Multicolor fluorescence in situ hybridization (FISH) applied to FISH-banding

During the last decade not only multicolor fluorescence in situ hybridization (FISH) using whole chromosome paints as probes, but also numerous chromosome banding techniques based on FISH have been developed for the human and for the murine genome. This review focuses on such FISH-banding techniques, which were recently defined as 'any kind of FISH technique, which provide the possibility to characterize simultaneously several chromosomal subregions smaller than a chromosome arm. FISH-banding methods fitting that definition may have quite different characteristics, but share the ability to produce a DNA-specific chromosomal banding'. While the standard chromosome banding techniques like GTG lead to a protein-related black and white banding pattern, FISH-banding techniques are DNA-specific, more colorful and, thus, more informative. For some, even high-resolution FISH-banding techniques the development is complete and they can be used for whole genome hybridizations in one step. Other FISH-banding methods are only available for selected chromosomes and/or are still under development. FISH-banding methods have successfully been applied in research in evolution- and radiation-biology, as well as in studies on the nuclear architecture. Moreover, their suitability for diagnostic purposes has been proven in prenatal, postnatal and tumor cytogenetics, indicating that they are an important tool with the potential to partly replace the conventional banding techniques in the future.

Multicolor banding technique, spectral color banding (SCAN): new development and applications

Conventional banding techniques can characterize chromosomal aberrations associated with tumors and congenital diseases with considerable precision. However, chromosomal aberrations that have been overlooked or are difficult to analyze even by skilled cytogeneticists were also often noted. Following the introduction of multicolor karyotyping such as spectral karyotyping (SKY) and multiplex-fluorescence in situ hybridization (M-FISH), it is possible to identify this kind of cryptic or complex aberration comprehensively by a single analysis. To date, multicolor karyotyping techniques have been established as useful tools for cytogenetic analysis. However, since this technique depends on whole chromosome painting probes, it involves limitations in that the origin of aberrant segments can be identified only in units of chromosomes. To overcome these limitations, we have recently developed spectral color banding (SCAN) as a new multicolor banding technique based on the SKY methodology. This new technique may be deemed as an ideal chromosome banding technique since it allows representation of a multicolor banding pattern matching the corresponding G-banding pattern. We applied this technique to the analysis of chromosomal aberrations in tumors that had not been fully characterized by G-banding or SKY and found it capable of (1) detecting intrachromosomal aberrations; (2) identifying the origin of aberrant segments in units of bands; and (3) precisely determining the breakpoints of complex rearrangements. We also demonstrated that SCAN is expected to allow cytogenetic analysis with a constant adequate resolution close to the 400-band level regardless of the degree of chromosome condensation. As compared to the conventional SKY analysis, SCAN has remarkably higher accuracy for a particular chromosome, allowing analysis in units of bands instead of in units of chromosomes and is hence promising as a means of cytogenetic analysis.

Multicolor chromosome bar codes

Chromosome bar codes are multicolor banding patterns produced by fluorescence in situ hybridization (FISH) with differentially labeled and pooled sub-regional DNA probes. These molecular cytogenetic tools facilitate chromosome identification and the delineation of both inter- and intra-chromosomal rearrangements. We present an overview of the various conceptual approaches which can be largely divided into two classes: Simple bar codes designed for chromosome identification and complex bar codes for high resolution aberration screening of entire karyotypes. We address the issue of color redundancy and how to overcome this limitation by complementation of bar codes with whole chromosome painting probes.

Multicolor PRINS and multicolor PNA

Both PRimed IN Situ (PRINS) and Peptide Nucleic Acid (PNA) technologies have emerged as research techniques, but they have quickly evolved to applications in biological diagnosis assays. The two procedures now constitute efficient alternatives to the conventional fluorescence in situ hybridization (FISH) procedure for in situ chromosome identification and aneuploidy detection. They present several advantages (specificity, speed, discriminating ability) that make them very attractive for a number of cytogenetic purposes. Multicolor PRINS and PNA protocols have been described for the specific identification of human chromosomes. Various applications have already been developed in human genetics and new adaptations are ongoing.

