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PubMed1981

Fine structure and behaviour of a pericentric inversion in the sand rat, Psammomys obesus.

In pachytene spermatocytes of the sand rat, Psammomys obesus, a long autosomal bivalent was observed, which was asynaptic for a large interstitial segment of its length in early pachytene. This bivalent also exhibited unaligned kinetochores. In late pachytene spermatocytes all autosomal bivalents were fully synapsed, but one of the shortest bivalents now possessed unaligned kinetochores. Evidence is presented in support of the proposition that the asynaptic interstitial region observed in early pachytene is due to the bivalent being heterozygous for a pericentric inversion. Using the maximum extent of homologous pairing, the break points were mapped at 26% from one end and 20% from the other. The unaligned kinetochores support the proposal that the aberration is an inversion and measurements of their positions confirm the estimated break points. In one cell a bivalent with interstitial (but no terminal) synapsis also confirms the inversion hypothesis. It is proposed that the bivalent is so small that topological considerations prevent the formation of the expected inversion loop. Evidence is also presented that complete synapsis of the bivalent during late pachytene can be attributed so 'synaptic adjustment', characterized by non-homologous synapsis (heterosynapsis). The position of the aberrant bivalent in relation to the sex chromosomes also changes during pachytene. When the bivalent is incompletely synapsed it generally associates by its ends with the ends of the sex chromosomes, but when it is non-changes during pachytene. When the bivalent is incompletely synapsed it generally associates by its ends with the ends of the sex chromosomes, but when it is non-homologously synapsed it is not associated with them.

Animals↗
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↗
PubMed2006

Testing chromosomal phylogenies and inversion breakpoint reuse in Drosophila.

A combination of cytogenetic and bioinformatic procedures was used to test the chromosomal phylogeny relating Drosophila buzzatii with D. repleta. Chromosomes X and 2, harboring most of the inversions fixed between these two species, were analyzed. First, chromosomal segments conserved during the divergence of the two species were identified by comparative in situ hybridization to the D. repleta chromosomes of 180 BAC clones from a BAC-based physical map of the D. buzzatii genome. These conserved segments were precisely delimited with the aid of clones containing inversion breakpoints. Then GRIMM software was used to estimate the minimum number of rearrangements necessary to transform one genome into the other and identify all possible rearrangement scenarios. Finally, the most plausible inversion trajectory was tested by hybridizing 12 breakpoint-bearing BAC clones to the chromosomes of seven other species in the repleta group. The results show that chromosomes X and 2 of D. buzzatii and D. repleta differ by 12 paracentric inversions. Nine of them are fixed in chromosome 2 and entail two breakpoint reuses. Our results also show that the cytological relationship between D. repleta and D. mercatorum is closer than that between D. repleta and D. peninsularis, and we propose that the phylogenetic relationships in this lineage of the repleta group be reconsidered. We also estimated the rate of rearrangement between D. repleta and D. buzzatii and conclude that rates within the genus Drosophila vary substantially between lineages, even within a single species group.

Animals↗
PubMed1976

Pericentric inversion of chromosome No. 8.

Chromosome studies of an infant with multiple malformations were made by means of the trypsin-Giemsa banding as well as conventional Giemsa staining methods. The propositus showed 46, XY +3, -C, and it was indicated that the abnormal metacentric chromosome was induced by the pericentric inversion of chromosome No. 8, in which chromosomal breakage had occurred most likely at the bands 8p23 and 8q23. The probable formula of the inversion is 46, XY, inv (8) (p23q23). Karyotypic analyses of the parents revealed no abnormalities, and the inversion therefore occurred spontaneously. Clinical features of the porpositus are postulated to be caused by a loss of very small portions of the chromosomal material with the occurrence of the pericentric inversion.

Abnormalities, Multiple↗
PubMed1993

Association of two esterase genes, a chromosomal inversion, and susceptibility to Plasmodium cynomolgi in the African malaria vector Anopheles gambiae.

