Homologous Chromosome Segments Research Articles

The concept of natural genome reconstruction.Part 1. Basic provisions of the "natural genome reconstruction" concept. Changing the genome of hematopoietic stem cells using several natural cellular mechanisms that are inherent in the hematopoietic cell and determine its biological status as "the source of the body's reparative potential".

We present a series of articles proving the existence of a previously unknown mechanism of interaction between hematopoietic stem cells and extracellular double-stranded DNA (and, in particular, double-stranded DNA of the peripheral bloodstream), which explains the possibility of emergence and fixation of genetic information contained in double-stranded DNA of extracellular origin in hematopoietic stem cells. The concept of the possibility of stochastic or targeted changes in the genome of hematopoietic stem cells is formulated based on the discovery of new, previously unknown biological properties of poorly differentiated hematopoietic precursors. The main provisions of the concept are as follows. The hematopoietic stem cell takes up and internalizes fragments of extracellular double-stranded DNA via a natural mechanism. Specific groups of glycocalyx factors, including glycoproteins/proteoglycans, glycosylphosphatidylinositol-anchored proteins and scavenger receptors, take part in the internalization event. The binding sites for DNA fragments are heparin-binding domains and clusters of positively charged amino acid residues that are parts of protein molecules of these factors. Extracellular fragments delivered to the internal compartments of hematopoietic stem cells initiate terminal differentiation, colony formation, and proliferation of hematopoietic precursors. The molecular manifestation of these processes is the emergence and repair of pangenomic single-strand breaks. The occurrence of pangenomic single-strand breaks and restoration of genome (genomic DNA) integrity are associated with activation of a "recombinogenic situation" in the cell; during its active phase, stochastic homologous recombination or other recombination events between extracellular fragments localized in the nucleus and chromosomal DNA are possible. As a result, genetic material of initially extracellular localization either integrates into the recipient genome with the replacement of homologous chromosomal segments, or is transitively present in the nucleus and can manifest itself as a new genetic trait. It is assumed that as a result of stochastic acts of homologous exchange, chromosome loci are corrected in hematopoietic stem cells that have acquired mutations during the existence of the organism, which are the cause of clonal hematopoiesis associated with old age. In this regard, there is a fundamental possibility of changing the hematopoietic status of hematopoietic stem cells in the direction of polyclonality and the original diversity of clones. Such events can form the basis for the rejuvenation of the blood-forming cell system. The results of the laboratory's work indicate that other stem cells in the body capture extracellular DNA fragments too. This fact creates a paradigm for the overall rejuvenation of the body.

Meiosis Remodeled: Inclusion of New Parts to Poppit Bead Models Enhances Understanding of Meiosis

A long-standing tradition uses strings of poppit beads of different colors to model meiosis, especially to show how segments of paired homologous chromosomes are recombined. Our use of orthodontic latex bands to model cohesion of sister chromatids, and plastic coffee stirrers as microtubules, extends what can normally be achieved with &lsquo;standard&rsquo; commercial kits of beads, so emphasizing the importance of four key elements of meiosis: (a) the role of chromosome replication before meiosis itself begins; (b) pairing and exchange (chiasma formation) of homologous chromosomes during meiosis I; (c) centromere (kinetochore) attachment and orientation within/on the spindle during meiosis I and meiosis II; and (d) the differential loss of arm and centromere cohesion at onset of anaphase I and anaphase II. These are essential elements of meiosis that students best need to visualize, not just read and think about. Bead modeling leads them in that direction, as our gallery of figures and accompanying text show. <em>Primary image:&nbsp;</em>Unassembled components of &lsquo;PoppitMeiosis&rsquo; &ndash; a poppit bead exercise aimed at student learning of meiosis. Beads are snapped together to model bivalent chromosomes (on the right side), with double-stick tape (top) representing the synaptonemal complex, orthodontic latex bands representing cohesion rings, and coffee stirrers representing microtubule bundles that connect centromeres to the spindle poles.

DNA Crossover Motifs Associated with Epigenetic Modifications Delineate Open Chromatin Regions in Arabidopsis.

