Primates karyological diagnosis and management programs applications

Exploring the Relationship between Spontaneous Sister Chromatid Exchange and Genome Instability in Two Cryptic Species of Non-Human Primates

There are extensive studies on chromosome morphology and karyotype diversity in primates, yet we still lack insight into genomic instability as a key factor underlying the enormous interspecies chromosomal variability and its potential contribution to evolutionary dynamics. In this sense, the assessment of spontaneous sister chromatid exchange (SCE) frequencies represents a powerful tool for evaluating genome stability. Here, we employed G-banding, fluorescence plus Giemsa (FPG), and chromosome orientation fluorescence in situ hybridization (CO-FISH) methodologies to characterize both chromosome-specific frequencies of spontaneously occurring SCE throughout the genome (G-SCE) and telomere-specific SCE (T-SCE). We analyzed primary fibroblast cultures from two male species of Ateles living in captivity: Ateles paniscus (APA) and Ateles chamek (ACH). High frequencies of G-SCEs were observed in both species. Interestingly, G-SCEs clustered on evolutionary relevant chromosome pairs: ACH chromosomes 1, 2, 3, 4, and 7, and APA chromosomes 1, 2, 3, 4/12, 7, and 10. Furthermore, a statistically significant difference between the observed and expected G-SCE frequencies, not correlated with chromosome size, was also detected. CO-FISH analyses revealed the presence of telomere-specific recombination events in both species, which included T-SCE, as well as interstitial telomere signals and telomere duplications, with APA chromosomes displaying higher frequencies, compared to ACH. Our analyses support the hypothesis that regions of Ateles chromosomes susceptible to recombination events are fragile sites and evolutionary hot spots. Thus, we propose SCE analyses as a valuable indicator of genome instability in non-human primates.

Assessment of genetic variability in captive capuchin monkeys (Primates: Cebidae)

Capuchin monkeys (genera Cebus and Sapajus) show a wide range distribution, from Honduras to Argentina. The aim of this work was to evaluate the genetic and phenotypic variability of captive specimens putatively belonging to S. cay (SCY) and S. nigritus (SNI) at their southernmost distribution limit. Forty-four individuals held in five captive centers from Argentina were analyzed based on external morphology, karyology and DNA sequences of mitochondrial control region (mtDNA-CR). Three morphotypes associated with their probable geographical origin in SCY and a single morphotype in SNI were found. For SCY we could associate each morphotype with the most frequent karyotype. SNI showed a single phenotype and a homogenous karyotype. Heterochromatin showed geographical patterns within species. A 515-bp mtDNA-CR fragment was sequenced, defining fourteen haplotypes at 59 polymorphic sites. A network constructed with our 14 haplotypes and other 77 from S. apella, S. macrocephalus, S. cay and S. nigritus from bibliography revealed some phylogeographic signals. Our SCY and SNI samples rendered four groups that differed in multiple mutational steps, with SCY being more similar to S. apella than to S. macrocephalus. Also, we identified two genetic divergent SCY groups: samples from NOA and from NEA with high mitochondrial diversity. Our results highlight the relevance of using complementary genetic tools throughout the distribution ranges of SCY and SNI for a better assessment of their diversity.

Genetic analysis of an insular population of Sapajus nigritus (Primates: Cebidae) in Rio de Janeiro state, Brazil

The black-horned capuchin (Sapajus nigritus) is a neotropical primate with wide distribution from southeastern Brazil to northeastern Argentina. Although this species has been described with coat pattern variation, even with intrapopulational differences, and characterized as having the greatest genetic diversity among Sapajus species, there are still few studies on natural populations that contribute to the knowledge of this intraspecific variability. We examined individuals from an as yet unstudied population of Ilha da Marambaia, Rio de Janeiro (RJ) state, Brazil, compared with published data for S. nigritus. We sought to confirm the species through phenotypic and genetic characterization using C-banding and fluorescence in situ hybridization with #11qHe+/21WCP probes for chromosomal constitutive heterochromatin (He+) patterns, and cytochrome c oxidase I and II gene sequences for phylogenetic analysis. The coat presented two color patterns, varying from brown to blackish on the body, yellow to brown on the chest, and white to yellow on the face, besides the presence and shape of the tufts on the head, corresponding to S. nigritus. He+ was identified in pairs 4, 12, 13 and 17, and less consistently in pairs 6, 19 and 21, already described for this species. While most Sapajus species have a large He+ block, here pair 11 was identified without extracentromeric He+, the same as reported for S. nigritus from Argentina. Molecular analysis showed divergence of this population from other S. nigritus sequences, reinforcing a trend already demonstrated when samples from RJ are compared with the rest of the distribution, which may represent an evolutionary deviation.

Association between Genomic Instability and Evolutionary Chromosomal Rearrangements in Neotropical Primates

During the last decades, the mammalian genome has been proposed to have regions prone to breakage and reorganization concentrated in certain chromosomal bands that seem to correspond to evolutionary breakpoints. These bands are likely to be involved in chromosome fragility or instability. In Primates, some biomarkers of genetic damage may be associated with various degrees of genomic instability. Here, we investigated the usefulness of Sister Chromatid Exchange as a biomarker of potential sites of frequent chromosome breakage and rearrangement in Alouatta caraya, Ateles chamek, Ateles paniscus, and Cebus cay. These Neotropical species have particular genomic and chromosomal features allowing the analysis of genomic instability for comparative purposes. We determined the frequency of spontaneous induction of Sister Chromatid Exchanges and assessed the relationship between these and structural rearrangements implicated in the evolution of the primates of interest. Overall, A. caraya and C. cay presented a low proportion of statistically significant unstable bands, suggesting fairly stable genomes and the existence of some kind of protection against endogenous damage. In contrast, Ateles showed a highly significant proportion of unstable bands; these were mainly found in the rearranged regions, which is consistent with the numerous genomic reorganizations that might have occurred during the evolution of this genus.

Two cases of polydactyly in wild brown howler monkeys (Alouatta guariba clamitans)

We report the first two cases of polydactyly in an atelid species: (i) a wild ca. 16-week-old infant female presenting seven digits in both feet and other bone malformations and (ii) a wild newborn male presenting six digits in both feet with the extra digit fused to the hallux.