Mapping of SINEs in the genome of Proechimys (Mammalia: Rodentia).

This study aimed to analyze the distribution of short interspersed elements (SINEs) in the chromosomes of five species of rodents of the genus Proechimys and in a variant karyotype of P. guyannensis. Molecular cytogenetic techniques were used to characterize the sequences of the B1, B4, MAR and THER SINEs, which were used as probes for hybridization in metaphase chromosomes. A wide distribution of SINEs was observed in the chromosomes of the Proechimys species examined, thus indicating differentiation of these retroelements. The signal of the B4 SINE was more evident than that of the B1 SINE, especially in P. echinothrix, P. longicaudatus, and P. cuvieri. Although the signal of the MAR SINE was more explosive than that of the THER SINE, in the species P. echinothrix, P. guyannensis (2n = 46) and P. longicaudatus, its distribution in the karyotypes was similar. The signals of these retroelements occurred at specific heterochromatic sites and were centromeric/pericentromeric and at the terminal regions in most chromosomes. This appears to be a typical distribution pattern of the SINEs and may indicate involvement with rearrangements during karyotypic diversification in Proechimys. The variation of the SINEs in the genome of Proechimys species demonstrates that these elements are distributed in a specific way in this genus and the preference for some sites, considered hotspots for chromosomal breakage, allows us to propose that these elements are related to the karyotypic evolution of Proechimys.

Chromosome Painting in Callicebus nigrifrons Provides Insights into the Genome Evolution of Titi Monkeys and the Ancestral Callicebinae Karyotype.

We studied the chromosomes of Callicebus nigrifrons with conventional and molecular cytogenetic methods. Our chromosome painting analysis in C. nigrifrons together with previous reports allowed us to hypothesize an ancestral Callicebinae karyotype with 2n = 48. The associations of human chromosomes (HSA) 2/22, 7/15, 10/11, and the inverted HSA2/16 would link Callicebus, Cheracebus, and Plecturocebus and would thus be present in the ancestral Callicebinae karyotype. Four fusions (HSA1b/1c, 3c/8b, 13/20, and 14/15/3/21) and 1 fission (HSA2/22) are synapomorphies of Callicebus. The associations HSA3/15 and HSA3/9 are chromosome features linking Callicebus and Cheracebus, whereas the association HSA13/17 would represent a link between Callicebus and the moloch group (Plecturocebus). Only 6 of the 33 recognized titi monkey species have now been painted with human chromosome-specific probes. Further analyses are needed to clarify the phylogenomic relationships in this species-rich group.