Mammalian oocytes are arrested at the G2-M phase transition of the first meiotic division. In vitro, fully grown oocytes liberated from their follicles spontaneously reinitiate meiosis I, characterized by germinal vesicle breakdown (GVBD), chromatin condensation, spindle assembly, emission of the first polar body and progression to metaphase of the second meiotic division (MII), at which stage they undergo a second arrest until fertilization. After spermatozoa penetrate the oocyte, the second polar body extrudes, male and female pronuclei form and syngamy occurs to start early embryo development. Nuclear changes during oocyte maturation and fertilization are co-ordinated with movements of genetic material and organelles, and with biochemical changes in the cytoplasm to ensure normal embryo development. The normality of early embryogenesis is directly related to the ordered expression of these developmental programmes (Van Blerkom, 1991).Of the numerous cytoplasmic changes that occur, the positioning of mitochondria may be involved in concentrating ATP or calcium to specific regions in oocytes or fertilized eggs to support normal developmental processes. Thus, the distribution of active mitochondria may be indicative of the energy or ion requirement of various key events during oocyte maturation, fertilization and early embryo development. In mice, the perinuclear accumulation of mitochondria between GVBD and metaphase I (MI) (Van Blerkom and Runner, 1984; Van Blerkom, 1991), and the polarized distribution of mitochondria to one half of the oocyte containing the MII spindle (Calarco, 1995) were observed and were regarded as one aspect of the developmental programme of cytoplasmic maturation. Previous observations also revealed that translocation of mitochondria is co-ordinated

Pigs are an attractive animal model to study the progression of cancer because of their anatomical and physiological similarities to human. However, the use of pig models for cancer research has been limited by availability of genetically engineered pigs which can recapitulate human cancer progression. Utilizing genome editing technologies such as CRISPR/Cas9 system allows us to generate genetically engineered pigs at a higher efficiency. In this study, specific CRISPR/Cas9 systems were used to target RUNX3, a known tumour suppressor gene, to generate a pig model that can induce gastric cancer in human. First, RUNX3 knockout cell lines carrying genetic modification (monoallelic or biallelic) of RUNX3 were generated by introducing engineered CRISPR/Cas9 system specific to RUNX3 into foetal fibroblast cells. Then, the genetically modified foetal fibroblast cells were used as donor cells for somatic cell nuclear transfer, followed by embryo transfer. We successfully obtained four live RUNX3 knockout piglets from two surrogates. The piglets showed the lack of RUNX3 protein in their internal organ system. Our results demonstrate that the CRISPR/Cas9 system is effective in inducing mutations on a specific locus of genome and the RUNX3 knockout pigs can be useful resources for human cancer research and to develop novel cancer therapies.

In this study we investigated the expression of brain-derived neurotrophic factor (BDNF) and c-fos mRNA in the hippocampal formation after febrile seizures (FSs) with in situ hybridization histochemistry using riboprobes. The induction of BDNF mRNA was firstly observed in the dentate gyrus at 30 min after FSs. The expression in the dentate gyrus peaked at 3 h and returned to basal level at 24 h. It was also observed in the CA3 of hippocampus from 2 to 3 h. The induction of c-fos mRNA was observed in the dentate gyrus at 30 min and 1 h. These observations suggest that BDNF and c-fos are the genes whose expression can be altered by FSs and might be related to pathologic alterations after FSs.

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