Ultra-high resolution array painting facilitates breakpoint sequencing

OBJECTIVE

To describe a considerably advanced method of array painting, which allows the rapid, ultra-high resolution mapping of translocation breakpoints such that rearrangement junction fragments can be amplified directly and sequenced.

METHOD

Ultra-high resolution array painting involves the hybridisation of probes generated by the amplification of small numbers of flow-sorted derivative chromosomes to oligonucleotide arrays designed to tile breakpoint regions at extremely high resolution.

RESULTS AND DISCUSSION

How ultra-high resolution array painting of four balanced translocation cases rapidly and efficiently maps breakpoints to a point where junction fragments can be amplified easily and sequenced is demonstrated. With this new development, breakpoints can be mapped using just two array experiments: the first using whole-genome array painting to tiling resolution large insert clone arrays, the second using ultra-high-resolution oligonucleotide arrays targeted to the breakpoint regions. In this way, breakpoints can be mapped and then sequenced in a few weeks.

Perspectives on the formation of radiation-induced exchange aberrations

Controversy surrounding the proposed mechanism of radiation-induced translocation has existed virtually since the inception of radiation genetics/cytogenetics, some 75 years ago. Chief among these controversies is how close chromosomes have to be to one another at the time of exposure for an exchange to occur. An historically related issue, and one that continues to generate lively debate, is whether both chromosomes participating in an exchange must sustain radiation damage, or whether instead a single damaged site on one chromosome is sufficient. The intent of this paper is to present one person's perspective as we revisit these two long-standing issues, armed with more recent knowledge in three key areas. These include a new-found appreciation for the complexity of chromosome rearrangements; molecular processes of recombination that are likely to be involved; and the architecture of the nucleus regarding the relationship among chromosomes during interphase.

Molecular cytogenetic characterization of chromosome 9-derived material in a human thyroid cancer cell line

The incidence of papillary thyroid carcinoma (PTC) increases significantly after exposure of the head and neck region to ionizing radiation, yet we know neither the steps involved in malignant transformation of thyroid epithelium nor the specific carcinogenic mode of action of radiation. Such increased tumor frequency became most evident in children after the 1986 nuclear accident in Chernobyl, Ukraine. In the eight years following the accident, the average incidence of childhood PTCs (chPTC) increased 70-fold in Belarus, 200-fold in Gomel, 10-fold in the Ukraine and 50-fold in Tschnigov, Kiev, Rovno, Shitomyr and Tscherkassy compared to the rate of about 1 tumor incidence per 106 children per year prior to 1986 (Likhtarev et al., 1995; Sobolev et al., 1997; Jacob et al., 1998). To study the etiology of radiation-induced thyroid cancer, we formed an international consortium to investigate chromosomal changes and altered gene expression in cases of post-Chernobyl chPTC. Our approach is based on karyotyping of primary cultures established from chPTC specimens, establishment of cell lines and studies of genotype-phenotype relationships through high resolution chromosome analysis, DNA/cDNA micro-array studies, and mouse xenografts that test for tumorigenicity. Here, we report the application of fluorescence in situ hybridization (FISH)-based techniques for the molecular cytogenetic characterization of a highly tumorigenic chPTC cell line, S48TK, and its subclones. Using chromosome 9 rearrangements as an example, we describe a new approach termed 'BAC-FISH' to rapidly delineate chromosomal breakpoints, an important step towards a better understanding of the formation of translocations and their functional consequences.

