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PubMed1994

Transcription activation mediated by chromosomal inversion in rat cells.

To investigate the relationship between the local configuration of a gene and its level of expression, we constructed a rat cell line, Hy5, carrying a mutant polyomavirus middle T oncogene (pmt) whose overexpression converted the cells to the transformed state. The structure of the transgene was such that pmt was able to undergo chromosomal inversion at a relatively high rate by a cross-over in flanking pBR322 sequences. Hy5 cells became spontaneously transformed at a rate of 10(-5) per cell generation and all of the transformants analysed had sustained pmt inversion. CpG sequences were partially methylated in the Hy5 insert but appeared demethylated in transformants. In two subclones derived from untransformed Hy5 cells, the pmt insert was densely methylated, transcriptionally inactive and unable to undergo homologous recombination. Our results suggest that DNA repair associated with recombinational events leads to a heritable hypomethylation of the locus which is responsible for its activation.

Animals↗
PubMed1991

Linkage disequilibrium analysis of chromosomal inversion polymorphisms of Drosophila.

The linkage disequilibrium pattern analysis is a method that allows one to detect present and past events of selection. We applied it to our data on the inversions of Drosophila mediopunctata and to published data of Drosophila subobscura, which are systems probably under complex modes of selection. The method gave meaningful results showing that it might be an excellent exploratory tool to identify problems worthy of further study. It is also suggested that it can be used as a criterion to determine the roots of inversion phylogenies.

Animals↗
PubMed1993

Rearrangement by chromosomal inversion in the T cell receptor gamma locus in a murine alpha beta T cell clone.

Analyzing the T-cell receptor (TCR) repertoire of T lymphocytes specific for minor histocompatibility antigens, we isolated a TCR-alpha beta bearing T cell clone, TGVH9, which also expresses three different TCR-gamma mRNA. The sequences of these messengers indicate that one of them results from the rearrangement of V gamma 1 and J gamma 2 genes. Since these two segments are in inverted genomic transcriptional orientation, the joining of V gamma 1 to J gamma 2 occurred by chromosomal inversion. This mechanism, which was previously reported in TCR-beta and TCR-delta loci, can thus also occur to enlarge the diversity of the TCR-gamma repertoire.

Amino Acid Sequence↗
PubMed1994

Isolation and analysis of the breakpoint sequences of chromosome inversion In(3L)Payne in Drosophila melanogaster.

Chromosomal rearrangements constitute a significant feature of genome evolution, and inversion polymorphisms in Drosophila have been studied intensely for decades. Population geneticists have long recognized that the sequence features associated with inversion breakpoints would reveal much about the mutational origin, uniqueness, and genealogical history of individual inversion polymorphisms, but the cloning of breakpoint sequences is not trivial. With the aid of a method for rapid recovery of DNA clones spanning rearrangement breakpoints, we recover and examine the DNA sequences spanning the breakpoints of the cosmopolitan inversion In(3L)Payne in Drosophila melanogaster. By examining the sequence diversity associated with six standard and seven inverted chromosomes from natural populations, we find that the inversion is monophyletic in origin, the sequences are genetically isolated from recombination at the breakpoints, and there is no association with features such as transposable elements. The inverted sequences show 17-fold less nucleotide polymorphism, but there are eight fixed differences in the region spanning both breakpoints. This suggests that this inversion is not recently derived. Finally, Northern analysis and transcript mapping find that the distal breakpoint has disrupted three transcripts that are normally expressed in the standard arrangement. Incidentally, the method introduced here can be used to isolate breakpoint sequences of arrangements associated with many human diseases.

Animals↗
PubMed2004

Swift laboratory thermal evolution of wing shape (but not size) in Drosophila subobscura and its relationship with chromosomal inversion polymorphism.

Latitudinal clinal variation in wing size and shape has evolved in North American populations of Drosophila subobscura within about 20 years since colonization. While the size cline is consistent to that found in original European populations (and globally in other Drosophila species), different parts of the wing have evolved on the two continents. This clearly suggests that 'chance and necessity' are simultaneously playing their roles in the process of adaptation. We report here rapid and consistent thermal evolution of wing shape (but not size) that apparently is at odds with that suggestion. Three replicated populations of D. subobscura derived from an outbred stock at Puerto Montt (Chile) were kept at each of three temperatures (13, 18 and 22 degrees C) for 1 year and have diverged for 27 generations at most. We used the methods of geometric morphometrics to study wing shape variation in both females and males from the thermal stocks, and rates of genetic divergence for wing shape were found to be as fast or even faster than those previously estimated for wing size on a continental scale. These shape changes did not follow a neat linear trend with temperature, and are associated with localized shifts of particular landmarks with some differences between sexes. Wing shape variables were found to differ in response to male genetic constitution for polymorphic chromosomal inversions, which strongly suggests that changes in gene arrangement frequencies as a response to temperature underlie the correlated changes in wing shape because of gene-inversion linkage disequilibria. In fact, we also suggest that the shape cline in North America likely predated the size cline and is consistent with the quite different evolutionary rates between inversion and size clines. These findings cast strong doubts on the supposed 'unpredictability' of the geographical cline for wing traits in D. subobscura North American colonizing populations.

