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Single Telomere Length Measurement in a Single Cell

Wednesday, December 5, 2018

2:00 PM-4:00 PM

BIOMED Master's Thesis Defense

Single Telomere Length Measurement in a Single Cell

Heba Zuhair Abid, MS Candidate
School of Biomedical Engineering, Science and Health Systems
Drexel University

Ming Xiao, PhD
Associate Professor
School of Biomedical Engineering, Science and Health Systems
Drexel University

Telomere is a repeated sequence that cap the end of the chromosomes in order to protect
it from damage. In human cells, there are 46 chromosomes with 92 telomeres each of which have a different length. Telomere length contribute to the cell genomic stability, biological function, aging, and diseases such as cancer. Telomere length of individual chromosomes in a single cell is important to study different biological function and understand disease development. The available telomere length measurement methods can only estimate the average telomere length in a cell population. Here we are developing a method to label and measure single telomere length at the single cell level. In addition, to maximize the number of single telomere length measurement in a single cell by performing sequential measurement. The telomeres are fluorescently labeled using telomere sequence specific fluorescence in situ hybridization (FISH) probes or and Cas9-mediated fluorescence in situ hybridization (CASFISH) gRNA probes. Telomere length measurement is estimated based on the fluorescent intensity of the telomere labels, as the longer the telomere, the more probes will tag the telomere.

To differentiate the individual chromosomes, we also designed chromosome specific FISH probes or Cas9 gRNA that are very close to the telomere to identify the chromosome specific telomeres by detecting the colocalization of the two-color signals from individual chromosome and telomere. We can potentially estimate multiple chromosome specific telomere lengths with different color chromosome specific probes. To further increase the number of measurable telomeres, we propose to perform sequential tagging of individual chromosomes. Sequential tagging was performed by removing specific chromosome tags, then add more tags for a different chromosome. The above methods were tested on interphase U2OS cells, a cancer cell line that uses Alternative Lengthening of Telomeres (ALT) for telomere repair and maintenance.

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