Amnionless (AMN) is a plasma membrane protein that binds to cubilin and megalin in various epithelia and mediates endocytosis of extracellular ligands. This function has been studied in the kidney where it plays a key role in vitamin B12 and vitamin D homeostasis. Present study aimed to elucidate developmental pattern of expression of AMN during the peri-implantation period in mouse embryos. In an effort to understand functional role of AMN in the histiotropic nutrition in blastocyst, endocytotic function of AMN for apoplipoprotein was examined in blastocyst. Eight-week-old female mice were superovulated by intraperitoneal injection of 5 IU PMSG and 5 IU hCG 48h later. To obtain embryos, females were mated with males. Mouse embryos were collected at 12, 48, 56, 65, 72 and 96 h post-hCG by flushing oviducts and uterus, and we also obtained gestation day 6.5, 7.5 and 8.5 embryos in uterus. All samples were subjected to quantitative RT-PCR, whole-mount immunofluorescence and immunohistochemistry analysis. To analyze endocytotic function of AMN, we examined uptake experiment of FICT labeled apolipoprotein A-I (ApoA-I-FITC) following functional blocking of AMN in blastocysts. AMN and cubilin mRNA was expressed in all developmental stages of mouse embryos. Megalin was the first detected at morula stage. AMN protein was expressed in trophectoderm (TE) and inner cell mass (ICM). AMN and cubilin were expressed in visceral endoderm of GD 6.5 and 7.5 embryos and visceral yolk sec of GD 8.5 embryos. In normal IgG treated embryos, ApoA-I-FITC was detected in intracellular vesicles of TE and ICM. However, in the presence of anti-AMN antibody, ApoA-I-FITC was weakly detected in apical surface of plasma membrane of TE. To date, AMN has been believed to be expressed in visceral endoderm of post implantation embryos. Our results demonstrated that AMN is the important molecular partner of cubilin and megalin in the preimplantation embryos and that AMN mediates endocytosis of apoplipoprotein, which may play a crucial role in embryonic development and normal growth via supporting histiotropic nutrition during peri-implantation period.

Coxsackievirus and adenovirus receptor (CAR) is a member of the Ig-type superfamily of cell adhesion molecules. In polarized epithelial cells CAR is expressed at the tight junction. The mouse CAR gene is composed of at least eight exons, and CAR splice variants that differ at the end of the cytoplasmic tail have been identified in a number of tissues. The present study aimed to examine the expression of (CAR), a TJ protein sealing the muticellular contact point during preimplantation embryos and role of CAR in the formation and integrity of the blastocoel. Eight-week-old female mice were superovulated by intraperitoneal injection of 5 IU PMSG and 5 IU hCG 48h later. Mouse embryos were collected at 12, 48, 56, 65, 72 and 96 h post-hCG in oviducts and uterus, and we also obtained gestation day 5 and 6.5 embryos in uterus. All samples were subjected to RT-PCR, immunofluorescence and immunohistochemistry analysis. To analyze epithelial permeability of CAR, we examined permeability of FITC-labeled dextran (MW 40 kDa) following functional blocking of CAR in blastocysts. Long isoform of CAR mRNA was expressed from throughout the preimplantation development and markedly increased at morulae stage onward. Small amount of short isoform CAR mRNA was expressed at blastocyst stage. On Western blot, 64 kDa protein was detected together with 43 kDa protein corresponding to short and long forms CAR, respectively in blastocysts. CAR immunoreactivity was found in cell contacts between blastomeres from 4-cell stage onward. Under Ca2+ switching condition blocking antibodies for CAR increased the permeability of blastocysts to FITC-dextran, a permeability tracer. At 5 dpc, trophoblasts of the implanting embryos were immunoreactive with anti-CAR IgG. At 6.5 dpc, the egg cylinder stage in mouse, the visceral and parietal endoderm were immunoreactive with anti-CAR IgG. Our results suggest that alternative splicing of CAR transcript is highly dependent on the development of expanding blastocyst. CAR may play a crucial role as a barrier to adenovirus infection and adhesion molecule for epithelial permeability during peri-implantation period.

Aquaporin5 (AQP5), a water channel plays an important role in the fluid homeostasis and cell volume control in epithelial cells. In an effort to understand fluid homeostasis in the oviduct, tissue specific expression of AQP 5 was examined together with hormonal regulation of AQP5 in the mouse oviduct. To understand the oviductal fluid homeostasis and its regulation by sex steroids, We examined AQP5 expression in mouse oviduct during developmental stage and estrous cycle, and in estrogen receptor α (ERα) knockout mice oviduct. In immature mouse oviduct, expression of AQP5 expression was examined after stimulation with gonadotropins. The effect of ERα agonist (PPT) and ERβ agonist (DPN) on the oviductal expression of AQP5 was examined in ovariectomized mouse. All samples were subjected to realtime-PCR and immunohistochemistry analysis. In oviduct epithelium, AQP5 was largely found in the apicolateral membrane and cytoplasm of ERα-positive non-ciliated cells but weakly expressed in the ciliated cells. Interstitial cells, muscle cells and blood vessels were also weakly positive for AQP5 immunoreactivity. In cyclic female mice oviductal AQP5 mRNA levels were the highest at estrous. In immature mouse oviduct AQP5 mRNA and epithelial immunoreactivity were increased by PMSG, and followed by a decrease after hCG. In ERα KO mice oviduct, AQP5 mRNA levels were significantly lower than those of WT females at diestrous stage. In immature and OVX mouse oviducts, AQP5 mRNA and epithelial immunoreactivity were significantly increased by E2 and PPT. Together, our results suggest the pivotal role of AQP5 in fluid secretion and absorption of water in non-ciliated cells in oviduct. AQP5 gene is tightly activated by estrogen – ERα signaling in non-ciliated cells in oviductal epithelium, mediating the effect of estrogen on gamete transport, fertilization and early embryo development via regulating the fluid homeostasis in oviduct.