Desmosomes in the Uterine Epithelium of Noninvasive Skink Placentae

Abstract

Australian species of viviparous skinks have noninvasive epitheliochorial placentation where there is no breeching or interruption of the uterine epithelial cell barrier. This is contrary to some African and South American species of skinks which exhibit invading chorionic cells and a localized endotheliochorial placenta. The desmosomes, which maintain the adhesive properties of the junctional complex between uterine epithelial cells, were found to decrease as gestation progressed in the uterus of two highly placentotrophic Australian skinks, but no changes in desmosomal numbers were present in the uterus of two Australian oviparous skinks or viviparous skinks with a simple placenta. In mammals, desmosomes decrease in the uterine epithelium of species with invasive hemochorial placentation, where less chemical and mechanical adhesion between cells assists the invading trophoblast at the time of implantation. However, Australian viviparous skinks do not have an invasive trophoblast; yet, similarities in decreasing lateral cellular adhesion exist in the uterus of both invasive and noninvasive placental types. This similarity in cellular mechanisms suggests a conservation of plasma membrane changes across placentation irrespective of reptilian or mammalian origin. Anat Rec, 293:502-512, 2010. V V C 2010 Wiley-Liss, Inc.

Desmoglein-2 during pregnancy and its role in the evolution of viviparity in a marsupial (Sminthopsis crassicaudata; Dasyuridae)

“…In some squamate reptiles, desmosome number decreases during pregnancy in a similar fashion to that observed in eutherian mammals (Illingworth et al, ; Biazik et al, ) which suggests that desmosome reduction is not limited to species with invasive placentation and so may play a role in the remodeling of the uterine epithelium during noninvasive placentation (Biazik et al, ; Brandley et al, ). The complexity of the placenta can have an impact on the expression of desmosomes as some squamates with noninvasive placental types show no change in the number of desmosomes (Biazik et al, ) or an increase in some desmosomal protein encoding genes during pregnancy (Brandley et al, ). Differences in desmosome expression across squamate species suggest that desmosomes have a different and unknown role during pregnancy in some amniotes (Brandley et al, ).…”

“…Marsupials diverged from placental mammals ∼160 million years ago (Luo et al, ) allowing time for differing mechanisms to evolve (Freyer et al, ; Graves, ) for cell adhesion and the process of live birth (viviparity). Despite marsupials having a short‐lived placenta with low contribution to offspring development compared with the placenta of most eutherians (Selwood and Johnson, ; Renfree et al, ), S. crassicaudata shows a similar redistribution and decrease in the number of desmosomes throughout pregnancy to those of eutherian mammals (Illingworth et al, ; Preston et al, ) and squamates (Biazik et al, ).…”

Uterine Gene Expression in the Live-Bearing Lizard, Chalcides ocellatus, Reveals Convergence of Squamate Reptile and Mammalian Pregnancy Mechanisms

“…We also evaluate expression of the highly upregulated cell adhesion and angiogenic genes because they have been subject to previous studies in squamate reptiles (Biazik et al 2007, 2008, 2010; Murphy, Belov, et al 2010; Wu et al 2011) and therefore provide a rare opportunity to assess the diversity of molecular mechanisms involved in reptilian pregnancy.…”

Reptile Pregnancy Is Underpinned by Complex Changes in Uterine Gene Expression: A Comparative Analysis of the Uterine Transcriptome in Viviparous and Oviparous Lizards

“…This made it possible to collect uterine tissue of the chorioallantoic placenta ( n = 3) and of the yolk sac placenta ( n = 3) separately. In P. entrecasteauxii and most viviparous squamates, there is little physical attachment between the uterus and the extra-embryonic membranes, so the uterus can be cleanly separated from embryonic tissue (Biazik et al 2010, 2012). In non-gravid females ( n = 2), egg chambers constituting stretched regions of the uterus were excised individually (Girling 2002).…”