Role of Dlx-1 and Dlx-2 genes in patterning of the murine dentition

Development ◽  
1997 ◽  
Vol 124 (23) ◽  
pp. 4811-4818 ◽  
Author(s):  
B.L. Thomas ◽  
A.S. Tucker ◽  
M. Qui ◽  
C.A. Ferguson ◽  
Z. Hardcastle ◽  
...  
Keyword(s):  
Neural Crest ◽  
Homeobox Gene ◽  
Branchial Arch ◽  
Cranial Neural Crest ◽  
Loss Of Function ◽  
Molecular Events ◽  
Maxillary Molar ◽  
Molar Teeth ◽  
Cranial Neural Crest Cells ◽  
Arch Neural

The molecular events of odontogenic induction are beginning to be elucidated, but until now nothing was known about the molecular basis of the patterning of the dentition. A role for Dlx-1 and Dlx-2 genes in patterning of the dentition has been proposed with the genes envisaged as participating in an ‘odontogenic homeobox gene code’ by specifying molar development. This proposal was based on the restricted expression of the genes in molar ectomesenchyme derived from cranial neural crest cells prior to tooth initiation. Mice with targeted null mutations of both Dlx-1 and Dlx-2 homeobox genes do not develop maxillary molar teeth but incisors and mandibular molars are normal. We have carried out heterologous recombinations between mutant and wild-type maxillary epithelium and mesenchyme and show that the ectomesenchyme underlying the maxillary molar epithelium has lost its odontogenic potential. Using molecular markers of branchial arch neural crest (Barx1) and commitment to chondrogenic differentiation (Sox9), we show that this population alters its fate from odontogenic to become chondrogenic. These results provide evidence that a subpopulation of cranial neural crest is specified as odontogenic by Dlx-1 and Dlx-2 genes. Loss of function of these genes results in reprogramming of this population of ectomesenchyme cells into chondrocytes. This is the first indication that the development of different shaped teeth at different positions in the jaws is determined by independent genetic pathways.

scholarly journals Chick cranial neural crest cells migrate by progressively refining the polarity of their protrusions

2017 ◽  
Author(s):  
Miriam A. Genuth ◽  
Christopher D.C. Allen ◽  
Takashi Mikawa ◽  
Orion D. Weiner
Keyword(s):  
Neural Crest ◽  
Quantitative Imaging ◽  
Cell Movement ◽  
Neural Crest Cells ◽  
Branchial Arch ◽  
Cranial Neural Crest ◽  
Directed Movement ◽  
Morphological Polarity ◽  
Cranial Neural Crest Cells

SummaryIn vivo quantitative imaging reveals that chick cranial neural crest cells throughout the migratory stream are morphologically polarized and migrate by progressively refining the polarity of their protrusions.AbstractTo move directionally, cells can bias the generation of protrusions or select among randomly generated protrusions. Here we use 3D two-photon imaging of chick branchial arch 2 directed neural crest cells to probe how these mechanisms contribute to directed movement, whether a subset or the majority of cells polarize during movement, and how the different classes of protrusions relate to one another. We find that cells throughout the stream are morphologically polarized along the direction of overall stream movement and that there is a progressive sharpening of the morphological polarity program. Neural crest cells have weak spatial biases in filopodia generation and lifetime. Local bursts of filopodial generation precede the generation of larger protrusions. These larger protrusions are more spatially biased than the filopodia, and the subset of protrusions that power motility are the most polarized of all. Orientation rather than position is the best correlate of the protrusions that are selected for cell movement. This progressive polarity refinement strategy may enable neural crest cells to efficiently explore their environment and migrate accurately in the face of noisy guidance cues.

Temporospatial cell interactions regulating mandibular and maxillary arch patterning

Development ◽  
2000 ◽  
Vol 127 (2) ◽  
pp. 403-412 ◽  
Author(s):  
C.A. Ferguson ◽  
A.S. Tucker ◽  
P.T. Sharpe
Keyword(s):  
Neural Crest ◽  
Ectopic Expression ◽  
Branchial Arch ◽  
Oral Epithelium ◽  
Cranial Neural Crest ◽  
Mandibular Arch ◽  
Cellular Origin ◽  
Cell Gene Expression ◽  
Cranial Neural Crest Cells ◽  
Maxillary Arch

