Professional Education


  • Bachelor of Science, Nankai University (2008)
  • Doctor of Philosophy, Beijing Normal University (2014)

Stanford Advisors


All Publications


  • No Significant Increase in the Delta 4-and Delta 7-Dafachronic Acid Concentration in the Long-Lived glp-1 Mutant, nor in the Mutants Defective in Dauer Formation G3-GENES GENOMES GENETICS Li, T., Liu, W., Lu, S., Zhang, Y., Jia, L., Chen, J., Li, X., Lei, X., Dong, M. 2015; 5 (7): 1473-1479
  • Site-Selective and Metal-Free Aliphatic C-H Oxidation Enabled Synthesis of [5,24,25-D3]-(25S)-Delta(7)-Dafachronic acid CHEMISTRY-A EUROPEAN JOURNAL Liu, W., Li, X., Chen, J., Li, T., Dong, M., Lei, X. 2015; 21 (14): 5345-5349

    Abstract

    Steroid hormones play significant roles in both worms and mammalians. (25S)-Δ(7)-Dafachronic acid (Δ(7)-DA, 1) is a member of the dafachronic acid hormonal series that regulates both development and lifespan of C. elegans. Despite its importance, effective tools for the illumination of its mode of action are lacking. Herein, we report an efficient synthesis of trideuterated Δ(7)-DA, [5,24,25-D3]-(25S)-Δ(7)-dafachronic acid ([D3]-Δ(7)-DA, 2), as a useful chemical tool for subsequent biological studies. Key steps for this bioinspired synthesis approach include site-selective aliphatic C-H oxidation mediated by methyl(trifluoromethyl)dioxirane (TFDO), and the iridium/phosphine-oxazoline-catalyzed late-stage asymmetric deuterium reduction.

    View details for DOI 10.1002/chem.201500324

    View details for Web of Science ID 000352504500011

    View details for PubMedID 25704922

  • E2F Transcription Factor 1 Regulates Cellular and Organismal Senescence by Inhibiting Forkhead Box O Transcription Factors JOURNAL OF BIOLOGICAL CHEMISTRY Xie, Q., Peng, S., Tao, L., Ruan, H., Yang, Y., Li, T., Adams, U., Meng, S., Bi, X., Dong, M., Yuan, Z. 2014; 289 (49): 34205-34213

    Abstract

    E2F1 and FOXO3 are two transcription factors that have been shown to participate in cellular senescence. Previous report reveals that E2F1 enhanced cellular senescence in human fibroblast cells, while FOXO transcription factors play against senescence by regulation reactive oxygen species scavenging proteins. However, their functional interplay has been unclear. Here we use E2F1 knock-out murine Embryonic fibroblasts (MEFs), knockdown RNAi constructs, and ectopic expression of E2F1 to show that it functions by negatively regulating FOXO3. E2F1 attenuates FOXO3-mediated expression of MnSOD and Catalase without affecting FOXO3 protein stability, subcellular localization, or phosphorylation by Akt. We mapped the interaction between E2F1 and FOXO3 to a region including the DNA binding domain of E2F1 and the C-terminal transcription-activation domain of FOXO3. We propose that E2F1 inhibits FOXO3-dependent transcription by directly binding FOXO3 in the nucleus and preventing activation of its target genes. Moreover, knockdown of the Caenorhabditis elegans E2F1 ortholog efl-1 significantly extends lifespan in a manner that requires the activity of the C. elegans FOXO gene daf-16. We conclude that there is an evolutionarily conserved signaling connection between E2F1 and FOXO3, which regulates cellular senescence and aging by regulating the activity of FOXO3. We speculate that drugs and/or therapies that inhibit this physical interaction might be good candidates for reducing cellular senescence and increasing longevity.

    View details for DOI 10.1074/jbc.M114.587170

    View details for Web of Science ID 000346077600043

    View details for PubMedID 25344604

  • Absolute Quantification of a Steroid Hormone that Regulates Development in Caenorhabditis elegans ANALYTICAL CHEMISTRY Li, T., Chen, J., Li, X., Ding, X., Wu, Y., Zhao, L., Chen, S., Lei, X., Dong, M. 2013; 85 (19): 9281-9287

    Abstract

    Under favorable conditions, Caenorhabditis elegans larvae grow into reproductive adults after a series of molting cycles. When environmental conditions are harsh, they arrest as dauer larvae. Dafachronic acid (DA), a C. elegans steroid hormone, is required for reproductive development. Here, we report a mass spectrometry (MS) method for absolute quantitation of DA in C. elegans. The extraction of DA from C. elegans was optimized to achieve a recovery rate of greater than 83%. The MS sensitivity to DA increased 100-fold after carboxyl group derivatization with 2-picolylamine. High-resolution selected ion monitoring (HR-SIM) on a Q-Orbitrap mass spectrometer Q Exactive outperformed targeted-MS2 on the same instrument and selected reaction monitoring (SRM) on a triple-quadrupole mass spectrometer TSQ Quantum Discovery. With a limit of quantification as low as 1 pg of DA, the HR-SIM method enables absolute quantification of endogenous DA during the reproductive development of C. elegans. We found that in wild-type (WT) worms, DA increases from 0.04 ± 0.02 ng/mg protein in the L1 larval stage to 1.21 ± 0.67 ng/mg protein in the L2 larval stage and decreases again after the L3 stage. In comparison, four genetic mutants that have a constitutive dauer-formation phenotype due to disrupted insulin, TGF-β, or cGMP signaling all have a very low DA level in the L2 stage (below 15% of the WT). These mutants are able to escape the dauer fate and most of them grow into fertile adults when supplied with exogenous DA. Therefore, a DA spike in the L2 stage is critical for the reproductive development of C. elegans.

    View details for DOI 10.1021/ac402025c

    View details for Web of Science ID 000330017500054

    View details for PubMedID 24010904

  • Characterization of PUD-1 and PUD-2, Two Proteins Up-Regulated in a Long-Lived daf-2 Mutant PLOS ONE Ding, Y., Du, Y., Luo, S., Li, Y., Li, T., Yoshina, S., Wang, X., Klage, K., Mitani, S., Ye, K., Dong, M. 2013; 8 (6)

    Abstract

    C. elegans PUD-1 and PUD-2, two proteins up-regulated in daf-2(loss-of-function) (PUD), are homologous 17-kD proteins with a large abundance increase in long-lived daf-2 mutant animals of reduced insulin signaling. In this study, we show that both PUD-1 and PUD-2 are abundantly expressed in the intestine and hypodermis, and form a heterodimer. We have solved their crystal structure to 1.9-Å resolution and found that both proteins adopt similar β-sandwich folds in the V-shaped dimer. In contrast, their homologs PUD-3, PUD-4, PUDL-1 and PUDL-2 are all monomeric proteins with distinct expression patterns in C. elegans. Thus, the PUD-1/PUD-2 heterodimer probably has a function distinct from their family members. Neither overexpression nor deletion of pud-1 and pud-2 affected the lifespan of WT or daf-2 mutant animals, suggesting that their induction in daf-2 worms does not contribute to longevity. Curiously, deletion of pud-1 and pud-2 was associated with a protective effect against paralysis induced by the amyloid β-peptide (1-42), which further enhanced the protection conferred by daf-2(RNAi) against Aβ.

    View details for DOI 10.1371/journal.pone.0067158

    View details for Web of Science ID 000320363300105

    View details for PubMedID 23799143