The rate of crossover, the reciprocal exchanges of homologous chromosomal segments, is not uniform along chromosomes differing between male and female meiocytes. To better understand the factors regulating this variable landscape, we performed a detailed genetic and epigenetic analysis of 737 crossover events in Arabidopsis thaliana. Crossovers were more frequent than expected in promoters. Three DNA motifs enriched in crossover regions and less abundant in crossover-poor pericentric regions were identified. One of these motifs, the CCN repeat, was previously unknown in plants. The A-rich motif was preferentially associated with promoters, while the CCN repeat and the CTT repeat motifs were preferentially associated with genes. Analysis of epigenetic modifications around the motifs showed, in most cases, a specific epigenetic architecture. For example, we show that there is a peak of nucleosome occupancy and of H3K4me3 around the CCN and CTT repeat motifs while nucleosome occupancy was lowest around the A-rich motif. Cytosine methylation levels showed a gradual decrease within ∼2 kb of the three motifs, being lowest at sites where crossover occurred. This landscape was conserved in the decreased DNA methylation1 mutant. In summary, the crossover motifs are associated with epigenetic landscapes corresponding to open chromatin and contributing to the nonuniformity of crossovers in Arabidopsis.

UPDtool: a tool for detection of iso- and heterodisomy in parent–child trios using SNP microarrays

UPDtool is a computational tool for detection and classification of uniparental disomy (UPD) in trio SNP-microarray experiments. UPDs are rare events of chromosomal malsegregation and describe the condition of two homologous chromosomes or homologous chromosomal segments that were inherited from one parent. The occurrence of UPD can be of major clinical relevance. Though high-throughput molecular screening techniques are widely used, detection of UPDs and especially the subclassification remains complex. We developed UPDtool to detect and classify UPDs from SNP microarray data of parent-child trios. The algorithm was tested using five positive controls including both iso- and heterodisomic segmental UPDs and 30 trios from the HapMap project as negative controls. With UPDtool, we were able to correctly identify all occurrences of non-mosaic UPD within our positive controls, whereas no occurrence of UPD was found within our negative controls. In addition, the chromosomal breakage points could be determined more precisely than by microsatellite analysis. Our results were compared with both the gold standard, microsatellite analysis and SNPtrio, another program available for UPD detection. UPDtool is platform independent, light weight and flexible. Because of its simple input format, UPDtool may also be used with other high-throughput technologies (e.g., next-generation sequencing). UPDtool executables, documentation and examples can be downloaded from http://www.uni-tuebingen.de/uni/thk/de/f-genomik-software.html.

Comparative Cytogenetics of Hamsters of the Genus Allocricetulus Argyropulo 1932 (Cricetidae, Rodentia)

Chromosome painting and G-banding analyses were used to delimit homologous chromosomal segments among 4 taxa of the hamsters genus Allocricetulus Argyropulo 1932 (Cricetidae, Murоidea, Rodentia) - A. curtatus (2n = 20), A. eversmanni eversmanni, A. eversmanni pseudocurtatus, and the hybrid A. eversmanni beljaevi × A. eversmanni pseudocurtatus (all 2n = 26). Comparative maps between the 4 karyotypes were established based on chromosome painting of chromosome-specific probes from the Syrian hamster (Mesocricetus auratus, 2n = 44). A putative ancestral karyotype for the genus Allocricetulus (AAK) was proposed and contains 12-13 ancestral autosomal elements. Integrated maps demonstrate extended conservation of syntenies within this rodent genus and show the predominant role of Robertsonian rearrangements in the karyotype evolution of the genus Allocricetulus. At the cytogenetic level, we clearly demonstrate karyological differences between karyotypes of species (A. curtatus vs. A. eversmanni) and subspecies A. e. eversmanni and A. e. beljaevi versus A. e. pseudocurtatus, but the karyotypes of A. e. eversmanni and A. e. beljaevi are identical at this level of resolution.

Homologous chromosomes make contact at the sites of double-strand breaks in genes in somatic G0/G1-phase human cells.

Double-strand DNA breaks (DSBs) are continuously induced in cells by endogenously generated free radicals and exogenous genotoxic agents such as ionizing radiation. DSBs activate the kinase activity in sensor proteins such as ATM and DNA-PK, initiating a complex DNA damage response that coordinates various DNA repair pathways to restore genomic integrity. In this study, we report the unexpected finding that homologous chromosomes contact each other at the sites of DSBs induced by either radiation or the endonuclease I-PpoI in human somatic cells. Contact involves short segments of homologous chromosomes and is centered on a DSB in active genes but does not occur at I-PpoI sites in intergenic DNA. I-PpoI-induced contact between homologous genes is abrogated by the transcriptional inhibitors actinomycin D and α-amanitin and requires the kinase activity of ATM but not DNA-PK. Our findings provide documentation of a common transcription-related and ATM kinase-dependent mechanism that induces contact between allelic regions of homologous chromosomes at sites of DSBs in human somatic cells.

