A Glossary of Terms
The following are a list of relevent terms that are found in this web site:
- Tbx4 - Gene responsible for inducing the developmental pattern normally found in the leg, leading to structures that resemble a chick leg including toes with claws, scales, and leg-like skeletal morphologies
- Tbx5 - Gene responsible for inducing the developmental pattern normally found in the wing, leading to structures that resemble a chick wing including wing digits, feathers, and wing-like skeletal morphologies
- AER - The Apical Ectodermal Ridge, formed on the dorsal/ventral axis, drives limb outgrowth along the proximal/distal axis and induces formation of the organizer ZPA
- ZPZ - The Zone of Polarizing Activity acts to promote proliferation of posterior leg mesenchyme and specification of the identity of the limb along the anterior/posterior axis
- Shh - The Sonic Hedgehog gene is essential for polarizing and thus, establishment of the A/P axis and the P/D limb pattern thoughout the ectoderm. In addition, it acts in some way to regulate the expression of the Hox genes
- FGF - The Fibroblast Growth Factor family plays a fundamental role in limb initiation through interactions with the T-Box genes
- Hox Genes - The Hox gene family influences limb patterning at several stages of development, regulates the rate and timing of cartilage proliferation, and is involved with limb outgrowth through interactions with WNT and FGF
- BMP - The Bone Morphogenic Protein is able to induce ectopic appearance of Tbx5 transcripts
- WNT - The Wnt-3a gene is involved in inducing FGF expression and limb outgrowth, while the Wnt-7a gene is involved in the doralization of the Lmx-1 signals. In addition, Wnt-7a is involved with the T-Box genes in specification of the position at which limbs develop
- RCAS - The Replication-Competent Avian Sarcoma retrovirus system is conventionally used to introduce foreign DNA in limb development studies
- En-1 - The Engrailed-1 protein is expressed solely in the ventral ectoderm and is involved in positioning of the AER and establishing the dorsal pattern
- r-Fng -The Radical Fringe gene is expressed solely in the dorsal ectoderm and thus, interacts with En-1 to position the AER
- Lmx-1 - LIM-Homeodomain protein Lmx-1 instructs dorsal patterning in limb bud mesenchyme
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