The ability of a selected strain of the malaria vector Anopheles gambiae to encapsulate the early oocysts of the malaria parasite Plasmodium cynomolgi B has previously been shown to be genetically linked to specific esterase phenotypes. This association between Plasmodium susceptibility and esterase phenotype is found in the An. gambiae G3 strain from which the Plasmodium-refractory and -susceptible mosquito strains were derived. Genetic crosses had suggested that the esterase phenotypes reflect the assortment of two alleles at one esterase genetic locus, with the two esterase homozygotes showing Plasmodium-susceptible and -refractory phenotypes and the esterase heterozygote being intermediate in susceptibility. By using a variety of specific esterase inhibitors in conjunction with esterase staining of gel-electrophoresed mosquito homogenates, we found that the bands previously thought to reflect one genetic locus are actually the product of two different esterase loci, Est1, a cholinesterase, and Est2, a carboxylesterase. In addition, examination of chromosomal inversions and the esterase phenotype in the An. gambiae G3 strain revealed that different forms of a polymorphic inversion on the left arm of chromosome two (the 2La inversion) are inseparably associated with different alleles at these two esterase loci. We conclude that the genetic association among the esterase-linked Plasmodium-susceptibility locus and the two esterase loci is maintained by the suppression of recombination in 2La inversion heterozygotes in the An. gambiae G3 strain and its selected derivatives.

Alleles↗
PubMed1992

[Correlation of the clinical phenotype with a pericentric inversion of chromosome 9].

Pericentric inversion of chromosome 9 is one of the most common structural balanced chromosomal aberrations. It is considered as a paraphysiological variant of a normal karyotype and it is possible to find it as occasional report in healthy subjects. In the last ten years different signals have appeared in literature, concerning carriers of pericentric inversion of chromosome 9, who showed different anomalies of the clinical condition. Today it is difficult, because of the rarity of the data to establish if a true correlation exists between phenotypical anomalies in the subjects studied and the pericentric inversion, or if they are only casual associations. We are trying to find possible correlations between the chromosomal rearrangements and eventual congenital defects. We describe 11 subjects with pericentric inversion of chromosome 9 examined for the presence of dysmorphic signs, mental retardation and repeated miscarriage.

Abnormalities, Multiple↗
PubMed2003

Paracentric inversion in the short arm of chromosome 1. Report of a family and review of the literature.

In general, carriers of paracentric inversions are phenotypically normal, although individual reports describe like occurrence of infertility, miscarriages and mental retardation in inversion carriers. We present a family with paracentric inversion of 1p [karyotype: 46,XY/XY, inv(1)(p13.2p36.2)] in 7 of the 12 investigated family members. The index patient, a four year-old boy was referred for motor and mental retardation. The possible relationship between the paracentric inversion and the MR/MCA syndrome in the index patient of this family is briefly discussed.

Child, Preschool↗
PubMed2005

Recombination aneusomy of subtelomeric regions of chromosome 5, resulting from a large familial pericentric inversion inv(5)(p15.33q35.3).

We present a family with three cases of recombination aneusomy rec(5)dup(5q) originating from a large parental pericentric inversion of chromosome 5. The proband--a 6-year-old girl with mental retardation, speech delay, microcephaly, and slight facial dysmorphism--was referred for subtelomere testing. FISH with a Multiprobe Chromoprobe T System (CytoCell) and with several BAC clones mapping to both subtelomere regions of chromosome 5, revealed a recombinant chromosome rec(5)dup(5q) originating from a paternal pericentric inversion inv(5)(p15.33q35.3). The same inversion was present in the proband's father's twin-brother and rec(5)dup(5q) was also identified in his two mentally retarded daughters. The distance of breakpoints from the telomere was: 0.234-1.4 Mb for 5p and 4.1-4.8 Mb for 5q. HR-CGH analysis confirmed the duplication of the 5q subtelomeric region but did not identify any concomitant deletion in the 5p subtelomere. Precise mapping of the aneusomic regions in the proband enabled mapping the cat cry and speech delay to 5p15.33, making the earlier localizations of these features more precise. Our family shows that the large pericentric inversion with both breakpoints at subtelomeric regions of chromosome 5 is associated with a high risk of rec(5)dup(5q) in the progeny.

Child↗
PubMedDate not supplied

Pericentric inversion inv(7)(p11q21.1): report on two cases and genotype-phenotype correlations.

