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No. 97 (PO 11)
5-Ethynyl-2′-deoxyuridine (EdU)-induced replication banding patterns
in human chromosomes
Osamu Hoshi
Anatomy and Physiological Science, Graduate School of Health Care Science, Tokyo Medical and
Dental University, Japan
We present a novel technique using incorporation of 5-ethynyl-2′-deoxyuridine (EdU) into replicating
DNA is reported for analysis of the replicating banding patterns of human metaphase chromosomes.
Human lymphocytes were synchronized with excess thymidine, and then treated with EdU during the
late S phase of the cell cycle. EdU-incorporated DNA was detected in metaphase chromosomes using
Alexa Fluor ® 488 azides, through the 1,3-dipolar cycloaddition reaction of organic azides with the
terminal acetylene group of EdU. Chromosomes with incorporated EdU during the late S phase showed
a banding pattern that was similar to the G-banding pattern of normal human chromosomes. Atomic
force microscopic (AFM) images under liquid conditions showed that the structure of the chromosomes
was well preserved even after EdU treatment. Comparisons between fluorescence microscopic images
and AFM images of the same chromosome 1 indicated the presence of ridges and grooves in the
chromatid arm, which corresponded to G-positive and G-negative bands, respectively. These results
suggest an intimate relationship between the EdU-induced replication bands and the G-bands in human
chromosomes. This technique combined with AFM is useful for analyzing the structure of chromosomes
in relation to their replication banding pattern.
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