Role of the paired-like gene Pitx1 in Xenopus head development.

The process of head development is complex and with the exception of the hindbrain region, it is unlike trunk development in as much as it does not involve discrete segmentation. Recent evidence suggests that the paired-like family of genes play a role in regulating anterior development. To further understand the role that these genes possess, we have cloned the Xenopus homolog of Prix1. XPitx1 is present as a maternal transcript with expression observed as a dorsal streak during gastrulation. This streak restricts to a small circular domain underlying the centre of presumptive neural plate. Concomitantly, a crescent of expression is observed at the border of anterior neural ectoderm. Expression of xPitx1 persists throughout the cement gland anlage during gastrulation. At the onset of organogenesis, xPitx1 is expressed within the cement gland, eye, lateral plate mesoderm, and first branchial arch derivatives. Misexpression of xPitx1 in whole embryos leads to the formation of enlarged or ectopic cement glands. In addition, variable posterior deficits are observed with extreme cases where the embryo exhibits no recognizable structures posterior to the cement gland. Expression of markers such as XCG-1, xOtx2, xPar6, and xTwist suggest that increases in cement gland and lower mandibular size are likely at the expense of other head tissues. Conversely, antagonization of xPitx1 with a mutant form of the gene results in cement gland inhibition and head malformations. Animal cap assays show that xPitx1 can directly induce cement gland formation and that induction requires DNA binding by xPitx1 . Source: Masters Abstracts International, Volume: 40-03, page: 0646. Adviser: Michael J. Crawford. Thesis (M.A.Sc.)--University of Windsor (Canada), 2000.