Bio

Honors & Awards


  • Dean's Postdoctoral Fellowships, Stanford School of Medicine (2012~2013)
  • The Breast Cancer Research Program (BCRP) Three Years Predoctoral Traineeship Award., Department of Defense (DOD) (2008~2011)

Professional Education


  • Doctor of Philosophy, Cornell University (2012)
  • M.S, National Yang Ming University, Microbiology and Immunology (2003)
  • B.S, National Yang Ming University, Life Sciences (2001)

Stanford Advisors


Publications

Journal Articles


  • Post-transcriptional homeostasis and regulation of MCM2-7 in mammalian cells NUCLEIC ACIDS RESEARCH Chuang, C., Yang, D., Bai, G., Freeland, A., Pruitt, S. C., Schimenti, J. C. 2012; 40 (11): 4914-4924

    Abstract

    The MiniChromosome Maintenance 2-7 (MCM2-7) complex provides essential replicative helicase function. Insufficient MCMs impair the cell cycle and cause genomic instability (GIN), leading to cancer and developmental defects in mice. Remarkably, depletion or mutation of one Mcm can decrease all Mcm levels. Here, we use mice and cells bearing a GIN-causing hypomophic allele of Mcm4 (Chaos3), in conjunction with disruption alleles of other Mcms, to reveal two new mechanisms that regulate MCM protein levels and pre-RC formation. First, the Mcm4(Chaos3) allele, which disrupts MCM4:MCM6 interaction, triggers a Dicer1 and Drosha-dependent ? 40% reduction in Mcm2-7 mRNAs. The decreases in Mcm mRNAs coincide with up-regulation of the miR-34 family of microRNAs, which is known to be Trp53-regulated and target Mcms. Second, MCM3 acts as a negative regulator of the MCM2-7 helicase in vivo by complexing with MCM5 in a manner dependent upon a nuclear-export signal-like domain, blocking the recruitment of MCMs onto chromatin. Therefore, the stoichiometry of MCM components and their localization is controlled post-transcriptionally at both the mRNA and protein levels. Alterations to these pathways cause significant defects in cell growth reflected by disease phenotypes in mice.

    View details for DOI 10.1093/nar/gks176

    View details for Web of Science ID 000305032500026

    View details for PubMedID 22362746

  • MCM4 mutation causes adrenal failure, short stature, and natural killer cell deficiency in humans JOURNAL OF CLINICAL INVESTIGATION Hughes, C. R., Guasti, L., Meimaridou, E., Chuang, C., Schimenti, J. C., King, P. J., Costigan, C., Clark, A. J., Metherell, L. A. 2012; 122 (3): 814-820

    Abstract

    An interesting variant of familial glucocorticoid deficiency (FGD), an autosomal recessive form of adrenal failure, exists in a genetically isolated Irish population. In addition to hypocortisolemia, affected children show signs of growth failure, increased chromosomal breakage, and NK cell deficiency. Targeted exome sequencing in 8 patients identified a variant (c.71-1insG) in minichromosome maintenance-deficient 4 (MCM4) that was predicted to result in a severely truncated protein (p.Pro24ArgfsX4). Western blotting of patient samples revealed that the major 96-kDa isoform present in unaffected human controls was absent, while the presence of the minor 85-kDa isoform was preserved. Interestingly, histological studies with Mcm4-depleted mice showed grossly abnormal adrenal morphology that was characterized by non-steroidogenic GATA4- and Gli1-positive cells within the steroidogenic cortex, which reduced the number of steroidogenic cells in the zona fasciculata of the adrenal cortex. Since MCM4 is one part of a MCM2-7 complex recently confirmed as the replicative helicase essential for normal DNA replication and genome stability in all eukaryotes, it is possible that our patients may have an increased risk of neoplastic change. In summary, we have identified what we believe to be the first human mutation in MCM4 and have shown that it is associated with adrenal insufficiency, short stature, and NK cell deficiency.

    View details for DOI 10.1172/JCI60224

    View details for Web of Science ID 000301021500009

    View details for PubMedID 22354170

  • Incremental Genetic Perturbations to MCM2-7 Expression and Subcellular Distribution Reveal Exquisite Sensitivity of Mice to DNA Replication Stress PLOS GENETICS Chuang, C., Wallace, M. D., Abratte, C., Southard, T., Schimenti, J. C. 2010; 6 (9)