Molecular Cytogenetic Studies in Strepsirrhine Primates, Dermoptera and Scandentia

Since the first chromosome painting study between human and strepsirrhine primates was performed in 1996, nearly 30 species in Strepsirrhini, Dermoptera and Scandentia have been analyzed by cross-species chromosome painting. Here, the contribution of chromosome painting data to our understanding of primate genome organization, chromosome evolution and the karyotype phylogenetic relationships within strepsirrhine primates, Dermoptera and Scandentia is reviewed. Twenty-six to 43 homologous chromosome segments have been revealed in different species with human chromosome-specific paint probes. Various landmark rearrangements characteristic for each different lineage have been identified, as cytogenetic signatures that potentially unite certain lineages within strepsirrhine primates, Dermoptera and Scandentia.

Whole-Genome Duplications Spurred the Functional Diversification of the Globin Gene Superfamily in Vertebrates

It has been hypothesized that two successive rounds of whole-genome duplication (WGD) in the stem lineage of vertebrates provided genetic raw materials for the evolutionary innovation of many vertebrate-specific features. However, it has seldom been possible to trace such innovations to specific functional differences between paralogous gene products that derive from a WGD event. Here, we report genomic evidence for a direct link between WGD and key physiological innovations in the vertebrate oxygen transport system. Specifically, we demonstrate that key globin proteins that evolved specialized functions in different aspects of oxidative metabolism (hemoglobin, myoglobin, and cytoglobin) represent paralogous products of two WGD events in the vertebrate common ancestor. Analysis of conserved macrosynteny between the genomes of vertebrates and amphioxus (subphylum Cephalochordata) revealed that homologous chromosomal segments defined by myoglobin + globin-E, cytoglobin, and the α-globin gene cluster each descend from the same linkage group in the reconstructed proto-karyotype of the chordate common ancestor. The physiological division of labor between the oxygen transport function of hemoglobin and the oxygen storage function of myoglobin played a pivotal role in the evolution of aerobic energy metabolism, supporting the hypothesis that WGDs helped fuel key innovations in vertebrate evolution.

Comparative Chromosome Painting of Four Siberian Vespertilionidae Species with Aselliscus stoliczkanus and Human Probes

Vespertilionidae is the largest chiropteran family that comprises species of different specialization and wide geographic distribution. Up to now, only a few vespertilionid species have been studied by molecular cytogenetic approaches. Here, we have investigated the karyotypic relationships of 4 Vespertilionidae species from Siberia by G-banding and comparative chromosome painting. Painting probes from Aselliscus stoliczkanus were used to establish interspecific homologous chromosomal segments in Myotis dasycneme (2n = 44), Murina hilgendorfi (2n = 44), Plecotus auritus (2n = 32), and Vespertilio murinus (2n = 38). Robertsonian translocations and a few inversions differentiated the karyotypes of the examined species. Painting of P. auritus karyotype with human probes revealed 3 previously undetected cryptic segments homologous to human chromosomes (Homo sapiens, HSA) 8, 15, and 19, respectively. As a consequence, the existence of 2 HSA 4 + 8 syntenies in the P. auritus karyotype has been proven. In addition, a pericentric inversion or centromere shift was revealed on the smallest metacentric P. auritus chromosome 16/17 using the HSA 16 probe explaining the different G-banding pattern in comparison to the homologous Myotis chromosome 16/17.

