Rapid, independent, and extensive amplification of telomeric repeats in pericentromeric regions in karyotypes of arvicoline rodents M. Th. Rovatsos & J. A. Marchal & I. Romero-Fernández & F. J. Fernández & E. B. Giagia-Athanosopoulou & Antonio Sánchez Received: 3 August 2011 /Revised and Accepted: 9 September 2011 /Published online: 7 October 2011 # Springer Science+Business Media B.V. 2011 Abstract The distribution of telomeric repeats was analyzed by fluorescence in situ hybridization in 15 species of arvicoline rodents, included in three different genera: Chionomys, Arvicola, and Microtus. The results demonstrated that in most or the analyzed species, telomeric sequences are present, in addition to normal telomeres localization, as large blocks in pericentromeric regions. The number, localization, and degree of amplification of telomeric sequences blocks varied with the karyotype and the morphology of the chromosomes. Also, in some cases telomeric amplification at non-pericentromeric regions is described. The interstitial telomeric sequences are evolutionary modern and have rapidly colonized and spread in pericentromeric regions of chromosomes by different mechanisms and probably independently in each species. Additionally, we colocalized telomeric repeats and the satellite DNA Msat-160 (also located in pericentromeric regions) in three species and cloned telomeric repeats in one of them. Finally, we discuss about the possible origin and implication of telomeric repeats in the high rate of karyotypic evolution reported for this rodent group. Keywords interstitial telomeric sequences . pericentromeric heterochromatin . karyotypic evolution . Arvicolidae . Microtus Abbreviations ITS Interstitial telomeric sequences PCR Polymerase chain reaction FISH Fluorescence in situ hybridization FITC Fluorescein isothiocyanate Myr Million years TRF1 Telomeric repeat binding factor 1 TRF2 Telomeric repeat binding factor 2 CHO Chinese hamster ovary Introduction Telomeric sequences are widely conserved among vertebrates and consist of extended arrays of the TTAGGG hexamer (Meyne et al. 1989; Zakian 1995). These sequences are normally found at the ends of chromosomes (telomeres); however, distribution at intrachromosomal sites (ITSs) have been observed in a variety of species (Meyne et al. 1990; Nanda and Chromosome Res (2011) 19:869–882 DOI 10.1007/s10577-011-9242-3 Responsible Editor: Fengtang Yang. M. Th. Rovatsos : E. B. Giagia-Athanosopoulou Section of Animal Biology, Department of Biology, University of Patras, GR-26500 Patras, Greece J. A. Marchal : I. Romero-Fernández : F. J. Fernández : A. Sánchez (*) Departamento de Biología Experimental, Facultad de Ciencias Experimentales, Universidad de Jaén, Paraje Las Lagunillas s/n, 23071 Jaén, Spain e-mail: abaca@ujaen.es