The cellular origin of the instructive information for hard tissue patterning of the jaws has been the subject of a long-standing controversy. Are the cranial neural crest cells prepatterned or does the epithelium pattern a developmentally uncommitted population of ectomesenchymal cells? In order to understand more about how orofacial patterning is controlled we have investigated the temporal signalling interactions and responses between epithelium and mesenchymal cells in the mandibular and maxillary primordia. We show that within the mandibular arch, homeobox genes that are expressed in different proximodistal spatial domains corresponding to presumptive molar and incisor ectomesenchymal cells are induced by signals from the oral epithelium. In mouse, prior to E10, all ectomesenchyme cells in the mandibular arch are equally responsive to epithelial signals such as Fgf8, indicating that there is no pre-specification of these cells into different populations and suggesting that patterning of the hard tissues of the mandible is instructed by the epithelium. By E10.5, ectomesenchymal cell gene expression domains are still dependent on epithelial signals but have become fixed and ectopic expression cannot be induced. At E11 expression becomes independent of epithelial signals such that removal of the epithelium does not affect spatial ectomesenchymal expression. Significantly, however, the response of ectomesenchyme cells to epithelial regulatory signals was found to be different in the mandibular and maxillary primordium. Thus, whereas both mandibular and maxillary arch epithelia could induce Dlx2 and Dlx5 expression in the mandible and Dlx2 expression in the maxilla, neither could induce Dlx5 expression in the maxilla. Reciprocal cell transplantations between mandibular and maxillary arch ectomesenchymal cells revealed intrinsic differences between these populations of cranial neural crest-derived cells. Research in odontogenesis has shown that the oral epithelium of the mandibular and maxillary primordia has unique instructive signaling properties required to direct odontogenesis, which are not found in other branchial arch epithelia. As a consequence, development of jaw-specific skeletal structures may require some prespecification of maxillary ectomesenchyme to restrict the instructive influence of the epithelial signals and allow development of maxillary structures distinct from mandibular structures.

Retinoic Acid Deficiency Underlies the Etiology of Midfacial Defects

2022 ◽  
pp. 002203452110620
Author(s):  
Y. Wu ◽  
H. Kurosaka ◽  
Q. Wang ◽  
T. Inubushi ◽  
K. Nakatsugawa ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Neural Crest ◽  
Substantial Reduction ◽  
Neural Crest Cells ◽  
Early Embryogenesis ◽  
Cranial Neural Crest ◽  
Loss Of Function ◽  
Shh Signaling ◽  
Cellular Events ◽  
Cranial Neural Crest Cells

Embryonic craniofacial development depends on the coordinated outgrowth and fusion of multiple facial primordia, which are populated with cranial neural crest cells and covered by the facial ectoderm. Any disturbance in these developmental events, their progenitor tissues, or signaling pathways can result in craniofacial deformities such as orofacial clefts, which are among the most common birth defects in humans. In the present study, we show that Rdh10 loss of function leads to a substantial reduction in retinoic acid (RA) signaling in the developing frontonasal process during early embryogenesis, which results in a variety of craniofacial anomalies, including midfacial cleft and ectopic chondrogenic nodules. Elevated apoptosis and perturbed cell proliferation in postmigratory cranial neural crest cells and a substantial reduction in Alx1 and Alx3 transcription in the developing frontonasal process were associated with midfacial cleft in Rdh10-deficient mice. More important, expanded Shh signaling in the ventral forebrain, as well as partial abrogation of midfacial defects in Rdh10 mutants via inhibition of Hh signaling, indicates that misregulation of Shh signaling underlies the pathogenesis of reduced RA signaling-associated midfacial defects. Taken together, these data illustrate the precise spatiotemporal function of Rdh10 and RA signaling during early embryogenesis and their importance in orchestrating molecular and cellular events essential for normal midfacial development.

Regulation of Hoxa2 in cranial neural crest cells involves members of the AP-2 family

Development ◽  
1999 ◽  
Vol 126 (7) ◽  
pp. 1483-1494 ◽  
Author(s):  
M. Maconochie ◽  
R. Krishnamurthy ◽  
S. Nonchev ◽  
P. Meier ◽  
M. Manzanares ◽  
...  
Keyword(s):  
Neural Crest ◽  
Specific Activity ◽  
Family Members ◽  
Neural Crest Cells ◽  
Branchial Arch ◽  
Cranial Neural Crest ◽  
Reporter Expression ◽  
Specific Expression ◽  
Conserved Sequence ◽  
Cranial Neural Crest Cells

Hoxa2 is expressed in cranial neural crest cells that migrate into the second branchial arch and is essential for proper patterning of neural-crest-derived structures in this region. We have used transgenic analysis to begin to address the regulatory mechanisms which underlie neural-crest-specific expression of Hoxa2. By performing a deletion analysis on an enhancer from the Hoxa2 gene that is capable of mediating expression in neural crest cells in a manner similar to the endogenous gene, we demonstrated that multiple cis-acting elements are required for neural-crest-specific activity. One of these elements consists of a sequence that binds to the three transcription factor AP-2 family members. Mutation or deletion of this site in the Hoxa2 enhancer abrogates reporter expression in cranial neural crest cells but not in the hindbrain. In both cell culture co-transfection assays and transgenic embryos AP-2 family members are able to trans-activate reporter expression, showing that this enhancer functions as an AP-2-responsive element in vivo. Reporter expression is not abolished in an AP-2(alpha) null mutant embryos, suggesting redundancy with other AP-2 family members for activation of the Hoxa2 enhancer. Other cis-elements identified in this study critical for neural-crest-specific expression include an element that influences levels of expression and a conserved sequence, which when multimerized directs expression in a broad subset of neural crest cells. These elements work together to co-ordinate and restrict neural crest expression to the second branchial arch and more posterior regions. Our findings have identified the cis-components that allow Hoxa2 to be regulated independently in rhombomeres and cranial neural crest cells.

