9 - The Requirement of TMED2 in Placenta Formation

Poster Board Number: 9
There are separate poster presentation times for odd and even posters.
Odd poster #s – first hour
Even poster #s – second hour

Co-authors:

Cassandra Millet-Boureima - Research Institute of the McGill University Health Centre at Glen Site; Talia Marc - Research Institute of the McGill University Health Centre at Glen Site; Loydie Jerome-Majewska, Ph.D. - McGill University

Abstract Body : Exchange between the maternal and fetal compartments occurs via the placental labyrinth layer, which is formed by attachment and fusion of two extraembryonic mesoderm derived tissues, the allantois and the chorion. TMED2 is expressed in the allantois and chorion and is required for placental labyrinth layer formation. To examine the role of TMED2 in extraembryonic mesoderm we used Mesp1-cre and mutant mice with LoxP sequences flanking exons 2 and 3 of Tmed2. We postulate that TMED2 is required in extraembryonic mesoderm for communication between the chorion and allantois during placental labyrinth layer development. To test our hypothesis, we collected Tmed2^LoxP/LoxP; Mesp1^Cre/+ embryos from Embryonic day (E) 9.5 – E12.5, for histological and morphological analysis. We used immunohistochemistry and in situ hybridization to examine expression of proteins and genes essential for placenta formation and function. Tmed2^LoxP/LoxP; Mesp1^Cre/+ embryos have placental labyrinth layer formation, but arrest at E12.5. At E9.5, expression of genes important for placental development are comparable in mutant and controls. However, the area of the placental labyrinth layer was reduced in a subset of E9.5 and E10.5 embryos, and this difference was significant at E11.5. The fetal and maternal compartments of the placental labyrinth layer had ectopic cells and was disorganized in E11.5 embryos. In addition, expression of fibronectin, a TMED2 cargo was increased, while MCT4, a syncytiotrophoblast-II marker was not detected in mutants. Our data indicates an essential role for TMED2 in the inner cell mass lineage from proper differentiation and expansion of the mouse placenta labyrinth layer.