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Carrier-specific breakpoint-spanning DNA probes: an approach to preimplantation genetic diagnosis in interphase cells.

Carriers of chromosomal inversions or other balanced rearrangements represent a significant fraction of patients in in-vitro fertilization (IVF) programmes due to recurrent reproductive problems. In most cases, chromosomal imbalance in fertilized oocytes is incompatible with embryo survival leading to increased rates of spontaneous abortions. Assuming that a fraction of the germ cells is karyotypically normal, these patients would greatly benefit from efficient procedures for generation and use of breakpoint-specific DNA hybridization probes in preconception and preimplantation genetic diagnosis (PGD). We describe the generation of such patient-specific probes to discriminate between normal and aberrant chromosomes in interphase cells. First, a large insert DNA library was screened for probes that bind adjacent to the chromosomal breakpoints or span them. Then, probe and hybridization parameters were optimized using white blood cells from the carrier to increase in hybridization signal intensity and contrast. Finally, the probes were tested on target cells (typically polar bodies or blastomeres) and a decision about the colour labelling scheme was made, before the probes can be used for preconception or preimplantation genetic analysis. Thus, it was demonstrated that cells with known structural abnormalities could be detected, based on hybridization of breakpoint spanning yeast artificial chromosome (YAC) DNA probes in interphase cells.

Blastomeres↗

Continuing studies on chromosomal polymorphism in a Korean natural population of Drosophila melanogaster.

Investigations on the chromosomal inversion polymorphism were conducted on a Korean (Taenung) natural population of D. melanogaster during the period 1978 to 1992. A total of 66 different endemic and cosmopolitan inversions were found on both major chromosome pairs II and III. Some of them proved to be rare cosmopolitan types (2LKA, 2LNS, 2LF, 2RCy, 3LM, 3RKI, and 3RK), while others were endemics. The distribution of breakpoints for endemic and rare cosmopolitan inversions are not random along the two autosome arms. With respect to frequency changes, the 15-year survey revealed that five of the cosmopolitan types (2Lt, 2RNS, 3LP, 3RC, and 3RMo) exhibit cyclical frequency changes, whereas gene arrangement 3RP shows relatively stable frequencies. Tests for correlations between gene arrangement frequencies and several climatic variables gave no clear evidence for such relationships. Only one correlation coefficient out of 64 was statistically significant.

Animals↗

A large dispersed chromosomal region required for chromosome segregation in sporulating cells of Bacillus subtilis.

The cis-acting sequences required for chromosome segregation are poorly understood in most organisms, including bacteria. Sporulating cells of Bacillus subtilis undergo an unusual asymmetric cell division during which the origin of DNA replication (oriC) region of the chromosome migrates to an extreme polar position. We have now characterized the sequences required for this migration. We show that the previously characterized soj-spo0J chromosome segregation system is not essential for chromosome movement to the cell pole, so this must be driven by an additional segregation mechanism. Observations on a large set of precisely engineered chromosomal inversions and translocations have identified a polar localization region (PLR), which lies approximately 150-300 kbp to the left of oriC. Surprisingly, oriC itself has no involvement in this chromosome segregation system. Dissection of the PLR showed that it has internal functional redundancy, reminiscent of the large diffuse centromeres of most eukaryotic cells.

Bacillus subtilis↗

Subfertile couple with inv(2),inv(9) and 16qh+.

This case report presents two chromosomal inversions in one of partners from a subfertile couple. The woman was referred due to a spontaneous abortion in the 5th week of pregnancy. Cytogenetic examination showed that the proband's karyotype was normal: 46,XX,16qh+, as centromeric heterochromatin is thought to be clinically insignificant. However, the proband's partner occurred to be a carrier of two pericentric inversions. His karyotype was 46,XY,inv(2)(p11q13),inv(9)(p11q13). The abnormal karyotype is recognised as a possible reason of fertility problems in the investigated couple. The risk of further miscarriages is considered high, but the risk of progeny with abnormal karyotypes is rather low, as small inversions may lead to lethal recombinants.

Abortion, Spontaneous↗

Larval polytene chromosomes of black flies (Simulium) from Thailand. I. Comparison among five species in the subgenus Gomphostilbia enderlein.

Larval polytene chromosome maps of Simulium (G.) asakoae and S. (G.) sp. g in the ceylonicum-group and S. (G.) angulistylum, S. (G.) decuplum and S. (G.) siamense in the batoense-group of the subgenus Gomphostilbia from Thailand are presented. These species have three pairs of chromosomes (2n = 6). Light stained centromeric bands were observed in the chromosomes of S. (G.) asakoae, S. (G.) sp. g, S. (G.) decuplum and S. (G.) siamense, whereas heavy dark centromeric bands were present in S. (G.) angulistylum. The best distinguishing character of Simulium species in the subgenus Gomphostilbia is the position of the nucleolar organizer in the short arm of chromosome I. The Ring of Balbiani and the double bubble are located in chromosome arm IIS in all species except for S. (G.) angulistylum, which showed these cytological markers in chromosome arm IIIS. A low chromosomal polymorphism was recorded in all species except for S. (G.) sp. g, which exhibited a standard polytene chromosome. Inversion polymorphisms found in this study conformed to Hardy-Weinberg equilibrium and were not associated with sex. These species have different specific markers and banding patterns although homologous banding sequences were found in chromosome arm IIS in S. (G.) asakoae, S. (G.) sp. g, S. (G.) decuplum and S. (G.) siamense and chromosome arm IIIS in S. (G.) angulistylum. Our results showed no evidence of a sibling species complex within any taxon.

