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PubMed1998

Agonist and inverse agonist activity at the dopamine D3 receptor measured by guanosine 5'--gamma-thio-triphosphate--35S- binding.

In this study, the ligand-receptor-G protein interactions of the dopamine D3 receptor expressed in Chinese hamster ovary cells were investigated using guanosine 5'-[gamma-thio]triphosphate-[35S] ([35S]GTPgammaS) and receptor binding experiments. Dopamine stimulated the [35S]GTPgammaS binding in a guanine nucleotide, magnesium and sodium-dependent manner. Dopamine and quinpirole produced maximal stimulation of the [35S]GTPgammaS binding whereas (+)-7-OH-DPAT and (-)-3-PPP were partial agonists. Interestingly, several compounds previously classified as D2 receptor antagonists behaved as inverse agonists at the D3 receptor, i.e., they inhibited the basal [35S]GTPgammaS binding in a dose dependent fashion. Haloperidol, (+)-UH-232, (+)-AJ-76 and raclopride were full inverse agonists but clozapine was a partial inverse agonist. Pertussis toxin treatment abolished the D3 receptor-mediated agonist as well as inverse agonist responses, indicating the involvement of Gi/Go proteins in both processes. According to the ternary complex model, agonists should bind with higher affinity to the G protein coupled receptor (RG) and thereby shift the equilibrium from free receptor (R) toward RG, which produces a biological response. However, an inverse agonist should bind with higher affinity to R than to RG and thereby inhibit the basal activity of the cell. We found that the high affinity agonist binding site (RG) was abolished by pertussis toxin treatment of the cells. However, the inverse agonists bound with the same affinity to untreated and pertussis toxin treated D3 receptor membranes. Thus, we found no evidence for the hypothesis that inverse agonists would shift the equilibrium from RG toward R by binding with higher affinity to R than to RG.

Animals↗
PubMed2004

A study of reciprocal translocations and inversions detected by light microscopy with special reference to origin, segregation, and recurrent abnormalities.

We analyzed 448 independently ascertained reciprocal translocations and 220 inversions referred to our diagnostic laboratory. Twenty-eight percent of the translocations and 8.5% of the inversions arose de novo, the proportion being influenced by the method of ascertainment. It was highest, 47%, among translocations ascertained through an abnormal phenotype. With the exception of the 3:1 unbalanced segregants, the remainders were equally likely to have been paternally or maternally inherited. The segregation from balanced translocation and inversion carriers showed an equal number of offspring with a normal chromosome constitution and with a balanced rearrangement. The number of unbalanced segregants among the translocations was 2.7% where the proband was balanced, and 19.2% where the proband was unbalanced. There was only a single unbalanced inversion. A search for recurring translocations showed only the well documented t(11;22) to occur with unusual frequency in our series and those of others, and we concluded that the few other translocations that were seen on more than one occasion were likely to be identical by descent (IBD). Similarly the majority of the recurring inversions, with the exception of "common variants," seemed likely to be IBD. However, eight inversions recurred in our data and in most other series and may well be genuine independent rearrangements. A search of the known olfactory receptor (OR) loci and duplicons suggested that such sequences did not form an important contribution to the breakpoints of recurring rearrangements detected by light microscopy.

Chromosome Aberrations↗
PubMed1994

Large DNA inversions, deletions, and TaqI site mutations in severe haemophilia A.

Large DNA inversions caused by an intrachromosomal recombination between homologous regions located in intron 22 and 5' of the factor VIII gene have recently been identified in patients with severe haemophilia A. To evaluate better the prevalence of this large inversion and to estimate the overall sensitivity of the Southern blot/hybridization method we analysed the factor VIII gene of 49 unrelated patients with severe haemophilia A. All patients were screened for the inversion mutation, TaqI site mutations, and deletions. Mutations were identified in 31 (63%) patients, and comprised 24 large inversions, 4 partial deletions, and 3 point mutations. Three different haplotypes were characterised in the patients presenting the inversion mutation, confirming its independent origin. Two novel deletions are reported: a large one spanning from intron 14 to intron 22 and a deletion of 86 bp comprising the 3' region of exon 1 and 39-41 bp of intron 1. DNA sequencing of the deletion junction showed no significant homology between normal 5' and 3' sequences around the breakpoints. A novel missense mutation is also reported: CGA-->GGA, Arg-2209 to Gly. These results confirm that the inversion mutation is the most common cause of severe haemophilia A and indicate that the Southern blot/hybridization assay should be used as the first method for screening of mutations in severe haemophilia A.