Cross-species chromosome painting

Comparative genomics is an important and expanding field of research, and the genome-wide comparison of the chromosome constitution of different species makes a major contribution to this field. Cross-species chromosome painting is a powerful technique for establishing chromosome homology maps, defining the sites of chromosome fusions and fissions, investigating chromosome rearrangements during evolution and constructing ancestral karyotypes. Here the protocol for cross-species chromosome painting is presented. It includes sections on cell culture and metaphase preparation, labeling of chromosome-specific DNA, fluorescent in situ hybridization (chromosome painting) and image analysis. Cell culture and metaphase preparation can take between 1 and 2 wk depending on the cell culture. Labeling of chromosome-specific DNA is completed in 1 d. Fluorescent in situ hybridization can be completed in a maximum of 4 d.

A procedure for image enhancement in chromosome painting

An image enhancement procedure was developed to produce high-contrast chromosome paint images. This procedure is well suited for images where brightness-contrast enhancement is subjective. Three examples are given to show that the procedure is very efficient to remove non-specific hybridization signals from the chromosome paint image. Chromosomes of roe deer contain large amounts of centromeric heterochromatic DNA. Echidna chromosomes show specific heterochromatic DNA distributed over several chromosomes. In both cases chromosome identification was hampered by bright heterochromatic regions. The enhancement tool was fully used in cross-species chromosome painting, which is the last example. The three examples show that the procedure is very simple to use and removes background in a controlled and defined manner.

Retrospective Assessment of Radiation Exposure Using Biological Dosimetry: Chromosome Painting, Electron Paramagnetic Resonance and the Glycophorin A Mutation Assay

Biological monitoring of dose can contribute important, independent estimates of cumulative radiation exposure in epidemiological studies, especially in studies in which the physical dosimetry is lacking. Three biodosimeters that have been used in epidemiological studies to estimate past radiation exposure from external sources will be highlighted: chromosome painting or FISH (fluorescence in situ hybridization), the glycophorin A somatic mutation assay (GPA), and electron paramagnetic resonance (EPR) with teeth. All three biodosimeters have been applied to A-bomb survivors, Chernobyl clean-up workers, and radiation workers. Each biodosimeter has unique advantages and limitations depending upon the level and type of radiation exposure. Chromosome painting has been the most widely applied biodosimeter in epidemiological studies of past radiation exposure, and results of these studies provide evidence that dose-related translocations persist for decades. EPR tooth dosimetry has been used to validate dose models of acute and chronic radiation exposure, although the present requirement of extracted teeth has been a disadvantage. GPA has been correlated with physically based radiation dose after high-dose, acute exposures but not after low-dose, chronic exposures. Interindividual variability appears to be a limitation for both chromosome painting and GPA. Both of these techniques can be used to estimate the level of past radiation exposure to a population, whereas EPR can provide individual dose estimates of past exposure. This paper will review each of these three biodosimeters and compare their application in selected epidemiological studies.

Multidirectional chromosome painting reveals a remarkable syntenic homology between the greater galagos and the slow loris

We report on the first reciprocal chromosome painting of lorisoids and humans. The chromosome painting showed a remarkable syntenic homology between Otolemur and Nycticebus. Eight derived syntenic associations of human segments are common to both Otolemur and Nycticebus, indicative of a considerable period of common evolution between the greater galago and the slow loris. Five additional Robertsonian translocations form the slow loris karyotype, while the remaining chromosomes are syntenically equivalent, although some differ in terms of centromere position and heterochromatin additions. Strikingly, the breakpoints of the human chromosomes found fragmented in these two species are apparently identical. Only fissions of homologs to human chromosomes 1 and 15 provide significant evidence of a cytogenetic link between Lemuriformes and Lorisiformes. The association of human chromosomes 7/16 in both lorisoids strongly suggests that this chromosome was present in the ancestral primate genome.

