Bio

Professional Education


  • Bachelor of Science, Yale University (2005)
  • Doctor of Philosophy, Massachusetts Institute of Technology (2011)
  • Bachelor of Science, Yale University, Mol. Biophys. & Biochem. (2005)

Stanford Advisors


Publications

Journal Articles


  • Expanding the MicroRNA Targeting Code: Functional Sites with Centered Pairing MOLECULAR CELL Shin, C., Nam, J., Farh, K. K., Chiang, H. R., Shkumatava, A., Bartel, D. P. 2010; 38 (6): 789-802

    Abstract

    Most metazoan microRNA (miRNA) target sites have perfect pairing to the seed region, located near the miRNA 5' end. Although pairing to the 3' region sometimes supplements seed matches or compensates for mismatches, pairing to the central region has been known to function only at rare sites that impart Argonaute-catalyzed mRNA cleavage. Here, we present "centered sites," a class of miRNA target sites that lack both perfect seed pairing and 3'-compensatory pairing and instead have 11-12 contiguous Watson-Crick pairs to the center of the miRNA. Although centered sites can impart mRNA cleavage in vitro (in elevated Mg(2+)), in cells they repress protein output without consequential Argonaute-catalyzed cleavage. Our study also identified extensively paired sites that are cleavage substrates in cultured cells and human brain. This expanded repertoire of cleavage targets and the identification of the centered site type help explain why central regions of many miRNAs are evolutionarily conserved.

    View details for DOI 10.1016/j.molcel.2010.06.005

    View details for Web of Science ID 000279297500005

    View details for PubMedID 20620952

  • Mammalian microRNAs: experimental evaluation of novel and previously annotated genes GENES & DEVELOPMENT Chiang, H. R., Schoenfeld, L. W., Ruby, J. G., Auyeung, V. C., Spies, N., Baek, D., Johnston, W. K., Russ, C., Luo, S., Babiarz, J. E., Blelloch, R., Schroth, G. P., Nusbaum, C., Bartel, D. P. 2010; 24 (10): 992-1009

    Abstract

    MicroRNAs (miRNAs) are small regulatory RNAs that derive from distinctive hairpin transcripts. To learn more about the miRNAs of mammals, we sequenced 60 million small RNAs from mouse brain, ovary, testes, embryonic stem cells, three embryonic stages, and whole newborns. Analysis of these sequences confirmed 398 annotated miRNA genes and identified 108 novel miRNA genes. More than 150 previously annotated miRNAs and hundreds of candidates failed to yield sequenced RNAs with miRNA-like features. Ectopically expressing these previously proposed miRNA hairpins also did not yield small RNAs, whereas ectopically expressing the confirmed and newly identified hairpins usually did yield small RNAs with the classical miRNA features, including dependence on the Drosha endonuclease for processing. These experiments, which suggest that previous estimates of conserved mammalian miRNAs were inflated, provide a substantially revised list of confidently identified murine miRNAs from which to infer the general features of mammalian miRNAs. Our analyses also revealed new aspects of miRNA biogenesis and modification, including tissue-specific strand preferences, sequential Dicer cleavage of a metazoan precursor miRNA (pre-miRNA), consequential 5' heterogeneity, newly identified instances of miRNA editing, and evidence for widespread pre-miRNA uridylation reminiscent of miRNA regulation by Lin28.

    View details for DOI 10.1101/gad.1884710

    View details for Web of Science ID 000277725300004

    View details for PubMedID 20413612

  • Loss of Cardiac microRNA-Mediated Regulation Leads to Dilated Cardiomyopathy and Heart Failure CIRCULATION RESEARCH Rao, P. K., Toyama, Y., Chiang, H. R., Gupta, S., Bauer, M., Medvid, R., Reinhardt, F., Liao, R., Krieger, M., Jaenisch, R., Lodish, H. F., Blelloch, R. 2009; 105 (6): 585-594

    Abstract

    Heart failure is a deadly and devastating disease that places immense costs on an aging society. To develop therapies aimed at rescuing the failing heart, it is important to understand the molecular mechanisms underlying cardiomyocyte structure and function.microRNAs are important regulators of gene expression, and we sought to define the global contributions made by microRNAs toward maintaining cardiomyocyte integrity.First, we performed deep sequencing analysis to catalog the miRNA population in the adult heart. Second, we genetically deleted, in cardiac myocytes, an essential component of the machinery that is required to generate miRNAs. Deep sequencing of miRNAs from the heart revealed the enrichment of a small number of microRNAs with one, miR-1, accounting for 40% of all microRNAs. Cardiomyocyte-specific deletion of dgcr8, a gene required for microRNA biogenesis, revealed a fully penetrant phenotype that begins with left ventricular malfunction progressing to a dilated cardiomyopathy and premature lethality.These observations reveal a critical role for microRNAs in maintaining cardiac function in mature cardiomyocytes and raise the possibility that only a handful of microRNAs may ultimately be responsible for the dramatic cardiac phenotype seen in the absence of dgcr8.