Base Sequence↗
PubMed1990

Chromosome inversions in Indian Drosophila melanogaster.

Ten laboratory stocks of Drosophila melanogaster initiated from females collected in different localities in India were analysed for chromosome inversions. Six inversions were found to be present, three in 2L, one in 2R, one in 3L and one in 3R. Out of these six inversions, three are new and are being reported for the first time. Furthermore, this is the first report of inversion polymorphism in Indian D. melanogaster. The persistence of inversion polymorphism in our laboratory stocks of D. melanogaster which were maintained for more than one year under laboratory conditions, suggests some heterotic advantage of inversion heterozygotes.

Animals↗
PubMed1981

Structural differences in pericentric inversions. Application to a model of risk of recombinants.

The potential chromosomal imbalance in offspring of pericentric inversion heterozygotes can be evaluated by measuring (% of haploid autosomal length, % HAL) the chromosomal segments distal to the breakpoints in the inversion. These distal segments were measured in presently reported and published cases of pericentric inversions, divided into two ascertainment groups: (I) those ascertained through recombinant offspring and (II) those ascertained through balanced heterozygotes. The distal segments in group II inversions were significantly larger than those of group I, i.e., the potentially larger chromosomal imbalances were not observed in full-term offspring. These results are discussed in relation to the model of risk of abnormal offspring in the progeny of heterozygotes for structural rearrangements (the chromosome imbalance size--viability model). The mean distal segment sizes for group I and group II pericentric inversions were respectively not significantly different from the mean interchange segment size for a sample of reciprocal translocations divided into the same two ascertainment groups. It was concluded that the restrictions on the size (% HAL) of chromosomal imbalance in offspring surviving until term are similar whether this imbalance arises from reciprocal translocations or pericentric inversions.

Chromosome Aberrations↗
PubMed1986

The significance of pericentric inversions of chromosome 2.

Thirteen new cases of a pericentric inversion 2 collected from different laboratories are reported. In addition 41 cases of a pericentric inversion 2 were reviewed from the literature. The pooled data were analysed using Weinberg's proband method to evaluate the risk of a carrier for either children with congenital anomalies or reproductive wastage. In the "corrected" sample of 166 lifeborn offspring of carriers of a pericentric inversion 2 there were five who showed phenotypic anomalies and two died a few hours after delivery. The reported anomalies are heterogeneous and probably reflect the basic risk of any couple for abnormal lifeborn offspring. There has been no observation of a lifeborn who inherited an unbalanced recombination of a parental pericentric inversion 2. A carrier of a pericentric inversion 2 obviously has an increased risk for reproductive wastage. This is indicated by (1) an increase of the rate of spontaneous abortions and (2) an increase of the rate of index patients ascertained because of previous miscarriages. The risk of a carrier of a pericentric inversion 2 for a spontaneous abortion or a stillbirth may be about twice the basic risk of the general population.

Abortion, Spontaneous↗
PubMed1986

Heterosynapsis and suppression of chiasmata within heterozygous pericentric inversions of the Sitka deer mouse.

The patterns of chromosomal pairing and chiasma distribution were analyzed in male Sitka deer mice (Peromyscus sitkensis) polymorphic for terminally positioned pericentric inversions of chromosomes 6 and 7. G- and C-banding of somatic metaphases indicated that the inversions involved 30% and 40% of chromosomes 6 and 7, respectively. Analysis of silver-stained synaptonemal complexes in surface-spread zygotene and pachytene nuclei from heterozygous individuals revealed that inversion loops were not formed. The inverted segments proceeded directly to heterosynapsis without an intervening homosynaptic phase, and the heteromorphic bivalents remained straight-paired throughout pachynema. C-banded pachytene nuclei corroborated the occurrence of heterosynapsis, as the heteromorphic bivalents exhibited nonaligned centromeres. Analysis of diplonema and diakinesis indicated that crossing over had not occurred within the heterosynapsed inverted segments. The observation of chiasma suppression within the inversions indicates that pericentric inversion heterozygosity does not lead to the production of unbalanced gametes. Heterosynapsis of the inverted segments during zygonema and pachynema and the resulting chiasma suppression therefore represent a meiotic mechanism for the maintenance of pericentric inversion polymorphisms in this population of P. sitkensis.

