Reproduction Abstracts

GLIS1 markedly enhances the generation of iPS cells from both mouse and human fibroblasts. In mouse, GLIS1 is enriched in unfertilized oocytes and 1-cell stage embryos. Therefore, it is possible that GLIS1 plays a critical role in early development through epigenetic regulation. We investigated the role of GLIS1 during the early development of bovine embryos using siRNAs targeted for GLIS1. GLIS1 transcript levels in unfertilized oocytes and early embryos at 1-cell to blastocyst stage were evaluated. GLIS1 siRNA (B-GLIS1-1 or B-GLIS1-2) or nonsilencing (control) siRNA were injected at the 1-cell stage. Some embryos were not injected with siRNA (Uninjected). PGK1, XIST, PDHA1 and HSPA8 levels at 8- to 16-cell stage were evaluated. Higher levels of GLIS1 were detected in unfertilized oocytes, 1-cell and 2-cell stage embryos. GLIS1 transcripts were decreased at 4- to 8-cell stages. No difference in developmental rate for the 2-cell to 16-cell stage was observed between GLIS1 siRNA injected and control embryos (Uninjected and control siRNA injected). However, B-GLIS1-1 injected embryos showed developmental arrest at 16-cell stage. The blastocyst rate of B-GLIS1-1 injected embryos (6.5%) was significantly (P<0.05) lower than those of the uninjected (43.9%), B-GLIS1-2 (37.2%) and control siRNA (34.5%) injected embryos. PGK1 and PDHA1 levels in B-GLIS1-1 injected embryos were lower (P<0.05) than uninjected embryos. Similarly, HSPA8 transcript was decreased in B-GLIS1-1 injected embryos. Our results indicate the critical importance of GLIS1 for early development of bovine embryos, and raise the possibility that GLIS1 is an important factor for epigenetic regulation of bovine embryos.