Distribution of Interstitial Telomeric Sequences in Primates and the Pygmy Tree Shrew (Scandentia)

It has been hypothesized that interstitial telomeric sequences (ITSs), i.e., repeated telomeric DNA sequences found at intrachromosomal sites in many vertebrates, could be correlated to chromosomal rearrangements and plasticity. To test this hypothesis, we hybridized a telomeric PNA probe through FISH on representative species of 2 primate infraorders, Strepsirrhini (Lemur catta, Otolemur garnettii, Nycticebus coucang) and Catarrhini (Erythrocebus patas, Cercopithecus petaurista, Chlorocebus aethiops, Colobus guereza), as well as on 1 species of the order Scandentia, Tupaia minor, used as an outgroup for primates in phylogenetic reconstructions. In almost all primate species analyzed, we found a telomeric pattern only. In Tupaia, the hybridization revealed many bright ITSs on at least 11 chromosome pairs, both biarmed and acrocentric. These ITS signals in Tupaia correspond to fusion points of ancestral human syntenic associations, but are also present in other chromosomes showing synteny to only a single human chromosome. This distribution pattern was compared to that of the heterochromatin regions detected through sequential C-banding performed after FISH. Our results in the analyzed species, compared with literature data on ITSs in primates, allowed us to discuss different mechanisms responsible for the origin and distribution of ITSs, supporting the correlation between rearrangements and ITSs.