Analysis of Variance↗
PubMed2001

Molecular characterization of a myelodysplasia-associated chromosome 7 inversion.

Chromosome 7 abnormalities are observed in a wide range of myeloid disorders, particularly myelodysplasia (MDS) and acute myeloid leukaemia (AML). Monosomy 7 and 7q deletions are the most frequent abnormalities, although translocations and inversions involving 7q also occur. The region 7q22--q34 may contain as many as four distinct minimal regions of deletion (MDRs), which are thought to contain one or more myeloid tumour-suppressor genes. We have defined previously the proximal breakpoint of a constitutional 7q22--q34 inversion, carried in a cell line derived from a member of a family with a history of MDS. A YAC clone spanning this breakpoint was identified. Both inversion breakpoints have now been cloned and sequenced, placing the proximal breakpoint 40 kb centromeric to the TAC2 (tachykinin 2) gene and the distal breakpoint 42 kb telomeric to the SSBP (mitochondrial single-stranded DNA-binding protein) gene. Sequence alignments revealed small (3--4 bp) duplications at the inversion breakpoints, suggesting that the mechanism of inversion involved the creation of staggered breaks and filling in of the overhanging ends. A 190-bp Alu--Alu deletion close to the distal breakpoint was also detected and may have contributed to the inversion.

Autoradiography↗
PubMed1988

Colonization of America by Drosophila subobscura: Experiment in natural populations that supports the adaptive role of chromosomal-inversion polymorphism.

North America and South America have recently been colonized by the Palearctic species Drosophila subobscura. This double colonization offers a rare opportunity for evolutionary studies. Correlations between chromosomal arrangement frequencies and latitude were calculated for the colonizing populations. Signs of these correlations are highly coincident with those found in the Old World. These results provide experimental support for the adaptive value of the chromosomal-inversion polymorphism; historical and other nonadaptive explanations are thus excluded or relegated to a secondary role.

Journal Article↗
PubMed1990

Constraints in chromosomal inversions in Escherichia coli are not explained by replication pausing at inverted terminator-like sequences.

Regions close to the replication terminus of the Escherichia coli chromosome are strongly refractory to genomic inversions. Since these regions also harbour polar replication terminator-like sequences or pause sites, we have investigated the possibility that slowing of replication as a result of pausing at inverted pause sites is responsible for inability to isolate stable inversions affecting these regions. A mutation in the tus gene is known to abolish replication pausing at terminators. We show here that the distribution of invertible and noninvertible segments along the chromosome is not affected by tus mutations. This observation eliminates replication pausing as a cause for the reduced fitness of bacteria harbouring certain chromosomal inversions.

Chromosome Inversion↗
PubMed1997

A new dominant retinal degeneration (Rd4) associated with a chromosomal inversion in the mouse.

An autosomal dominant retinal degeneration, called Rd4, was found in a stock carrying the inversion In(4)56Rk, which was induced in a DBA/2J male. The inversion encompasses nearly all of Chromosome 4. It is homozygous lethal and in heterozygotes is always associated with retinal degeneration. In affected mice, the retinal outer nuclear and plexiform layers begin to reduce at 10 days of age, showing total loss at 6 weeks. The recordable electroretinograms (ERG) showed poorly at 3 to 6 weeks and were barely detected after 6 weeks of age. Retinal vessel attenuation, pigment spots, and optic atrophy appeared in the fundus at 4 weeks of age. Rd4 has not recombined with the inversion in an outcross, suggesting that the Rd4 locus is located very close to or is disrupted by one of the breakpoints of the inversion, either near the centromere or near the telomere. A human homolog would be expected to be located on human chromosomes 1p or 8q.

Animals↗
PubMed2000

ATIC-ALK: A novel variant ALK gene fusion in anaplastic large cell lymphoma resulting from the recurrent cryptic chromosomal inversion, inv(2)(p23q35).

