Molecular Cytogenetic Analysis of One African and Five Asian Macaque Species Reveals Identical Karyotypes as in Mandrill.

BACKGROUND: The question how evolution and speciation work is one of the major interests of biology. Especially, genetic including karyotypic evolution within primates is of special interest due to the close phylogenetic position of Macaca and Homo sapiens and the role as in vivo models in medical research, neuroscience, behavior, pharmacology, reproduction and Acquired Immune Deficiency Syndrome (AIDS). MATERIALS & METHODS: Karyotypes of five macaque species from South East Asia and of one macaque species as well as mandrill from Africa were analyzed by high resolution molecular cytogenetics to obtain new insights into karyotypic evolution of old world monkeys. Molecular cytogenetics applying human probes and probe sets was applied in chromosomes of Macaca arctoides, M. fascicularis, M. nemestrina, M. assamensis, M. sylvanus, M. mulatta and Mandrillus sphinx. Established two- to multicolor-fluorescence in situ hybridization (FISH) approaches were applied. Locus-specific probes, whole and partial chromosome paint probes were hybridized. Especially the FISH-banding approach multicolor-banding (MCB) as well as probes oriented towards heterochromatin turned out to be highly efficient for interspecies comparison. CONCLUSION: Karyotypes of all seven studied species could be characterized in detail. Surprisingly, no evolutionary conserved differences were found among macaques, including mandrill. Between the seven here studied and phenotypically so different species we expected several via FISH detectable karyoypic and submicroscopic changes and were surprised to find none of them on a molecular cytogenetic level. Spatial separation, may explain the speciation and different evolution for some of them, like African M. sylvanus, Mandrillus sphinx and the South Asian macaques. However, for the partially or completely overlapping habitats of the five studied South Asian macaques the species separation process can also not be deduced to karyotypic separation.

Comprehensive characterization of evolutionary conserved breakpoints in four New World Monkey karyotypes compared to Chlorocebus aethiops and Homo sapiens.

Comparative cytogenetic analysis in New World Monkeys (NWMs) using human multicolor banding (MCB) probe sets were not previously done. Here we report on an MCB based FISH-banding study complemented with selected locus-specific and heterochromatin specific probes in four NWMs and one Old World Monkey (OWM) species, i.e. in Alouatta caraya (ACA), Callithrix jacchus (CJA), Cebus apella (CAP), Saimiri sciureus (SSC), and Chlorocebus aethiops (CAE), respectively. 107 individual evolutionary conserved breakpoints (ECBs) among those species were identified and compared with those of other species in previous reports. Especially for chromosomal regions being syntenic to human chromosomes 6, 8, 9, 10, 11, 12 and 16 previously cryptic rearrangements could be observed. 50.4% (54/107) NWM-ECBs were colocalized with those of OWMs, 62.6% (62/99) NWM-ECBs were related with those of Hylobates lar (HLA) and 66.3% (71/107) NWM-ECBs corresponded with those known from other mammalians. Furthermore, human fragile sites were aligned with the ECBs found in the five studied species and interestingly 66.3% ECBs colocalized with those fragile sites (FS). Overall, this study presents detailed chromosomal maps of one OWM and four NWM species. This data will be helpful to further investigation on chromosome evolution in NWM and hominoids in general and is prerequisite for correct interpretation of future sequencing based genomic studies in those species.

First detailed reconstruction of the karyotype of Trachypithecus cristatus (Mammalia: Cercopithecidae).

BACKGROUND: The chromosomal homologies of human (Homo sapiens = HSA) and silvered leaf monkey (Trachypithecus cristatus = TCR) have been previously studied by classical chromosome staining and by fluorescence in situ hybridization (FISH) applying chromosome-specific DNA probes of all human chromosomes in the 1980s and 1990s, respectively. RESULTS: However, as the resolution of these techniques is limited we used multicolor banding (MCB) at an ~250-band level, and other selected human DNA probes to establish a detailed chromosomal map of TCR. Therefore it was possible to precisely determine evolutionary conserved breakpoints, orientation of segments and distribution of specific regions in TCR compared to HSA. Overall, 69 evolutionary conserved breakpoints including chromosomal segments, which failed to be resolved in previous reports, were exactly identified and characterized. CONCLUSIONS: This work also represents the first molecular cytogenetic one characterizing a multiple sex chromosome system with a male karyotype 44,XY1Y2. The obtained results are compared to other available data for old world monkeys and drawbacks in hominoid evolution are discussed.

Flying lemurs--the 'flying tree shrews'? Molecular cytogenetic evidence for a Scandentia-Dermoptera sister clade.

