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PubMed2006

Sperm-FISH analysis in a pericentric chromosome 1 inversion, 46,XY,inv(1)(p22q42), associated with infertility.

No phenotypic effect is observed in most inversion heterozygotes. However, reproductive risks may occur in the form of infertility, spontaneous abortions or chromosomally unbalanced children as a consequence of meiotic recombination between inverted and non-inverted chromosomes. An odd number of crossovers within the inverted segment results in gametes bearing recombinant chromosomes with a duplication of the region outside of the inversion segment of one arm and a deletion of the terminal segment of the other arm [dup(p)/del(q) and del(p)/dup(q)]. Using fluorescence in-situ hybridization (FISH), the chromosome segregation of a pericentric inversion of chromosome 1 was studied in spermatozoa of a inv(1)(p22q42) heterozygous carrier. Three-colour FISH was performed on sperm samples using a probe mixture consisting of chromosome 1p telomere-specific probe, chromosome 1q telomere-specific probe and chromosome 18 centromere-specific alpha satellite DNA probe. The frequency of the non-recombinant product was 80.1%. The frequencies of the two types of recombinants carrying a duplication of the short arm and a deletion of the long arm, and vice versa, were respectively 7.6 and 7.2%, and these frequencies were not statistically significant from the expected ratio of 1:1. Sperm-FISH allows the further understanding of segregation patterns and their effect on reproductive failure and allows an accurate genetic counselling.

Adult↗
PubMedDate not supplied

The clinical significance of pericentric inversion of the human Y chromosome: a rare "third" type of heteromorphism.

A 28-year-old normal East Indian was found to have a pericentric inversion of the Y chromosome. After reviewing the literature, it was concluded that an inverted Y chromosome does not impede the production of normal sperm and does not predispose to non-disjunction of other chromosomes in the progeny. Thus, the earlier concept of nondisjunction was rejected, and it is suggested that aberrant cases with aneuploidy and an inverted Y are fortuitous. The pericentric inverted Y is inherited from generation to generation and has no clinical significance. The prevalence of males with pericentric Y inversion in the general population is approximately 1 per 1000. It is suggested that a pericentric inversion of the Y chromosome is a rare chromosomal heteromorphism and should be called type III.

Adult↗
PubMed2000

Chloroplast DNA inversion polymorphism in populations of Abies and Tsuga.

Polymorphism for a 42-kb chloroplast DNA inversion was detected in five species of Abies and two species of Tsuga based on a sample of 1,281 individuals and both Southern hybridization and polymerase chain reaction (PCR) analyses. Two haplotypes were observed in all populations and species. The 42-kb inversion is associated with a short inverted repeat that includes trnS, psaM, and trnG. The frequencies of the two haplotypes within species were very similar among the five species of Abies This polymorphism has been maintained within populations and species in both Abies and Tsuga, probably because the mutation rate of the inversion is high. Haplotype frequencies had no geographical tendencies for any species except Abies mariesii, in which haplotype frequencies varied clinally, possibly as a result of rapid dissemination after the most recent glacial period and random genetic drift.

Blotting, Southern↗
PubMed2000

Uterine inversion and corpus malignancies: a historical review.

Inversion of the uterus is a rare clinical problem. It is encountered as an obstetric emergency and a diagnostic challenge in gynecology. Association of uterine inversion with malignancies such as endometrial carcinoma or sarcoma is even rarer. Accurate diagnosis is essential before treatment, so that appropriate management is offered. A history of uterine inversion and a review of literature is presented especially of its association with corpus malignancies.

Diagnosis, Differential↗
PubMed1999

Mapping studies on a pericentric inversion (18) (p11.31 q21.1) in a family with both schizophrenia and learning disability.

Chromosomal abnormalities that co-occur with psychiatric disorders can be useful direct pointers to the locus of susceptibility genes. Two families with pericentric inversions of chromosome 18, inv 18(p11.3 q21.1) and psychiatric illness have previously been described. We have fine mapped the chromosomal breakpoints of the rearrangement in a clinically well, inversion carrier from one of these families where other inversion carriers suffered from chronic schizophrenia or severe learning disability. Yeast artificial chromosomes (YACs) from the Whitehead/MIT physical maps of human chromosome 18 have been positioned relative to the chromosomal breakpoints and a number of YACs that span these breakpoints have been identified. Linkage and association studies have previously suggested these regions of chromosome 18q and 18p as candidate loci harbouring genes involved in bipolar disorder and schizophrenia.

Chromosome Inversion↗
PubMed2005

Gene conversion and evolution of Xq28 duplicons involved in recurring inversions causing severe hemophilia A.