We report on two unrelated cases of pericentric inversion 46,XY,inv(7)(p11q21.1) associated with distinct pattern of malformation including mental retardation, development delay, ectrodactyly, facial dismorphism, high arched palate. Additionally, one case was found to be characterized by mesodermal dysplasia. Cytogenetic analysis of the families indicated that one case was a paternally inherited inversion whereas another case was a maternally inherited one. Molecular cytogenetic studies have shown paternal inversion to have a breakpoint within centromeric heterochromatin being the cause of alphoid DNA loss. Maternal inversion was also associated with a breakpoint within centromeric heterochromatin as well as inverted euchromatic chromosome region flanked by two disrupted alphoid DNA blocks. Basing on molecular cytogenetic data we hypothesize the differences of clinical manifestations to be produced by a position effect due to localization of breakpoints within variable centromeric heterochromatin and, alternatively, due to differences in the location breakpoints, disrupteding different genes within region 7q21-q22. Our results reconfirm previous linkage analyses suggested 7q21-q22 as a locus of ectrodactily and propose inv (7)(p11q21.1) as a cause of recognizable pattern of malformations or a new chromosomal syndrome.

Adolescent↗
PubMed1991

Pericentric inversion of chromosome 13: familial study and review of the literature.

A family is described in which a pericentric inversion of chromosome 13 (13(p11 q22] was discovered after amniocentesis was performed in a patient with a previous stillborn child with multiple congenital abnormalities, and one surviving Down syndrome offspring with the maternal inversion and an additional trisomy 21. No association between pericentric inversion of chromosome 13 and other chromosomal abnormalities was found in the literature. This study discuss the possible involvement of this type of inversion in the occurrence of chromosomal and phenotypic alterations in the carrier offspring, as well as its role in genetic counseling and in the indication of prenatal diagnosis.

Adult↗
PubMed1990

[Pericentric inversion of chromosome 9. Summary of the authors' results].

A review is given of our experience in the pericentric inversions of chromosome 9 (26 cases). We examine the relevance of this pericentric inversion in the phenotype of the carriers, the significance of pericentric inversions of chromosome 9 in infertility, and the occurrence of aneusomic recombinants. We also discuss the importance of pericentric inversions of chromosome 9 in the genetic counselling and their use as a family maker.

Abnormalities, Multiple↗
PubMed1989

[Pericentric inversion of the human Y chromosome].

Pericentric inversion of the human Y chromosome has an estimated frequency of the one per thousand. This inversion is always inherited but also is possible a de novo presentation. Sometimes this inverted chromosome is associated with the Down, Klinefelter and other chromosomal syndromes. For the carriers of pericentric inversion the risk of the mental retardation or multiple abortion is not apparently increase and there is not relation with abnormal phenotypic features. For some authors the pericentric inversion of the human Y chromosome is only a rare chromosomal heteromorphism.

Adolescent↗
PubMed1989

A dicentric recombinant 9 derived from a paracentric inversion: phenotype, cytogenetics, and molecular analysis of centromeres.

A 4-year-old girl with multiple malformations and severe developmental delay has been shown to have a karyotype of 46,XX-9,+rec(9),dup p,inv(9) (q22.1q34.3)mat, with duplication 9pter-q22.1 and deficiency 9q34.3-qter. This case confirms that a stable recombinant chromosome can result from a paracentric inversion. The recombinant was derived by two crossovers, one within the inversion loop and a second outside the inversion loop, between 9q21 and the beginning of the meiotic inversion at 9q22.1. In 87 cells the rec(9) had one Cd-positive primary constriction. In 13 cells the rec(9) had two primary constrictions; in 12 of these cells there was one Cd-positive centromere, and in one of these cells both primary constrictions were Cd-positive. Nuclear projections were observed in 10% of fibroblast interphase cells harvested in situ, suggesting that there was some spindle-fiber activity of the "latent" centromere. In situ hybridization with a centromere-specific probe (p82H) and a satellite III probe (L6) revealed no differences between the two C-band regions of the rec(9) and the normal 9 or inverted 9 chromosomes.

Abnormalities, Multiple↗
PubMed1986

Theoretical study of inversions affecting human chromosomes.

A theoretical study of inversions affecting human chromosomes is proposed. Taking into consideration the number of bands and the fact that breaks occur at interfaces between bands, it is concluded that: 7.659 different pericentric inversions might be detected in a prometaphasic 802-band karyotype; this number decreases to 917 in a metaphasic 273-band karyotype; 8.607 and 862 different paracentric inversions might be detected in the same karyotypes respectively, but these results are likely to be overestimated. These theoretical data are used for showing that the pericentric inversions detected in human cytogenetic laboratories, are too frequently recurrent and are not distributed at random.

Chromosome Inversion↗
PubMed1986

Radiation induced inversions in human somatic cells.

