Development of polymorphic microsatellite DNA markers from the Korean field mouse, Apodemus peninsulae

We isolated and characterized eight polymorphic microsatellite DNA markers from the Korean field mouse, Apodemus peninsulae. The primers developed in this study yielded an average polymorphic information content of 0.78 (range 0.44–0.90), with an average of 10.9 alleles per locus (range 5–16). Observed and expected heterozygosities ranged from 0.46 to 1.00 and from 0.49 to 0.93, respectively. These polymorphic loci may provide useful tools for understanding the species’ genetic structure and ecology.     

B chromosomes of Korean field mouse Apodemus peninsulae (Rodentia,Murinae) analysed by microdissection and FISH

Organization of B chromosomes in the Korean field mouse Apodemus peninsulae was analyzed. We painted its metaphase chromosomes with whole and partial chromosome paints generated by microdissection and DOP-PCR. The results of the painting indicated that all B chromosomes contained a large amount of repeated DNA sequences. The repeats could be classified in terms of their homology and predominant location. Pericentromeric repeats of B chromosomes were present in many copies in pericentromeric C-blocks of all autosomes and in non-centromeric C-blocks of the sex chromosomes. B arm specific type 1 repeats comprised the main body of the arms of almost all B chromosomes and were present in the arms of A chromosomes as interspersed sequences. B arm-specific type 2 repeats were found at the ends of some B chromosomes that did not undergo compaction at the interphase- metaphase transition and remained uncondensed. On the basis of comparative analysis of localization of B chromosome repeats in the chromosomes of two related species, A. peninsulae and A. agrarius, we suggest a hypothesis of B chromosome origin and evolution in the genus Apodemus.     

Comparative analysis of micro and macro B chromosomes in the Korean field mouse Apodemus peninsulae (Rodentia, Murinae) performed by chromosome microdissection and FISH

Comparative analysis of micro B and macro B chromosomes of the Korean field mouse Apodemus peninsulae, collected in populations from Siberia and the Russian Far East, was performed with Giemsa, DAPI, Ag-NOR staining and chromosome painting with whole and partial chromosome probes generated by microdissection and DOP-PCR. DNA composition of micro B chromosomes was different from that of macro B chromosomes. All analyzed micro B chromosomes contained clusters of DNA repeats associated with regions characterized by an uncondensed state in mitosis. Giemsa and DAPI staining did not reveal these regions. Their presence in micro B chromosomes led to their special morphology and underestimation in size. DNA repeat clusters homologous to DNA of micro B chromosome arms were also revealed in telomeric regions of some macro B chromosomes of specimens captured in Siberian regions. Neither active NORs nor clusters of ribosomal DNA were found in the uncondensed regions of micro B chromosomes. Possible evolutionary pathways for the origin of macro and micro B chromosomes are discussed.     

The complete mitochondrial genome of the Korean field mouse Apodemus peninsulae (Rodentia, Murinae) from Korea

We have determined the complete mitochondrial genome of a subspecies of the Korean field mouse, Apodemus peninsulae peninsulae, from South Korea. The total length of the A. p. peninsulae genome is 16,268 bp with a base composition of 34.5% A, 30.7% T, 22.6% C, and 12.2% G.     

B chromosome morphotypes of Apodemus peninsulae (Rodentia) from the Russian Far East

Polymorphism of B chromosome morphotypes in the natural populations of the Korean field mouse Apodemus peninsulae (n = 367) has been studied in five regions of the Russian Far East: Magadan and Amur regions, the Jewish Autonomous region, Khabarovsk and Primorskii regions. Six groups of B chromosome morphotypes have been described on the size and morphological parameters. On the basis of their combinations 78 cell clones have been revealed, 23 of which are found in the animals with a stable karyotype and 76--in mosaics. The mosaics have also more diverse and unique combinations of B chromosome morphotypes. No differences between the geographic and local populations of mice on the studied characteristics have been found. Homogeneous structure of DNA in the B chromosomes of this species at the territory of the Russian Far East, as shown previously, allowed us to combine the numerical and dimensional data for each clone by introduction conditional "mass quantity" of B chromosomes (mB index). The leading role of natural selection in production of "critical" mass of supernumerary chromosomes in individuals with a stable karyotype and the weakening of its role in mosaics has been suggested.     

