Lately, it has been shown that contrary to what happens in other tissues, where HOX genes define domains of expression, these genes are expressed in individual cells as part of the combinatorial codes involved in cell type specification.
In PcG mutants, target genes are expressed outside their usual domains of expression, leading to defects in body development.
If the combined model were applied to AG Pases the initial preservation of paralogous AGPase genes immediately after duplication might reflect subfunctionalization but this process would be followed by adaptation to the more specialized domains of expression in which each of the paralogs are expressed.
Parr, B. A., Shea, M. J., Vassileva, G. & McMahon, A. P. Mouse Wnt genes exhibit discrete domains of expression in the early embryonic CNS and limb buds.
Conversely, treatment of wild-type embryos with retinoic acid greatly expands the periotic domains of expression of fgf3, fgf8, and pax8 and leads to formation of supernumerary and ectopic otic vesicles.
However, the roles of the BMP antagonist Noggin in formation of the craniofacial skeleton remain unclear, in part because of its multiple domains of expression during formative stages.
Comparison of the spatial domains of expression of mouse homeobox genes reveals a pattern consistent with the idea that they play a role in anteroposterior positional specification during embryogenesis.
No exact correspondence with sox10 (Figure 5G G″) and tbx1 domains of expression was found.
Similarly, it has been recently reported that Jag1 mutants reveal accelerated neurogenesis within its domains of expression, resulting in the overproduction of V1-derived interneurons [15].
Nevertheless, given the stability of ArmΔCXM19 in both the central and lateral domains of expression, it is likely that much of the endogenous protein was excluded.
In juveniles, the expression of each Hox gene spans a few segments, and adjacent Hox genes show partially overlapping but staggered domains of expression in the VNC.