Peri- and paracentric inversions induced by various types of ionizing radiation (gamma and alpha-rays, neutron and neon beams) are analysed. Their frequencies significantly increase for radiation doses greater than or equal to .5 Gy. Their distribution does not seem to be at random. Pericentric are detected 3 to 4 times more frequently than paracentric inversions. Some identical inversions are recurrently induced. A proportion reproduces inversions detected in human cytogenetics laboratories and a larger proportion, chromosomes of other primate species. It seems that breakages, which numbers are roughly proportional to chromosome lengths, lead to reassociations with a limited number of combinations.

Alpha Particles↗
PubMed1986

Meiotic behaviour of familial pericentric inversions of chromosomes 1 and 9.

Pachytene analysis was carried out in two infertile brothers, one heterozygous for two pericentric inversions of chromosomes 1 and 9, the second heterozygous for the pericentric inversion of chromosome 1. The synaptic behaviour of the bivalent 1 inversion was the most informative. Analysis of the chromomere pattern combined with centromeric heterochromatin staining and synaptonemal complexes visualization allowed precise description of synaptic initiation and extension leading to the homosynapsed loop. Heterosynapsis following alignment of the inverted segments was demonstrated. Non-homologous synapsed bivalents had the morphological aspects of straight bivalents with two distant blocks of centromeric heterochromatin. The possible sterilizing effect caused by the autosomal inversion is discussed.

Adult↗
PubMed1995

Characterization of factor VIII gene inversions using a non-radioactive detection method: a survey of 102 unrelated haemophilia A families from northern France.

Intrachromosomal rearrangements of the long arm of chromosome X, between gene A (F8A) in intron 22 of the factor VIII gene and one of its two telomeric copies, are responsible for about half of the severe cases of haemophilia A. A group of 98 unrelated patients from Northern France with moderate to severe haemophilia A was screened for this gene inversion using a non-radioactive Southern blotting method. Whereas none of the 18 moderately affected patients presented the FVIII gene rearrangement, gene inversion was found in 38 (48%) of the 80 severe haemophilia A patients. Recombinations involving the distal copy of gene A (group 1) were more frequent (79%) than those involving the proximal copy (group 2). Individual variation in the number of gene A copies on the X chromosome probably explains an alternative Southern blot profile, referred to as group 3 inversion, which was observed in one of our patients. In the severely affected patients, neither the prevalence of inhibitor development nor the frequency of sporadic cases differed significantly in the group presenting gene inversion as compared to the group without chromosomal rearrangement. Study of four families where no patient was available enabled in one case direct carrier detection and prenatal diagnosis in the absence of an affected member. The Southern blotting technique described in the present work is relevant to about 50% of cases of severe haemophilia A, can be performed without use of a radiolabelled probe and represents a major advance in the diagnosis of the disease.

Biomarkers↗
PubMed1995

Pericentric inversion 9--incidence and clinical significance.

Pericentric inversion of the chromosome 9, inv(9)(p11q13), is such a common occurrence that some cytogeneticists would consider them as normal variants. The incidence is said to be about 1% to 1.65% in the general population. Despite being categorised as a minor chromosomal rearrangement which does not correlate with abnormal phenotypes, many reports in the literature raised conflicting views regarding the association with subfertility and recurrent abortions, abnormal clinical conditions, as well as chromosomal abnormalities arising as a result of having this inversion. We studied the incidence and clinical significance of inv(9)(p11q13) patients retrospectively from 2448 antenatal cytogenetic analysis and 1058 peripheral blood karyotype collected over a 3-year period. Thirty cases of inv(9)(p11q13) from 29 families were found from the antenatal group, which gave an incidence of 1.2% and 6 cases from the peripheral blood karyotype analysis (incidence of 0.6%). The parental origin of the inv(9)(p11q13) in the antenatal group was of equal proportion and there was also no sex predilection for the fetuses carrying the inversion. The babies with the inversion were born with no phenotypic abnormalities. The 6 cases picked up from the peripheral blood karyotype analysis were 2 cases of paediatric patients with associated chromosomal abnormalities (one Trisomy 21 and the other del 13(q22q32)) and 4 adult patients with obstetric and fertility problems. The incidence of subfertility (36%) appeared to be high amongst the adult patients with inv(9)(p11q13). This may represent a true reflection of subfertility in inv(9)(p11q13) patients or a selective bias towards the older subfertile women who conceive at a later age and thus utilising the antenatal diagnostic setup.

Abortion, Habitual↗