Inversions breaking the 1041 bp int1h-1 or the 9.5-kb int22h-1 sequence of the F8 gene cause hemophilia A in 1/30,000 males. These inversions are due to homologous recombination between the above sequences and their inverted copies on the same DNA molecule, respectively, int1h-2 and int22h-2 or int22h-3. We find that (1) int1h and int22h duplicated more than 25 million years ago; (2) the identity of the copies (>99%) of these sequences in humans and other primates is due to gene conversion; (3) gene conversion is most frequent in the internal regions of int22h; (4) breakpoints of int22h-related inversions also tend to involve the internal regions of int22h; (5) sequence variations in a sample of human X chromosomes defined eight haplotypes of int22h-1 and 27 of int22h-2 plus int22h-3; (6) the latter two sequences, which lie, respectively, 500 and 600 kb telomeric to int22h-1 are five-fold more identical when in cis than when in trans, thus suggesting that gene conversion may be predominantly intrachromosomal; (7) int1h, int22h, and flanking sequences evolved at a rate of about 0.1% substitutions per million years during the divergence between humans and other primates, except for int1h during the human-chimpanzee divergence, when its rate of evolution was significantly lower. This is reminiscent of the slower evolution of palindrome arms in the male specific regions of the Y chromosome and we propose, as an explanation, that intrachromosomal gene conversion and cosegregation of the duplicated regions favors retention of the ancestral sequence and thus reduces the evolution rate.

Animals↗
PubMed2006

Comparative analysis of the bovine MHC class IIb sequence identifies inversion breakpoints and three unexpected genes.

The bovine major histocompatibility complex (MHC) or BoLA is organized differently from typical mammalian MHCs in that a large portion of the class II region, called class IIb, has been transposed to a position near the centromere on bovine chromosome 23. Gene mapping indicated that the rearrangement resulted from a single inversion, but the boundaries and gene content of the inverted segment have not been fully determined. Here, we report the genomic sequence of BoLA IIb. Comparative sequence analysis with the human MHC revealed that the proximal inversion breakpoint occurred approximately 2.5 kb from the 3' end of the glutamate-cysteine ligase, catalytic subunit (GCLC) locus and that the distal breakpoint occurred about 2 kb from the 5' end from a divergent class IIDRbeta-like sequence designated DSB. Gene content, order and orientation of BoLA IIb are consistent with the single inversion hypothesis when compared with the corresponding region of the human class II MHC (HLA class II). Differences with HLA include the presence of a single histone H2B gene located between the proteasome subunit, beta type, 9 (PSMB9) and DMB loci and a duplicated TAP2 with a variant splice site. BoLA IIb spans approximately 450 kb DNA, with 20 apparently intact genes and no obvious pseudogenes. The region contains 227 simple sequence repeats (SSRs) and approximately 167 kb of retroviral-related repetitive DNA. Nineteen of the 20 genes identified in silico are supported by bovine EST data indicating that the functional gene content of BoLA IIb has not been diminished because it has been transposed from the remainder of BoLA genes.

Animals↗
PubMed2005

The latitudinal cline in the In(3R)Payne inversion polymorphism has shifted in the last 20 years in Australian Drosophila melanogaster populations.

Clinal variation has been described in a number of inversions in Drosophila but these clines are often characterized by cytological techniques using small sample sizes, and associations with specific genes are rarely considered. Here we have developed a molecular assay for In(3R)Payne in Drosophila melanogaster from eastern Australia populations. It shows in repeated samples that the inversion cline is very tightly associated with latitude and is almost fixed in tropical populations while relatively rare in temperate populations. This steep cline has shifted in position in the last 20 years. The heat shock gene, hsr-omega, located centrally inside the inversion sequence, shows a different clinal pattern to In(3R)Payne. These results suggest strong ongoing selection on In(3R)Payne over the last 100 years since the colonization of Australia that is partly independent of hsr-omega.

Animals↗
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↗
PubMed1995

Mechanism of antigenic variation in Mycoplasma pulmonis: interwoven, site-specific DNA inversions.

The chromosome of the murine pathogen Mycoplasma pulmonis undergoes rearrangements at a high frequency. We show that some of these rearrangements regulate the phase-variable expression of a cluster of genes (the vsa locus) that encode the variable V-1 surface antigens. Only one vsa gene is associated with an expression site; the other vsa genes are transcriptionally silent. The silent genes lack the 5' end region (promoter and ribosome-binding site) that is present in the expressed gene, and DNA rearrangements regulate gene expression by reassorting the 5' end region from an expressed gene with the 3' end region from a previously silent gene. All vsa rearrangements identified so far are site-specific DNA inversions that occur between copies of a specific 34 bp sequence that is conserved in each vsa gene. Interestingly, DNA inversions within the vsa locus apparently occur in concert with inversion of the hsd1 element, which regulates restriction and modification activity in M. pulmonis.

Amino Acid Sequence↗
PubMed2004

Tyrosine site-specific recombinases mediate DNA inversions affecting the expression of outer surface proteins of Bacteroides fragilis.

The chromosome of Bacteroides fragilis has been shown to undergo 13 distinct DNA inversions affecting the expression of capsular polysaccharides and mediated by a serine site-specific recombinase designated Mpi. In this study, we demonstrate that members of the tyrosine site-specific recombinase family, conserved in B. fragilis, mediate additional DNA inversions of the B. fragilis genome. These DNA invertases flip promoter regions in their immediate downstream region. The genetic organization of the genes regulated by these invertible promoter regions suggests that they are operons and many of the products are predicted to be outer membrane proteins. Phenotypic analysis of a deletion mutant of one of these DNA invertases, tsr15 (aapI), which resulted in the promoter region for the downstream genes being locked ON, confirmed the synthesis of multiple surface proteins by this operon. In addition, this deletion mutant demonstrated an autoaggregative phenotype and showed significantly greater adherence than wild-type organisms in a biofilm assay, suggesting a possible functional role for these phase-variable outer surface proteins. This study demonstrates that DNA inversion is a universal mechanism used by this commensal microorganism to phase vary expression of its surface molecules and involves at least three conserved DNA invertases from two evolutionarily distinct families.

Amino Acid Sequence↗
PubMed1982

A familial pericentric inversion of chromosome 8 analysed with a high resolution chromosome banding technique.

A familial pericentric inversion of chromosome 8 is described. The break points were localized by a high resolution chromosome banding technique and found to be inv(8)(p23.108q12.100). None of the family members had an unbalanced product of the inversion. There were no phenotypical abnormalities in the carriers. The break points and segregation pattern are compared with those of previously reported pericentric inversion of chromosome 8.

Adult↗
PubMed1993

Molecular cytogenetic analysis of a familial pericentric inversion of chromosome 12.

We describe the application of multi-color fluorescence in situ hybridization (FISH) in the characterization of a familial pericentric inversion. Using chromosome 12 short- and long-arm specific DNA probes, fast and reliable discrimination between normal and inversion chromosome 12 or recombinant inversion chromosome 12 was possible. FISH thus provides a reliable means for prenatal detection of balanced or unbalanced chromosome 12 rearrangements in this family. This approach is possible for identification of similar chromosome rearrangements provided that probes for the putatively involved chromosome region are available.

Adult↗
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↗
PubMedDate not supplied

Uterine inversion by a mixed müllerian tumor of the corpus.

Mixed müllerian tumors (MMT) of the uterus have been reported following the use of tamoxifen. Rarely, these tumors lead to an uterine inversion. The surgical approach of a uterine inversion forms a therapeutic challenge. In this article, a case of uterine inversion due to a MMT is reported, together with a literature review regarding the developing mechanisms and management.

Aged↗
PubMed1997

Large chromosomal inversions occur in Pseudomonas aeruginosa clone C strains isolated from cystic fibrosis patients.

An analysis of the chromosomal structure of 21 Pseudomonas aeruginosa clone C genotypes of various origins was carried out. The circular chromosomes showed various insertions and deletions which did not alter the gene order in 6 environmental and one ear isolate in comparison with strain PAO and strain C. However, the chromosome structure differed by at least one large inversion in 50% of the genotypes (7/14) isolated from cystic fibrosis patients. Recombination endpoints were scattered throughout the chromosome. All but one inversion included the terminus of replication which was displaced by the recombination events. The rearrangements shifted the positions of the rrn operons with respect to the origin of replication, but the transcription of the rrn operons remained in the same direction as replication. The exclusive detection of inversions in isolates from cystic fibrosis lungs, which represent an atypical habitat for P. aeruginosa, supports the theory that peculiar features of this new ecological niche may select, cause or tolerate genomic changes.

Chromosome Inversion↗
PubMed1997

The effect of polymorphic inversions on body size in two natural populations of Drosophila buzzatii from Argentina.

Previous works in a colonized and an original population of Drosophila buzzatii have shown a consistent relationship between the inversion polymorphism and thorax length, a measure of body size. However, the populations studied in those reports share a close genealogical relationship as suggested by several lines of evidence. In the present paper, we revisit this issue by analysing the correlation between second chromosome arrangements and thorax length in two Argentinian natural populations (Termas de Río Hondo and Arroyo Escobar) from different biogeographic areas with different host plants. Our findings are: (1) inversion frequencies were significantly different between populations; (2) the mean thorax length of flies collected in both populations was not significantly different; and (3) we obtain confirming evidence that flies carrying 2st, the ancestral gene order, have on average a smaller body size than those carrying the derived arrangements (2j and 2jz3). These results suggest that the biometrical effect of inversions on body size previously described are due to genetic differences between arrangements and not to the close historical relationship between the populations studied in previous reports.

Animals↗
PubMed1990

Sequence analysis of the inversion region containing the pilin genes of Moraxella bovis.

Moraxella bovis EPP63 is able to produce two antigenically distinct pili called Q and I pili (previously called beta and alpha pili). Hybridization studies have shown that the transition between the types is due to inversion of a 2.1-kilobase segment of chromosomal DNA. We present the sequence of a 4.1-kilobase region of cloned DNA spanning the entire inversion region in orientation 1 (Q pilin expressed). Comparison of this sequence with the sequence of the polymerase chain reaction-amplified genomic DNA from orientation 2 (I pilin expressed) allows the site-specific region of recombination to be localized to a 26-base-pair region in which sequence similarity to the left inverted repeat of the Salmonella typhimurium hin system was previously noted. In addition, 50% sequence similarity was seen in a 60-base-pair segment of our sequence to the recombinational enhancer of bacteriophage P1, an inversion system related to the hin system of S. typhimurium. Finally, two open reading frames representing potential genes were identified.

Amino Acid Sequence↗