New insights into sex chromosome evolution in anole lizards (Reptilia, Dactyloidae).

Anoles are a clade of iguanian lizards that underwent an extensive radiation between 125 and 65 million years ago. Their karyotypes show wide variation in diploid number spanning from 26 (Anolis evermanni) to 44 (A. insolitus). This chromosomal variation involves their sex chromosomes, ranging from simple systems (XX/XY), with heterochromosomes represented by either micro- or macrochromosomes, to multiple systems (X1X1X2X2/X1X2Y). Here, for the first time, the homology relationships of sex chromosomes have been investigated in nine anole lizards at the whole chromosome level. Cross-species chromosome painting using sex chromosome paints from A. carolinensis, Ctenonotus pogus and Norops sagrei and gene mapping of X-linked genes demonstrated that the anole ancestral sex chromosome system constituted by microchromosomes is retained in all the species with the ancestral karyotype (2n = 36, 12 macro- and 24 microchromosomes). On the contrary, species with a derived karyotype, namely those belonging to genera Ctenonotus and Norops, show a series of rearrangements (fusions/fissions) involving autosomes/microchromosomes that led to the formation of their current sex chromosome systems. These results demonstrate that different autosomes were involved in translocations with sex chromosomes in closely related lineages of anole lizards and that several sequential microautosome/sex chromosome fusions lead to a remarkable increase in size of Norops sagrei sex chromosomes.

Mitochondrial DNA analysis of ancient sheep from Altai.

A comparative analysis of the genetic diversity of ancient and modern sheep can shed light on the origin of these animals and their distribution as well as help to evaluate the role of humans at each formation stage of different sheep breeds. Here we isolated ancient DNA and performed sequencing of the mitochondrial DNA D-loop from 17 sheep bone remains (~4000-1000 years old) found in the archaeological complexes in the south of Altai (Western Siberia). The length of the sequences obtained ranged between 318 and 586 bp. The haplotype diversity and nucleotide diversity were 0.801 ± 0.081 and 0.0096 ± 0.0014 respectively. The average number of nucleotide differences was ~3.1. Nucleotide sequence analysis revealed that 15 specimens were nested within previously described A,B,C,D and E lineages and that two specimens had a basal position relative to the rest of the analyzed samples. A relatively high diversity of sheep haplotypes, including the presence of two basal haplotypes, indicates that the Altai region may have been a transport route of human migration. Further ancient DNA analysis of other specimens and deeper genome sequencing of samples with novel haplotypes is needed to better understand the demographic history of sheep in Southern Siberia.

Mitochondrial DNA D-loop haplogroup contributions to the genetic diversity of East European domestic chickens from Russia.

To elucidate geographical and historical aspects of chicken dispersal across Eastern Europe, we analysed the complete mitochondrial DNA D-loop sequence of 86 representatives from chicken breeds traditionally raised in the territory of the East European Plain (Orloff, Pavlov, Russian White, Yurlov Crower, Uzbek Game and Naked Neck). From the 1231-1232 bp D-loop sequence, 35 variable sites that defined 22 haplotypes were identified in modern chicken. All populations, except Uzbek Game, exhibited high values of haplotype and nucleotide diversity suggesting a wide variation in maternal diversity. Inclusion of mtDNA sequences from other European and Asian countries revealed representatives from this study belonging to haplogroups A, E1 and C1. We also assessed fossil chicken material dated to the 9th-18th century from archaeological sites in Northern and Eastern Europe. Three haplotypes found in the fossil specimens belonged to haplogroup E1, while one sample dated to the 18th century was assigned to the C1 haplogroup. This is the first report of the occurrence of the C1 haplogroup in European chicken populations prior to the 20th century based on the fossil material. These results provide evidence for a relatively recent introduction of all haplotypes other than E1 into the East European chicken gene pool with the significant impact of the C1 haplogroup mainly distributed in Southern China.

