Massive LINE‐1 retrotransposon enrichment in tamarins of the Cebidae family (Platyrrhini, Primates) and its significance for genome evolution.

To study heterochromatin distribution differences among tamarins, we applied LINE‐1 probes using fluorescence in situ hybridization onto chromosomes of Saguinus mystax, Leontocebus fuscicollis, and Leontopithecus rosalia with the aim to investigate possible evolutionary implications. LINE‐1 repeats were shown to be involved in genome architecture and in the occurrence of chromosomal rearrangements in many vertebrates. We found bright LINE‐1 probe signals at centromeric or pericentromeric areas, GC rich, on almost all chromosomes in three tamarin species. We also found non‐centromeric signals along chromosome arms. In a phylogenetic perspective, we analyzed the pattern of LINE‐1 distribution considering human chromosomal homologies and C banding patterns. Our data indicate that LINE‐1 centromeric expansions and accumulation presumably arose in a common tamarin ancestor and that the presence of LINE‐1 at the junction of human chromosome associations is presumably linked to interchromosomal rearrangements. For example, we found bright centromeric signals as well as non‐centromeric signals on chromosomes 1 and 2, in all species analyzed, in correspondence to human chromosome associations 13/9/22 and 20/17/13, which are synapomorphic for all tamarins. Furthermore, we found other faint signals that could be apomorphisms linked both to intrachromosomal rearrangements as well as to retro‐transposition events. Our results confirm that the three species have similar karyotypes but small differences in LINE‐1 and heterochromatin amplification and distribution; in particular on chromosome pairs 19–22, where we show the occurrence of small inversions, in agreement with previous classic cytogenetic hypotheses. [ABSTRACT FROM AUTHOR]