Intraspecies autosomal polymorphism and chromosome replication in Akodon molinae (Rodentia-Cricetidae).
Explore the source record for details and available documents.
Animals↗
SEARCH · Search PubMed
Results for “Rodentia”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
DNA of Akodon (Rodentia, Cricetidae). II. Molecular hybridization of repetitive DNA sequences.
Interspecies repetitive DNA homology was studied in akodont rodents related at generic and suprageneric levels. The homology was determined by taking the species Akodon molinae as the reference species. The 3H-DNA/DNA hybridization on filters showed a closer relationship between A. molinae and A. azarae, A. dolores and A. mollis than between A. molinae and Bolomys obscurus. These data agree with the taxonomical ranking of the species. The quantity and quality of the hybrid DNAs were measured by investigating their thermal stabilities and subsequent comparison to the results obtained on the reference species. These data indicate high similitude between the repetitive DNA of A. dolores and A. molinae. Increasing differences were shown to occur in the repetitive DNA of A. mollis, B. obscurus and A. azarae, respectively. Since these results coincide with the G-banding homologies and differ slightly from the taxonomical rank, it is speculated that the divergency between the DNA of A. molinae and A. azarae is the result of a differential process of DNA amplification which is not related to the phylogenetical distance separating the two species.
Animals↗
[Electrophoretic variability in a total of 11 structural sites in murine rodents (Muridae, Rodentia)].
Forty-six rodent species of the Muridae family were submitted to sequential electrophoresis for the study of 11 protein loci, using 12 buffer systems which differed in pH and ionic composition. The complete set of electrophoretic conditions yielded 135 variants of which 68 were detected through a single condition. The twofold increase of revealed variants was essentially limited to intergeneric comparisons because few additional variants within genera were revealed, despite the use of several buffers. These results show that estimation of the degree of genetic differentiation among taxa at a higher level than that of the genus by standard electrophoretic data may, although of current use, lead to erroneous results.
Animals↗
The role of B chromosomes in the population dynamics of yellow-necked wood mice Apodemus flavicollis (Rodentia, Mammalia).
Seasonal changes in the frequency of animals with B chromosomes were studied during 1989 in the population of yellow-necked wood mice, Apodemus flavicollis, on the mountain Jastrebac in Yugoslavia. During the study the estimated density of animals reached a very large value (378.8 individuals/ha for the April sample), which produced stress conditions leading to population decline. Six samples with a total of 247 specimens were karyotypically analyzed. Animals with Bs were present in all samples in frequencies that differed significantly at the 5% level. This difference was produced by the reduction in frequencies of specimens with Bs between the April and May samples (0.53 versus 0.29; chi 2(1) = 9.44; p < 0.002) and appeared mostly as a result of increased elimination of B-carrying animals from the prereproductive group. Young animals with Bs were inferior in stress conditions produced by overabundance of animals. From the first to the last sample, the frequency of animals with one B among B-containing animals constantly decreased, while the frequency of animals with more than one B increased. The possible role of Bs in regulating population dynamics is discussed.
Age Factors↗
Comparative chromosome analysis (R- and C-bands) of two South African murid species, Lemniscomys rosalia and Rhabdomys pumilio (Rodentia, murinae).
We carried out a comparative chromosome analysis (R- and C-bands) on two South African murid rodent species, Lemniscomys rosalia and Rhabdomys pumilio, whose banded karyotypes are reported here for the first time. The study revealed that, in spite of minor differences in diploid number and the number of autosomal arms (48 vs. 46 and 58 vs. 60, respectively), these species differ by at least 10 structural rearrangements, comprising seven Robertsonian translocations (two of which share monobrachial homology), two tandem translocations, and one pericentric inversion. Despite the high level of chromosomal differentiation observed, almost complete homologous banding patterns were detected between the two species. The present study therefore strengthens the hypothesis about the close phylogenetic affinities between L. rosalia and R. pumilio and their belonging to a set of genera referred to as "arvicanthine" rodents.
Animals↗
Induction and characterization of hypoxanthine-phosphoribosyltransferase (Hprt-) deficient cell lines of Akodon cursor (Rodentia, Sigmodontinae).
Hypoxanthine-phosphoribosyltransferase negative (Hprt-) cell lines derived from an Akodon cursor liposarcoma were obtained by induced mutagenesis. All but one Hprt- cell line lacked Hprt mRNA transcripts while one (AKO 3) coded for a truncated protein. Cell fusion and karyotypic analyses showed that one cell line (AKO 1-15) could be successfully used for constructing hybrid panels and allow for a clear identification of human chromosomes in hybrid cells.
Aneuploidy↗
Polymorphism and polytypy for pericentric inversions in 38-chromosome Mastomys (Rodentia, Murinae) and possible taxonomic implications.
Chromosome banding analysis (R- and C-bands) of two 38-chromosome Mastomys specimens originating from the Ivory Coast and Uganda revealed different numbers of autosome arms (NFa), equal to 51 and 60, respectively. Comparison of their chromosome banding patterns with those of Mastomys specimens from the Sudan (NFa = 41) and Senegal (NFa = 51-54), studied previously, showed that variation of the NFa from 40 to 60 throughout the species distribution is the result of a pericentric inversion polymorphism involving 3-12 chromosome pairs. At the population level, this variation is much narrower and never results from more than two chromosome pairs involved in inversion polymorphism. Taking into account that the NFa values recorded to date form a well-defined discontinuous row, we presume that introgressive hybridization between populations differing from each other by 3-5 to 11-12 pericentric inversions is interrupted. From there, the hypothesis of the existence of at least three cryptic species (designated provisionally as MER-1, MER-2, and MER-3) within 38-chromosome Mastomys populations previously assigned to M. erythroleucus can be made. It looks likely that one of them, possessing a karyotype with an NFa = 50-56, is widely distributed throughout sub-Saharan Africa and includes karyotyped populations from Senegal, the Ivory Coast, Mali, Benin, Cameroon, Zaire, and the Sudan. The second species (MER-2) includes the specimens karyotyped (NFa = 40-41) from Chad and the Sudan. Finally, a third tentative species (MER-3) corresponds to specimens with NFa = 59-60 found in East Zaire and Uganda, as well as possibly Mali and Chad.
Animals↗
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.
Animals↗
Explosive chromosome evolution and speciation in the gerbil genus Taterillus (Rodentia, Gerbillinae): a case of two new cryptic species.
The five morphologically sibling gerbil species of the genus Taterillus in West Africa were first identified from karyotypes. These species possess an XX/XY(1)Y(2) sex-chromosome system and are characterized by significant karyotypic reorganization, thus making them a suitable model for studying the role of chromosomal rearrangements in the speciation process. We present here a description of two new cytotypes, Taterillus sp. 1 and Taterillus sp. 2, from the Lake Chad area, the former having a 2n = 22/23, NFa = 40, and the latter 2n = 24/25, NFa = 44. Comparison of their G- and C- banding patterns with those of T. pygargus (2n = 22/23, NFa = 38/40), examined in an earlier paper, revealed that all three species differ from each other by 7 to 11 chromosomal rearrangements, comprising tandem translocations, pericentric inversions, and Robertsonian metacentrics displaying monobrachial homology. Meiotic configurations formed in potential hybrids among any of these three forms would consist of complex rings and chains, alone or in combination, resulting, as expected, in a significant disruption of gametogenesis. These results provide support for assigning Taterillus sp. 1 and Taterillus sp. 2 to two different biological species, which, as demonstrated by our preliminary molecular studies, would have emerged recently. Possible factors responsible for the rapid karyotypic evolution and speciation in this West African gerbil complex are discussed.
Animals↗
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.
Animals↗
Chromosomal localization of telomeric sequences in three species of Akodon (Rodentia, Sigmodontinae).
The distribution of the vertebrate telomeric sequence T2AG3 in three species of the rodent genus Akodon was examined by FISH with a peptide nucleic acid probe. In addition to the expected telomeric hybridization, non-telomeric signals were observed in the three species. In A. dolores, centromeric signals were visible in two of the four biarmed autosome pairs featuring Robertsonian polymorphism, indicating the retention of at least part of the telomeric sequences during the fusion process, and an interstitial signal of lower intensity was observed in the short arm of another. In A. boliviensis, a strong signal was observed near the centromeric end of the first chromosome pair. The first pair of A. azarae (homologous to the first pair of A. boliviensis) showed a similar but markedly amplified signal, and a subcentromeric signal in the X chromosome corresponding to a heterochromatic region; additionally, interstitial signals of lower intensity were present in one to four chromosomes in the majority of cells examined.
Animals↗
Heterochromatin differentiation shows the pathways of karyotypic evolution in Israeli mole rats (Spalax, Spalacidae, Rodentia).
C-banding, base-specific fluorochrome staining (CMA3/DA/DAPI), and comparative genomic hybridization (CGH) were used to analyze the constitutive heterochromatin in two Israeli Spalax species, S. galili (2n = 52) and S. judai (2n = 60). It was shown that C-positive centromeric heterochromatin and some telomeric sites comprise GC-rich DNA sequences in both species. Comparative genomic in situ hybridization revealed slight qualitative differences in highly repetitive sequences in the two Spalax species. Eight acrocentric pairs in S. judai that are involved in Robertsonian rearrangements, possessed composite heterochromatin with a preference of S. judai highly repetitive sequences in the proximal region. Heterochromatin of the sex chromosomes, two biarmed homologous pairs (4 and 5) in both species, and acrocentric chromosomes from the group with a variable centromere position in S. judai was entirely species-specific. The high level of homology in the composition of heterochromatin may relate to the recent divergence of Israeli Spalax. Interspecies heterochromatin differences are discussed in the context of possible mechanisms in the Spalax chromosome evolution.
Animals↗
Non-telomeric sites as evidence of chromosomal rearrangement and repetitive (TTAGGG)n arrays in heterochromatic and euchromatic regions in four species of Akodon (Rodentia, Muridae).
Comparative studies among four species--Akodonazarae (2n = 38), A. lindberghi (2n = 42), A. paranaensis (2n = 44) and A. serrensis (2n = 46)--employing classic cytogenetics (C- and G-bands) and fluorescence in situ hybridization with telomeric (TTAGGG)n sequencesare reported here. Non-telomeric signals in addition to the regular telomeric sites were detected in three species:A. azarae, A. lindberghi and A. serrensis. One interstitial telomeric site (ITS) was observed proximally at the long arm of chromosome 1 of A. azarae. The comparison of G-banding patterns among the species indicated that the ITS was due to a tandem fusion/fission rearrangement. Non-telomeric signals of A. lindberghi and A. serrensis were not related to chromosomal rearrangements; instead, the sequences co-localized with (i) heterochromatic regions of all chromosomes in A. serrensis; (ii) some heterochromatic regions in A. lindberghi, and (iii) both euchromatic and heterochromatic regions in the metacentric pair of A. lindberghi. These exceptional findings revealed that ITS in Akodon can be related to chromosomal rearrangements and repetitive sequences in the constitutive heterochromatin and that the richness of TTAGGG-like sequences in the euchromatin could be hypothesized to be a result of amplification of the referred sequence along the chromosome arms.
Animals↗
Innervation of propatagial musculature in a flying squirrel, Glaucomys volans (Rodentia, Sciuridae).
The propatagium of gliding and flying mammals is of both functional and phylogenetic interest. The innervation of the propatagial muscle, platysma II, was studied with the axonal tracer wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) in a flying squirrel, Glaucomys volans. Injections of WGA-HRP into the proximal third of platysma II labeled motoneurons in the lateral part of the medial subdivision of the ipsilateral facial nucleus and in the ipsilateral ventral horn of the brachial enlargement. Injections into distal regions of platysma II labeled motoneurons in the ipsilateral ventral horn of spinal segments C5-C8 but not in the facial nucleus. Injections along the whole length of the muscle labeled afferent axons in the ipsilateral dorsal horn of spinal segments C4-T1. These results demonstrate a mixed facial and spinal motor innervation of propatagial musculature in the flying squirrel and indicate that this pattern of mixed innervation is more widespread among flying and gliding mammals than previously reported. Mixed facial and cervical propatagial innervation, independently derived in different flying and gliding mammals, may represent a common solution in the design of the propatagium. These findings complicate the use of propatagial muscle innervation patterns for the establishment of phylogenetic relationships among flying and gliding mammals.
Afferent Pathways↗
The chromosomes of the field mouse Akodon azarae (Cricetidae, Rodentia) with special reference to sex chromosome anomalies.
Explore the source record for details and available documents.
Animals↗
The chromosomes of Spermophilus townsendi (Rodentia: Sciuridae) and report of a new subspecies.
Explore the source record for details and available documents.
Animals↗
Standardized karyotype of deer mice, Peromyscus (Rodentia). The Committee for Standardization of Chromosomes of Peromyscus.
A standard G-band karyotype is proposed for the genus Peromyscus. G-banded chromosomes of Peromyscus boylii glasselli (NF=56), numbered and arranged according to euchromatic lengths, serve as the standard. It is suggested that rearrangements of the standard pattern which occur in other species of Peromyscus be described using the general methods of the PARIS CONFERENCE (1971).
Animals↗
Chromosomes of Peromyscus (rodentia, cricetidae). VI. The genomic size.
In the genus Peromyscus cells of all species contain 48 chromosomes; however, the fundamental number varies from 56 (P. Crinitus, P. boylei) to 96 (P. eremicus). In some cases biarmed chromosomes are the result of pericentric inversions, while in others they are the result of addition of large amounts of constitutive heterochromatin. Flow microfluorometric DNA-per-cell determinations demonstrated that in some species (P. eremicus) the genome is increased by 36% over the amount of DNA found in most mammalian species. Studies of unique karyotypes with increased amounts of DNA added as constitutive heterochromatin may ultimately help in the elucidation of the mechanisms involved in karyotype evolution and speciation.
Animals↗