Severe damage on placental fetal capillary network causes mid to late fetal lethality and reduction of placental size in Peg11/Rtl1 KO mice [day 12.5]. Mus musculus

Paternally expressed 11/Retrotransposon-like 1 (Peg11/Rtl1) knockout (KO) mice exhibited mid to late fetal lethality or late fetal growth retardation associated with frequent neonatal lethality. The lethal phenotype was largely dependent on genetic background and became more severe with each succeeding generation in the course of backcross experiments to C57BL/6 (B6). We previously suggested these lethal and growth phenotypes were due to severe defects in placental fetal capillaries in labyrinth layer. In this study, we reexamined KO fetuses exhibiting mid fetal lethality with internal bleeding. Importantly, basal region of fetal capillary network was specially damaged, therefore, also leading to poor expansion of the labyrinth layer and placental size reduction in later stage. Apparent up-regulation of Guanine nucleotide binding protein, alpha 2 (Gnai2) and decrement of Transmembrane protein 100 (Tmem100), Mesenchyme homeobox 2 (Meox2) and Lymphatic vessel hyaluronan Receptor 1 (LYVE1) expression were observed in earlier stage of placentas even before apparent morphological changes occurred, suggesting that these genes are involved in the maintenance of fetal capillaries associated with Peg11/Rtl1 in development. Overall design: Gene expression profiles of WT and Peg11/Rtl1 KO placentas at day 12.5 were analyzed to identify genes involved in the maintenance of fetal capillary endothelial cells during earlier stage of the placenta.