MiR-290 family maintains developmental potential by targeting p21 in mouse preimplantation embryos‡.

The miR-290 family is a mouse-specific microRNA cluster, which maintains mouse embryonic stem cells (ESCs) pluripotency by increasing OCT3/4 and C-MYC expression. However, its functions in mouse preimplantation embryos remain unclear, especially during zygotic genome activation (ZGA). In this study, miR-290 family expression increased from the two-cell embryo stage through the blastocyst stage. Inhibition of miR-294-3p/5p did not affect ZGA initiation or embryo development, whereas pri-miR-290 knockdown decreased ZGA gene expression and slowed embryonic development. In addition, pluripotency decreased in ESCs derived from pri-miR-290 knockdown blastocysts. To clarify the mechanism of action, 33 candidate miR-294-3p target genes were screened from three databases, and miR-294-3p directly targeted the 3'-untranslated region of Cdkn1a (p21) mRNA. Similar to pri-miR-290 knockdown, P21 overexpression impeded embryonic development, whereas simultaneous overexpression of P21 and pri-miR-290 partially rescued embryonic development. The results indicate that the miR-290 family participates in promoting ZGA process and maintaining developmental potency in embryos by targeting p21.

[Analysis of the landscape diversity dynamics of small watershed in the Loess Plateau].

Taking Zhifanggou Gully as the study area, some landscape diversity indexes were attained under the support of GIS technology. Utilizing the indexes such as patch size, average fractal dimension, diversity index, dominance, evenness, fragmentation and conglomeration, the changes of landscape diversity in the small watershed in Loess Plateau during the past 40 years were studied. The landscape diversities had been increasing for the recent 40 years due to the effect of both human activity and plants' endogenesis succession. The patches number increased, and the dryland matrix was substituted gradually by other matrixes such as meadow and woodland. The landscape pattern trended to be fragmentized and the indexes of landscape type diversity and evenness increased, while landscape diversities changed greater during 1978-1998 than during 1958-1978. Homogeneous dryland matrix landscape ecosystem in 1958 had already changed into heterogeneous meadow and woodland matrix landscape ecosystem, which had greater structure stability and stronger function than before.