Animals↗
PubMed1982

A pachytene analysis of two male-fertile paracentric inversions in chromosome 1 of the mouse and in the male-sterile double heterozygote.

Meiotic studies have been made at pachytene on two paracentric inversions in chromosome 1 of the mouse. Surface-spread preparations of primary spermatocytes have been analysed at the light microscope level in males heterozygous for the inversions In (1) 1 Rk and In (1) 12 Rk and in the double heterozygote In (1) 1 RK/In (1) 12 Rk. In singly heterozygous form, neither inversion produces any serious effect on male fertility. In the double heterozygote, spermatogenesis is arrested in the majority of cells at the spermatocyte stage and males are rendered totally sterile by azoospermia. In the double heterozygote, a complex loop, indicating the inversion bivalent, is found in 90% of pachytene cells analysed. In the In (1) Rk/+ heterozygote, a looped bivalent was seen in 47 per cent of pachytene cells but in In (1) 12 Rk/+ no cells containing loops could be found. -- 80% of pachytene spermatocytes from the In (1) 1 Rk/In (1) 12 Rk double heterozygote showed apposition of the inversion bivalent to the sex bivalent. Such an association was rarely seen in pachytene cells of either of the fertile single heterozygotes. Spermatogenic failure in the double heterozygote may be related to interference, by the inversion bivalent, with X chromosome inactivation at meiotic prophase.

Animals↗
PubMed1990

Inversion polymorphism in populations of Drosophila sulphurigaster albostrigata and Drosophila nasuta albomicans from Phuket, Thailand.

Two species of the Drosophila nasuta subgroup of the Drosophila immigrans group, D. sulphurigaster albostrigata and D. nasuta albomicans were investigated in this study. Collections of both species were made from Phuket, Thailand. Both species have similar salivary chromosomes, with four autosomal arms and one sex chromosome arm, and both are highly polymorphic for paracentric inversions. D.s. albostrigata accounted for the majority of the isolines collected and exhibited the greater number of inversions. One inversion, C14 was common to both species, indicating common ancestry. A non-random distribution of inversions was observed on the proximal end of chromosome III in both D.s. albostrigata and D. n. albomicans. An inter-collection comparison revealed that both rigid and flexible chromosomal polymorphism were operating in the two species, with a seasonal variation noted for one inversion in D. s. albostrigata. A non-random association of two inversions was observed in D. n. albomicans. Based on a comparison of the indices of crossing over, both D. s. albostrigata and D. n. albomicans were found to be more heterozygous than in previous studies, with D. n. albomicans appearing to have evolved further than D. s. albostrigata.

Animals↗
PubMed1988

Common features of three inversions in wheat chloroplast DNA.

We have determined the DNA sequences of regions involved in two of the three inversions known to have occurred during the evolution of wheat chloroplast DNA. This establishes the extent of the second largest of the three inversions. Examination of these sequences suggests that although short repeated sequences are present, the endpoints of the second and third inversions are not associated with repeated sequences as long as those associated with the first inversion. However the endpoints of all three inversions are all adjacent to at least one tRNA gene, and there is evidence that three of the tRNA genes have been subjected to partial duplication, possibly at the time of inversion. This suggests that tRNA genes might be involved with rearrangements of chloroplast DNA, as has also been postulated for mitochondrial DNA.

Base Sequence↗
PubMed2003

Inversion of the uterus at caesarean section.

