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The generic status of Lasiopodomys and its division into subgenera Lasiopodomys (L. mandarinus, L. brandtii) and Stenocranius (L. gregalis, L. raddei) are not generally accepted because of contradictions between the morphological and molecular data. To obtain cytogenetic evidence for the Lasiopodomys genus and its subgenera and to test the autosome to sex chromosome translocation hypothesis of sex chromosome complex origin in L. mandarinus proposed previously, we hybridized chromosome painting probes from the field vole (Microtus agrestis, MAG) and the Arctic lemming (Dicrostonyx torquatus, DTO) onto the metaphases of a female Mandarin vole (L. mandarinus, 2n = 47) and a male Brandt's vole (L. brandtii, 2n = 34). In addition, we hybridized Arctic lemming painting probes onto chromosomes of a female narrow-headed vole (L. gregalis, 2n = 36). Cross-species painting revealed three cytogenetic signatures (MAG12/18, 17a/19, and 22/24) that could validate the genus Lasiopodomys and indicate the evolutionary affinity of L. gregalis to the genus. Moreover, all three species retained the associations MAG1bc/17b and 2/8a detected previously in karyotypes of all arvicolins studied. The associations MAG2a/8a/19b, 8b/21, 9b/23, 11/13b, 12b/18, 17a/19a, and 5 fissions of ancestral segments appear to be characteristic for the subgenus Lasiopodomys. We also validated the autosome to sex chromosome translocation hypothesis on the origin of complex sex chromosomes in L. mandarinus. Two translocations of autosomes onto the ancestral X chromosome in L. mandarinus led to a complex of neo-X1, neo-X2, and neo-X3 elements. Our results demonstrate that genus Lasiopodomys represents a striking example of rapid chromosome evolution involving both autosomes and sex chromosomes. Multiple reshuffling events including Robertsonian fusions, chromosomal fissions, inversions and heterochromatin expansion have led to the formation of modern species karyotypes in a very short time, about 2.4 MY. [ABSTRACT FROM AUTHOR]

Karyotype evolution in Carnivora is thoroughly studied by classical and molecular cytogenetics and supplemented by reconstructions of Ancestral Carnivora Karyotype (ACK). However chromosome painting information from two pinniped families (Odobenidae and Otariidae) is noticeably missing. We report on the construction of the comparative chromosome map for species from each of the three pinniped families: the walrus (Odobenus rosmarus, Odobenidae–monotypic family), near threatened Steller sea lion (Eumetopias jubatus, Otariidae) and the endemic Baikal seal (Pusa sibirica, Phocidae) using combination of human, domestic dog and stone marten whole-chromosome painting probes. The earliest karyological studies of Pinnipedia showed that pinnipeds were characterized by a pronounced karyological conservatism that is confirmed here with species from Phocidae, Otariidae and Odobenidae sharing same low number of conserved human autosomal segments (32). Chromosome painting in Pinnipedia and comparison with non-pinniped carnivore karyotypes provide strong support for refined structure of ACK with 2n = 38. Constructed comparative chromosome maps show that pinniped karyotype evolution was characterized by few tandem fusions, seemingly absent inversions and slow rate of genome rearrangements (less then one rearrangement per 10 million years). Integrative comparative analyses with published chromosome painting of Phoca vitulina revealed common cytogenetic signature for Phoca/Pusa branch and supports Phocidae and Otaroidea (Otariidae/Odobenidae) as sister groups. We revealed rearrangements specific for walrus karyotype and found the chromosomal signature linking together families Otariidae and Odobenidae. The Steller sea lion karyotype is the most conserved among three studied species and differs from the ACK by single fusion. The study underlined the strikingly slow karyotype evolution of the Pinnipedia in general and the Otariidae in particular. [ABSTRACT FROM AUTHOR]