    View details for DOI 10.1161/CIRCRESAHA.109.200451

    View details for Web of Science ID 000269711900010

    View details for PubMedID 19679836

  • Early origins and evolution of microRNAs and Piwi-interacting RNAs in animals NATURE Grimson, A., Srivastava, M., Fahey, B., Woodcroft, B. J., Chiang, H. R., King, N., Degnan, B. M., Rokhsar, D. S., Bartel, D. P. 2008; 455 (7217): 1193-U15

    Abstract

    In bilaterian animals, such as humans, flies and worms, hundreds of microRNAs (miRNAs), some conserved throughout bilaterian evolution, collectively regulate a substantial fraction of the transcriptome. In addition to miRNAs, other bilaterian small RNAs, known as Piwi-interacting RNAs (piRNAs), protect the genome from transposons. Here we identify small RNAs from animal phyla that diverged before the emergence of the Bilateria. The cnidarian Nematostella vectensis (starlet sea anemone), a close relative to the Bilateria, possesses an extensive repertoire of miRNA genes, two classes of piRNAs and a complement of proteins specific to small-RNA biology comparable to that of humans. The poriferan Amphimedon queenslandica (sponge), one of the simplest animals and a distant relative of the Bilateria, also possesses miRNAs, both classes of piRNAs and a full complement of the small-RNA machinery. Animal miRNA evolution seems to have been relatively dynamic, with precursor sizes and mature miRNA sequences differing greatly between poriferans, cnidarians and bilaterians. Nonetheless, miRNAs and piRNAs have been available as classes of riboregulators to shape gene expression throughout the evolution and radiation of animal phyla.

    View details for DOI 10.1038/nature07415

    View details for Web of Science ID 000260462100034

    View details for PubMedID 18830242

  • PRG-1 and 21U-RNAs interact to form the piRNA complex required for fertility in C-elegans MOLECULAR CELL Batista, P. J., Ruby, J. G., Claycomb, J. M., Chiang, R., Fahlgren, N., Kasschau, K. D., Chaves, D. A., Gu, W., Vasale, J. J., Duan, S., Conte, D., Luo, S., Schroth, G. P., Carrington, J. C., Bartel, D. P., Mello, C. C. 2008; 31 (1): 67-78

    Abstract

    In metazoans, Piwi-related Argonaute proteins have been linked to germline maintenance, and to a class of germline-enriched small RNAs termed piRNAs. Here we show that an abundant class of 21 nucleotide small RNAs (21U-RNAs) are expressed in the C. elegans germline, interact with the C. elegans Piwi family member PRG-1, and depend on PRG-1 activity for their accumulation. The PRG-1 protein is expressed throughout development and localizes to nuage-like structures called P granules. Although 21U-RNA loci share a conserved upstream sequence motif, the mature 21U-RNAs are not conserved and, with few exceptions, fail to exhibit complementarity or evidence for direct regulation of other expressed sequences. Our findings demonstrate that 21U-RNAs are the piRNAs of C. elegans and link this class of small RNAs and their associated Piwi Argonaute to the maintenance of temperature-dependent fertility.

    View details for DOI 10.1016/j.molcel.2008.06.002

    View details for Web of Science ID 000257727600010

    View details for PubMedID 18571452

  • Relationship between salt-bridge identity and 14-helix stability of beta(3)-peptides in aqueous buffer ORGANIC LETTERS Guarracino, D. A., Chiang, H. J., Banks, T. N., Lear, J. D., Hodsdon, M. E., Schepartz, A. 2006; 8 (5): 807-810

    Abstract

    We report a systematic analysis of the relationship between salt bridge composition and 14-helix structure within a family of model beta-peptides in aqueous buffer. We find an inverse relationship between side-chain length and the extent of 14-helix structure as judged by CD. Introduction of a stabilizing salt bridge pair within a previously reported beta-peptide ligand for hDM2 led to changes in structure that were detectable by NMR.

    View details for DOI 10.1021/ol0527532

    View details for Web of Science ID 000235746600002

    View details for PubMedID 16494446

Stanford Medicine Resources: