Genetics and evolution of the mink Lpm-system. VIII. Characteristic changes in the antigenic structure of Lpm-protein and alpha2- macroglobulin in Mustelidae family

Interspecific variability of the isotypic structure of two macroglobulins (Lpm and alpha 2M) in Mustelidae family was investigated using monospecific rabbit antisera against Lpm and alpha 2M Mustela vison. It was established that all the species studied may be divided into four groups, according to the degree of their homology with Lpm: 1) M. vison; 2) M. altaica, M. erminea, Kolonocus sibirica, Putorius eversmany, P. putorius, Luteola lutreola; 3) Vormela peregusna; 4) Martes martes, M. foina, M. zibellina. The greatest divergence of Martes gene species from M. vison and other species studied is determined by two different immunogenetic approaches, the first based on the whole isotype of Lpm and the other using allotypic markers of individual Lpm genes. The variability of the isotypic structure of alpha 2M was lower than that revealed in Lpm. V. peregusna is the only species which significantly differs from all above-mentioned species, including M. vison. The differences established for degree of variability between Lpm and alpha 2M in Mustelidae family may be connected with the evolutionary peculiarities of these two genetic system of serum alpha-macroglobulins, which being phylogenetically related, are still structurally divergent.     

EcoRI- and BamHI-families of repeated sequences in mustelids

The restriction enzymes EcoRI and BamHI digest the genomic DNAs from six mustelids species Mustela lutreola, M. vision, M. erminea, M. sibirica, Vormela peregusna, producing repeated fragments varying in length. Some fragments were hybridized to chromosomes and restriction digests of DNAs from some mustelids and other mammals. The 0.7 kb EcoRI repeats from DNA of M. erminea are dispersed over chromosomes of carnivors. The 1.35, 1.9 and 2.7 kb BamHI repeats from DNA of polecat M. putorius furo are specific for mustelids. These repeats demonstrate interspecific variation in length and the number of copies. All BamHI repeats have no strict tandem organization. The 1.9 kb BamHI repeats are concentrated in the heterochromatic pericentromeric regions and additional chromosome arms. The 1.35 kb BamHI repeats are only located in the centromeric regions of chromosomes of five species and are absent in Vormela peregusna.     

Helminth communities of the autochthonous mustelids Mustela lutreola and M. putorius and the introduced Mustela vison in south-western France

This study presents the first comprehensive helminthological data on three sympatric riparian mustelids (the European mink Mustela lutreola, the polecat M. putorius and the American mink M. vison) in south-western France. One hundred and twenty-four specimens (45 M. lutreola, 37 M. putorius and 42 M. vison) from eight French departments were analysed. Globally, 15 helminth species were detected: Troglotrema acutum, Pseudamphistomum truncatum, Euryhelmis squamula, Euparyphium melis and Ascocotyle sp. (Trematoda), Taenia tenuicollis (Cestoda), Eucoleus aerophilus, Pearsonema plica, Aonchotheca putorii, Strongyloides mustelorum, Molineus patens, Crenosoma melesi, Filaroides martis and Skrjabingylus nasicola (Nematoda) and larval stages of Centrorhynchus species (Acanthocephala). The autochthonous European mink harboured the highest species richness (13 species) followed by the polecat with 11 species. The introduced American mink presented the most depauperate helminth community (nine species). The prevalence and worm burden of most of the helminths found in M. putorius and M. lutreola were also higher than those of M. vison. Some characteristics of their helminth communities were compared to relatively nearby populations (Spain) and other very distant populations (Belarus). This comparison emphasized M. patens as the most frequent parasite in all of the analysed mustelid populations. It was possible to conclude that the invasive M. vison contributes to the maintenance of the life cycle of the pathogenic T. acutum and S. nasicola helminths, with possible implications for the conservation of the endangered European mink.     

Evolution of satellite DNAs from the genus Palorus--experimental evidence for the "library" hypothesis

