Abnormal Placental Development and Early Embryonic Lethality in EpCAM-Null Mice

Abstract

BackgroundEpCAM (CD326) is encoded by the tacstd1 gene and expressed by a variety of normal and malignant epithelial cells and some leukocytes. Results of previous in vitro experiments suggested that EpCAM is an intercellular adhesion molecule. EpCAM has been extensively studied as a potential tumor marker and immunotherapy target, and more recent studies suggest that EpCAM expression may be characteristic of cancer stem cells.Methodology/Principal FindingsTo gain insights into EpCAM function in vivo, we generated EpCAM −/− mice utilizing an embryonic stem cell line with a tacstd1 allele that had been disrupted. Gene trapping resulted in a protein comprised of the N-terminus of EpCAM encoded by 2 exons of the tacstd1 gene fused in frame to βgeo. EpCAM +/− mice were viable and fertile and exhibited no obvious abnormalities. Examination of EpCAM +/− embryos revealed that βgeo was expressed in several epithelial structures including developing ears (otocysts), eyes, branchial arches, gut, apical ectodermal ridges, lungs, pancreas, hair follicles and others. All EpCAM −/− mice died in utero by E12.5, and were small, developmentally delayed, and displayed prominent placental abnormalities. In developing placentas, EpCAM was expressed throughout the labyrinthine layer and by spongiotrophoblasts as well. Placentas of EpCAM −/− embryos were compact, with thin labyrinthine layers lacking prominent vascularity. Parietal trophoblast giant cells were also dramatically reduced in EpCAM −/− placentas.ConclusionEpCAM was required for differentiation or survival of parietal trophoblast giant cells, normal development of the placental labyrinth and establishment of a competent maternal-fetal circulation. The findings in EpCAM-reporter mice suggest involvement of this molecule in development of vital organs including the gut, kidneys, pancreas, lungs, eyes, and limbs.

Cleavage and Cell Adhesion Properties of Human Epithelial Cell Adhesion Molecule (HEPCAM)

“…A role for Epcam in the formation of functional adherens junctions via E-cadherin was further described during epiboly processes in the developing zebrafish embryo and in embryonic development of Xenopus laevis (10,11). Similar to reports by Nagao et al (6), depletion of Epcam in Xenopus was lethal, suggesting an essential role for Epcam in embryonic development (11). Work by Zöller and co-workers (12) further revealed a physical interaction of Epcam with Claudin 7 and a regulatory role in the formation of metastases from rat carcinoma cells.…”

“…Results of the knock-out of murine Epcam (mEpcam) by three different groups were not completely accordant. In the first published knock-out report, deletion of mEpcam resulted in embryonic lethality at day 12.5 of gestation due to placental defects in the differentiation or survival of parietal giant trophoblast cells (6). Later, Guerra et al (7) and Lei et al (8) independently published a perinatally lethal phenotype of mEpcam knock-out mice, due to severe intestinal problems, resembling a human lethal disorder termed congenital tufting enteropathy, which is associated with mutations of the epcam gene (9).…”

Cancer-associated epithelial cell adhesion molecule (EpCAM; CD326) enables epidermal Langerhans cell motility and migration in vivo

“…For this reason, in vivo studies of EpCAM function are of particular relevance. To date, only a few studies have assessed endogenous EpCAM function in vivo, and the studies that have been carried out involve seemingly very different contexts [epithelial morphogenesis in zebrafish (53), gastrulation in Xenopus (54), placental development (32), and, in this report, LC migration in mice].…”

“…To begin to relate EpCAM expression to LC function, several years ago we generated EpCAM KO mice (32) using preexisting ES cells that carried a targeted EpCAM allele that had been generated by gene trapping (33). Although heterozygous EpCAM −/− mice did not exhibit abnormalities, intercrossing these individuals failed to yield viable EpCAM −/− animals because EpCAM −/− embryos became nonviable at approximately embryonic day 12 secondary to placental insufficiency (32). This mortality precluded studies of LC and other lineages in postnatal EpCAM KO mice.…”

Putative oncogene Brachyury ( T ) is essential to specify cell fate but dispensable for notochord progenitor proliferation and EMT

“…Twelve hundred hour (noon) on the day of the postcoital plug was considered to be E0.5. Collection and processing of embryos for in situ hybridization, flow cytometry (FACS), immunofluorescence, BrdU incorporation, and for LacZ, lysotracker or skeletal staining, were all performed as previously described (27,40). For immunofluorescence, anti-T from R&D Systems (AF2085), anti-EpCAM (Rat-G8.8) and anti-Nestin (Rat-401) from the Developmental Studies Hybridoma Bank, and antiTwist-1 from Millipore (ABD29) were used.…”