Measuring Exact Telomere Length
Reference #: 2019-028
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Despite intense interest in the relationships between telomere biology and human disease, a method that can truly assess the changes in telomere constitution using DNA samples is currently not available. A number of methods exist for measuring telomere lengths exist, but most all are either too laborious, unable to provide absolute measurement of individual telomere lengths, or limited to certain chromosomes or cell types.
Researchers at Georgetown University’s Department of Oncology developed a novel DNA fluorescent in situ hybridization (DNA-FISH) assay to rapidly measure the absolute lengths (basepairs) of single telomere molecules using conventional fluorescent microscopy with high precision and high sensitivity. The method can measure telomeres as small as 100 base-pairs. Using a series of cloned telomere molecules (0.1, 0.2, 0.4, 0.9, 1.2 and 2.4 kb), the correlation between telomere length measured by DNA-FISH and telomere length measured by sequencing is 0.99. This DNA-FISH method of telomere length measurement uses a small amount (e.g., 200 ng) of DNA and because no enzymatic reaction is required, it works well with all sources of genomic DNA that are not degraded.
The method is relatively inexpensive and is well suited for high-throughput use and large population studies. Furthermore, it is capable of measure telomere length distribution, generating four telomere parameters: 1) average telomere length per telomere; 2) telomere length variation; 3) frequency of short telomeres (≤1 kb in length); and 4) frequency of long telomeres (≥15 kb in length). These four parameters provide a depiction not only of telomere lengths but also length distributions, and are improved telomere biomarkers to delineate the relationships between telomere characteristics and environmental exposures, psychosocial stress, aging, disease susceptibility and progression.
Yun Ling Zheng, Ph.D., M.D., MPH
Associate Professor in the Departments of Oncology
International Patent Application No. PCT/US2020/044171