INTRODUCTION: Inversion of the uterus through the uterine incision during caesarean section is a rare event. Therapy is usually simple and maternal morbidity is low when re-inversion of the uterus can be accomplished immediately. In cases of prolonged uterine inversion thereof, haemodynamic instability and shock, often out of proportion to the degree of blood loss, have been reported as serious sequelae. CASE REPORT: We describe such a case with a prolonged inversion to re-inversion interval where the patient suffered an intraoperative cardiovascular arrest during unrepositioned uterine inversion. Reposition of the uterus led to an immediate return of the patient's vital signs and improvement of her haemodynamic status. DISCUSSION: The mechanisms of haemodynamic instability and the technical aspects of manual reduction of the inverted, heavily contracted uterus during caesarean section are discussed.

Adult↗
PubMed2006

A paracentric inversion suppresses genetic recombination at the FON3 locus with breakpoints corresponding to sequence gaps on rice chromosome 11L.

Paracentric inversion is known to inhibit genetic recombination between normal and inverted chromosomal segments in heterozygous arrangements. Insect inversion polymorphisms have been studied to reveal adaptive processes for maintaining genetic variation. We report the first paracentric inversion in rice (Oryza sativa), which was discovered in our effort to clone the floral organ number gene FON3. Recombination at the FON3 locus on the long arm of chromosome 11 was severely suppressed over a distance of more than 36 cM. An extensive screening among 8,242 F(2) progeny failed to detect any recombinants. Cytological analysis revealed a loop-like structure on pachytene chromosomes, whereas FISH analysis showed the migration of a BAC clone from a distal location to a position closer to the centromere. Interestingly, the locations where the genetic recombination suppression began were coincided with the positions of two physical gaps on the chromosome 11, suggesting a correlation between the physical gaps, the inversion breakpoints. Transposons and retrotransposons, and tandemly arranged members of gene families were among the sequences immediately flanking the gaps. Taken together, we propose that the genetic suppression at the FON3 locus was caused by a paracentric inversion. The possible genetic mechanism causing such a spontaneous inversion was proposed.

Base Sequence↗
PubMed2006

Inversion polymorphism and a new polytene chromosome map of Zaprionus indianus Gupta (1970) (Diptera: Drosophilidae).

Zaprionus indianus is a recent invader in Brazil and was probably introduced from the West Afrotropical zone. So far, studies regarding its chromosomal polymorphism were limited to India. We found that Brazilian populations were very different from Indian ones. Five new inversions have been discovered. In(II)A, already described in India, where it is quite common, has also been found in Brazil, where it is very rare. The X-chromosome has three inversions; In(X)Na, In(X)Ke and In(X)Eg, which are frequent in all Brazilian populations studied. In every case, we observed strong linkage disequilibrium among these gene arrangements. During the primary collection period (2001-2002), we noticed a significant positive correlation between the frequency of these inversions and latitude, but this was not confirmed in later investigations. Rearrangement In(IV)EF was also common in all populations, while inversion In(V)B was only found in southern populations. Our data suggest that the founders that recently invaded Brazil were polymorphic for the six inversions observed. The place of origin might be identified more precisely by investigating West African populations. In order to facilitate further investigations, we present an updated polytene chromosome photomap, locating the breakpoints of every inversion observed in Brazilian populations.

Animals↗
PubMed1978

Regulation of gene expression by site-specific inversion.

A site-specific inversion event is responsible for phase transition in Salmonella, as indicated by heteroduplex analysis of recombinant molecules carrying the gene coding for H2 flagellin in Salmonella. The inversion region corresponds to approximately 800 base pairs in length, and the inversion process does not appear to be dependent upon the E. coli RecA recombination pathway. Specific deletion derivatives of the cloned fragments no longer produce H2-specific flagella, effectively mapping the H2 gene within about 300 bp of the inversion region. Recombinant products of the hybrid molecules arose spontaneously, and they were used in the mapping of restriction sites within the inversion region. The restriction maps further demonstrate the extent and nature of the inversion.

Bacterial Proteins↗
PubMed2005

Unexpected identification of two interstitial deletions in a patient with a pericentric inversion of a chromosome 4 and an abnormal phenotype.

