mRNAs encoding aquaporins are present during murine preimplantation development

The present study was conducted to investigate the mechanisms underlying fl uid movement across the trophectoderm during blastocyst formation by determ ining whether aquaporins (AQPs) are expressed during early mammalian develo pment. AQPs belong to a family of major intrinsic membrane proteins and fun ction as molecular water channels that allow water to flow rapidly across p lasma membranes in the direction of osmotic gradients. Ten different AQPs h ave been identified to date. Murine preimplantation stage embryos were flus hed from the oviducts and uteri of superovulated CD1 mice. Reverse transcri ption-polymerase chain reaction (RT-PCR) methods employing primer sets desi gned to amplify conserved sequences of AQPs (1-9) were applied to murine em bryo cDNA samples. PCR reactions were conducted for up to 40 cycles involvi ng denaturation of DNA hybrids at 95 degreesC, primer annealing at 52-60 de greesC and extension at 72 degreesC. PCR products were separated on 2% agar ose gels and were stained with ethidium bromide. AQP PCR product identity w as confirmed by sequence analysis. mRNAs encoding AQPs 1, 3, 5, 6, 7, and 9 were detected in murine embryos from the one-cell stage up to the blastocy st stage. AQP 8 mRNAs were not detected in early cleavage stages but were p resent in morula and blastocyst stage embryos. The results were confirmed i n experimental replicates applied to separate embryo pools of each embryo s tage. These results demonstrate that transcripts encoding seven AQP gene pr oducts are detectable during murine preimplantation development. These find ings predict that AQPs may function as conduits for trophectoderm fluid tra nsport during blastocyst formation. (C) 2000 Wiley-Liss, Inc.