What we know about the heterochromatin of Cebus (Primates, Platyrrhini)? An in-depth genomic revision.

NIEVES, MARIELA; FANTINI, LUCIA; MUDRY, MARTA D.

Congreso; 21st INTERNATIONAL CHROMOSOME CONFERENCE; 2016

Heterochromatin has been proposed as a putative factor involved in karyological diversification among vertebrates and in mechanisms leading to speciation. Our work in Cebus, one of the most complex groups within platyrrhine primates, highlightened a peculiar genomic feature: the presence of conspicuous regions of repeated sequences distributed throughout the karyotype. This trait refers not only to most of the chromosome pairs with heterochromatic blocks but also to the composition of them. Here we analyze the heterochromatin implication in Cebus´ genome dynamics by studying different genomic parameters and components. We addressed a molecular cytogenetic approach of more than 250 individuals from 7 of 12 recognized species. Cebus spp. showed a high degree of homology with each other. The proportion of heterochromatin in their karyotypes correlates with genome size, from smallest to largest: C. xanthosternos, C. nigritus, C. cay, C. libidinosus, C. apella, C. olivaceus and C. albifrons. FISH applying our own specific heterocromatic probe of C. cay in different Cebus and other Platyrrihi species allowed proposing that this heterochromatin is genus-specific with taxonomic diagnostic value. C-band heteromorphisms and polymorphisms frequencies were not randomly distributed. Chromosomic pairs 6, 17 and 19 were the most variable for C. cay and C. nigritus. DAPI-CMA3 patterns were similar among Cebus species, where C-blocks showed conspicuous heterochromatic CMA3 bands, corresponding to regions of DNA with a GC-rich composition. CGH analyses showed that interspecific divergence is mostly related to differences in Y chromosome composition. For C. nigritus and C. cay we found differences in the proportion of DNA between different genomic regions, with C. cay having more repetitive DNA and C. nigritus more coding DNA. Our results showed that heterochromatin has an evident role in Cebus´ genome dynamics and support the hypothesis that larger genomes with GC-rich heterochromatic DNA are more stable and protected. Financial support: CONICET Project PIP 0744 and UBACyT Project X154 to MDM.