Conservation and characterization of unique porcine interstitial telomeric sequences

Guangzhen Ji,Maja Okuka,Christina Glytsou,Yang Yang,Kai Liu,Chengbin Chen,Lin Liu,Weimin Ruan,Wenqing Song,Ning Li,Sarantis Gagos

doi:10.1007/s11427-012-4420-x

Abstract

Telomeres are composed of TTAGGG repeats and located at the ends of chromosomes. Telomeres protect chromosomes from instability in mammals, including mice and humans. Repetitive TTAGGG sequences are also found at intrachromosomal sites, where they are named as interstitial telomeric sequences (ITSs). Aberrant ITSs are implicated in chromosomal instability and found in cancer cells. Interestingly, in pigs, vertebrate telomere sequences TTAGGG (vITSs) are also localized at the centromeric region of chromosome 6, in addition to the end of all chromosomes. Surprisingly, we found that botanic telomere sequences, TTTAGGG (bITSs), also localize with vITSs at the centromeric regions of pig chromosome 6 using telomere fluorescence in situ hybridization (FISH) and by comparisons between several species. Furthermore, the average lengths of vITSs are highly correlated with those of the terminal telomeres (TTS). Also, pig ITSs show a high incidence of telomere doublets, suggesting that pig ITSs might be unstable and dynamic. Together, our results show that pig cells maintain the conserved telomere sequences that are found at the ITSs from of plants and other vertebrates. Further understanding of the function and regulation of pig ITSs may provide new clues for evolution and chromosomal instability.

Highlights

Telomeres are located at the ends of liner chromosomes, protecting chromosomes from instability [1]
We found that vertebrate interstitial telomeric sequences (vITSs) (TTAGGG)n repeats were hybridized at the terminal and interstitial regions (Figure 1B), while bITSs (TTTAGGG)n were only at the interstitial region of pig chromosome 6 (Figure 1A)
Far, plant (TTTAGGG)n sequences had never been reported in Metazoa [2,40], we identified bITSs in domestic pigs that again co-localized with vITS (Figure 2)

Summary

Introduction

Telomeres are located at the ends of liner chromosomes, protecting chromosomes from instability [1]. Pig ITSs sequences that are homologous to segments of human chromosomes 1 and 19 were found to be located approximately at the centromeric region of chromosome 6 [31]. With the exception of nematodes and arthropods, the (TTAGGG)n repeat is conserved in most Metazoa [2] We found both vertebrate and botanic telomeric sequences (bITSs and vITSs) at ITS of pig chromosome 6. This novel finding of plant (TTTAGGG)n telomeric repeats in mammal may provide new clues into the involvement of telomeres in species evolution and a possible interpretation for the specific characteristics of pig telomeres. We show that the lengths of vITSs are associated with the length of terminal telomeres (TTSs) and are dynamic and unstable

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Conclusion