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[10] [11] Morphogens in Drosophila include decapentaplegic and hedgehog. [10] During development, retinoic acid, a metabolite of vitamin A, is used to stimulate the growth of the posterior end of the organism. [12] Retinoic acid binds to retinoic acid receptors that acts as transcription factors to regulate the expression of Hox genes. Exposure ...
Hox genes, a subset of homeobox genes, are a group of related genes that specify regions of the body plan of an embryo along the head-tail axis of animals. Hox proteins encode and specify the characteristics of 'position', ensuring that the correct structures form in the correct places of the body.
The Shh gene, and genes belonging to the BMP, Hox, T-box, FGF, and Wnt families, all play a pivotal role in cell signaling and differentiation to regulate and promote successful limb formation. Various other genes listed above, one example being Dach1, are DNA-binding proteins that regulate gene expression.
Most of the Hox genes in mammals show an expression pattern that parallels the homeotic genes in flies. In mammals, there are four copies of the Hox genes. Each set of Hox genes are paralogous to the others (Hox1a is a paralogue of Hox1b, etc.) These paralogs show overlapping expression patterns and could act redundantly.
Among the most important of the toolkit genes are those of the Hox gene cluster, or complex. Hox genes, transcription factors containing the more broadly distributed homeobox protein-binding DNA motif, function in patterning the body axis. Thus, by combinatorially specifying the identity of particular body regions, Hox genes determine where ...
Complex communication ensues as AER-secreted FGF signals and ZPA-secreted Shh signals initiate and regulate Hox gene expression in the developing limb bud. [18] Though many of the finer details remain to be resolved, a number of significant connections between Hox gene expression and the impact on limb development have been discovered.
The Hox genes, which initially establish the anterior-posterior axis of the entire embryo, continue to participate in the dynamic regulation of limb development even after the AER and ZPA have been established. Complex communication ensues as AER-secreted FGFs and ZPA-secreted Shh initiate and regulate Hox gene expression in the developing limb ...
This leads to activation of other genes such as Hox genes, FGF genes and BMP genes in the posterior region, setting up digit patterning. BMP, plays a role in limb morphology, specifically, digit positioning, but the specific regulation of BMP is unclear. In particular, the Hox genes A and D are likely to be controlled by Shh within the ZPA. [16]