Phylogenomics of several deer species revealed by comparative chromosome painting with Chinese muntjac paints

A set of Chinese muntjac (Muntiacus reevesi) chromosome-specific paints has been hybridized onto the metaphases of sika deer (Cervus nippon, CNI, 2n = 66), red deer (Cervus elaphus, CEL, 2n = 62) and tufted deer (Elaphodus cephalophus, ECE, 2n = 47). Thirty-three homologous autosomal segments were detected in genomes of sika deer and red deer, while 31 autosomal homologous segments were delineated in genome of tufted deer. The Chinese muntjac chromosome X probe painted to the whole X chromosome, and the chromosome Y probe gave signals on the Y chromosome as well as distal region of the X chromosome of each species. Our results confirmed that exclusive Robertsonian translocations have contributed to the karyotypic evolution of sika deer and red deer. In addition to Robertsonian translocation, tandem fusions have played a more important role in the karyotypic evolution of tufted deer. Different types of chromosomal rearrangements have led to great differences in the genome organization between cervinae and muntiacinae species. Our analysis testified that six chromosomal fissions in the proposed 2n = 58 ancestral pecoran karyotype led to the formation of 2n = 70 ancestral cervid karyotype and the deer karyotypes is more derived compare with those of bovid species. Combining previous cytogenetic and molecular systematic studies, we analyzed the genome phylogeny for 11 cervid species.

Reconstruction of a 450-My-old ancestral vertebrate protokaryotype

From recent work the putative eutherian karyotype from 100 Mya has been derived. Here, we have applied a new in silico technique, electronic chromosome painting (E-painting), on a large data set of genes whose positions are known in human, chicken, zebrafish and pufferfish. E-painting identifies conserved syntenies in the data set, and it enables a stepwise reconstruction of the ancestral vertebrate protokaryotype comprising 11 protochromosomes. During karyotype evolution in land vertebrates interchromosomal rearrangements by translocation are relatively frequent, whereas the karyotypes of birds and fish are much more conserved. Although the human karyotype is one of the most conserved in eutherians, it can no longer be considered highly conserved from a vertebrate-wide perspective.

Cross-species chromosome painting unveils cytogenetic signatures for the Eulipotyphla and evidence for the polyphyly of Insectivora

Insectivore-like animals are traditionally believed among the first eutherian mammals that have appeared on the earth. The modern insectivores are thus crucial for understanding the systematics and phylogeny of eutherian mammals as a whole. Here cross-species chromosome painting, with probes derived from flow-sorted chromosomes of human, was used to delimit the homologous chromosomal segments in two Soricidae species, the common shrew (Sorex araneus, 2n = 20/21), and Asiatic short-tailed shrew (Blarinella griselda, 2n = 44), and one Erinaceidae species, the shrew-hedgehog (Neotetracus sinensis, 2n = 32), and human. We report herewith the first comparative maps for the Asiatic short-tailed shrew and the shrew-hedgehog, in addition to a refined comparative map for the common shrew. In total, the 22 human autosomal paints detected 40, 51 and 58 evolutionarily conserved segments in the genomes of common shrew, Asiatic short-tailed shrew, and shrew-hedgehog, respectively, demonstrating that the common shrew has retained a conserved genome organization while the Asiatic short-tailed shrew and shrew-hedgehog have relatively rearranged genomes. In addition to confirming the existence of such ancestral human segmental combinations as HSA 3/21, 12/22, 14/15 and 7/16 that are shared by most eutherian mammals, our study reveals a shared human segmental combination, HSA 4/20, that could phylogenetically unite the Eulipotyphlan (i.e., the core insectivores) species. Our results provide cytogenetic evidence for the polyphyly of the order Insectivora and additional data for the eventual reconstruction of the ancestral eutherian karyotype.

Direct labelling of BAC-DNA by rolling-circle amplification

Efficient amplification and labelling of probes are crucial for successful sequence detection by fluorescent in situ hybridization (FISH). In particular, chromosome painting to visualize chromosome segments or entire chromosomes by FISH requires large amounts of probes derived from extended templates. There are a number of techniques for probe labelling. The most widespread is nick translation, based on the replicational incorporation of modified nucleotides. Here we demonstrate successful rolling-circle amplification (RCA) of very low amounts of long circular template sequences (single bacterial artificial chromosomes (BACs) or pools of BACs). The amplicons were suitable for labelling by nick translation and subsequent FISH. A novel achievement is the use of RCA for simultaneous amplification and labelling of single BACs or BAC pools in a labour- and cost-effective manner.

