Basic Science

New Theoretical Back-up for Clone Tech

A team of researchers, led by Dr. Xu Guoliang and Dr. Li Jinsong from the Institute of Biochemistry and Cell Biology (SIBCB), Shanghai Institutes for Biological Sciences, CAS, in collaboration with other groups published a research letter entitled "The role of Tet3 DNA dioxygenase in epigenetic reprogramming by oocytes" in the journal Nature online on Sep. 5, 2011. This work was mainly carried out by graduate students Gu Tianpeng, Guo Fan and Yang Hui. The paternal genome in a zygote undergoes active DNA demethylation before the first mitosis, Gu et al. find this coincides with oxidation of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC), and the maternal Tet3 is required for this conversion that triggers the demethylation of paternal pluripotency genes such as Oct4 and Nanog. Embryos lacking maternal Tet3 reveal a high frequency of degeneration and the appearance of morphological abnormalities. Furthermore, oocytes lacking Tet3 also appear to have reduced ability to reprogram the injected nuclei from somatic cells. Therefore, reprogramming in somatic cell nuclear transfer might share a common mechanism with paternal genome remodeling in fertilized eggs. This finding has substantially broadened the knowledge of reprogramming in early embryos and provided theoretical basis for enhancing efficiency in animal cloning.

Self-assembly of Nanoparticles

Prof. Tang Zhiyong and Dr. Xia Yunsheng at the Lab for nanomaterials of the National Center for Nanoscience and Technology, have achieved controllable self-assembly of inorganic nanoparticles in solution on the basis of previous research (J. Am. Chem. Soc. 2010, 132, 2886-2888; J. Am. Chem. Soc. 2010, 132, 6006-6013; J. Am. Chem. Soc. 2010, 132, 8202-8206; Angew. Chem. Int. Ed. 2011, 50, 1593-1596; Angew. Chem. Int. Ed. 2011, 50, 5860-5864; Nano Lett. 2011, 11, 3174-3183; J. Am. Chem. Soc. DOI: 10.1021/ja205712a; Angew. Chem. Int. Ed. anie.201103762) in collaboration with groups headed by Prof. Kotov and Prof. Glotzer at the University of Michigan. Both experiment and simulation results reveal that polydisperse (20-30%) nanoparticles can spontaneously assemble into self-limiting, monodisperse (7-9%) supraparticles with the morphologies of loose cores and tight shells, which is governed by the balance between Coulomb repulsion and Van der Waals attraction of nanoparticles themselves. This self-limiting assembly strategy can be used not only for controllable assembly of various semiconductor materials (such as CdSe, CdS, ZnS, PbS, etc.), but also for construction of isotropic or anisotropic gold/semiconductor core/shell nanostructures. The results are significant for guiding us to understand the formation mechanisms of monodisperse virus in biological systems as well as the superstructures formed by organic macromolecules. The above results have been published in Nature Nanotechnology (2011, 6, 580-587).