Satellite DNA profiles have been characterized in the congeneric species Palorus ratzeburgii, Palorus subdepressus, Palorus genalis, and Palorus ficicola (Coleoptera, Insecta), each of which contains a single, A + T-rich satellite DNA comprising a considerable portion of the genome (20%-40%). These satellites exhibit insignificant mutual sequence similarity. Using PCR assay, it has been shown that all four sequences are present in each of the tested Palorus species: one of them is amplified into a high copy number or a major satellite, while the three others are in the form of low-copy-number repeats estimated to make up approximately 0.05% of the genome. Each of the four satellites is interspecifically high conserved concerning the sequence, monomer length, and tandem repeat organization. Major, as well as low- copy-number, satellites are colocalized in the regions of pericentromeric heterochromatin on all chromosomes of the complement. The low-copy-number satellites are dispersed between the large arrays of the major satellite over the whole heterochromatic block. Our results explain satellite DNA evolution, confirming the hypothesis that related species share a "library" of conserved satellite sequences, some of which could be amplified into a major satellite. Due to the evolutionary dynamics of satellite DNAs, the content of the "library" is variable; the elimination of some sequences parallels the creation of the new ones. Quantitative changes in satellite DNAs, induced by occasional amplification of satellite repeat from the "library", could possibly occur in the course of the speciation process, thus forming a species-specific profile of satellite DNAs.      

Isolation and characterisation of satellite DNA from Brassica juncea (L.) Czern

Nuclear DNA isolated from hypocotyls (H), proliferating callus (PC) and differentiating callus (DC) of Brassica juncea contains a satellite DNA which can be resolved in actinomycin-D/CsCl gradients. The satellite DNA undergoes changes, when an in vitro culture is raised from hypocotyl tissue and forms a higher percentage of the genome in PC and DC than in mature differentiated tissue (hypocotyl). All the three satellite DNAs are GC-rich compared to main band DNAs. Satellite DNA of H has higher Tm and GC content than that of the PC and DC satellites. A 200 bp basic repeat unit from hypocotyl nuclear DNA has been cloned and characterised.     

Mapping Simple Repeated DNA Sequences in Heterochromatin of Drosophila Melanogaster

Heterochromatin in Drosophila has unusual genetic, cytological and molecular properties. Highly repeated DNA sequences (satellites) are the principal component of heterochromatin. Using probes from cloned satellites, we have constructed a chromosome map of 10 highly repeated, simple DNA sequences in heterochromatin of mitotic chromosomes of Drosophila melanogaster. Despite extensive sequence homology among some satellites, chromosomal locations could be distinguished by stringent in situ hybridizations for each satellite. Only two of the localizations previously determined using gradient-purified bulk satellite probes are correct. Eight new satellite localizations are presented, providing a megabase-level chromosome map of one-quarter of the genome. Five major satellites each exhibit a multichromosome distribution, and five minor satellites hybridize to single sites on the Y chromosome. Satellites closely related in sequence are often located near one another on the same chromosome. About 80% of Y chromosome DNA is composed of nine simple repeated sequences, in particular (AAGAC)(n) (8 Mb), (AAGAG)(n) (7 Mb) and (AATAT)(n) (6 Mb). Similarly, more than 70% of the DNA in chromosome 2 heterochromatin is composed of five simple repeated sequences. We have also generated a high resolution map of satellites in chromosome 2 heterochromatin, using a series of translocation chromosomes whose breakpoints in heterochromatin were ordered by N-banding. Finally, staining and banding patterns of heterochromatic regions are correlated with the locations of specific repeated DNA sequences. The basis for the cytochemical heterogeneity in banding appears to depend exclusively on the different satellite DNAs present in heterochromatin.     

The distribution of satellite and main-band DNA components in the melanogaster species subgroup of Drosophila

Fractionation of total adult DNA of five of the seven species of the melanogaster species sub-group of Drosophila in actinomycin D and distamycin A caesium density gradients has revealed the presence of three main-band DNA components, common to all species, and ten satellite DNAs that are distributed between the species. Satellite DNAs are either unique to a species or common to two or more species. The abundance of a common satellite DNA varies between species. There is no simple relationship between the presence of a satellite DNA and a branch point of phylogenetic divergence; nevertheless the arrangement of the species in a phylogeny that is based on the numbers of satellites held in common accurately reflects the pattern of relationships between the same species based on differences in inversions of polytene chromosomes. The species can be similarly arranged according to the compositions of their mitochondrial DNAs. It is possible that the same basic set of sequences, each of low frequency, is common to all species with arbitrary or selected amplification of particular sequences to differing extents in individual species. The conservation of satellites in the group and the close parallel between the distributions of satellites and inversions between the species suggests that either the processes that operate to change both chromosomal phenomena are similarly time-dependent and occurring at relatively low rates or that their rates of change are restricted according to some undetermined functions of these aspects of the genome.     

Cryptic satellites rich in inverted repeats comprise 30% of the genome of a hermit crab

One major very highly repeated (VHR) DNA (approximately 7 X 10(6) copies/genome; repeat unit = 156 base pairs (bp)), a family of three minor VHR DNAs (approximately 2.8 X 10(6) copies/genome; repeat units = 71-74 bp), and a number of trace components account for almost 30% of the genome of a hermit crab. The repeat units of the three minor variants are defined by identical 14-bp G + C-rich inverted repeats that might form cruciforms. Two copies of the repeat unit (CCTA) of one of two patent satellites of this crab (Skinner, D. M., and Beattie, W. G. (1974) Biochemistry 13, 3922-3929; Skinner, D. M., Beattie, W. G., Blattner, F. R., Stark, B. P., and Dahlberg, J. E. (1974) Biochemistry 13, 3930-3937) occur at the center of one in seven of the G + C-rich inverted repeats; copies of the other patent satellite (Chambers, C. A., Schell, M. P., and Skinner, D. M. (1978) Cell 13, 97-110) are found in main component DNA. The sequences of both the major and minor VHR DNAs are characterized by short tracts of An and/or Tn (n = 4-7) residues whose presence would permit the formation of perfectly matched stems separated by loops of 8-16 bp. The An and/or Tn tracts are interspersed with segments of G + C-rich DNA and are arranged differently in the major and minor VHR DNAs. Although the repeat units of the major and the three minor VHR DNAs are arranged in tandem, the composition and sequence of their bases are such that they do not form distinct bands in CsCl gradients; they are cryptic satellites.     

Aleutian mink disease parvovirus in wild riparian carnivores in Spain

Serious declines in populations of native European mink (Mustela lutreola) have occurred in Europe. One responsible factor may be infectious diseases introduced by exotic American mink (Mustela vison). In order to investigate a possible role for Aleutian mink disease parvovirus (ADV), we surveyed native riparian carnivores and feral American mink. When serum samples from 12 free-ranging European and 16 feral American mink were tested, antibodies to ADV were detected from three of nine European mink. ADV DNA was detected by polymerase chain reaction in whole cell DNA from four of seven carcasses; two American mink, one European mink and a Eurasian otter (Lutra lutra). Lesions typical of Aleutian disease were present in one of the American mink. A portion of the ADV VP2 capsid gene was sequenced and the results suggested that two sequence types of ADV were circulating in Spain, and that the Spanish ADVs differed from other described isolates from North America and Europe. Future conservation and restoration efforts should include measures to avoid introduction or spread of ADV infection to native animals.     

The biological significance of variation in satellite DNA and heterochromatin in newts of the genus Triturus: an evolutionary perspective

The functional and evolutionary significance of highly repetitive, simple sequence (satellite) DNA is analysed by examining available information on the patterns of variation of heterochromatin and cloned satellites among newts (family Salamandridae), and particularly species of the European genus Triturus. This information is used to develop a model linking evolutionary changes in satellite DNAs and chromosome structure. In this model, satellites accumulate initially in large tandem blocks around centromeres of some or all of the chromosomes, mainly by repeated chromosomal exchanges in these regions. Centromeric blocks later become broken up and dispersed by small, random chromosome rearrangements in these regions. They are dispersed first to pericentric locations and then gradually more distally into the chromosome arms and telomeres. Dispersal of a particular satellite is accompanied by changes in sequence structure (for example, base substitutions, deletions, etc.) and a corresponding decrease in its detectability at either the molecular or cytological level. On the basis of this model, observed satellites in newt species may be classified as 'old', 'young', or of 'intermediate' phylogenetic age. The functions and effects of satellite DNA and heterochromatin at the cellular and organismal levels are also discussed. It is suggested that satellite DNA may have an impact on cell proliferation through the effect of late-replicating satellite-rich heterochromatin on the duration of S-phase of the cell cycle. It is argued that even small alterations in cell cycle time due to changes in heterochromatin amount may have magnified effects on organismal growth that may be of adaptive significance.     

Satellite DNA relationships in man and the primates

We have investigated the genomes of a series of primates to identify the presence of sequences related to human satellite DNAs I, II and III by restriction enzyme digestion and hybridisation with probes of these satellite DNAs. Where we have found such related sequences we have examined the extent to which they have diverged by measuring the stability of the hybrids. DNA satellite III is the oldest sequence being common to species which have diverged some 24 million years ago. In contrast DNA satellites I and II are of much more recent origin. Our results permit us to draw conclusions about the way these sequences have evolved, and how the evolution of repeated DNA sequences may be related to the evolution of the primate lineage.     

Satellite DNA of Anopheles stephensi liston (Diptera: Culicidae)

Four satellite DNAs in the Anopheles stephensi genome have been defined on the basis of their banding properties in Hoechst 33258-CsCl density gradients. Two of these satellites, satellites I and II, are visible on neutral CsCl density gradients as a light density peak forming approximately 15% of total cellular DNA. Hoechst-CsCl density gradient profiles of DNA extracted from polytene tissues indicates that these satellites are underreplicated in larval salivary gland cells and adult female Malpighian tubules and possibly also in ovarian nurse cells. The chromosomal location of satellite I on mitotic and polytene chromosomes has been determined by in situ hybridisation. Sequences complementary to satellite I are present in approximately equal amounts on a heterochromatic arm of the X and Y chromosomes and are also present, in smaller amounts, at the centromere of chromosome 3. A quantitative analysis of the in situ hybridisation experiments indicates that sequences complementary to satellite I at these two sites differ in their replicative behaviour during polytenisation: heterosomal satellite I sequences are under-replicated relative to chromosome 3 sequences in polytene larval salivary gland and ovarian nurse cell nuclei.     

Satellite DNA-correlated nucleosomal proteins in Drosophila virilis

Three major satellite DNAs comprise 40–45% of the genome of Drosophila virilis. Since these satellites are not substrates for most restriction enzymes, we were able to digest D. virilis nuclei with HaeIII and micrococcal nuclease and isolate chromatin fractions containing variable levels of satellite DNA. Electrophoretic analysis of these chromatin fractions revealed that the level of the acid-soluble chromosomal protein, cp17.3, was directly related to the percentage of satellite DNA in chromatin. The correlation between cp17.3 and satellite DNA abundance suggests that cp17.3 is involved in the heterochromatic condensation of satellite DNAs. cp17.3 occurs at a frequency of one molecule per 10–20 nucleosomes. It is detected in an electrophoretically distinguishable class of mononucleosomes, provisionally identified as MN1uH2A, which contains ubiquitinated histone H2A (uH2a) but lacks histone H1. It is not detected in MN1, a second class of mononucleosomes, which lacks uH2A and H1. Since cp17.3 is correlated with satellite DNAs and present in nucleosome cores, it might be a histone variant specifically associated with satellite DNAs.This work was supported by Grant GM22138 from the National Institutes of Health. G.A.V. was a predoctoral trainee supported by Grant GM07094 from the National Institutes of Health.     

Comparative study of satellite sequences and phylogeny of five species from the genus Palorus (Insecta, Coleoptera).

Major satellite sequences are analysed in the three tenebrionid beetles Palorus cerylonoides, P. genalis, and P. ficicola, and compared with the ones from P. ratzeburgii and P. subdepressus reported elsewhere. All of them are A+T rich, pericentromerically located, and with lengths of about 150 bp, either in the form of monomers or formed by more complex repeating units. A preliminary phylogenetic analysis of Palorus species using the 3' end of the mitochondrial Cytochrome Oxidase I gene shows that the five Palorus species have been diverging for a considerable amount of evolutionary time, with the pair P. ratzeburgii and P. genalis being the most closely related. Only these two taxa showed some similarity between their respective high-copy-number satellite sequences, while other satellites are mutually unrelated and might have originated independently. However, all the satellites have in common tertiary structure induced by intrinsic DNA curvature, a characteristic which is conserved within the genus. Palorus major satellites were previously detected in the genomes of congeneric species as low-copy-number clusters (Mestrovi? et al., Mol. Biol. Evol. 15: 1062-1068. 1998). Given the divergences between the analysed species, the substitution rate deduced from high- and low-copy-number repeats is unexpectedly low. The presence of sequence-induced DNA curvature in all Palorus satellites and similar satellite DNAs in the species pair P. ratzeburgii and P. genalis suggest (i) that constraints are at the tertiary structure; and (ii) that the satellite DNA evolutionary turnover can be dependent on the history of the taxa under study, resulting in retention of similar satellites in related taxa.     

Comparative analysis of three guinea pig satellite DNA's by restriction nucleases.

The structures of guinea pig satellite DNAs I, II, and III have been analyzed by digestion with seven restriction nucleases. From the cleavage patterns it is obvious that the long-range periodicities in these three satellites differ rather characteristically Satellite I is fairly resistant to six nucleases and gives only a number of weak discrete bands which do not show a simple regularity. By the restriction nuclease from Arthrobacter luteus, however, it is cleaved extensively and yields very heterogeneous breakdown products. This is consistent with the high extent of divergence previously found for this satellite, e. g. by sequence analysis. Satellite II is almost completely resistant to all nucleases, indicative of a high degree of sequence homogeneity of this satellite. Satellite III is completely broken by the restriction nuclease from Bacillus subtilis into fragments which form a novel, highly regular series of bands in gel electrophoresis. The patterns show that the satellite is composed of tandem repeats ofapproximately 215 nucleotide pairs length, each repeat unit containing two cleavage sites for this nuclease. The data are consistent with the assumption that 30--40% of all cleavage sites have been eliminated by a random process. Satellite III DNA yields weak degradation patterns of the same periodicity with a number of other restriction nucleases. Cleavage sites for these nuclease are clustered on separatesmall segments of the satellite DNA. In this respect, the satellite is similar to others, notably the mouse satellite DNA. The three guinea pig satellites are examples of more general types of satellite structures also found in othe organisms. Similarities and differences to other satellites are discussed with special consideration to theories on the evolution of this class of DNA.     

The fate of DNA statellites I,II, III and ribosomal DNA in a familial dicentric chromosome 13:14

Summary In a family with a stable dicentric 13:14 translocation chromosome, the distribution of DNA sequences complementary to satellite DNAs I, II and III and ribosomal RNA were studied. The translocation chromosome showed a loss of sequences complementary to all three satellite DNAs, located in the short arms of all the acrocentric chromosomes, but slightly more of the sequences complementary to satellite I were retained than of the other two satellite DNAs. The fact that material was lost from all three satellites indicates that they are not present as single discrete blocks in these chromosomes, when we would expect to find the distal sequences lost and the proximal ones retained, but consist of interspersed blocks with each sequence represented by more than one, and probably several blocks. There was a total loss of ribosomal DNA from the nucleolar organiser regions of the chromosomes involved in the 13:14 translocation, but an interesting finding was the presence of extra ribosomal DNA and satellite DNAs I, II and III in one chromosome 22 which was found in seven out of nine individuals of the family with the 13:14 translocation, and in only one of five individuals without the translocation. There may be a compensatory mechanism present when certain sequences are eliminated during chromosomal rearrangements. The relationship of such mechanisms to reproductive fitness is discussed.     

Behaviour of sex chromosome associated satellite DNAs in somatic and germ cells in snakes

Sex chromosome associated satellite DNAs isolated from the snakes Elaphe radiata (sat III) (Singh et al., 1976) and Bungarus fasciatus (Elapidae) (minor satellite) are evolutionarily conserved throughout the suborder Ophidia. An autosome limited satellite DNA (B. fasciatus major satellite) is not similarly conserved. Both types of satellites have been studied by in situ hybridisation in various somatic tissues and germ cells where it has been observed that the W sex chromosome remains condensed in interphase nuclei. In growing oocytes however, the W chromosome satellite rich heterochromatin decondenses completely whilst the autosomal satellite rich regions remain condensed. Later, the cycle is reversed and the W chromosome condenses whilst the autosomal satellite regions decondense. In a primitive snake (Eryx johni johni) where the sex chromosomes are not differentiated and where there is no satellite DNA specific to them, these phenomena are absent. — The differential behaviour of autosomal and sex chromosome associated satellite DNAs is discussed in the light of gene regulation.     

Cloning, characterization and physical mapping of three cervid satellite DNA families in the genome of the Formosan muntjac (Muntiacus reevesi micrurus)

Due to their high sequence diversity even among closely related species, satellite DNA sequences can be a useful molecular marker for phylogenetic and taxonomic analyses. To characterize the satellite DNA in the genome of a native muntjac species of Taiwan, the Formosan muntjac, satellite DNA clones representing three different cervid satellite DNA families from this species were isolated and analyzed. Genomic organization study of these satellite DNAs was also undertaken. Three Formosan muntjac satellite DNA clones were obtained and designated as FM-satI (1,391 bp), FM-satII (1,143 bp) and FM-satIV (1,103 bp), and found to share approximately 82, 81 and 98% sequence homology with the Chinese muntjac satellite I clone (C5), Indian muntjac satellite II clone (Mmv-0.7) and Chinese muntjac satellite IV clone (MR-1.0), respectively. These three satellite DNA families are organized in a pter<--FM-satII-FM-satIV-FM-satI-->qter orientation in the centromeric region with satII closely associated with the telomeric sequences. Satellite DNA sequence comparison, in combination with chromosome data concludes that the Formosan muntjac is likely a subspecies of M. reevesi, closely related to the Chinese muntjac. With the kinetochore satellite II DNA co-localizing with the telomeric sequences, the Formosan muntjac chromosomes could be truly telocentric.