Animals↗

Sequence variants in SLITRK1 are associated with Tourette's syndrome.

Tourette's syndrome (TS) is a genetically influenced developmental neuropsychiatric disorder characterized by chronic vocal and motor tics. We studied Slit and Trk-like 1 (SLITRK1) as a candidate gene on chromosome 13q31.1 because of its proximity to a de novo chromosomal inversion in a child with TS. Among 174 unrelated probands, we identified a frameshift mutation and two independent occurrences of the identical variant in the binding site for microRNA hsa-miR-189. These variants were absent from 3600 control chromosomes. SLITRK1 mRNA and hsa-miR-189 showed an overlapping expression pattern in brain regions previously implicated in TS. Wild-type SLITRK1, but not the frameshift mutant, enhanced dendritic growth in primary neuronal cultures. Collectively, these findings support the association of rare SLITRK1 sequence variants with TS.

3' Untranslated Regions↗

Dissection of an inverted X(p21.3q27.1) chromosome associated with mental retardation.

In a 6 year old boy referred for mental retardation, fragile X syndrome was ruled out by cytogenetic and molecular analyses. Cytogenetic investigations revealed an inverted X chromosome (p21.3q27.1). A similar chromosomal rearrangement was detected in his mildly mentally retarded mother. Fluorescence in situ hybridization (FISH), using a panel of ordered YAC clones, allowed the identification of YACs spanning both the Xp21.3 and Xq27.1 breakpoints, where many non-specific mental retardation loci have been reported so far. Further investigations by FISH showed that the IL1RAPL1 gene at Xp21.3 was disrupted by the X chromosome inversion and therefore its inactivation may be related to the mental retardation observed in our patients.

Child↗

The estimation of epistasis in components of fitness in experimental populations of Drosophila melanogaster I. A two-stage maximum likelihood model.

Laboratory populations of Drosophila melanogaster bearing the Curly and Plum marked second chromosome inversions were observed in selection experiments for ten discrete generations. Maximum likelihood estimates of the relative fitnesses of Curly, Plum, Curly-Plum, and wild phenotypes were obtained from selection trajectories. Using these estimates, measures of multiplicative and additive epistasis were calculated. These were partitioned into pre-sampling and post-sampling components, and both were found to be significant. In several cases the sign of the epistasis of the two components was reversed, and the direction of net epistasis depended on the particular inversion. The significance of partitioning epistasis into components is discussed in the light of two locus population genetic theory.

Animals↗

Mitochondrial DNA variation among the Drosophila athabasca semispecies and Drosophila affinis.

Morphology, allozymes, and levels of postreproductive isolation indicate that the semispecies of Drosophila athabasca are as recently diverged as typical populations within a Drosophila species. However, levels of behavioral isolation, divergence in male mating song, and divergence in X-chromosome inversions suggest a much more ancient divergence. In this article, we have examined mitochondrial DNA restriction site variation within and among the three semispecies. These data support the hypothesis that the three semispecies of Drosophila athabasca are at least as recently diverged as are typical populations within other species of Drosophila. Male mating song, behavioral isolation, and X-chromosome differences thus appear to have evolved very rapidly. In addition, hypothesized phylogenetic relationships of these three semispecies, based on our mtDNA data, are identical to those based on allozymes and chromosomal inversions. According to this phylogeny, recency of ancestry is not well correlated with levels of behavioral isolation, whereas patterns of sympatry and allopatry are. These patterns strongly implicate the action of selection in the rapid evolution of behavioral isolation and X-chromosome gene arrangement.

Animals↗

A chromosome rearrangement suggests that donor and recipient sites are associated during Tam3 transposition in Antirrhinum majus.

We describe the structure of a chromosome rearrangement which changes the spatial pattern of expression of the pallida gene of Antirrhinum majus. The rearrangement involves a chromosome inversion of ~6 map units with one breakpoint at the end of a copy of the transposable element Tam3 located in the promoter region of the pallida locus. The sequence at the breakpoints shows that 5-7 bp, present once in the progenitor, has been duplicated and flanks both ends of the inversion. We propose that this structure arose from an aberrant Tam3 transposition, suggesting a model for normal transposition which involves physical association between donor and recipient sites. This may explain why transposition of plant transposable elements such as Ac in maize occurs preferentially to recipient sites closely linked to the donor site. Excision of the Tam3 copy located at the end of the chromosome inversion, results in a unique spatial pattern of pallida gene expression as a consequence of replacing all sequence 70 bp upstream of transcription by a new sequence. This pattern may be the result of deleting specific upstream components which regulate pallida expression and/or of changing the relative chromosome position of the pallida gene.