Inapproximability of maximal strip recovery

In comparative genomics, the first step of sequence analysis is usually to decompose two or more genomes into syntenic blocks that are segments of homologous chromosomes. For the reliable recovery of syntenic blocks, noise and ambiguities in the genomic maps need to be removed first. Maximal Strip Recovery (MSR) is an optimization problem proposed by Zheng, Zhu, and Sankoff for reliably recovering syntenic blocks from genomic maps in the midst of noise and ambiguities. Given d genomic maps as sequences of gene markers, the objective of MSR- d is to find d subsequences, one subsequence of each genomic map, such that the total length of syntenic blocks in these subsequences is maximized. For any constant d ≥ 2 , a polynomial-time 2 d -approximation for MSR- d was previously known. In this paper, we show that for any d ≥ 2 , MSR- d is APX-hard, even for the most basic version of the problem in which all gene markers are distinct and appear in positive orientation in each genomic map. Moreover, we provide the first explicit lower bounds on approximating MSR- d for all d ≥ 2 . In particular, we show that MSR- d is NP-hard to approximate within Ω ( d / log d ) . From the other direction, we show that the previous 2 d -approximation for MSR- d can be optimized into a polynomial-time algorithm even if d is not a constant but is part of the input. We then extend our inapproximability results to several related problems including CMSR- d , δ -gap-MSR- d , and δ -gap-CMSR- d .

Cross-species chromosome painting in bats from Madagascar: the contribution of Myzopodidae to revealing ancestral syntenies in Chiroptera

The chiropteran fauna of Madagascar comprises eight of the 19 recognized families of bats, including the endemic Myzopodidae. While recent systematic studies of Malagasy bats have contributed to our understanding of the morphological and genetic diversity of the island's fauna, little is known about their cytosystematics. Here we investigate karyotypic relationships among four species, representing four families of Chiroptera endemic to the Malagasy region using cross-species chromosome painting with painting probes of Myotis myotis: Myzopodidae (Myzopoda aurita, 2n = 26), Molossidae (Mormopterus jugularis, 2n = 48), Miniopteridae (Miniopterus griveaudi, 2n = 46), and Vespertilionidae (Myotis goudoti, 2n = 44). This study represents the first time a member of the family Myzopodidae has been investigated using chromosome painting. Painting probes of M. myotis were used to delimit 29, 24, 23, and 22 homologous chromosomal segments in the genomes of M. aurita, M. jugularis, M. griveaudi, and M. goudoti, respectively. Comparison of GTG-banded homologous chromosomes/chromosomal segments among the four species revealed the genome of M. aurita has been structured through 14 fusions of chromosomes and chromosomal segments of M. myotis chromosomes leading to a karyotype consisting solely of bi-armed chromosomes. In addition, chromosome painting revealed a novel X-autosome translocation in M. aurita. Comparison of our results with published chromosome maps provided further evidence for karyotypic conservatism within the genera Mormopterus, Miniopterus, and Myotis. Mapping of chromosomal rearrangements onto a molecular consensus phylogeny revealed ancestral syntenies shared between Myzopoda and other bat species of the infraorders Pteropodiformes and Vespertilioniformes. Our study provides further evidence for the involvement of Robertsonian (Rb) translocations and fusions/fissions in chromosomal evolution within Chiroptera.

Comparative genomics and evolution of conserved noncoding elements (CNE) in rainbow trout

BackgroundRecent advances in the accumulation of genetic mapping and DNA sequence information from several salmonid species support the long standing view of an autopolyploid origin of these fishes (i.e., 4R). However, the paralogy relationships of the chromosomal segments descendent from earlier polyploidization events (i.e., 2R/3R) largely remain unknown, mainly due to an unbalanced pseudogenization of paralogous genes that were once resident on the ancient duplicated segments. Inter-specific conserved noncoding elements (CNE) might hold the key in identifying these regions, if they are associated with arrays of genes that have been highly conserved in syntenic blocks through evolution. To test this hypothesis, we investigated the chromosomal positions of subset of CNE in the rainbow trout genome using a comparative genomic framework.ResultsThrough a genome wide analysis, we selected 41 pairs of adjacent CNE located on various chromosomes in zebrafish and obtained their intervening, less conserved, sequence information from rainbow trout. We identified 56 distinct fragments corresponding to about 150 Kbp of sequence data that were localized to 67 different chromosomal regions in the rainbow trout genome. The genomic positions of many duplicated CNE provided additional support for some previously suggested homeologies in this species. Additionally, we now propose 40 new potential paralogous affinities by analyzing the variation in the segregation patterns of some multi-copy CNE along with the synteny association comparison using several model vertebrates. Some of these regions appear to carry signatures of the 1R, 2R or 3R duplications. A subset of these CNE markers also demonstrated high utility in identifying homologous chromosomal segments in the genomes of Atlantic salmon and Arctic charr.ConclusionCNE seem to be more efficacious than coding sequences in providing insights into the ancient paralogous affinities within the vertebrate genomes. Such a feature makes these elements extremely attractive for comparative genomics studies, as they can be treated as 'anchor' markers to investigate the association of distally located candidate genes on the homologous genomic segments of closely or distantly related organisms.

Genetic analysis of agronomic and fibre traits using four interspecific chromosome substitution lines in cotton

AbstractBackcrossed chromosome substitution lines (CS‐B) have been developed with a homologous pair of chromosomes or chromosome arms of Gossypium barbadense (3‐79) germplasm substituted for the homologous Gossypium hirsutum(TM‐1) chromosomes or chromosome segments. We report on agronomic and fibre trait performance of four backcrossed chromosome or chromosome arm substitution lines including chromosomes 01, 11sh (chromosome 11 short arm), 12 sh and 26 Lo (chromosome 26 long arm). Data for agronomic and fibre traits were collected from replicated field experiments at two different locations in 2 years, and analysed under an additive dominance genetic model. CS‐B 12sh had higher, while CS‐B 01 and CS‐B 26Lo had lower boll weight than TM‐1. The presence of significant negative additive effects for micronaire with CS‐B 01 and significant positive additive effects for elongation and fibre strength with CS‐B 11sh suggested the substituted chromosome arms of 3‐79 in these CS‐B lines were more likely carrying genes causing these effects. Results revealed that several CS‐B lines had significant homozygous and heterozygous dominance effects for different agronomic and fibre traits suggesting that specific CS‐B lines may be useful for improving agronomic and fibre traits in hybrid cottons. These CS‐B lines also provide novel genetic resources for improving upland cotton germplasm.

The phylogeny of nine species of the Drosophila obscura group inferred by the banding homologies of chromosomal regions

The phylogenetic relationships among nine species of Drosophila belonging to the obscura group were investigated by establishing (according to their banding similarities) the homologous chromosome segments of element E (equivalent to chromosome O of D. subobscura). The phylogenetic relationships were based on the existence of segments in different triads of species, which could only be produced by overlapping inversions. This permitted the ordering of the species belonging to each triad. Drosophila obscura, D. ambigua and D. tristis were found to be very closely related and thus forming a cluster in which D. ambigua occupies an intermediate position between the other two species. Drosophila obscura seems to be the species more directly linked to three other separate lineages, that of D. subsilvestris, the two African species (D. microlabis and D. kitumensis), and the subobscura cluster. The species from this last cluster may be ordered as follows: D. subobscura-D. madeirensis-D. guanche. It is not clear which species of this triad is the direct link to D. obscura. These results completely agree with those produced in an independent study, where element B was considered for the same nine species. Furthermore, the present study clarifies some ambiguities concerning the phylogenetic relationships which remained obscure due to the conservative nature of chromosome B.

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

BackgroundFlying 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.ResultsTo 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.ConclusionComparative 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.

Chromosomal phylogeny of four Akodontini species (Rodentia, Cricetidae) from Southern Brazil established by Zoo-FISH using Mus musculus (Muridae) painting probes

We established chromosome homology maps between Mus musculus (MMU) and five species of the Akodontini tribe, Akodon cursor (2n = 14, 15 and 16), A. montensis (2n = 24), A. paranaensis (2n = 44), A. serrensis (2n = 46) and Oligoryzomys flavescens (2n = 66) by Zoo-FISH (fluorescence in situ hybridization) using mouse chromosome-specific probes. The aims of this study were (1) to detect the chromosomal rearrangements responsible for the karyotype variation in this tribe and (2) to reconstruct the phylogenetic relationships among these species. We observed four common syntenic associations of homologous chromosome segments, of which the MMU 7/19 has been described previously in other rodents from Africa, Asia and Europe, and might represent a phylogenetic link between the Old World and Neotropical rodents. The remaining three associations (3/18, 6/12 and 8/13) have been observed exclusively in Neotropical rodents so far, which at present can be considered synapomorphic traits of this group. Five further mouse chromosomes (MMU 4, 9, 14, 18 and 19) were each found evolutionarily conserved as a separate syntenic unit. Our phylogenetic analysis using parsimony and heuristic search detected one consistent group, separating the Akodontini from other rodents.

Chromosome homology between mouse and three Muridae species, Millardia meltada, Acomys dimidiatus and Micromys minutus, and conserved chromosome segments in murid karyotypes

Comparative chromosome painting with mouse (Mus musculus, MMU) chromosome-specific DNA probes was performed for three Muridae species, the Indian soft-furred field rat (Millardia meltada), the spiny mouse (Acomys dimidiatus) and the harvest mouse (Micromys minutus). All probes except for the Y probe were successfully hybridized to the chromosomes of all species, and homologous chromosome segments between mouse and the three species were identified at the molecular level. Comparison of our data with the published data of six other genera (Mus, Rattus, Apodemus, Otomys, Rhabdomys and Cricetulus) of the Muridae suggested that the associations MMU1b/17a, 2b/13a, 5b/11a, 7/19, 10b/17b, 10c/17c, 11b/16a, 12/17d and 13b/15, and the single painted chromosomes and chromosome segments MMU3, 4, 5a, 8a, 8b, 16b, 18 and X were probably contained by the ancestral karyotype of the Muridae, and have been strongly conserved throughout murid evolution.

Disruption of topoisomerase II perturbs pairing in drosophila cell culture.

Homolog pairing refers to the alignment and physical apposition of homologous chromosomal segments. Although commonly observed during meiosis, homolog pairing also occurs in nonmeiotic cells of several organisms, including humans and Drosophila. The mechanism underlying nonmeiotic pairing, however, remains largely unknown. Here, we explore the use of established Drosophila cell lines for the analysis of pairing in somatic cells. Using fluorescent in situ hybridization (FISH), we assayed pairing at nine regions scattered throughout the genome of Kc167 cells, observing high levels of homolog pairing at all six euchromatic regions assayed and variably lower levels in regions in or near centromeric heterochromatin. We have also observed extensive pairing in six additional cell lines representing different tissues of origin, different ploidies, and two different species, demonstrating homolog pairing in cell culture to be impervious to cell type or culture history. Furthermore, by sorting Kc167 cells into G1, S, and G2 subpopulations, we show that even progression through these stages of the cell cycle does not significantly change pairing levels. Finally, our data indicate that disrupting Drosophila topoisomerase II (Top2) gene function with RNAi and chemical inhibitors perturbs homolog pairing, suggesting Top2 to be a gene important for pairing.

Karyotype evolution and phylogenetic relationships of hamsters (Cricetidae, Muroidea, Rodentia) inferred from chromosomal painting and banding comparison

The evolutionary success of rodents of the superfamily Muroidea makes this taxon the most interesting for evolution studies, including study at the chromosomal level. Chromosome-specific painting probes from the Chinese hamster and the Syrian (golden) hamster were used to delimit homologous chromosomal segments among 15 hamster species from eight genera: Allocricetulus, Calomyscus, Cricetulus, Cricetus, Mesocricetus, Peromyscus, Phodopus and Tscherskia (Cricetidae, Muroidea, Rodentia). Based on results of chromosome painting and G-banding, comparative maps between 20 rodent species have been established. The integrated maps demonstrate a high level of karyotype conservation among species in the Cricetus group (Cricetus, Cricetulus, Allocricetulus) with Tscherskia as its sister group. Species within the genera Mesocricetus and Phodopus also show a high degree of chromosomal conservation. Our results substantiate many of the conclusions suggested by other data and strengthen the topology of the Muroidea phylogenetic tree through the inclusion of genome-wide chromosome rearrangements. The derivation of the muroids karyotypes from the putative ancestral state involved centric fusions, fissions, addition of heterochromatic arms and a great number of inversions. Our results provide further insights into the karyotype relationships of all species investigated.

Zoo-FISH in the European mole (Talpa europaea) detects all ancestral Boreo-Eutherian human homologous chromosome associations

Zoo-FISH with human whole-chromosome paint probes delineated syntenic association of human homologous chromosome segments 3-21, 14-15, 16-19, 4-8, 7-16 and 12-22 (twice) in the European mole (Talpa europaea, Talpidae, Eulipotyphla, Mammalia). These segment associations represent shared ancestral Boreo-Eutherian traits, half of which were previously not described for Eulipotyphla. The karyotype of the European mole acquired a minimum of 19 translocations and six inversions compared to the presumed Boreo-Eutherian ancestor.