DIVERSITY OF SEX DETERMINING MECHANISMS IN RAY-FINNED FISHES (ACTINOPTERYGII).

Ray-finned fishes (Actinopterygii) is a very diverse and numerous clade of vertebrates. Besides the diversity of ecological niches and morphology, species of this clade have substantial differences in mechanisms of sex determination. Unfortunately, our modern knowledge about sex determining mechanisms is limited to a small number of species. Even from the modest number of published works on this topic it is obvious that evolution of sex determining system in ray-finned fishes is very plastic: in some closely related species sex systems can be significantly different, there are taxa with quite conservative systems, and the same genomic loci may play sex determination role independently in various groups. Such diversity allows considering ray-finned fishes to be used as a convenient model taxon for researching emergence and development of different sex determining systems.

[Ancient DNA: Results and Prospects (the 30th Anniversary)].

Evolutionary genetics has reached a new level of research thanks to the opportunity to study the genomes of not only present-day but also of ancient organisms. The obtaining of reliable data when working with ancient DNA is possible only in the case of interdisciplinary collaboration between archaeologists, paleontologists, molecular geneticists, and bioinformaticians. Despite laborious and high-cost technologies, the results never cease to amaze and can not only fill the gaps in the knowledge of the evolutionary history of different species but can also review the existing ideas on population development and dynamics. In this review, we discuss the history of the development of investigative techniques in ancient DNA research and the most striking results of these studies, including the most recent achievements.

[Genomic structure and sex determination in squamate reptiles].

Squamata is the largest reptilian order including snakes and lizards which occupies a key position in phylogeny of amniotes. A variety of sex determination modes in lizards is one of the most interesting parts of the biology of this order. These mechanisms are genomic sex determination (both XY and ZW systems) and temperature-dependent sex determination. Studies of squamata sex chromosomes are pivotal for understanding evolution of other vertebrate sex chromosomes. Unfortunately, this clade has long been neglected by molecular geneticists. In this paper, we describe recent data on molecular cytogenetics and genomics of squamates, evolution of their sex chromosomes and sex determination mechanisms.

Distortion of Population Statistics due to the Use of Different Methodological Approaches to the Construction of Genomic DNA Libraries.

Several different methods of DNA library preparation for paleogenetic studies are now available. However, the chemical reactions underlying each of them can affect the primary sequence of ancient DNA (aDNA) in the libraries and taint the results of a statistical analysis. In this paper, we compare the results of a sequencing of the aDNA libraries of a Bronze Age sample from burials of the Caucasian burial ground Klady, prepared using three different approaches: (1) shotgun sequencing, (2) strategies for selecting target genomic regions, and (3) strategies for selecting target genomic regions, including DNA pre-treatment with a mixture of uracil-DNA glycosylase (UDG) and endonuclease VIII. The impact of the studied approaches to genomic library preparation on the results of a secondary analysis of the statistical data, namely F4 statistics, ADMIXTURE, and principal component analysis (PCA), was analyzed. It was shown that preparation of genomic libraries without the use of UDG can result in distorted statistical data due to postmortem chemical modifications of the aDNA. This distortion can be alleviated by analyzing only the single nucleotide polymorphisms caused by transversions in the genome.

Chromosome evolution in Perissodactyla.

Comparative painting has provided a wealth of useful information and helped to reconstruct the pathways of karyotype evolution within major eutherian phylogenetic clades. New data have come from gene localizations, BAC mapping and high throughout sequencing projects that enrich and provide new details of genome evolution. Extensive research on perissodactyl genomes has revealed not only increased rates of chromosomal rearrangements, but also an exceptionally high number of centromere repositioning events in equids. Here were combined new physical mapping, comparative painting and genome sequencing data to refine the putative ancestral karyotype maps and to revise the previously proposed scenario of perissodactyl karyotype evolution.

Chromosomal evolution in Rodentia.