The suitability of FISH chromosome painting and ESR-spectroscopy of tooth enamel assays for retrospective dose reconstruction

A comparative analysis of two groups of highly irradiated victims was carried out in order to evaluate the suitability of two assays for retrospective dose assessment: late translocations and electron spin resonance (ESR) dosimetry. The first group comprised 24 subjects who exhibited acute radiation syndrome (ARS) due to overexposure as a result of nuclear submarine accidents during the period 1961-1985. Their grades of ARS and individual doses were ascertained by Navy physicians who carried out primary examinations and treatment of the exposed seamen. Cytogenetic analyses were made 16-40 y after their accidents. During medical treatment seven tooth samples were collected for ESR analysis from this group. The second group consisted of ten highly irradiated men from the Chernobyl accident. Comparison was made between estimates of their average whole-body penetrating radiation doses derived from several biological parameters. In three cases ESR measurements on tooth enamel from this group were also made. Retrospective dosimetry using FISH translocations was attempted 10-13 y later. Yields of late translocations were in good agreement with initially estimated doses and with doses obtained by ESR spectroscopy analysis of tooth enamel long after exposure. It was concluded that both persisting stable translocations and ESR spectroscopy signals are suitable with similar efficiencies for retrospective biodosimetry after acute whole-body exposure.

Characterization of the TSU-PR1 cell line by chromosome painting and flow cytometry

TSU-PR1 was originally reported as a prostatic carcinoma cell line derived from a lymph node metastasis. Recently, however, this cell line was reported to be derived from T24 bladder carcinoma cells, and thus further definition of its origin is needed. Conventional cytogenetic study of TSU-PR1 showed aneuploidy, ranging from 65 to 86 chromosome with a modal number of 80, and with 10 marker chromosomes, thus conventional cytogenetics cannot be used to determine which chromosomes or regions of chromosomes are critical in cancer development and progression of this cell line. The present study was conducted to characterize genetic changes of the cell line using comparative genomic hybridization (CGH), fluorescence in situ hybridization (FISH), and flow cytometry. CGH results showed that green-to-red fluorescence ratios were within the range of 0.85-1.15, except for a few chromosomes, which reflected near tetraploidy in TSU-PR1. Flow cytometric analysis of TSU-PR1 revealed a DNA index of 3.46n, which is close to the 3.48n calculated from a modal number of 80. The copy numbers of chromosomes 4, 6, 7, 17, and 20 determined by the DNA index and the CGH analyses were 2.85 +/- 0.09, 3.22 +/- 0.77, 3.01 +/- 0.26, 4.05 +/- 0.44, and 4.99 +/- 0.48, respectively. These numbers are also in accordance with the chromosome copy numbers determined with FISH: 2.98 +/- 0.23, 2.91 +/- 0.44, 2.74 +/- 0.44, 3.93 +/- 0.38, and 5.05 +/- 0.78 for chromosomes 4, 6, 7, 17, and 20, respectively (P > 0.05).

Chromosome reshuffling in birds of prey: the karyotype of the world's largest eagle (Harpy eagle, Harpia harpyja) compared to that of the chicken (Gallus gallus)

Like various other diurnal birds of prey, the world's largest eagle, the Harpy (Harpia harpyja), presents an atypical bird karyotype with 2n=58 chromosomes. There is little knowledge about the dramatic changes in the genomic reorganization of these species compared to other birds. Since recently, the chicken provides a "default map" for various birds including the first genomic DNA sequence of a bird species. Obviously, the gross division of the chicken genome into relatively gene-poor macrochromosomes and predominantly gene-rich microchromosomes has been conserved for more than 150 million years in most bird species. Here, we present classical features of the Harpy eagle karyotype but also chromosomal homologies between H. harpyja and the chicken by chromosome painting and comparison to the chicken genome map. We used two different sets of painting probes: (1) chicken chromosomes were divided into three size categories: (a) macrochromosomes 1-5 and Z, (b) medium-sized chromosomes 6-10, and (c) 19 microchromosomes; (2) combinatorially labeled chicken chromosome paints 1-6 and Z. Both probe sets were visualized on H. harpyja chromosomes by multicolor fluorescence in situ hybridization (FISH). Our data show how the organization into micro- and macrochromosomes has been lost in the Harpy eagle, seemingly without any preference or constraints.