Background: Acipenseriformes take a basal position among Actinopteri and demonstrate a striking ploidy variation among species. The sterlet (Acipenser ruthenus, Linnaeus, 1758; ARUT) is a diploid 120-chromosomal sturgeon distributed in Eurasian rivers from Danube to Enisey. Despite a high commercial value and a rapid population decline in the wild, many genomic characteristics of sterlet (as well as many other sturgeon species) have not been studied. Results: Cell lines from different tissues of 12 sterlet specimens from Siberian populations were established following an optimized protocol. Conventional cytogenetic studies supplemented with molecular cytogenetic investigations on obtained fibroblast cell lines allowed a detailed description of sterlet karyotype and a precise localization of 18S/28S and 5S ribosomal clusters. Localization of sturgeon specific HindIII repetitive elements revealed an increased concentration in the pericentromeric region of the acrocentric ARUT14, while the total sterlet repetitive DNA fraction (C0t30) produced bright signals on subtelomeric segments of small chromosomal elements. Chromosome and region specific probes ARUT1p, 5, 6, 7, 8 as well as 14 anonymous small sized chromosomes (probes A-N) generated by microdissection were applied in chromosome painting experiments. According to hybridization patterns all painting probes were classified into two major groups: the first group (ARUT5, 6, 8 as well as microchromosome specific probes C, E, F, G, H, and I) painted only a single region each on sterlet metaphases, while probes of the second group (ARUT1p, 7 as well as microchromosome derived probes A, B, D, J, K, M, and N) marked two genomic segments each on different chromosomes. Similar results were obtained on male and female metaphases. Conclusions: The sterlet genome represents a complex mosaic structure and consists of diploid and tetraploid chromosome segments. This may be regarded as a transition stage from paleotetraploid (functional diploid) to diploid genome condition. Molecular cytogenetic and genomic studies of other 120- and 240-chromosomal sturgeons are needed to reconstruct genome evolution of this vertebrate group. [ABSTRACT FROM AUTHOR]

Background Pronghorn (Antilocapridae, 2n = 58) and saola (Bovidae, 2n = 50) are members of Pecora, a highly diversified group of even-toed hoofed mammals. Karyotypes of these species were not involved in chromosome painting studies despite their intriguing phylogenetic positions in Pecora. Results To trace the chromosome evolution during very fast radiation of main families from the common Pecoran ancestor, high-resolution comparative chromosome maps of pronghorn and saola with human (HSA) and dromedary camel (CDR) painting probes were established. The human and dromedary camel painting probes revealed 50 and 64 conserved segments respectively in the pronghorn genome, while 51 and 63 conserved segments respectively in the saola genome. Integrative analysis with published comparative maps showed that inversions in chromosomes homologous to CDR19/35/19 (HSA 10/20/10), CDR12/34/12 (HSA12/22/12/22), CDR10/33/10 (HSA 11) are present in representatives of all five living Pecoran families. The pronghorn karyotype could have formed from a putative 2n = 58 Pecoran ancestral karyotype by one fission and one fusion and that the saola karyotype differs from the presumed 2n = 60 bovid ancestral karyotype (2n = 60) by five fusions. Conclusion The establishment of high-resolution comparative maps for pronghorn and saola has shed some new insights into the putative ancestral karyotype, chromosomal evolution and phylogenic relationships in Pecora. No cytogenetic signature rearrangements were found that could unite the Antilocapridae with Giraffidae or with any other Pecoran families. Our data on the saola support a separate position of Pseudorigyna subtribe rather than its affinity to either Bovina or Bubalina, but the saola phylogenetic position within Bovidae remains unresolved. [ABSTRACT FROM AUTHOR]

Background: Most eukaryotic species represent stable karyotypes with a particular diploid number. B chromosomes are additional to standard karyotypes and may vary in size, number and morphology even between cells of the same individual. For many years it was generally believed that B chromosomes found in some plant, animal and fungi species lacked active genes. Recently, molecular cytogenetic studies showed the presence of additional copies of protein-coding genes on B chromosomes. However, the transcriptional activity of these genes remained elusive. We studied karyotypes of the Siberian roe deer (Capreolus pygargus) that possess up to 14 B chromosomes to investigate the presence and expression of genes on supernumerary chromosomes. Results: Here, we describe a 2 Mbp region homologous to cattle chromosome 3 and containing TNNI3K (partial), FPGT, LRRIQ3 and a large gene-sparse segment on B chromosomes of the Siberian roe deer. The presence of the copy of the autosomal region was demonstrated by B-specific cDNA analysis, PCR assisted mapping, cattle bacterial artificial chromosome (BAC) clone localization and quantitative polymerase chain reaction (qPCR). By comparative analysis of B-specific and non-B chromosomal sequences we discovered some B chromosome-specific mutations in protein-coding genes, which further enabled the detection of a FPGT-TNNI3K transcript expressed from duplicated genes located on B chromosomes in roe deer fibroblasts. Conclusions: Discovery of a large autosomal segment in all B chromosomes of the Siberian roe deer further corroborates the view of an autosomal origin for these elements. Detection of a B-derived transcript in fibroblasts implies that the protein coding sequences located on Bs are not fully inactivated. The origin, evolution and effect on host of B chromosomal genes seem to be similar to autosomal segmental duplications, which reinforces the view that supernumerary chromosomal elements might play an important role in genome evolution. [ABSTRACT FROM AUTHOR]

The taxonomy of the genus Calomyscus remains controversial. According to the latest systematics the genus includes eight species with great karyotypic variation. Here, we studied karyotypes of 14 Calomyscus individuals from different regions of Iran and Turkmenistan using a new set of chromosome painting probes from a Calomyscus sp. male (2n = 46, XY; Shahr-e-Kord-Soreshjan-Cheshme Maiak Province). We showed the retention of large syntenic blocks in karyotypes of individuals with identical chromosome numbers. The only rearrangement (fusion 2/21) differentiated Calomyscus elburzensis, Calomyscus mystax mystax, and Calomyscus sp. from Isfahan Province with 2n = 44 from karyotypes of C. bailwardi, Calomyscus sp. from Shahr-e-Kord, Chahar Mahal and Bakhtiari-Aloni, and Khuzestan-Izeh Provinces with 2n = 46. The individuals from Shahdad tunnel, Kerman Province with 2n = 51–52 demonstrated non-centric fissions of chromosomes 4, 5, and 6 of the 46-chromosomal form with the formation of separate small acrocentrics. A heteromorphic pair of chromosomes in a specimen with 2n = 51 resulted from a fusion of two autosomes. C-banding and chromomycin A3-DAPI staining after G-banding showed extensive heterochromatin variation between individuals. [ABSTRACT FROM AUTHOR]

Pinnipedia karyotype evolution was studied here using human, domestic dog, and stone marten whole-chromosome painting probes to obtain comparative chromosome maps among species of Odobenidae (Odobenus rosmarus), Phocidae (Phoca vitulina, Phoca largha, Phoca hispida, Pusa sibirica, Erignathus barbatus), and Otariidae (Eumetopias jubatus, Callorhinus ursinus, Phocarctos hookeri, and Arctocephalus forsteri). Structural and functional chromosomal features were assessed with telomere repeat and ribosomal-DNA probes and by CBG (C-bands revealed by barium hydroxide treatment followed by Giemsa staining) and CDAG (Chromomycin A3-DAPI after G-banding) methods. We demonstrated diversity of heterochromatin among pinniped karyotypes in terms of localization, size, and nucleotide composition. For the first time, an intrachromosomal rearrangement common for Otariidae and Odobenidae was revealed. We postulate that the order of evolutionarily conserved segments in the analyzed pinnipeds is the same as the order proposed for the ancestral Carnivora karyotype (2n = 38). The evolution of conserved genomes of pinnipeds has been accompanied by few fusion events (less than one rearrangement per 10 million years) and by novel intrachromosomal changes including the emergence of new centromeres and pericentric inversion/centromere repositioning. The observed interspecific diversity of pinniped karyotypes driven by constitutive heterochromatin variation likely has played an important role in karyotype evolution of pinnipeds, thereby contributing to the differences of pinnipeds' chromosome sets. [ABSTRACT FROM AUTHOR]

A meiotic linkage map is essential for mapping traits of interest and is often the first step toward understanding a cryptic genome. Specific strains of silver fox (a variant of the red fox, Vulpes vulpes), which segregate behavioral and morphological phenotypes, create a need for such a map. One such strain, selected for docility, exhibits friendly dog-like responses to humans, in contrast to another strain selected for aggression. Development of a fox map is facilitated by the known cytogenetic homologies between the dog and fox, and by the availability of high resolution canine genome maps and sequence data. Furthermore, the high genomic sequence identity between dog and fox allows adaptation of canine microsatellites for genotyping and meiotic mapping in foxes. Using 320 such markers, we have constructed the first meiotic linkage map of the fox genome. The resulting sex-averaged map covers 16 fox autosomes and the X chromosome with an average inter-marker distance of 7.5 cM. The total map length corresponds to 1480.2 cM. From comparison of sex-averaged meiotic linkage maps of the fox and dog genomes, suppression of recombination in pericentromeric regions of the metacentric fox chromosomes was apparent, relative to the corresponding segments of acrocentric dog chromosomes. Alignment of the fox meiotic map against the 7.6x canine genome sequence revealed high conservation of marker order between homologous regions of the two species. The fox meiotic map provides a critical tool for genetic studies in foxes and identification of genetic loci and genes implicated in fox domestication. [ABSTRACT FROM AUTHOR]