scholarly journals Analysis of cranial neural crest migratory pathways in axolotl using cell markers and transplantation

Development ◽  
2000 ◽  
Vol 127 (12) ◽  
pp. 2751-2761 ◽  
Author(s):  
H. Epperlein ◽  
D. Meulemans ◽  
M. Bronner-Fraser ◽  
H. Steinbeisser ◽  
M.A. Selleck
Keyword(s):  
Transcription Factor ◽  
Neural Crest ◽  
Neural Crest Cells ◽  
Branchial Arch ◽  
Cranial Neural Crest ◽  
Branchial Arches ◽  
Trunk Neural Crest ◽  
Cranial Neural Crest Cells ◽  
Random Nature

We have examined the ability of normal and heterotopically transplanted neural crest cells to migrate along cranial neural crest pathways in the axolotl using focal DiI injections and in situ hybridization with the neural crest marker, AP-2. DiI labeling demonstrates that cranial neural crest cells migrate as distinct streams along prescribed pathways to populate the maxillary and mandibular processes of the first branchial arch, the hyoid arch and gill arches 1–4, following migratory pathways similar to those observed in other vertebrates. Another neural crest marker, the transcription factor AP-2, is expressed by premigratory neural crest cells within the neural folds and migrating neural crest cells en route to and within the branchial arches. Rotations of the cranial neural folds suggest that premigratory neural crest cells are not committed to a specific branchial arch fate, but can compensate when displaced short distances from their targets by migrating to a new target arch. In contrast, when cells are displaced far from their original location, they appear unable to respond appropriately to their new milieu such that they fail to migrate or appear to migrate randomly. When trunk neural folds are grafted heterotopically into the head, trunk neural crest cells migrate in a highly disorganized fashion and fail to follow normal cranial neural crest pathways. Importantly, we find incorporation of some trunk cells into branchial arch cartilage despite the random nature of their migration. This is the first demonstration that trunk neural crest cells can form cartilage when transplanted to the head. Our results indicate that, although cranial and trunk neural crest cells have inherent differences in ability to recognize migratory pathways, trunk neural crest can differentiate into cranial cartilage when given proper instructive cues.

scholarly journals Cadherin-6B proteolysis promotes the neural crest cell epithelial-to-mesenchymal transition through transcriptional regulation

2016 ◽  
Vol 215 (5) ◽  
pp. 735-747 ◽  
Author(s):  
Andrew T. Schiffmacher ◽  
Vivien Xie ◽  
Lisa A. Taneyhill
Keyword(s):  
Neural Crest ◽  
Epithelial To Mesenchymal Transition ◽  
Neural Crest Cell ◽  
Cranial Neural Crest ◽  
Mesenchymal Transition ◽  
Effector Genes ◽  
A Disintegrin And Metalloproteinase ◽  
And Migration ◽  
Cranial Neural Crest Cells

During epithelial-to-mesenchymal transitions (EMTs), cells disassemble cadherin-based junctions to segregate from the epithelia. Chick premigratory cranial neural crest cells reduce Cadherin-6B (Cad6B) levels through several mechanisms, including proteolysis, to permit their EMT and migration. Serial processing of Cad6B by a disintegrin and metalloproteinase (ADAM) proteins and γ-secretase generates intracellular C-terminal fragments (CTF2s) that could acquire additional functions. Here we report that Cad6B CTF2 possesses a novel pro-EMT role by up-regulating EMT effector genes in vivo. After proteolysis, CTF2 remains associated with β-catenin, which stabilizes and redistributes both proteins to the cytosol and nucleus, leading to up-regulation of β-catenin, CyclinD1, Snail2, and Snail2 promoter-based GFP expression in vivo. A CTF2 β-catenin–binding mutant, however, fails to alter gene expression, indicating that CTF2 modulates β-catenin–responsive EMT effector genes. Notably, CTF2 association with the endogenous Snail2 promoter in the neural crest is β-catenin dependent. Collectively, our data reveal how Cad6B proteolysis orchestrates multiple pro-EMT regulatory inputs, including CTF2-mediated up-regulation of the Cad6B repressor Snail2, to ensure proper cranial neural crest EMT.

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