Chromosome rearrangements in canine fibrosarcomas

We have previously reported the use of six- and seven-color paint sets in the analysis of canine soft tissue sarcomas. Here we combine this technique with flow sorting of translocation chromosomes, reverse painting, and polymerase chain reaction (PCR) analysis of the gene content of the reverse paint in order to provide a more detailed analysis of cytogenetic abnormalities in canine tumors. We examine two fibrosarcomas, both from female Labrador retrievers, and show abnormalities in chromosomes 11 and 30 in both cases. Evidence of involvement of TGFBR1 is presented for one tumor.

Comparative map between the domestic pig and dog

Cross-species chromosome painting with probes derived from flow-sorted dog and human chromosomes was used to construct a high-resolution comparative map for the pig. In total 98 conserved autosomal segments between pig and dog were detected by probes specific for the 38 autosomes and X Chromosome of the dog. Further integration of our results with the published human--dog and cat--dog comparative maps, and with data from comparative gene mapping, increases the resolution of the current pig--human comparative map. It allows for the conserved syntenies detected in the pig, human, and cat to be aligned against the putative ancestral karyotype of eutherian mammals and for the history of karyotype evolution of the pig lineage to be reconstructed. Fifteen fusions, 17 fissions, and 23 inversions are required to convert the ancestral mammalian karyotype into the extant karyotype of the pig.

Absence of mouse REC8 cohesin promotes synapsis of sister chromatids in meiosis

REC8 is a key component of the meiotic cohesin complex. During meiosis, cohesin is required for the establishment and maintenance of sister-chromatid cohesion, for the formation of the synaptonemal complex, and for recombination between homologous chromosomes. We show that REC8 has an essential role in mammalian meiosis, in that Rec8 null mice of both sexes have germ cell failure and are sterile. In the absence of REC8, early chromosome pairing events appear normal, but synapsis occurs in a novel fashion: between sister chromatids. This implies that a major role for REC8 in mammalian meiosis is to limit synapsis to between homologous chromosomes. In all other eukaryotic species studied to date, REC8 phenotypes have been restricted to meiosis. Unexpectedly, Rec8 null mice are born in sub-Mendelian frequencies and fail to thrive. These findings illuminate hitherto unknown REC8 functions in chromosome dynamics during mammalian meiosis and possibly in somatic development.

Karyotypic conservatism in the suborder Feliformia (Order Carnivora)

Multidirectional comparative chromosome painting was used to investigate the karyotypic relationships among representative species from three Feliformia families of the order Carnivora (Viverridae, Hyaenidae and Felidae). Complete sets of painting probes derived from flow-sorted chromosomes of the domestic dog, American mink, and human were hybridized onto metaphases of the spotted hyena (Crocuta crocuta, 2n = 40) and masked palm civet (Paguma larvata, 2n = 44). Extensive chromosomal conservation is evident in these two species when compared with the cat karyotype, and only a few events of chromosome fusion, fission and inversion differentiate the karyotypes of these Feliformia species. The comparative chromosome painting data have enabled the integration of the hyena and palm civet chromosomes into the previously established comparative map among the domestic cat, domestic dog, American mink and human and improved our understanding on the karyotype phylogeny of Feliformia species.

