Specification of Jaw Subdivisions by Dlx Genes

  title={Specification of Jaw Subdivisions by Dlx Genes},
  author={Michael J. Depew and Thomas Lufkin and John L. R. Rubenstein},
  pages={381 - 385}
The success of vertebrates was due in part to the acquisition and modification of jaws. Jaws are principally derived from the branchial arches, embryonic structures that exhibit proximodistal polarity. To investigate the mechanisms that specify the identity of skeletal elements within the arches, we examined mice lacking expression ofDlx5 and Dlx6, linked homeobox genes expressed distally but not proximally within the arches.Dlx5/6–/– mutants exhibit a homeotic transformation of lower jaws to… 
Jaw Development: Chinless Wonders
Transitory expression of and in maxillary arch Dlx 5 Dlx 6 precursors is essential for upper jaw morphogenesis
Using 3D reconstruction, it is shown that inactivation of and does not only affect the mandibular arch, but results in the Dlx5 DlX6 simultaneous transformation ofMandibular and maxillary skeletal elements which assume a similar morphology with gain of symmetry.
Jaws of the Fates
New findings are discussed that reveal the molecular cause of an asymmetrical jaw by vertebrates and a developmental code of nested Dlx gene expression in jaw precursor cells instructs these cells to become upper or lower jaw structures.
Transitory expression of Dlx5 and Dlx6 in maxillary arch precursors is essential for upper jaw morphogenesis.
It is shown that inactivation of Dlx5 and Dllx6 does not only affect the mandibular arch, but results in the simultaneous transformation of mandIBular and maxillary skeletal elements which assume a similar morphology with gain of symmetry.
Transitory expression of and in maxillary arch precursors is essential for upper jaw Dlx 5 Dlx 6 morphogenesis
  • Biology
  • 2019
The observations provide the first genetic demonstration of the ‘Hinge and Caps’ model and support the notion that ‘cap’ signals could originate from epithelial derivatives of expressing progenitors which Dlx5migrate and colonize the maxillary arch epithelium.
Evidence for the prepattern/cooption model of vertebrate jaw evolution
A new scenario for jaw evolution is presented in which incorporation of Bapx and Gdf5/6/7 into a preexisting DV patterning program drove the evolution of the jaw by altering the identity of intermediate first-arch chondrocytes.
Specification of jaw identity by the Hand2 transcription factor
Evidence is provided that Hand2 is sufficient for upper jaw (maxilla)-to-mandible transformation by regulating the expression of homeobox transcription factors in mice and suggests that Hand 2 regulates mandibular development through downstream genes of Hand2 and is therefore a major determinant of jaw identity.
Probing the origin of matching functional jaws: roles of Dlx5/6 in cranial neural crest cells
It is concluded that: (1) Dlx5/6 activation in NCCs invariably determines lower jaw identity; and (2) the morphogenetic processes that generate functional matching jaws depend on the harmonization of Dl x 5/6 expression in N CCs and in distinct ectodermal territories.


Evolutionary biology: Lamprey Hox genes and the origin of jaws
It is shown that in the lamprey, a primitively jawless (agnathan) fish that is a sister group to the gnathostomes, a Hox gene is expressed in the mandibular arch of developing embryos, which suggests that loss of Hox expression from the mandibia arch of gnathOSTomes may have facilitated the evolution of jaws.
Heterotopic Shift of Epithelial-Mesenchymal Interactions in Vertebrate Jaw Evolution
The homology and gene expression of the oral region are uncoupled during the transition from agnathan to gnathostome; it is concluded that a heterotopic shift of tissue interaction was involved in the evolution of the jaw.
Neural crest patterning and the evolution of the jaw
Characteristics of the cranial neural crest provide for a plausible von Baerian explanation for the problematic inside‐outside change in topology of the gills and their supports between these 2 major groups of vertebrates.
Null mutation of Dlx-2 results in abnormal morphogenesis of proximal first and second branchial arch derivatives and abnormal differentiation in the forebrain.
Results show that Dlx-2 controls development of the branchial arches and the forebrain and suggests its role in craniofacial evolution, and shows that the affected skull bones from the first arch have undergone a transformation into structures similar to those found in reptiles.
Mouse Otx2 functions in the formation and patterning of rostral head.
The homo- and heterozygous mutant phenotypes suggest Otx2 functions as a gap-like gene in the rostral head where Hox code is not present, suggesting its evolutionary significance for the innovation of the neurocranium and the jaw.
Dlx5 regulates regional development of the branchial arches and sensory capsules.
The distinct focal defects within the branchial arches of the Dl1, Dlx2 and DlX5 mutants, along with the nested expression of their RNAs, support a model in which these genes have both redundant and unique functions in the regulation of regional patterning of the craniofacial ectomesenchyme.
Lamprey Dlx genes and early vertebrate evolution.
Cloned Dlx genes from the lamprey Petromyzon marinus, an agnathan vertebrate that occupies a critical phylogenetic position between cephalochordates and gnathostomes, are cloned and identified and used as a model for how this gene family evolved in the vertebrate lineage.
The roles of the homeobox genes aristaless and Distal-less in patterning the legs and wings of Drosophila.
A correlation between a temporal requirement for Dll and position along the proximodistal axis is revealed and how this may relate to the generation of the P/D axis is discussed.