Distribution of L1-retroposons on the giant sex chromosomes of Microtus cabrerae (Arvicolidae, Rodentia): functional and evolutionary implications

Long interspersed nuclear elements (L1 or LINE-1) are the most abundant and active retroposons in the mammalian genome. Traditionally, the bulk of L1 sequences have been explained by the 'selfish DNA' hypothesis; however, recently it has been also argued that L1s could play an important ro...

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Bibliographic Details
Published in:Chromosome research 2006-03, Vol.14 (2), p.177-186
Main Authors: Marchal, J A, Acosta, M J, Bullejos, M, Puerma, E, Díaz de la Guardia, R, Sánchez, A
Format: Article
Language:English
Subjects:
Animals
Arvicolidae
Arvicolinae - genetics
Chromosomes
Cloning, Molecular
Evolution, Molecular
Female
Heterochromatin - genetics
In Situ Hybridization, Fluorescence
Long Interspersed Nucleotide Elements - genetics
Male
Methylation
Microtus
Models, Genetic
Retroelements - genetics
Rodentia
Sex Chromosomes - genetics
Sex Chromosomes - metabolism
Species Specificity
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Summary:Long interspersed nuclear elements (L1 or LINE-1) are the most abundant and active retroposons in the mammalian genome. Traditionally, the bulk of L1 sequences have been explained by the 'selfish DNA' hypothesis; however, recently it has been also argued that L1s could play an important role in genome and gene organizations. The non-random chromosomal distribution of these retroelements is a striking feature considered to reflect this functionality. In the present study we have cloned and analyzed three different L1 fragments from the genome of the rodent Microtus cabrerae. In addition, we have examined the chromosomal distribution of this L1 in several species of Microtus, a very interesting group owing to the presence in some species of enlarged ('giant') sex chromosomes. Interestingly, in all species analyzed, L1-retroposons have preferentially accumulated on both the giant- and the normal-sized sex chromosomes compared with the autosomes. Also we have demonstrated that L1-retroposons are not similarly distributed among the heterochromatic blocks of the giant sex chromosomes in M. cabrerae and M. agrestis, which suggest that L1 retroposition and amplification over the sex heterochromatin have been different and independent processes in each species. Finally, we proposed that the main factors responsible for the L1 distribution on the mammalian sex chromosomes are the heterochromatic nature of the Y chromosome and the possible role of L1 sequences during the X-inactivation process.
ISSN:0967-3849
1573-6849
DOI:10.1007/s10577-006-1034-9