Telomeric DNA allocation in chromosomes of common shrew (Sorex araneus, eulipotyphla)

Recently we have displayed shrew species, Iberian shrew S. granarius, with telomeres of unusual for mammals structure, including long telomeres on the short acrocentrics arms containing 213 kb on average and short telomeres (3.8 kb) on the other chromosomal ends (Zhdanova et al., 2005, 2007). However, it is not clear if such telomeres are characteristic of all shrew species or only of S. granarius. S. granarius and common shrew Sorex araneus are the sibling species. In this investigation by using modified Q-FISH, we demonstrated that telomeres in S. araneus from different chromosomal races differing in the numbers of metacentrics contain 6.8-15.2 kb of telomeric tracts. Thus, the S. araneus telomere lengths appeared to correspond with telomere lengths both in shrews and majority wild mammalian species, and S. granarius has telomeres with unique or scarce structure. Furthermore, using DNA and RNA modified with probe high specificity to telomeric repeats (PNA and LNA) we showed that interstitial telomeric sites in S. araneus chromosomes contained mainly telomeric DNA and their localization coincided with some evolutionary breakpoints. Interstitial telomeric DNA in S. granarius chromosomes was not revealed. Thus, distribution of telomeric DNA can greatly differ even in closely related species whose chromosomes are composed from almost identical chromosomal arms.