xPitx1 plays a role in specifying cement gland and head during early Xenopus development.

Preprint in PDF format (This is a preprint of an article published in genesis 29(2): 78-90
©2001Wiley-Liss,Inc. )

Chang, W., Koshrowshahian F., Chang, R., Crawford, M. (2001).

Dept. Biological Sciences, University of Windsor
Windsor, Ontario, N9B 3P4, Canada.

Abstract

Xenopus Pitx1 is a homeobox gene whose family members are structurally and functionally conserved in organisms as diverse as Drosophila, chick, mouse, human, and frog.  Present as a maternal transcript, the gene is zygotically expressed during gastrulation in a dorsal streak of cells.  This streak restricts to a small circular domain underlying the centre of presumptive neural plate. Shortly thereafter, a crescent of expression develops at the border of anterior neural ectoderm, and as the central plate domain diminishes, the crescent coalesces to define the presumptive cement gland.  Expression remains high throughout cement gland development, and subsequently expands to include ectodermal cells involved in stomodeal invagination.  During early organogenesis, expression ensues in developing eye, posterior lateral mesoderm, and first branchial arch derivatives.  Ectopic expression of xPitx1 causes head deformities including enlarged cement gland, ectopic cement glands, and posterior deformities or, in extreme cases, inhibition of recognizable structures posterior to the cement gland.  Expression of markers such as XCG-1, xOtx2, xPax6, neuralb tubulin and xTwist suggest that increases in cement gland and lower mandibular size are likely at the expense of other head tissues.  Paradoxically, over-expression is sufficient to partially rescue embryos which are axially perturbed by ultraviolet irradiation or retinoic acid administration.  Ectopic expression of xPitx1 in ectodermal explants directly promotes cement gland development since there was no evidence that mesodermal or neural tissue was present in explants.