Rodentia is the most species-rich mammalian order and includes several important laboratory model species. The amount of new information on karyotypic and phylogenetic relations within and among rodent taxa is rapidly increasing, but a synthesis of these data is currently lacking. Here, we have integrated information drawn from conventional banding studies, recent comparative painting investigations and molecular phylogenetic reconstructions of different rodent taxa. This permitted a revision of several ancestral karyotypic reconstructions, and a more accurate depiction of rodent chromosomal 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.

Unusual congenital polydactyly in mini-pigs from the breeding group of the Institute of Cytology and Genetics (Novosibirsk, Russia).

The article describes a new phenomenon in the breeding group of mini-pigs at the Institute of Cytology and Genetics (ICG, Novosibirsk): polydactyly (extra digits), which is unusual because the additional digits are situated at the lateral surface of legs or at the lateral and medial ones. This anomaly was f irst found here in 2017 in adult animals intended for culling due to incorrect positioning of the legs caused by f lexor tendon laxity and resulting in weight-bearing on the palmar surface of the proximal phalanges ("bear's paw"). Therefore, the polydactyly of mini-pigs has a pronounced negative selection effect. A visual survey of the livestock was conducted, and a description of the detected anomaly was compiled. The polydactyly in mini-pigs is a stand-alone trait and is not part of any syndromes. Individuals with polydactyly may have extra digits either on pectoral or on pectoral and pelvic limbs. On thoracic limbs, there may be either one lateral digit or a lateral digit and a medially located rudimentary hoof let. On pelvic limbs, only lateral extra digits can occur. Anatomical and morphological analyses showed that the lateral extra digit is an anatomically complete ("mature") structure, whereas the medial rudimentary digit consists of only a hoof let without other structures characteristic of normal digits. Cytological examination revealed no specif ic karyotypic features, except for Robertsonian translocation Rb 16;17 previously reported for the mini-pigs of the same livestock. Cytological f indings indicated that the polydactyly and Robertsonian translocation are not linked genetically. Genealogical analysis and results of crosses are consistent with a working hypothesis of recessive inheritance of the trait. Overall, the study shows that this type of polydactyly is anatomically and morphologically unique and not typical of Sus scrofa. In this species, only polydactyly types with medial accessory toes have been described and are usually inherited as a dominant trait with incomplete penetrance. In our case, the results of test crosses indicate recessive inheritance of the trait with varying expression and incomplete penetrance, because of which poorly expressed phenotypes are not visually detectable.

Reconstruction of the putative cervidae ancestral karyotype by chromosome painting of Siberian roe deer (Capreolus pygargus) with dromedary probes.

The Siberian roe deer (Capreolus pygargus) is one of a few deer species presumably preserving the ancestral cervid karyotype. The comparative genomic data of the Siberian roe deer are critical for our understanding of the karyotypic relationships within artiodactyls. We have established chromosomal homologies between the Siberian roe deer and the dromedary (Camelus dromedarius) by cross-species chromosome painting with dromedary chromosome-specific painting probes. Dromedary chromosome paints detected 53 autosomal homologies in the genome of the Siberian roe deer. The identification of chromosomal homologies between the Siberian roe deer and cattle resulted from previously detected cattle-dromedary homologies. We have found 8 chromosomal rearrangements (6 fissions in the Siberian roe deer, 1 fission in the cattle and 1 inversion on the CPY11) that have separated the karyotypes of the cattle and the Siberian roe deer. The inversion on CPY11 might be an apomorphic trait of cervids, since we detected its presence in the gray brocket deer (Mazama gouazoubira). Thus our data further prove the scenario of chromosomal rearrangements that was previously proposed and add some new data.

[Supernumerary chromosomes, segmental duplications, and evolution].

The present study depicts the phenomenon of supernumerary chromosomes as autonomous genome elements, similar in features with segmental duplications. Possible role of B chromosomes in evolution and the reasons of their nonrandom distribution in different mammalian taxa are discussed.

