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PubMed2005

Mechanisms of genetic exchange within the chromosomal inversions of Drosophila pseudoobscura.

We have used the inversion system of Drosophila pseudoobscura to investigate how genetic flux occurs among the gene arrangements. The patterns of nucleotide polymorphism at seven loci were used to infer gene conversion events between pairs of different gene arrangements. We estimate that the average gene conversion tract length is 205 bp and that the average conversion rate is 3.4 x 10(-6), which is 2 orders of magnitude greater than the mutation rate. We did not detect gene conversion events between all combinations of gene arrangements even though there was sufficient nucleotide variation for detection and sufficient opportunity for exchanges to occur. Genetic flux across the inverted chromosome resulted in higher levels of differentiation within 0.1 Mb of inversion breakpoints, but a slightly lower level of differentiation in central inverted regions. No gene conversion events were detected within 17 kb of an inversion breakpoint suggesting that the formation of double-strand breaks is reduced near rearrangement breakpoints in heterozygotes. At least one case where selection rather than proximity to an inversion breakpoint is responsible for reduction in polymorphism was identified.

Animals↗
PubMed1998

A rare 920-kilobase chromosomal inversion mediated by IS1 transposition causes constitutive expression of the yiaK-S operon for carbohydrate utilization in Escherichia coli.

The regulator of the yiaK-S operon, currently assigned a carbohydrate utilization function in Escherichia coli, is inactivated by a genome rearrangement that leads to the constitutive expression of the operon. The yiaK-S constitutive cells acquire the ability to utilize the rare pentose L-lyxose. Restriction analysis and sequencing of the regulator gene indicate that it is disrupted by foreign DNA. The insert consists of a large inverted fragment of DNA of 920 kilobases flanked by two IS1 elements with opposite polarity. One corresponds to that found naturally at min 0.4 of the bacterial chromosome and the other to a new copy transposed into the regulator gene located at min 80.6. This insertion-inversion could be the result of the intramolecular transposition mechanism itself, a gene rearrangement rarely originated by IS1. Alternatively, it could be attributed to the homologous recombination between the IS1 at min 0.4 and the IS1 transposed intermolecularly into the yiaK-S regulator gene. The participation of a rare IS1-mediated inversion in the evolution of a stable phenotype is thus identified.

Amino Acid Sequence↗
PubMed1993

Multiple polyps of esophagus, stomach, colon, and rectum accompanying rectal cancer in a patient with constitutional chromosomal inversion.

BACKGROUND: It has been reported that colorectal carcinomas are caused by a multistage process. In patients with familial adenomatous polyposis, carcinoma of the colorectum frequently develops and occasionally polyps develop in the upper gastrointestinal tract. Chromosomal deletion often is found for chromosomes 5, 17, and 18, on which tumor suppressor genes are located. Furthermore, loss of the alleles of loci on chromosome 3 has been reported in renal cell carcinoma, small cell lung carcinoma, and mixed salivary gland tumor in hereditary and sporadic cases. These data support the concept of a recessive mechanism for the development of human tumors. PATIENTS AND RESULTS: The authors report the case of a 48-year-old woman with rectal cancer accompanied by multiple polyps in the esophagus, stomach, and colorectum. Histologically, the polypoid lesions in the esophagus, stomach, and colorectum showed a thickened mucosa, hyperplastic polyps, and mixed hyperplastic adenomatous polyps, respectively. Karyotype analysis showed 46, xx, inv(3)(p12.2q25.3) in all 20 inspected peripheral lymphocytes. By Southern blot with a c-raf probe, one allele of the c-raf-1 gene, which has been mapped on chromosome 3p25, was deleted from the rearranged chromosome 3 in the peripheral lymphocytes, intact colonic mucosa, and cancer tissue. CONCLUSIONS: These results suggest that the development of hyperplastic polyps and carcinoma of the rectum results from the allelic loss in chromosome 3p, as has been reported for solid tumors at other sites.

Chromosome Aberrations↗
PubMed1970

Two radiation-induced chromosomal inversions in mice (Mus musculus).

Whole-body x-irradiation of male mice has produced presumptive paracentric inversions in 15 animals, as evidenced by high frequencies of first meiotic anaphase bridges. Two of the highest frequencies observed have been propagated through several generations and found to behave as dominant genes. Acentric fragments were observed associated with about 10% of the bridges. The first inversion, in linkage group XIII, has been designated In(13)1Rk, and the second, in linkage group XVII, In(17)2Rk. For In(13)1Rk, recombination was reduced between loci inside and outside the inverted segment.

Animals↗
PubMed1993

Three cases of the myelodysplastic syndrome with pericentric inversion of chromosome 16.

Inversion of chromosome 16, inv(16)(p13q22), is characteristic of acute myeloid leukaemia (AML) with eosinophilia and is rarely found in the myelodysplastic syndrome (MDS). We report three cases of MDS in which inv(16) was observed. They were classified to FAB subtypes RA, RARS and RAEBT; eosinophilia or abnormal eosinophils were not observed. The disease appeared to be stable in all three patients. MDS with inv(16) without eosinophilia may be a rare subgroup associated with a good prognosis.

Adolescent↗
PubMed1981

Peri- and paracentric inversions in chromosome 12: prenatal diagnosis and family study.

Three different types of chromosome 12 inversion were seen in 15 individuals out of 44 individuals examined in one 8 generation family. Type 1: a pericentric inversion inv(12) (p112; q131) was found in 7 individuals and twice at prenatal diagnosis. Type 2: a paracentric inversion inv(12) (p123; p131) was seen in two individuals. Two individuals carried both inversion chromosomes, namely type 1 and type 2. The two inversion chromosomes were transmitted from each of the parents. Type 3: a double pericentric and paracentric inversion (type 3) inv(12) (p123; p131) (p112; q131) was observed in the daughter of one of the carriers of type 1 and 2 inversions and again at prenatal diagnosis in her son. The double inversion most likely arose through crossing-over in between the two inversion loops. A balanced translocation t(7; 13) and the inversion type 1 was observed in one individual, who transmitted the translocation only to an offspring. The frequency of inversions in amniotic fluid cells observed in our laboratory was 1.9 per cent. The clinical implications of these findings are discussed.

Adult↗
PubMed1999

Cytogenetic findings in 250 schizophrenics: evidence confirming an excess of the X chromosome aneuploidies and pericentric inversion of chromosome 9.

Chromosomal abnormalities may be of help in identifying disease genes. To search for susceptibility loci for schizophrenia, we have performed chromosomal examinations by using the GTG banding technique for 250 schizophrenics. We found five cases with an aneuploidy of the X chromosome and ten cases with pericentric inversion of chromosome 9 [inv (9)]. These results confirmed an excess of the X chromosome aneuploidies in schizophrenia, indicating a possible involvement of the X chromosome in the pathogenesis of the illness. The observed incidence (4.0%) of inv (9) in our schizophrenic sample was significantly higher (p=0.013) than that reported in the general population in Japan (1.7%). Although inv (9) has been considered to be a normal variant, our observation implies a possible association between inv (9) and schizophrenia, suggesting that a susceptibility locus for the disease may be located at a breakpoint of the inversion on chromosome 9.

Adult↗