    Abstract

    Mutations causing replication stress can lead to genomic instability (GIN). In vitro studies have shown that drastic depletion of the MCM2-7 DNA replication licensing factors, which form the replicative helicase, can cause GIN and cell proliferation defects that are exacerbated under conditions of replication stress. To explore the effects of incrementally attenuated replication licensing in whole animals, we generated and analyzed the phenotypes of mice that were hemizygous for Mcm2, 3, 4, 6, and 7 null alleles, combinations thereof, and also in conjunction with the hypomorphic Mcm4(Chaos3) cancer susceptibility allele. Mcm4(Chaos3/Chaos3) embryonic fibroblasts have ?40% reduction in all MCM proteins, coincident with reduced Mcm2-7 mRNA. Further genetic reductions of Mcm2, 6, or 7 in this background caused various phenotypes including synthetic lethality, growth retardation, decreased cellular proliferation, GIN, and early onset cancer. Remarkably, heterozygosity for Mcm3 rescued many of these defects. Consistent with a role in MCM nuclear export possessed by the yeast Mcm3 ortholog, the phenotypic rescues correlated with increased chromatin-bound MCMs, and also higher levels of nuclear MCM2 during S phase. The genetic, molecular and phenotypic data demonstrate that relatively minor quantitative alterations of MCM expression, homeostasis or subcellular distribution can have diverse and serious consequences upon development and confer cancer susceptibility. The results support the notion that the normally high levels of MCMs in cells are needed not only for activating the basal set of replication origins, but also "backup" origins that are recruited in times of replication stress to ensure complete replication of the genome.

    View details for DOI 10.1371/journal.pgen.1001110

    View details for Web of Science ID 000282369200048

    View details for PubMedID 20838603

  • Comparison of Tir from enterohemorrahgic and enteropathogenic Escherichia coli strains: two homologues with distinct intracellular properties JOURNAL OF BIOMEDICAL SCIENCE Chuang, C. H., Chiu, H. J., Hsu, S. C., Ho, J. Y., Syu, W. J. 2006; 13 (1): 73-87

    Abstract

    Tir of enteropathogenic Escherichia coli (EPEC) or enterohemorrahgic E. coil (EHEC) is translocated by a type III secretion system to the host cell membranes where it serves as a receptor for the binding of a second bacterial membrane protein. In response to the binding, EPEC Tir is phosphorylated at Tyr474, and this phosphorylation is necessary for the signaling of pedestal formation. Tir of EHEC has no equivalent phosphorylation site but it is similarly needed for cytoskeleton rearrangement. How these two Tir molecules achieve their function by apparently different mechanisms is not completely clear. To examine their intrinsic differences, the two Tirs were expressed in HeLa cells and compared. Actin in complexes could be pelleted down from the lysate of cells expressing EHEC Tir but not EPEC Tir. By immunostaining, neither Tir molecule was found in phosphorylated state. In the cytoplasm, EHEC Tir was frequently found in fibrous structures whereas EPEC Tir was observed completely in a diffusive form. The determinant critical for the EHEC Tir fibrous formation was mapped to the C-terminal region of the molecule that deviates from the EPEC counterpart. This region may play a role in taking an alternative route different from Tyr474 phosphorylation to transduce signals.

    View details for DOI 10.1007/s11373-005-9034-x

    View details for Web of Science ID 000234924100007

    View details for PubMedID 16228285

  • Construction of a tagging system for subcellular localization of proteins encoded by open reading frames JOURNAL OF BIOMEDICAL SCIENCE Chuang, C. H., Hsu, S. C., Hsu, C. L., Hsu, T. C., Syu, W. J. 2001; 8 (2): 170-175

    Abstract

    We have previously characterized a monoclonal antibody (SC1D7) that is directed to maltose-binding protein (MBP) of Escherichia coli and other closely related enteric bacteria. SC1D7 does not cross-react with proteins in eucaryotes and appears to be a highly specific tool in immunochemical analyses. To better map the epitope, we took advantage of an available plasmid, pMAL-c2, that encodes the E. coli MBP-coding sequence and constructed plasmids to express MBP fragments. A construct containing the N-terminal portion of MBP does not react with SC1D7, whereas a second construct expressing glutathione S-transferase fused with the C-terminal half of MBP does react with SC1D7. To precisely define the epitope, random peptides displayed on M13 were used to react with SC1D7. Sequences of reactive peptides were aligned, and a consensus sequence of XDXRIPX was deduced. This sequence matches MBP with an amino acid stretch of KDPRIAA. To consolidate the mapping result, a sequence encoding this epitope was inserted into an expression vector and the resulting recombinant protein did react with SC1D7. Thereafter, this epitope was incorporated into a eucaryotic expression plasmid containing a previously defined hepatitis delta virus epitope for protein tagging. This two-epitope-tagging vector is useful in various molecular analyses. We demonstrate its usage for localization of a bacterial virulence factor in host cells. This vector should be applicable for high-throughput characterization of new open reading frames found in genome sequencing.

    View details for Web of Science ID 000167637400003

    View details for PubMedID 11287747

Stanford Medicine Resources: