Cytogenetic characteristics of species of the Chironomus plumosus group (Chironomidae, Diptera) in Finland

The cytogenetic characteristics of species of the Chironomus plumosus group in Finland were examined. The species included C. balatonicus Devai, Wülker, Scholl, C. entis Shobanov, C. plumosus L., C. muratensis Ryser, Scholl, Wülker, and two karyotypes of unknown species. All belonged to the thummi complex having 2n = 8 chromosomes, with arm combinations of AB, CD, EF, G. In C. balatonicus arms A to G the band sequences corresponded with those of other populations. A new band sequence was found in arm B. In C. entis an arm A had a band sequence similar to those in C. agilis. A large pericentric inversion was observed in chromosome AB. The arms B to G had band sequences typical for C. entis. The chromosome arms A and B in C. plumosus from Lake Marsjon had band sequences corresponding to those of C. agilis and C. entis, respectively. C. plumosus from Helsinki may be a more divergent population with a large amount of centromere heterochromatin. C. muratensis was not distinguishable by band sequences from those of other Palaearctic populations. Two new karyotypes similar to those of species of the plumosus group have been described.     

Molecular characterization of the pericentric inversion of chimpanzee chromosome 11 homologous to human chromosome 9

In addition to the fusion of human chromosome 2, nine pericentric inversions are the most conspicuous karyotype differences between humans and chimpanzees. In this study we identified the breakpoint regions of the pericentric inversion of chimpanzee chromosome 11 (PTR 11) homologous to human chromosome 9 (HSA 9). The break in homology between PTR 11p and HSA 9p12 maps to pericentromeric segmental duplications, whereas the breakpoint region orthologous to 9q21.33 is located in intergenic single-copy sequences. Close to the inversion breakpoint in PTR 11q, large blocks of alpha satellites are located, which indicate the presence of the centromere. Since G-banding analysis and the comparative BAC analyses performed in this study imply that the inversion breaks occurred in the region homologous to HSA 9q21.33 and 9p12, but not within the centromere, the structure of PTR 11 cannot be explained by a single pericentric inversion. In addition to this pericentric inversion of PTR 11, further events like centromere repositioning or a second smaller inversion must be assumed to explain the structure of PTR 11 compared with HSA 9.     

Unique genomic sequences in human chromosome 16p are conserved in the great apes

In humans, acute myelomonocytic leukemia (AMML) with abnormal bone marrow eosinophilia is diagnosed by the presence of a pericentric inversion in chromosome 16, involving breakpoints p13;q23 [i.e., inv(16)(p13;q23)]. A pericentric inversion involves breaks that have occurred on the p and q arms and the segment in between is rotated 180° and reattaches. The recent development of a “human micro-coatasome” painting probe for 16p contains unique DNA sequences that fluorescently label only the short arm of chromosome 16, which facilitates the identification of such inversions and represents an ideal tool for analyzing the “divergence/convergence” of the equivalent human chromosome 16 (PTR 18, GGO 17 and PPY 19) in the great apes, chimpanzee, gorilla and orangutan. When the probe is used on the type of pericentric inversion characteristic of AMML, signals are observed on the proximal portions (the regions closest to the centromere) of the long and short arms of chromosome 16. The probe hybridized to only the short arm of all three ape chromosomes and signals were not observed on the long arms, suggesting that a pericentric inversion similar to that seen in AMML has not occurred in any of these great apes. Received: 4 July 1996 / Accepted: 18 September 1996     

On the validization of the name Chironomus (Camptochironomus) pallidivittatus sensu edwards, 1929 and elimination of the name Chironomus pallidivittatus Malloch, 1915

The name Chironomus pallidivittatus sensu Edwards is widely used by specialists for the European species described by Edwards, whereas the use of the name Ch. tentans var. pallidivittatus Malloch is limited. In the light of the wide use of the name Chironomus pallidivittatus sensu Edwards, particularly in fields outside taxonomy, combined with virtually no publications on the Ch. tentans variety pallidivittatus Malloch, we recommend that the original Malloch’s application of the name should be suppressed in favor of that of Edwards, 1929. At the same time, synonymy of Ch. pallidivittatus s. Malloch with Ch. tentans Fabricius supposed by Townes (1945) is erroneous. Detailed cytogenetic (Kiknadze et al., 1996) and morphological (Shobanov et al., 1999) studies of North American, European, and Asian populations demonstrated the common occurrence of Ch. dilutus Shobanov, Kiknadze et Butler, 1999 in the Nearctic. This species is different from Ch. tentans but identical with Ch. tentans var. pallidivittatus Malloch, 1915 and the “Nearctic Ch. tentans” sensu Townes (1945).     

Chromosomal restructuring of three species of chiromonads from the Chernobyl region (Diptera, Chironomidae)

Chromosomal polymorphism of three species--Chironomus plumosus, Ch. balatonicus and Glyptotendipes glaucus collected from the Chernobyl Zone demonstrated following characteristics: lack of standard karyotype, the presence of hetero- and homozygotic inversions (seven para- and one pericentric), increase in centromeric heterochromatin (55% larvae in homo- and heterozygotic state), the presence of B chromosomes (21%)--in Ch. plumosus; only two larvae had a standard karyotype, the rest demonstrating hetero- and homozygotic inversions (eleven paracentrics), reciprocal translocations of the IVF and IA arms, B chromosomes (5.4%), increase in telomeric (43.6%) and centromeric (1.8%) heterochromatin--in Ch. balatonicus; two types of hetero- and homozygotic inversions, replacement of standard sequences in C and D for inversional homozygotic ones--in Gl. glaucus.     

A polymorphic structural rearrangement in the chromosomes of two populations of orangutan

A rearranged chromosome 9 was found in 12 of 23 specimens of orangutan, 4 of Bornean and 8 of Sumatran origin. Nine animals were heterozygous, and 3 were homozygous carriers for the variant chromosome, which was also traced in 4 other animals not studied by us. This type of chromosome rearrangement has been previously described (Seuánez et al., 1976) and is probably the same chromosome shown by Lucas et al. (1973) and reported by Turleau et al. (1975) in other specimens. There is obviously a very high incidence of this variant chromosome 9 in Pongo pygmaeus, and it is unlikely that it could result from independent rearrangements occurring in unrelated specimens from two geographically isolated populations (Sumatran and Bornean). It is concluded that the rearrangement is of ancient origin and that it has been maintained in the populations of Pongo as a balanced polymorphism. This type of complex rearrangement resulting from two pericentric inversions, one inside the other, is compared with certain sporadic pericentric inversions in the human complement, with pericentric inversions which are polymorphic in other mammals, and with pericentric inversions involved in chromosome evolution in the Hominoidea.     

Karyofund of Chironomus plumosus (Diptera, Chronomidae) in the Palearctic region

Quantitative and qualitative analyses of chromosomal polymorphism in 38 Palearctic populations of Chironomus plumosus were made. It was shown that most of the populations studied were highly polymorphic: in average 63.2 +/- 4.0% of larvae were heterozygous for inversions with 0.95 + 0.08 heterozygous inversion per larvae. Polymorphism on the size of centromeric heterochromatin and the presence of B-chromosomes were observed in many populations studied. The karyofund of Ch. plumosus in Palearctic was estimated. In total 35 banding sequences were found in Palearctic Ch. plumosus. Fifteen banding seguences have been described for the first time. On mapping the used banding sequences, we employed the conventions of Keyl (Keyl, 1962; Devai et al., 1989) and Maximova (Maximova, 1976; Shobanov, 1994a) for arms A, C, D, E and F, and the conventions of Maximova for arms B and G.     

Mapping of class alpha glutathione S-transferase 2 (GST-2) genes to the vicinity of the d locus on mouse chromosome 9

Recombinant inbred strains of mice were used to localize the genes coding for the class alpha glutathione S-transferase 2 (Gst-2). The genes showed three distinct strain distribution patterns, indicating that they occur in at least three clusters separable by recombination. All three clusters are located in the vicinity of the d locus on mouse chromosome 9, but two of them are closer to d than the third. Linked to Gst-2 on mouse chromosome 9 are two enzyme-encoding loci, Pgm-3 and Mod-1. The human counterparts of Gst-2, Pgm-3, and Mod-1 map to 6p12, 6q12, and 6q12, respectively. Thus, the pericentric region of human chromosome 6 has its homolog in the segment spanning Gst-2, Pgm-3, and Mod-1 on mouse chromosome 9. The fact that the syntenic group extends across the centromere of human chromosome 6 can best be explained by a pericentric inversion postulated to have taken place in the primate lineage leading to Catarhini.     

Centromere Epigenetics in Plants

The centromere is an essential chromosome site at which the kinetochore forms and loads proteins needed for faithful segregation during the cell cycle and meiosis(Houben et al., 1999;Cleveland et al.,2003;Ma et al.,2007;Birchler and Han,2009).Centromere specific sequences such as tandem repeats or transposable elements evolve quickly both within and between the species but have conserved kinetochore proteins(Henikoff and Furuyama,2010).The universal feature     

Evidence for a role of the synaptonemal complex in provision for normal chromosome disjunction at meiosis II in maize

The meiotic behavior of heterozygotes from three different maize pericentric inversion stocks was quantitatively observed at a variety of stages throughout meiosis I and II. With heterozygosity for either of two of these inversions, the usual mode of pairing observed at pachytene involved synapsis of the centromere containing inverted region, and synaptic failure of the centromere region was rarely found. Abnormal chromosome behavior at subsequent meiotic stages was rare in these cases. With heterozygosity for the third inversion, however, homologous synapsis was generally found in the distal regions of the chromosome involved, the inverted region was often non-homologously synapsed, and a substantial frequency of cells apparently showed synaptic failure in the centromere containing inverted region. A substantial frequency of cells at anaphase II in this case contained two lagging monads in the plate region of the spindle. Where cells could be identified as sisters, sister cells showed identical behavior at anaphase II. Findings seem to be most simply explained by the supposition that pachytene synapsis of the centromere region is important to provision for sister centromere association until anaphase II.     

The dynamic nature and evolutionary history of subtelomeric and pericentromeric regions

The organization and evolution of the subtelomeric and pericentromeric regions of human chromosomes exhibit unique characteristics compared to other regions of the genome. As shown in Fig. 1 the functional elements of the centromere and telomere are comprised of highly repetitive DNA sequences, which are responsible for carrying out the main mechanistic duties of these two regions: chromosome segregation and end replication, respectively. The nature of the repeats in these two regions and their function have been reviewed separately and, therefore, will not be discussed in more detail here (Sullivan et al., 1996, 2001; McEachern et al., 2000; Henikoff et al., 2001). Adjacent to these functional element regions, the centromere and telomere regions share an interesting architecture as depicted in Fig. 1. For both pericentromeric and subtelomeric regions, blocks of recent genomic duplications form a zone of shared sequence homologies between certain subsets of human chromosomes. The dynamic nature and evolutionary history of these regions and the unique DNA sequence adjacent to them will be the focus of this review.     

The first finding of chromosome variations in wild-born western hoolock gibbons

Hoolock gibbons (genus Hoolock) are a group of very endangered primate species that belong to the small ape family (family Hylobatidae). The entire population that is distributed in the northeast and southeast of Bangladesh is estimated to include only around 350 individuals. A conservation program is thus necessary as soon as possible. Genetic markers are significant tools for planning such programs. In this study, we examined chromosomal characteristics of two western hoolock gibbons that were captured in a Bangladesh forest. During chromosome analysis, we encountered two chromosome variations that were observed for the first time in the wild-born western hoolock gibbons (Hoolock hoolock). The first one was a nonhomologous centromere position in chromosome 8 that was observed in the two examined individuals. The alteration was identical in the two individuals, which were examined by G-band and DAPI-band analyses. Chromosome paint analyses revealed that the difference in the centromere position was due to a single small pericentric inversion. The second variation was a heterozygous elongation in chromosome 9. Analysis by sequential techniques of fluorescence in situ hybridization with 18S rDNA and silver nitrate staining revealed a single and an inverted tandem duplication, respectively, of the nucleolus organizer region in two individuals. These chromosome variations provide useful information for the next steps to consider the evolution and conservation of the hoolock gibbon.     

A primate transfer RNA gene cluster and the evolution of human chromosome 1.

The localisation of tRNA(Asn) gene clusters in the karyotypes of primates has been studied by means of in situ hybridisation. In the human and orangutan (Pongo pygmaeus) karyotypes there are two such gene clusters, one each on the long and short arms of chromosome 1. Old World monkeys, however, contain both gene clusters on their equivalent of the human chromosome 1 short arm, which can be explained by a pericentric inversion which (amongst other chromosome changes) distinguishes the human and Old World monkey chromosomes 1. The capuchin (Cebus appella), however, a New World monkey, has only one tRNA(Asn) gene cluster, at least on the elements equivalent to human chromosome 1. This cluster is located proximal to the centromere on a chromosome that has been tentatively identified (by others) as the equivalent of the long arm of human chromosome 1. Should this prove to be correct, it would indicate that the large primate metacentric came into being in the form found today in the great apes, rather than in the form currently found in Old World monkeys. These data further show that the tRNA(Asn) gene cluster has been split in two since before the Old World monkeys and hominids diverged, i.e., over 30 million years ago, and also that the original transfer of these genes from one arm of chromosome 1 to the other was unlikely to have involved a pericentric inversion but, rather, some form of replicative transposition.     

Karyotypic polymorphism of the zebra finch Z chromosome

We describe a karyotypic polymorphism on the zebra finch Z chromosome. This polymorphism was discovered because of a difference in the position of the centromere and because it occurs at varying frequencies in domesticated colonies in the USA and Germany and among two zebra finch subspecies. Using DNA fluorescent in situ hybridization to map specific Z genes and measurements of DNA replication, we show that this polymorphism is the result of a large pericentric inversion involving the majority of the chromosome. We sequenced a likely breakpoint for the inversion and found many repetitive sequences. Around the breakpoint, there are numerous repetitive sequences and several copies of PAK3 (p21-activated kinase 3)-related sequences (PAK3Z) which showed testes-specific expression by RT-PCR. Our findings further suggest that the sequenced genome of the zebra finch may be derived from a male heterozygote for the Z chromosome polymorphism. This finding, in combination with regional differences in the frequency of the polymorphism, has important consequences for future studies using zebra finches.     

A recombinant X chromosome in a short statured girl resulting from a maternal pericentric inversion

Summary a 73/4-year-old girl with short stature was found to have a recombinant (X), dup q chromosome resulting from an apparently unique pericentric inversion (X)(p11.2q26) present in her mother and maternal grandmother. The recombinant X chromosome was shown to be late replicating and the inversion X chromosome to be randomly inactivated. This appears to be only the eighth report (7 female, 1 male) of a recombinant resulting from an X pericentric inversion despite all diagnosed females having mild clinical abnormalities. Reasons for the rarity of such recombinant X chromosomes in man are examined.     

Cytogenetics of the European plethodontid salamanders of the genus Hydromantes (Amphibia,Urodela)

A karyological analysis was carried out on different European species of the genus Hydromantes (Plethodontidae). All the species examined share the same chromosome number (2n=28) and, with the exception represented by pair XIV, morphologically similar karyotypes. While the karyotypes display a similar distribution — mainly centromeric and pericentric — of C-heterochromatin, quantitative variations in pericentric heterochromatin are observed among species. In the continental species Hydromantes italicus and ambrosii as well as in the eastern Sardinian species imperialis, flavus and specie nova, pair XIV consists of heteromorphic sex chromosomes of the XX/XY type. It is proposed that the differentiation of the Y might have taken place through the occurrence of a structural rearrangement, such as a pericentric inversion, starting from a hypothetical, homomorphic pair XIV. A sex-related heteromorphism is not found in the western Sardinian species H. genei. A further karyological differentiation among these species concerns the position of the nucleolus organizing region (NOR), which is located on chromosome XII (H. italicus and ambrosii) or on chromosome X, close to the centromere (H. genei, H. imperialis and H. specie nova), or in an intercalary position (H. flavus). The location and the number of the 5 S DNA sites have been conserved during species divergence. On the basis of these karyological data, as well as of results obtained through a preliminary restriction enzyme analysis of the ribosomal and genomic DNAs, the phyletic relationships among the European Hydromantes species are discussed.     

Molecular analysis of a case of meiotic recombination leading to cri-du-chat syndrome

This paper describes a molecular investigation of a woman with an apparent large pericentric inversion of chromosome 5, inv(5)(p14;q35), and one normal chromosome 5 and her child, who was born with cri-du-chat syndrome. The four chromosome 5 homologs from the proband and his mother were isolated in somatic cell hybrids, and their haplotypes were determined at nine loci polymorphic for restriction enzyme sites. The deleted chromosome in the proband was shown to carry alleles from both maternal homologs, verifying molecularly that a meiotic recombination event in the mother gave rise to her son's deleted chromosome 5. The single crossover was presumably near the centromere.     

Differential staining of polytene chromosome bands in Chironomus by Giemsa banding methods

Two Giemsa banding methods (C banding and RB banding) are described which selectively stain the centromere bands of polytene salivary gland chromosomes in a number of Chironomus species. — By the C banding method the polytene chromosome appearance is changed grossly. Chromosome bands, as far as they are identifiable, are stained pale with the exception of the centromere bands and in some cases telomeres, which then are intensely stained reddish blue. — By the RB method the centromere bands are stained bright blue, whereas the remainder of the polytene bands stain red to red-violet. — Contrary to all other species examined, in Chironomus th. thummi numerous interstitial polytene chromosome bands, in addition to the centromere regions, are positively C banded and blue stained by RB banding. In the hybrid of Ch. th. thummi x Ch. th. piger only those interstitial thummi bands which are known to have a greater DNA content than their homologous piger bands are C banding positive and blue stained by the RB method whereas the homologous piger bands are C banding negative and red stained by RB banding. Ch. thummi and piger bands with an equal amount of DNA both show no C banding and stain red by RB banding. — It seems that the Giemsa banding methods used are capable of demonstrating, in addition to centromeric heterochromatin, heterochromatin in those interstitial polytene chromosome bands whose DNA content has been increased during chromosome evolution.     

A pericentric inversion of chromosome six in a patient with Peutz-Jeghers’ syndrome and the use of FISH to localise the breakpoints on a genetic map

Karyotypic analysis in a patient with Peutz-Jeghers’ syndrome demonstrated a pericentric inversion on chromosome 6. Further investigation was undertaken using fluorescence in situ hybridisation (FISH) with yeast artificial chromosome clones selected to contain genetic markers from chromosome 6, and a probe for the centromeric alphoid repeat array. This analysis located one inversion breakpoint within the alphoid array, in a 1-cM interval between D6S257 and D6S402, and the other in a 4-cM interval between D6S403 and D6S311. The oestrogen receptor gene locus (ESR) is excluded from the latter interval. Received: 23 January 1996 / Revised: 26 February 1996