New insights into the karyotypic relationships of Chinese muntjac (Muntiacus reevesi), forest musk deer (Moschus berezovskii) and gayal (Bos frontalis)

To investigate the karyotypic relationships between Chinese muntjac (Muntiacus reevesi), forest musk deer (Moschus berezovskii) and gayal (Bos frontalis), a complete set of Chinese muntjac chromosome-specific painting probes has been assigned to G-banded chromosomes of these three species. Sixteen autosomal probes (i.e. 6-10, 12-22) of the Chinese muntjac each delineated one pair of conserved segments in the forest musk deer and gayal, respectively. The remaining six autosomal probes (1-5, and 11) each delineated two to five pairs of conserved segments. In total, the 22 autosomal painting probes of Chinese muntjac delineated 33 and 34 conserved chromosomal segments in the genomes of forest musk deer and gayal, respectively. The combined analysis of comparative chromosome painting and G-band comparison reveals that most interspecific homologous segments show a high degree of conservation in G-banding patterns. Eleven chromosome fissions and five chromosome fusions differentiate the karyotypes of Chinese muntjac and forest musk deer; twelve chromosome fissions and six fusions are required to convert the Chinese muntjac karyotype to that of gayal; one chromosome fission and one fusion separate the forest musk deer and gayal. The musk deer has retained a highly conserved karyotype that closely resembles the proposed ancestral pecoran karyotype but shares none of the rearrangements characteristic for the Cervidae and Bovidae. Our results substantiate that chromosomes 1-5 and 11 of Chinese muntjac originated through exclusive centromere-to-telomere fusions of ancestral acrocentric chromosomes.

Reciprocal painting between humans, De Brazza's and patas monkeys reveals a major bifurcation in the Cercopithecini phylogenetic tree

We report on reciprocal painting between humans and two Cercopithecini species, Erythrocebus patas (patas monkey) and Cercopithecus neglectus (De Brazza's monkey). Both human and monkeys chromosome-specific probes were made by degenerate oligonucleotide primed PCR (DOP-PCR) from flow sorted chromosomes. Metaphases of both monkey species were first hybridized with human chromosome-specific probes and then human metaphases were hybridized with chromosome paints from each monkey species. The human paint probes detected 34 homologous segments on the C. neglectus karyotype, while the C. neglectus probes, including the Y, revealed 41 homologous segments on the human karyotype. The probes specific for human chromosomes detected 29 homologous segments in the E. patas karyotype, while the patas monkey probes painted 34 segments on the human karyotype. We tested various hypotheses of Cercopithecini phylogeny and taxonomy developed by morphologists, molecular biologists and cytogeneticists. Our hybridization data confirm that fissions (both Robertsonian and non-Robertsonian) are the main mechanism driving the evolutionary trend in Cercopithecini toward higher diploid numbers and strongly suggest an early phylogenetic bifurcation in Cercopithecini. One branch leads to Cercopithecus neglectus/Cercopithecus wolfi while the other line leads to Erythrocebus patas/Chlorocebus aethiops. Allenopithecus nigroviridis may have diverged prior to this major phylogenetic node.

Application of molecular cytogenetics for chromosomal evolution of the Lemuriformes (Prosimians)

R-banding chromosomal studies of 21 species of Lemuriformes allowed us to reconstruct the presumed ancestral karyotype of all the Lemuriformes except for Daubentoniidae and permitted the construction of their phylogenetic tree. Chromosome painting with fluorescently labeled heterologous DNA probes permitted comparative chromosome maps to be established. The Zoo-FISH method was used to reassess the karyotypes of 22 species or subspecies. While our results largely confirm the previous reconstruction of the ancestral karyotype, they resulted in a modification of the previously established phylogenetic tree. The Daubentoniidae emerged first followed by the divergence of the families Cheirogaleidae, Indriidae, Lepilemuridae and Lemuridae. Eight chromosome rearrangements occurred in all Lemuriformes except for Daubentoniidae in the common trunk. The present findings do not allow us to propose the occurrence of any rearrangement common to Daubentoniidae and other Lemuriformes, and probably other Prosimii. Conserved syntenies previously described in various mammalian orders were also conserved, while others were specific to the Lemuriformes.