Studying single cell characteristics: new platforms for imaging and se…

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  • 2016-07-19


[BK21 Plus Seminar]

▶Subject: Studying single cell characteristics: new platforms for imaging and sequencing single cells

▶Speaker: Hee-Sun Han, Ph.D. (Harvard University)

▶Date: 3:00 PM/August. 8(Mon.)/2016

▶Place: Life Science Bldg. #104

Analysis of the microenvironments and genetic/epigenetic profiles of single cells is critical for accurate prediction of cell fate. In addition, single cell analysis would vastly expand our understanding on heterogeneous samples like those found in stem-cell biology, immunology, cancer biology and tissue engineering. In this talk, I will introduce new platforms developed for single cell imaging in live animals and single cell/virus sequencing.

Multiplexed, phenotypic, intravital cytometric imaging requires novel fluorophore conjugates that have appropriate size for long circulation and diffusion, and show virtually no nonspecific binding to cells/serum while binding to cells of interest with high specificity. In addition, those conjugates must be stable and bright in the in vivo environments. Using the newly developed quantum dot (QD)-antibody conjugates, which satisfy all the requirements, we successfully (i) imaged endogenous hematopoietic stem ad progenitor (HSPC) cells, (ii) analyzed the location of the niche and (iii) directly measured their oxygenation. We found that the HSPC niches are in close proximity to both blood vessels and bone, and thus characterized by a normoxic microenvironment. Our findings indicate that hypoxia may not play a critical role in HSC regulation. By enabling imaging and tracking of single endogenous cells in live animals, our work leads to new studies on single cell movements, cell-to-cell interactions and the micro-environments of single cells in their native states.

While single cell imaging studies in vivo enable us to monitor cellular behaviors and their microenvironments in live animals, fundamental understanding of cellular behaviors requires molecular profiling of the cells. For high throughput analysis of the genetic or transcriptomic profile of single cells or viruses, we developed microfluidic platforms enabling isolation, detection, purification and amplification of single target cells from a heterogeneous sample. In the platform, individual cells or viruses are encapsulated into pico-liter drops, which serve as reaction vessels for single cell/virus assays. After completing the single cell/virus assays in drops, drops are screened and sorted at the rates of ~1000/s to select cells/viruses-of-interest for further characterizations. Using this platform, we purified the target viral species from a complex virus mixture and assembled their complete genome sequence. Extending this work, we are currently developing new platforms for high-throughput genome sequencing of single viruses or cells. The new platforms will be used to identify the genome sequence of novel viruses present in environmental samples and also be used for whole genome haplotyping of eukaryotic cells.

These new tools can be combined to probe both the in vivo characteristics and molecular profiles of single cells. By developing new single cell analysis techniques and combining the new techniques, we will get a step closer to extensive understanding of tissues at their cellular level.

▶Inquiry: Prof. Lee, Seung-Jae(279-2351)
* This seminar will be given in English.
please refrain from taking photos during seminars. *