Interstitial deletions and pericentric inversions of chromosome 4 appear to be unusual phenomena. Here, we report the case of a 14-year-old boy with severe psychomotor retardation with a de novo 46,XY,der(4)del(p15.2p15.31)inv(4)(p15.2q13.3)del(4)(q13.2q13.2) karyotype. We used FISH analysis with YAC and BAC clones to characterise the inversion's breakpoints. A complex event with six breakpoints was found, characterised by a pericentric inversion and two deletions, the first on the short arm of chromosome 4 (4p) and the second on the long arm of chromosome 4 (4q). The deletion events had removed two segments, one of approximately 5 Mb, from 4p, outside the inversion, and the other 2 Mb from 4q, inside the inversion. These rearrangements were not found in the parents. Microsatellite marker analysis showed that the inversion carrying chromosome 4 was derived from the father. Bioinformatic analysis of the human genome sequence allowed us to identify several hemizygotic genes in the patient, which might be involved in the pathogenesis of this clinical phenotype.

Abnormalities, Multiple↗
PubMed2006

The chimpanzee-specific pericentric inversions that distinguish humans and chimpanzees have identical breakpoints in Pan troglodytes and Pan paniscus.

Seven of nine pericentric inversions that distinguish human (HSA) and chimpanzee karyotypes are chimpanzee-specific. In this study we investigated whether the two extant chimpanzee species, Pan troglodytes (common chimpanzee) and Pan paniscus (bonobo), share exactly the same pericentric inversions. The methods applied were FISH with breakpoint-spanning BAC/PAC clones and PCR analyses of the breakpoint junction sequences. Our findings for the homologues to HSA 4, 5, 9, 12, 16, and 17 confirm for the first time at the sequence level that these pericentric inversions have identical breakpoints in the common chimpanzee and the bonobo. Therefore, these inversions predate the separation of the two chimpanzee species 0.86-2 Mya. Further, the inversions distinguishing human and chimpanzee karyotypes may be regarded as early acquisitions, such that they are likely to have been present at the time of human/chimpanzee divergence. According to the chromosomal speciation theory the inversions themselves could have promoted human speciation.

Animals↗
PubMed2005

Chromosomal inversion discovered in C3H/HeJ mice.

Mice of the inbred mouse strain C3H/HeJ have been shown to be homozygous for a chromosomal inversion on Chromosome (Chr) 6. The inversion encompasses about 20% of the chromosome from approximately 73 Mb to approximately 116 Mb. The importance of this finding is that linkage crosses using C3H/HeJ will show no recombination in this region of Chr 6. The inversion has no apparent effect on the phenotype of C3H/HeJ mice and its presence should not affect biological studies; however, use of C3H/HeJ mice for genetic analysis of Chr 6 should be avoided or the results interpreted with the inversion in mind. The inversion has been named In(6)1J (inversion Chr 6, Jackson 1).

Animals↗
PubMed1999

Inversion due to intrachromosomal recombination produced by carcinogens in a transgenic mouse model.

Somatic intrachromosomal recombination (SICR) can result in inversions and deletions in the DNA. pKZ1 mice possess an Escherichia coli (E. coli) lacZ transgene which is only expressed after a DNA inversion involving the transgene occurs. The E. coli beta-galactosidase protein can then be detected in frozen tissue sections using a chromogenic substrate. Therefore, pKZ1 mice can be used to detect SICR inversion events in vivo in different tissues. We have tested the pKZ1 mouse for its potential as a general mutagenesis model for detecting SICR in spleen in response to carcinogens which have widely different mechanisms of genotoxicity. Animals were given a single exposure of carcinogen and spleen cells were examined 3 days later for inversion events by histochemical staining of tissue sections. Mitomycin C, X-irradiation, etoposide and methylene chloride caused significant induction of inversion events in spleen tissue, ranging from 1.6- to 4.2-fold induction with the doses used here. This is the first time that inversion events induced by these carcinogens have been specifically studied in vivo in a mouse model and the findings expand the repertoire of mutation events known to be caused by these agents. We suggest that the pKZ1 mouse can be used as a general mutagenesis model for detection of SICR events and is likely to be a useful model for studying the mechanism of SICR in response to DNA damaging agents.

Animals↗