Journal Article↗

[Pericentric inversion of human chromosomes and its risks] ].

Pericentric inversions of human chromosomes represent rearrangements are formed between two breaks on the short and on long arms of the chromosome with following rotation and new connection of the separated segment in the reversed position. The abnormality does not result in most of the carriers to any clinical manifestations. However, the basic risk the carriers of such inversion are exposed is the possibility of formation of a recombinant aneusomy--later transformation of the inverted chromosome during gametogenesis. Conception by the recombinant gamete usually results in spontaneous abortion or to a birth of seriously affected individual. The risk of recombination has to be in every newly registered inversion individually considered. The larger part of chromosome is taken into the pericentic inversion, the smaller is the extent of resulting duplication and smaller is the deficiency of chromosomal parts, which results from the recombination. The higher is then the viability of the affected foetus. In families with detected recombination, chromosomal examination is fully recommended. Prenatal examination is also indicated when the transformation is listed among the risk inversions or it has larger extent then recorded inversions. Beside the risk inversions, also the "safe" inversions exist, which include minor and frequently occurring transformation of chromosome No 2--inv(2)(p11q13) and inversion of chromosome 10--inv(10)(p11q21).

Chromosome Aberrations↗

Comparative mapping of the human 9q34 region in Fugu rubripes.

Twenty-seven genes have been cloned and mapped in Fugu which have orthologues within the human chromosome 9q34 region. The genes are arranged into five cosmid and BAC contigs which physically map to two different Fugu chromosomes. Considering the gene content of these contigs, it is more probable that a translocation event took place early in the Fugu lineage to split the ancestral 9q34 region onto two chromosomes rather than the alternative hypothesis of a large-scale duplication of the region into two chromosomes with subsequent rapid and dramatic gene loss. There are considerable differences in gene order between the two species, which would appear to be the result of a series of complex chromosome inversions; thus suggesting that there have been no positional constraints on this particular gene set.

Animals↗

Evolutionary genetics of Drosophila mediopunctata.

Drosophila mediopunctata belongs to the tripunctata group, which is the second largest Neotropical group of Drosophila with 64 species described. Here I review the work done with this forest dwelling species, and some applications of the methods developed using it as a model organism, to other species. Specifically I look at: the phylogenetic status of the tripunctata group and its relation with other groups in the Hirtodrosophila-immigrans radiation; D. mediopunctata's chromosome inversion polymorphism (altitudinal cline of frequencies and evidences of selection); the morphological variation of the wing and the development and applications of the ellipse method to describe the morphology of the wing; the variation on the number of aristal branches; the genetic basis of the polychromatism present in D. mediopunctata and its association with chromosome inversions; the sex-ratio trait and its use in the demonstration of Fisher's principle; and, finally, the finding of the transposable P-element in this species.

Animals↗

Relative effects of female fecundity and male mating success on fertility selection in Drosophila pseudoobscura.

The fertility component of natural selection acting on chromosomal inversions in two experimental populations of Drosophila pseudoobscura was subdivided into the effects of female fecundity and male mating success. The offspring of the three female genotypes could be distinguished by their mitochondrial DNA haplotypes, thus permitting a direct measurement of the relative fecundities of the female genotype. The effects of male mating success on inversion frequency were measured by comparing inversion frequencies in parents and their offspring. Selection by fertility caused significant changes in inversion frequency in both populations. In one population, the changes in inversion frequency due to female fecundity and to male mating success were comparable. In the other population, however, the changes in inversion frequency due to male mating success were considerably larger than those due to female fecundity. The difference between the two populations underscores the intrinsic variability of the fertility component of fitness.

Animals↗

Proof of an adaptive linkage association.

Linked X-chromosome inversions of an eastern woods fly, Drosophila robusta, occur in two different nonrandom arrays. Since only one can be the nonrandom condition expected on the approach toward random equilibrium, at least one of the observed arrays must have an adaptive basis.

Animals↗

A large pericentric inversion of human chromosome 8.

A large pericentric inversion, inv(8) (p11q24), was ascertained in a male investigated because his wife had had repeated miscarriages. The inversion segregated in 3 generations of the family, and no chromosomally unbalanced offspring were detected. The miscarriage and the inversion could not be causally related.

Abortion, Spontaneous↗

Genetic differentiation and inversion clines in Indian natural populations of Drosophila melanogaster.

To study the genetic differentiation and inversion clines in Indian natural populations of Drosophila melanogaster, 14 natural populations (6 from the north and 8 from the south) were screened for chromosome inversions. The chromosomal analysis revealed the presence of 23 paracentric inversions, which include 4 common cosmopolitan, 4 rare cosmopolitan, 2 recurrent endemic, and 13 unique endemic (new inversions detected for the first time) inversions. The difference in karyotype frequencies between populations from the north and south were highly significant and the level of inversion heterozygosity was higher in populations from the south. Statistically significant negative correlations were found between each of the four common cosmopolitan inversions and latitude. These findings are in accord with results from other worldwide geographic regions and show that Indian populations of D. melanogaster have undergone considerable genetic differentiation at the level of inversion polymorphism.

Animals↗

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.

Animals↗