of these growth factors may be limited by the local availability of SPCs.

Expression patterns of Wnts, Frizzleds, sFRPs, and misexpression in transgenic mice suggesting a role for Wnts in pancreas and foregut pattern formation

2002 ◽  
Vol 225 (3) ◽  
pp. 260-270 ◽  
Author(s):  
R. Scott Heller ◽  
Darwin S. Dichmann ◽  
Jan Jensen ◽  
Chris Miller ◽  
Gordon Wong ◽  
...  
Keyword(s):  
Pattern Formation ◽  
Transgenic Mice ◽  
Expression Patterns

The dominant hemimelia mutation uncouples epithelial-mesenchymal interactions and disrupts anterior mesenchyme formation in mouse hindlimbs

Development ◽  
1999 ◽  
Vol 126 (21) ◽  
pp. 4729-4736
Author(s):  
L. Lettice ◽  
J. Hecksher-Sorensen ◽  
R.E. Hill
Keyword(s):  
Gene Expression ◽  
Pattern Formation ◽  
Limb Development ◽  
Limb Bud ◽  
Mouse Mutation ◽  
Number Of Factors ◽  
Limb Outgrowth ◽  
Gene Functions ◽  
Regulatory Loop ◽  
Limb Initiation

Epithelial-mesenchymal interactions are essential for both limb outgrowth and pattern formation in the limb. Molecules capable of communication between these two tissues are known and include the signaling molecules SHH and FGF4, FGF8 and FGF10. Evidence suggests that the pattern and maintenance of expression of these genes are dependent on a number of factors including regulatory loops between genes expressed in the AER and those in the underlying mesenchyme. We show here that the mouse mutation dominant hemimelia (Dh) alters the pattern of gene expression in the AER such that Fgf4, which is normally expressed in a posterior domain, and Fgf8, which is expressed throughout are expressed in anterior patterns. We show that maintenance of Shh expression in the posterior mesenchyme is not dependent on either expression of Fgf4 or normal levels of Fgf8 in the overlying AER. Conversely, AER expression of Fgf4 is not directly dependent on Shh expression. Also the reciprocal regulatory loop proposed for Fgf8 in the AER and Fgf10 in the underlying mesenchyme is also uncoupled by this mutation. Early during the process of limb initiation, Dh is involved in regulating the width of the limb bud, the mutation resulting in selective loss of anterior mesenchyme. The Dh gene functions in the initial stages of limb development and we suggest that these initial roles are linked to mechanisms that pattern gene expression in the AER.

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.

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