Effects of disruption of the embryonic alkaline phosphatase gene on preimplantation development of the mouse

Embryonic alkaline phosphatase (EAP) is expressed during the preimplantatio n period of mouse development; however, its function is unknown. To determi ne whether the absence of an EAP gene affects development of preimplantatio n embryos, we studied mice homozygous for the disrupted EAP gene (EAP.ko mi ce). Time to reach morphologically defined-preimplantation stages, preimpla ntation loss, cell count, gestation length, and litter size were monitored, and it was found that EAP.ko embryos have slower development and higher ra tes of degeneration during in vitro preimplantation development. In vivo, E AP.ko mice had a longergestation, smaller litter size, and fewer cells at 9 3 hr after human chorionic gonadotropin injection. Furthermore, there was n o compensation for the absence of EAP gene in EAP.ko embryos by other isozy mes of alkaline phosphatase. We conclude that the presence of an active EAP gene is beneficial for preimplantation development of the mouse embryo, an d its absence leads to fewer blastocysts in vivo, delay ed parturition, and reduced litter size in vivo. (C) 2000 Wiley-Liss, Inc.