Extent and variability of interstitial telomeric sequences and their effects on estimates of telomere length

Telomeres often shorten with time, although this varies between tissues, individuals and species, and their length and/or rate of change may reflect fitness and rate of senescence. Measurement of telomeres is increasingly important to ecologists, yet the relative merits of different methods for estimating telomere length are not clear. In particular the extent to which interstitial telomere sequences (ITSs), telomere repeats located away from chromosomes ends, confound estimates of telomere length is unknown. Here we present a method to estimate the extent of ITS within a species and variation among individuals. We estimated the extent of ITS by comparing the amount of label hybridized to in-gel telomere restriction fragments (TRF) before and after the TRFs were denatured. This protocol produced robust and repeatable estimates of the extent of ITS in birds. In five species, the amount of ITS was substantial, ranging from 15% to 40% of total telomeric sequence DNA. In addition, the amoun...端粒(Telomeres)通常随时间推移而缩短，但该过程因组织、个体及物种的不同存在差异，其长度和/或变化速率或可反映机体适合度与衰老速率。端粒测量在生态学研究中的重要性与日俱增，但目前学界尚未明确不同端粒长度估算方法的相对优劣。尤为值得关注的是，位于染色体末端之外的间质端粒序列(ITSs)会在多大程度上干扰端粒长度的估算，这一问题仍未得到解答。本研究提出了一种可用于估算某一物种内间质端粒序列占比以及个体间差异的方法：通过比较端粒限制性片段(TRF)变性前后，与凝胶内该片段结合的标记物总量，来估算间质端粒序列的占比。该实验方案可在鸟类中获得可靠且可重复的间质端粒序列占比估算结果。在五个鸟类物种中，间质端粒序列的占比可观，可达总端粒序列DNA的15%至40%。此外，