Terminal restriction fragment analysis
TRFs were obtained from genomic DNA by complete digestion with the restriction enzymes HinfI and RsaI. TRFs were separated by pulsed-field gel electrophoresis. Gels were dried, denatured and subjected to in-gel hybridization with a γ-[32P]-ATP-labeled (CCCTAA)4 oligonucleotide probe. Gels were washed and the telomeric signal visualized by phosphorimage analysis. TRFs were processed by ImageJ 1.52a analysis software to quantitate mean telomere length.