A new pericentromeric repeated DNA sequence in <i>Microtus thomasi</i>

Abstract

Several karyotypic forms have been previously described in populations of the vole species Microtus thomasi from Greece. In particular, the karyomorphs Microtus thomasi ‘thomasi’ and ‘atticus’ differ in X chromosome morphology, being acrocentric and subtelocentric, respectively. Furthermore, remarkable heterochromatin content variability has been described in sex chromosomes of both karyomorphs. Genomic DNA digestion with AluI allowed us to clone an 884 bp long repeated DNA sequence (Mth-Alu900) from the karyomorph M. thomasi ‘atticus’. This repeated DNA is AT rich and seems to be organized mainly as a dimer of the 884-bp unit, which presents three simple repeats (CAAAT, CAGAT and CAGAC) that constitute 80% of the total unit length. This repeated DNA is exclusive to M. thomasi, since it is absent from the genome of other studied Arvicolinae species. The chromosomal location of Mth-Alu900 was analyzed on M. thomasi ‘thomasi’ and M. thomasi ‘atticus’ karyomorphs, with different sex chromosome constitution. It was mainly located on the pericentromeric heterochromatin of most autosomes and X chromosomes on both karyomorphs. Results are also discussed in relation to karyotypic and sex chromosome variations in M. thomasi. To our knowledge, Mth-Alu900 constitutes a new – the third discovered so far – pericentromeric repeated DNA sequence described in Microtus species.

Molecular and Physical Characterization of the Complex Pericentromeric Heterochromatin of the Vole Species Microtus thomasi

“…results]. Similarly, 7 Y chromosome variants exist, either acrocentric (Y 0 to Y 4 ) or metacentric (Y m and Y m1 ), all of them almost fully heterochromatic and also highly variable in size [Acosta et al, 2009;Mitsainas et al, 2009;Rovatsos et al, 2011a;Rovatsos and Giagia-Athanasopoulou, 2012, and unpubl. results].…”

“…Furthermore, this species shows an extreme polymorphism in size and morphology of its sex chromosomes [Acosta et al, 2009;Mitsainas et al, 2009;Rovatsos et al, 2011a]. At least 9 different X chromosomes have been found, with either acrocentric (X 0 to X 5 ) or subtelocentric (X st0 to X st2 ) morphology and variable length of heterochromatin [Acosta et al, 2009;Mitsainas et al, 2009;Rovatsos et al, 2011a, and unpubl.…”

“…At least 9 different X chromosomes have been found, with either acrocentric (X 0 to X 5 ) or subtelocentric (X st0 to X st2 ) morphology and variable length of heterochromatin [Acosta et al, 2009;Mitsainas et al, 2009;Rovatsos et al, 2011a, and unpubl. results].…”

“…In the species of the Arvicolinae group, 6 repeated DNAs have been reported from the pericentromeric heterochromatin: Msat-160, Msat-21, MS2, STR47, MthAlu900, and interstitial telomeric sequences (ITSs) [Modi, 1992[Modi, , 1993aIvanov and Modi, 1996;Mayorov et al, 1996;Fernández et al, 2001;Shevchenko et al, 2002;Modi et al, 2003;Acosta et al, 2007Acosta et al, , 2009Acosta et al, , 2010Rovatsos et al, 2011b]. Msat-160 is a satellite DNA, with a monomer unit of 160 bp, present in most species of 3 arvicoline genera (Microtus, Chionomys and Arvicola) analyzed to date [Shevchenko et al, 2002;Marchal et al, 2003;Modi et al, 2003;Acosta et al, 2007Acosta et al, , 2010.…”

Comparative Analysis by Chromosome Painting of the Sex Chromosomes in Arvicolid Rodents

“…These investigations have characterized different families of complex repeated DNAs, satellites DNAs, retroelements, and pseudogenes as components of the sex chromosomes [partially reviewed in Marchal et al, 2003Marchal et al, , 2004aMarchal et al, , 2006Marchal et al, , 2008Acosta et al, 2009]. Many of these sequences are significantly accumulated on the heterochromatic blocks of the giant sex chromosomes and display patterns of distribution, organization, and amplification that are highly variable within species.…”