Populational chromosomal polymorphism the Asian forest mouse Apodemus peninsulae]

29 individuals of Apodemus peninsulae, an Asian forest mouse from the Suputin State Nature Reserve (Maritime Territory) were studied karyologically. Diploid chromosome sets of the animals studied contained from 48 to 52 chromosomes. The difference in the diploid chromosome numbers is caused by the presence in some individuals of supernumerary metacentric chromosomes (up to 4). The set is always represented by 48 acrocentric chromosomes, gradually decreasing in size. The supernumerary metacentric chromosomes vary in size from medium-sized to the smallest in the set. The character of intrapopulational chromosome polymorphism of continental and island populations of Apodemus peninsulae is discussed. Attempts are made to explain the polymorphism with respect to supernumerary chromosomes as the result of some viral diseases.     

A note on the presence of B chromosome in the small Japanese field mouse,Apodemus argenteus,in central Honshu,Japan

Previously, many studies have revealed the presence of B chromosomes in wild mouse taxa of the genus Apodemus (Rodentia, Muridae). In one of the Apodemus species, A. argenteus, which is endemic to Japan, it is known that B chromosomes were confirmed only in individuals (2n = 46 + B chromosome) from Hokkaido, Japan. There is no report of the presence of B chromosomes from other localities in the Japanese Islands. In this study, we analyzed the chromosomal constitutions of 43 individuals of A. argenteus from three localities in Honshu, Japan. A total of three individuals from central Honshu showed 2n = 47, and each individual carried a dot-like B chromosome. In addition, these B chromosome features were analyzed by differential staining methods, and the C- and QM-banding patterns of the B chromosomes were identical to those of the X chromosomal heterochromatic region showing the delayed-fluorescent response. Thus, it is considered that these B chromosomes would be derived from the heterochromatin of the X chromosomes, as reported in previously published papers.     

Synaptonemal complex analysis of B-chromosome behavior in meiotic prophase I in the East-Asiatic mouse Apodemus peninsulae (Muridae, Rodentia)

The mitotic and meiotic chromosomes of four male East-Asiatic mice, Apodemus peninsulae, having three to seven chromosomes in addition to the standard karyotype (2n = 48), were investigated. B-chromosomes were represented by medium-sized metacentric and dotlike chromosomes. Mosaicism of bone marrow cells due to a numerical variation of accessory chromosomes was established for the males examined. Capacity of B-chromosomes to form axial elements and synaptonemal complexes in meiotic prophase I was revealed by electron microscopy. The occurrence of univalents of different morphology, bivalents, and multivalents, corresponding to B-chromosomes, was demonstrated. An increase in the number of B-chromosomes was found in spermatocytes at zygotene-pachytene relative to the number in bone marrow cells, which may be evidence of B-chromosome accumulation in the germ cell line of the East-Asiatic mouse.     

The clinal variability of the B-chromosome system in the East Asian mouse Apodemus peninsulae from Buryatia and Mongolia]

Karyological investigation of 22 East-Asiatic mice from different points of the North Mongolia showed the availability in all the mice from 1 to 13 B chromosomes, including from 1 to 5 middle-sized and small two-shoulder chromosomes, from 0 to 11 dot-like B chromosomes, and, seldom, 1 small acrocentric B chromosome. Nearly every mouse is characterized by its variant of B-chromosome system. Most frequent mice with 3, 4 and 8 B chromosomes were met. The comparison of the B-chromosome system variants in mice from Buryatia, Chita Province (USSR) and the North Mongolia, showed an increase in the number of B chromosomes, mainly at the expense of the number of dot-like B chromosomes, in the direction from Ulan-Ude to the south and to the east.     

Stability of the population variants of the B-chromosome system in the East-Asian mouse Apodemus peninsulae from the Baikal region and Northern Mongolia

Analysis of the B-chromosome frequency and morphotypes in 160 mice Apodemus peninsulae from 17 localities of the Baikal region, Northern Mongolia, Trans-Baikalia, and the Russian Far East showed that the mice were from five geographical populations. The interpopulation difference was determined by variations of 0?C4 macro B chromosomes and 0?C11 micro B chromosomes. The B-chromosome number and morphotypes proved to be stable over the past 30 years in the geographical populations under study.     

中华姬鼠与大林姬鼠头骨的几何形态学研究

中华姬鼠Apodemus draco和大林姬鼠A.peninsulae形态与习性相似,北京地区的这两种鼠都存在还是只有大林姬鼠存在一直存在争议.通过新兴的几何形态测量技术对北京地区捕获的137只姬鼠头骨与黑龙汀的9只大林姬鼠头骨进行背面和侧面的形态对比分析.系统聚类分析结果、主成分分析结果和判别函数分析结果显示,北京地...     

Increase in the number of the B-chromosomes and variants of their system in mouse Apodemus peninsulae in Mountain Altai population over 26 years

A new evolutionary genetic phenomenon - increase in the number of B-chromosomes (almost threefold) accompanied by change in B chromosome morphotypes - was discovered in the Artybash population of East Asian mouse Apodemus peninsulae (Mountain Altai) over a historically short period (22 years), comparable with a small number of mouse generations (ten generations). The process of increase in the number of A. peninsulae B-chromosomes in Mountain Altai has been monitored over 26 years (1980, 1986, 1988, 1990, 2002, and 2006). A concept of a new type of genomic mutations - mutations in the number of B-chromosomes-has been substantiated. The phenomenon of genomic mutations in pro-B-chromosomes has been discovered only in the Mountain Altai populations. This region differs from the remaining A. peninsulae dwelling localities by pollution with unspent liquid propellant (UDMH, heptyl). It is assumed that the variants of mouse B chromosome system in the studied A. peninsulae populations in the overall habitation area over long-term periods are likely to remain relatively stable and that their variation is controlled by homeostatic processes. Disturbance of these processes, in particular, due to anthropogenic load, can disrupt the cyclic pattern of increase and decrease in the number of A. peninsulae B-chromosomes in individual years.     

A spatial aspect on mitochondrial DNA genealogy in Apodemus peninsulae from East Asia

Apodemus peninsulae is a field mouse that inhabits the broad-leafed forests of temperate Eurasia. We examined the mitochondrial cytochrome b gene in 57 individuals of A. peninsulae from northeastern Asia, including Siberia, Primorye, Magadan region, Sakhalin, Hokkaido, and the Korean Peninsula. The genealogy of the mitochondrial DNA (mtDNA) in A. peninsulae was shown to have substantial geographic affinity, suggesting geographic architecture of northeastern Asia, including the islands of Sakhalin and Hokkaido, played important roles on the cladogenesis. Taking into account the presence of region-specific anciently divergent mtDNA types, three parts of the regions of Primorye, Siberia, and the Korean Peninsula can be denoted as refugia for A. peninsulae during the substantial period of the Quaternary glacial ages. Among the geographic regions examined, Primorye is likely to be the most influential one, from which the mtDNA is thought to have migrated to the neighboring regions of Sakhalin, Hokkaido, the Magadan region, and Siberia during the evolution of this species.     

The mitochondrial genome of Apodemus peninsulae (Rodentia, Muridae)

The complete mitochondrial (mt) genome of the Korean field mouse Apodemus peninsulae was sequenced and found to be 16,266 bp in length. The mt protein-coding genes of A. peninsulae had ATG, GTG, ATC, and ATA as initiation codons and TAA, TAG, TA, and T as termination codons. Two forms each of trnL and trnS and the three tRNA clusters, IQM, WANCY, and HSL were identified, as in the typical Rodentia mt genome. Among tRNAs, abnormal cloverleaf structure of trnS((AGY)) was identified in DHU arm. The l-strand replication origin has the potential to form a stable stem-loop structure and control region has several conserved sequence elements.     

Synaptonemal complexes of the A- and B-chromosomes of the spermatocytes from the East Asian mouse Apodemus peninsulae

The analysis of whole-mount preparations of synaptonemal complexes (SCs) from surface-spread spermatocytes of A. peninsulae (2n = 48A + 1, 2, ... 12 B) had revealed SCs of 23 autosomal bivalents, sex bivalent XY, axial cores and SCs of the B-chromosomes. The intercellular and interindividual variability of the number of B-chromosomes varied from 1 to 12 per cell. The SCs of autosomal bivalents were shown to have a typical structure. The structure and behaviour of SCs of sex bivalent throughout meiotic prophase I appeared to be similar to those observed in other species of this order. Mainly B-univalents and less frequently B-bivalents containing SCs were found to be formed in meiotic prophase I. The full homologues appear to be rarely seen among B-chromosomes of the East-Asiatic mouse. A tendency of forming clusters of B-univalents near the sex bivalent was found, in addition to B-bivalents with lateral elements, having the form of bi- and tri-stranded elements with rare synaptic fragments. Besides this, the SCs of the autosomes of pachytene cells were found to contain structures resembling the recombination nodules.     

Instability of B-chromosomes in somatic and germline cells of Apodemus peninsulae

Instability of B-chromosomes was estimated in somatic and germline cells of samples Apodemus peninsulae from different localities of the species range. In 84 out of 188 animals (45%), in cells assessed for B-chromosome mosaicism, bone marrow cells with different B-chromosome number were observed. The numbers of B-chromosomes in spermatocytes at the pachytene stage were estimated in ten males. It was shown that the average number of B-chromosomes and the number of cell clones in germline cells was higher than the corresponding numbers in bone marrow cells. The higher number of B-chromosomes and their higher variability in germline cells than in somatic cells suggest the existence of a mechanism of premeiotic accumulation of B-chromosomes in spermatogenesis of A. peninsulae.     

Polymorphism and mosaicism of B chromosome number in Korean field mouse <Emphasis Type="Italic">Apodemus peninsulae</Emphasis> (Rodentia) in the Russian Far East

A karyotype analysis of the Apodemus peninsulae (n = 355) from 41 trapping points from the Russian Far East has allowed us to identify B chromosomes in 87.9% of the animals, 61.7% of which are mosaics. Different levels of variability in the B chromosome numbers have been studied, including both the inter- and intrapopulational, as well as intraindividual variability (mosaicism). It was found that the frequencies of the occurrence of individuals with B chromosomes and mosaicism between different population samples were not constant. The range of the modal B chromosome number variability and variation of the xB index (zero to four; on average, the xB amounted to 1.67) were studied for the first time in different samples and populations of this species. Individuals with the predominant numbers of B chromosome (as a rule, zero to two) were revealed in both groups of animals (with stable and mosaic karyotypes), but the frequency was different in geographical regions. The spectra of B chromosome variability were wider in mosaics (zero to seven) compared to animals with stable karyotypes (zero to four). The importance of this for species of the high frequency of individuals with B chromosomes and with mosaicism has been discussed. The adaptive role of the low number of B chromosomes (one to two), as well as the imbalance of the B chromosome system for the species as a whole is assumed.     

Karyotype and heterochromatin pattern of the field mouse,Apodemus argenteus Temminck

The field mouse,Apodemus argenteus Temminck, has 46 chromosomes. The autosomes comprise 20 pairs of acrocentrics and 2 pairs of metacentrics. The X chromosome is represented by an outstandingly large submetacentric element, while the Y is an acrocentric corresponding in size to the 5th or 6th pair of autosomes. All of the autosomes and gonosomes can be unequivocally identified by their characteristic Q-band or G-band patterns. The constitutive heterochromatin, as revealed by C-banding, is localized at the centromeric regions of all autosomes, the short arm and the proximal 1/3 of the long arm of the X chromosome, and the entire Y chromosome. The C-band-positive segments which constitute 33.5% of the genome exhibit dark fluorescence after Q-banding, late DNA replication, faint or positive staining reaction to G-banding, fast reassociation of DNA revealed by AO staining, and allocyclic behavior of the sex-bivalent in male meiosis. An exception to the above is the distal segment of the Y which is positive to both C- and Q-banding. The giant X chromosome occupies 13.1% of the genome, leaving 5.6% of euchromatic segments, the latter value being equivalent to that of the original type X.