[Comparative cytogenetics of main Laurasiatheria taxa].

This short communication is a review of key trends in the karyotypic evolution of mammalian taxa Laurasiatheria, inferred from comparative chromosome painting.

Mapping of KIT adjacent sequences on canid autosomes and B chromosomes.

B chromosomes are often considered to be one of the most mysterious elements of karyotypes (Camacho, 2004). It is generally believed that mammalian B chromosomes do not contain any protein coding genes. The discovery of a conserved KIT gene in Canidae B chromosomes has changed this view. Here we performed analysis of sequences surrounding KIT in B chromosomes of the fox and raccoon dog. The presence of the RPL23A pseudogene was shown in canid B chromosomes. The 3' end fragment of the KDR gene was found in raccoon dog B chromosomes. The size of the B-specific fragment homologous to the autosome fragment was estimated to be a minimum of 480 kbp in both species. The origin and evolution of B chromosomes in Canidae are discussed.

The origin of B chromosomes in yellow-necked mice (Apodemus flavicollis)-Break rules but keep playing the game.

B chromosomes (Bs) are known for more than hundred years but their origin, structure and pattern of evolution are not well understood. In the past few years new methodological approaches, involving isolation of Bs followed by whole DNA amplification, DNA probe generation, and fluorescent in situ hybridization (FISH) or the B chromosome DNA sequencing, has allowed detailed analysis of their origin and molecular structure in different species. In this study we explored the origin of Bs in the yellow-necked wood mouse, Apodemus flavicollis, using generation of microdissected DNA probes followed by FISH on metaphase chromosomes. Bs of A. flavicollis were successfully isolated and DNA was used as the template for B-specific probes for the first time. We revealed homology of DNA derived from the analyzed B chromosomes to the pericentromeric region (PR) of sex chromosomes and subtelomeric region of two pairs of small autosomes, but lower homology to the rest of the Y chromosome. Moreover, all analysed Bs had the same structure regardless of their number per individual or the great geographic distance between examined populations from the Balkan Peninsula (Serbia) and Eastern Europe (south region of Russia and central Belarus). Therefore, it was suggested that B chromosomes in A. flavicollis have a unique common origin from the PR of sex chromosomes, and/or similar evolutionary pattern.

[Comparative chromosome painting]. / Sravnitel'nyi khromosomnyi péinting.

The review of the data on comparative chromosomal painting in mammals is presented. The development of new molecular-cytogenetic methods has resulted in the accumulation of the detailed information on homology of chromosomal segments of more than 50 species from 11 orders. In this review, modern methods of obtaining painting probes are considered in detail, and the basic tendencies of karyotype evolution in different taxa are discussed. Putative karyotypes of the ancestors of primates, carnivores, and placental mammals are considered.

Complex structure of B-chromosomes in two mammalian species: Apodemus peninsulae (Rodentia) and Nyctereutes procyonoides (Carnivora).

B-chromosomes (Bs) of two mammalian species, raccoon dog (Nyctereutesprocyonoides, Carnivora) and Asian wood mouse (Apodemus peninsulae, Rodentia) were investigated using chromosome segment microdissection and double-colour FISH. In the raccoon dog, all B-chromosomes showed homology with each other but not with the A-chromosomes. Two segment-specific probes (from proximal and distal parts of B) have been localized in corresponding chromosome parts, with significant variation in their sizes. In Asian wood mice, two types of B-specific chromatin were revealed--B1 and B2. Most Bs were either B1 or B2 specific; furthermore, some Bs were found to be composed of both types of chromatin. B-chromosome-specific libraries of A. peninsulae contain sequences homologous to the heterochromatic regions of sex and some A-chromosomes and dispersed repeated sequences. B1-specific probes gave signals on sex chromosomes of Apodemus speciosus and Apodemus agrarius. The origin and evolution of B-chromosomes in mammals are discussed.