Measurement of telomere length in haematopoietic cells using in situ hybridization techniques

The DNA of human chromosomes terminates in several kilobases of telomere re peats that are gradually lost with age and with replication in vitro. Defec tive telomere maintenance has been shown to be causally linked to cell cycl e exit and apoptosis. In order to overcome the limitations imposed by South ern blotting, we have established a quantitative fluorescence in situ hybri dization (Q-FISH) technique. This technique allows estimation of telomere l ength in specific chromosome arms from metaphase cell preparations. Further more, we have extended quantitative in situ hybridization to flow cytometry (flow FISH) in order to obtain information on the mean telomere repeat con tent in suspended cells. Telomere length in granulocytes, monocytes, CD8 an d CD4 T lymphocytes and natural killer cells was found to differ slightly i n the peripheral blood of adults. However, strikingly longer telomeres were observed in B lymphocytes(similar to 1.3 kb longer), suggesting a function al role for telomere maintenance in this cell subset. In summary, Q-FISH an d flow FISH represent new methods for measuring telomere length in single c ells and allow studies of telomere dynamics in haematopoietic subpopulation s at various stages of normal and abnormal antigen responses.