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In higher animals including humans, retinoic acid regulates differential expression of Hox genes along the anteroposterior axis. [36] Genes in the 3' ends of Hox clusters are induced by retinoic acid resulting in expression domains that extend more anteriorly in the body compared to 5' Hox genes that are not induced by retinoic acid resulting ...
Signals that control anteroposterior neural development include FGF and retinoic acid, which act in the hindbrain and spinal cord. [16] The hindbrain, for example, is patterned by Hox genes , which are expressed in overlapping domains along the anteroposterior axis under the control of retinoic acid.
The discovery of the homeobox in Drosophila flies and its conservation in other animals has led to advancements in understanding the anterior/posterior patterning. 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.
Limb mesenchymal cells, when dissociated and grown in culture or reintroduced within ectodermal "hulls" can recapitulate essential aspects of pattern formation, morphogenesis and differentiation. [36] [37] Peculiarities of the limb skeletal pattern in the mouse Doublefoot mutant are predicted outcomes of a Turing-type mechanism. [38]
In human and non-human anatomy, three principal planes are used: The sagittal plane or lateral plane ( longitudinal, anteroposterior ) is a plane parallel to the sagittal suture . It divides the body into left and right.
Wnt (the family wingless) genes are crucial for the development of the ZLI both directly and indirectly in all animal systems. Along with the role of Wnt genes in patterning the anteroposterior axis through gradient polarization, Wnt8b is expressed within the ZLI itself and may help guide dorsal movement of Shh expression. [9]
Patterning along the limb bud requires signals from many sources. Specifically, proteins called transcription factors (TF) help control the rate at which a gene is transcribed. The limb bud expresses a TF called ALX4 at the anterior part of the mesoderm, with the TF HOXB8 being expressed at the posterior portion. The Alx4 region, the medial ...
In animals, these developmental genes specifically control the development of organs on their anteroposterior axis. [1] In plants, however, the developmental genes affected by homeosis may control anything from the development of a stamen or petals to the development of chlorophyll. [ 2 ]