BACKGROUND: Flying lemurs or Colugos (order Dermoptera) represent an ancient mammalian lineage that contains only two extant species. Although molecular evidence strongly supports that the orders Dermoptera, Scandentia, Lagomorpha, Rodentia and Primates form a superordinal clade called Supraprimates (or Euarchontoglires), the phylogenetic placement of Dermoptera within Supraprimates remains ambiguous. RESULTS: To search for cytogenetic signatures that could help to clarify the evolutionary affinities within this superordinal group, we have established a genome-wide comparative map between human and the Malayan flying lemur (Galeopterus variegatus) by reciprocal chromosome painting using both human and G. variegatus chromosome-specific probes. The 22 human autosomal paints and the X chromosome paint defined 44 homologous segments in the G. variegatus genome. A putative inversion on GVA 11 was revealed by the hybridization patterns of human chromosome probes 16 and 19. Fifteen associations of human chromosome segments (HSA) were detected in the G. variegatus genome: HSA1/3, 1/10, 2/21, 3/21, 4/8, 4/18, 7/15, 7/16, 7/19, 10/16, 12/22 (twice), 14/15, 16/19 (twice). Reverse painting of G. variegatus chromosome-specific paints onto human chromosomes confirmed the above results, and defined the origin of the homologous human chromosomal segments in these associations. In total, G. variegatus paints revealed 49 homologous chromosomal segments in the HSA genome. CONCLUSION: Comparative analysis of our map with published maps from representative species of other placental orders, including Scandentia, Primates, Lagomorpha and Rodentia, suggests a signature rearrangement (HSA2q/21 association) that links Scandentia and Dermoptera to one sister clade. Our results thus provide new evidence for the hypothesis that Scandentia and Dermoptera have a closer phylogenetic relationship to each other than either of them has to Primates.

Genetic relationships of langur species using AFLP markers.

Cytogenetic studies of five langur species using conventional banding pattern were investigated. All species studied have an identical number of 44 diploid chromosomes, they are assumed to have common evolutionary relationships. For in depth study, molecular markers were assessed using the Amplified Fragment Length Polymorphism (AFLP) method. With seven successful primer combinations, a total of 1043 scorable bands were generated. The percentage of polymorphic bands for each primer ranged from 48.60 to 94.12%. The resulting bands were used for dendrogram construction. From the dendrogram, the individuals of Trachypithecus species are grouped into two major clusters, T. phayrei is clustered with T. obscurus, while T. cristatus is clustered with T. francoisi. The bootstrap value between two groups is 94%. The other cluster, Presbytis femoralis is separated from the Trachypithecus species with a bootstrap value of 94%. Averages of inter-specific genetic similarity values among all langur species studied are 70.16% (between T. obscurus and P. femoralis) to 88.12% (between T. phayrei and T. obscurus). In summary T. phayrei might be a subspecies of T. obscurus. The development of specific molecular markers of a species is beneficial for genetic differentiation of this group of primates.

Analysis of the genetic relationships among Thai gibbon species using AFLP markers.

Cytogenetic studies of three gibbon species using conventional banding patterns were investigated showing an identical number of 44 diploid chromosomes. They are assumed to have common evolutionary relationships. For in depth study, molecular markers were assessed using the Amplified Fragment Length Polymorphism (AFLP) method. With seven successful primer combinations, a total of 1669 scorable bands were generated. The resulting bands were used for dendrogram construction. From the dendrogram, the individuals of Hylobates lar are closely related to H. agilis more than H. pileatus with a bootstrap value of 78%. Averages of inter-specific genetic similarity values among all gibbon species studied are 67.15% (between H. lar and H. pileatus) to 71.03% (between H. lar and H. agilis). In summary three gibbon species show genetic stability within a species. The development of specific molecular markers of a species is beneficial for genetic differentiation of this group of primates.

Genetic relationships among wild Felidae in Thailand using AFLP markers.

The cytogenetics of eight Felidae species in Thailand were investigated by the colchicines-hypotonic fixation-air drying technique followed by a conventional technique. All species studied have an identical number of 38 diploid chromosomes, indicating a close genetic relationship among species. At a deep study level, the genetic relationships of eight Felidae species were accessed by the AFLP method. Blood samples were collected from sources locating in their original regions for DNA extraction. With ten successful primer combinations, a total of 4208 scorable bands were generated. Of these bands, 18.91% are polymorphic. Percentages of Polymorphic Bands (PPB) for each primer combination range from 15.00 to 23.59%. The generating bands were used for dendrogram construction. The average genetic similarity values among all Felidae species are 68.20% (between Panthera tigris and Neofelis nebulosa) to 85.53% (between Prionailurus bengalensis and Prionailurus viverrinus). The dendrogram shows that the eight Felidae species were clustered together and the subfamily Pantherinae and Felinae with Neofelis nebulosa are distinguished. The Felinae, Prionailurus bengalensis, Prionailurus viverrinus, Catopuma temminckii, Felis chaus, Pardofelis marmorata and Neofelis nebulosa were clustered together with 91% bootstrap support and the Pantherinae, Panthera pardus is clustered with Panthera tigris with 92% bootstrap support. In summary, the ten successful primer combinations can be used to determine genetic differences among eight Thailand Felidae species.

New Robertsonian translocation chromosomes in captive Thai gaur (Bos gaurus readei).

Robertsonian translocation have been well documented in domestic cattle, with the most commonly occurring fusion involving chromosomes 1 and 29. The widespread nature of this translocation is indicative of its ancient origin. Fifty Giemsa's stained metaphase spreads derived from lymphocyte cultures of the Thai gaur were analyzed for each animal. The Thai gaur had diploid chromosome number of 2n = 57 in male and 2n = 56 in female instead of the normal 2n = 58. The 2n = 57 in male chromosomes presence of an extra submetacentric chromosome and loss of two acrocentric chromosomes was observed [XY, 57, rob (1;29)]. The 2n = 56 in female chromosomes presence of two extra submetacentric chromosomes and loss of four acrocentric chromosomes was observed [XX, 56, rob (1;29)]. Results from the Giemsa's stained analyses confirm that the two autosomes (2n = 57) and four autosomes (2n = 56) involved in the translocation are the bovine homologues 1 and 29.