STUDIES ON REGULATION OF DEVELOPMENT BY GENOMIC IMPRINTING

本项目旨在通过对印记基因表达和胚胎发育的研究，阐明在小鼠卵母细胞生长过程中何时建立基因组印记。生长期卵母细胞缺乏成熟到第二次减数分裂中期并支持发育的能力。为了了解生长期卵母细胞的核能力，通过核移植构建了生长期卵母细胞的成熟卵母细胞。体外受精后，含有直径为60μm的幼鼠生长核的卵母细胞可发育至足月。以成年小鼠卵巢卵母细胞为核供体时，直径为50μm的卵母细胞核支持后期发育。为了评估印记状态对发育的响应，用RT-PCR检测了来自人工卵母细胞的胎儿印记基因的表达。结果表明，在不生长的卵母细胞等位基因中，父系和母系表达的基因分别被激活和抑制，并且这种调控是在卵母细胞生长的早期和后期分别建立的。这些结果表明，在卵母细胞生长过程中发生的母体基因组的修改对哺乳动物蛋白的发育是必不可少的。

This project was carried out to clarify when the genomic imprinting during oocyte growth is established in mice by investigations on imprinted gene expression and embryo development. Growing stage oocytes lack ability to mature into the metaphase of the second meiosis and support the development. To know nuclear competence of growing stage oocytes, fully-grown oocytes with nuclei from growing stage one were constructed by nuclear transfer. Following in vitro fertilization, the oocytes contained nuclei from growing one, 60μm in diameter, of juvenile mice were able to develop term. When oocytes from adult mice ovary were used as nuclear donors, the nucleus from oocytes of 50μm in diameter supported the term development. To evaluate the imprinted status in response to the developments, the expression of imprinted genes in the fetuses derived from constructed oocytes was examined by RT-PCR. The results showed that paternally and maternally expressed genes were activated and inhibited respectively in non-growing oocyte alleles, and that the regulation was established individually from early to late growing stage in oocytes. These results demonstrate that modifications in the maternal genome that occur during oocyte growth are essential for mammalin development.