The subset of CD30-positive anaplastic large cell lymphomas (ALCL) with the NPM-ALK gene fusion arising from the t(2;5)(p23;q35) forms a distinct clinical and prognostic entity. Recently, various cytogenetic, molecular, and protein studies have provided evidence for the existence of several types of variant ALK fusions in up to 20% of ALK+ ALCL, of which only one, a TPM3-ALK fusion resulting from a t(1;2)(q25;p23), has so far been cloned. A cryptic inv(2)(p23q35) has been described as another recurrent cytogenetic alteration involving ALK and an unidentified fusion partner in some ALCL. In a screen for variant ALK gene fusions, we identified two ALCL that were negative for NPM-ALK by reverse transcriptase-polymerase chain reaction, but were positive for cytoplasmic ALK with both polyclonal and monoclonal antibodies to the ALK tyrosine kinase domain, consistent with ALK deregulation by an alteration other than the t(2;5) Case 1 was a T-lineage nodal and cutaneous ALCL in a 52-year-old woman, and Case 2 was a T-lineage nodal ALCL in a 12-year-old girl. FISH analysis confirmed ALK rearrangement in both cases. An inverse polymerase chain reaction approach was then used to identify the ALK translocation partner in Case 1. We found an in-frame fusion of ALK to ATIC, a gene previously mapped to 2q34-q35. We then confirmed by DNA polymerase chain reaction the localization of ATIC to yeast artificial chromosome (YAC) 914E7 previously reported to span the 2q35 break in the inv(2)(p23q35). FISH analysis in Case 1 confirmed rearrangement of YAC 914E7 and fusion to ALK. The ATIC-ALK fusion was confirmed in Case 1 and also identified in Case 2 by conventional reverse transcriptase-polymerase chain reaction using ATIC forward and ALK reverse primers. ATIC encodes an enzyme involved in purine biosynthesis which, like other fusion partners of ALK, is constitutively expressed and appears to contain a dimerization domain. ATIC-ALK fusion resulting from the inv(2)(p23q35) thus provides a third mechanism of ALK activation in ALK+ ALCL.

Child↗
PubMed1980

Developmental variation in amylase allozyme activity associated with chromosome inversions in Drosophila persimilis.

The amylase locus in Drosophila persimilis is polymorphic for allozymes, two of which show associations with naturally occurring chromosome 3 inversions. Amy1.09 occurs at high frequencies only in Whitney (WT), while the other common arrangements-Standard (ST), Klamath (KL) and Mendocino (MD)-are predominantly Amy 1.00. We have examined numerous strains, representing various electromorphs and inversions, for variation in cis-specific activity expression in both third-instar larvae and adults. Comparisons of these two life stages also allows the survey of developmental variation in amylase activities. The amount of activity variation exceeds electrophoretic variation at this locus. Moreover, this variation is largely nonrandom and reveals more genic divergence among inversions. The 1.00 allozyme of MD is more active than 1.00 KL in larvae and adults and shows a different developmental pattern. The activity of the 1.00 allozyme of KL is greater than 1.00 allozyme of ST in larvae and adults, but these two arrangements have similar developmental patterns. WT 1 with a 1.00 allele is dramatically different from the 1.00 allozymes of other arrangements in its developmental pattern. The 1.09 allozymes has high activity in WT and KL, but these arrangements differ in their developmental pattern of expression, WT being more active in adults. F2 segregational analyses are consistent with the variation being due to either structural enzyme variants or closely linked cis-acting regulatory elements. We argue that the suppression of recombination between arrangements has allowed the divergence in amylase activity among inversions.

Amylases↗
PubMed1986

A naturally occurring large chromosomal inversion in Escherichia coli K12.

Strain 1485IN and its derivatives were found to have a large inversion extending to about 35% of the chromosome. Because of this, the question arose as to whether 1485IN had arisen from an Escherichia coli strain other than K12. However, 1485IN had a flagellar antigen and a restriction-modification system indistinguishable from those of W3110, a major line of K12, and had retained an amber suppressor and lambda sensitivity that are characteristics of W1485 from which this strain seems to have arisen. Strain 1485IN had acquired proline auxotrophy, but showed the same growth rate as W1485 in nutrient broth at 37 degrees C. Interrupted matings with Hfr strains of 1485IN revealed a gene arrangement of nalA-gal-trp-his-lac-proA-thrleu-ilv, in which gal, trp, and his were on the inverted segment. The termini of the inversion were inferred to be situated between tsx (9.5 min) and purE (12 min) and between his (44 min) and cdd (46.5 min).

Chromosome Inversion↗
PubMed1988

Investigation of three XX males by cytogenetic and DNA analyses. Suggestion of Y chromosome inversion polymorphism.

We report cytogenetic and DNA studies in three XX males. Two males seemed to have extra chromosomal material on the tip of one X chromosome. All three males were shown to have Y chromosome material as indicated by hybridization of Y-specific DNA probes to genomic DNA. One male was unusual in that as he showed the 15-kb fragment detected by pDP34 that is thought to map close to the Y centromere. It is suggested that this finding might point to an inversion on the Y chromosome.

Chromosome Inversion↗