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PubMed1995

Type I bipolar disorder associated with a fragile site on chromosome 1.

The objective of this paper is to study the association between chromosomal fragile sites and type I bipolar disorder. This case-control study compares bipolar patients with normal controls. Ten cases of type I bipolar disorder diagnosed according to DSM-III-R criteria and the Composite International Diagnostic Interview (CIDI) were selected from the Escola Paulista affective disorders outpatient clinic and 10 healthy controls (CIDI negative for psychiatric diagnoses) matched for sex and age were drawn from the otorhinolaryngologic outpatient clinic of the same hospital. The cytogenetic analysis was carried out with blood lymphocytes, which were cultured in a folic acid-free medium. A total of 100 mitoses per subject were blindly analyzed to the psychiatric diagnostic assignment, and fragile sites were identified according to a minimum expected frequency of events per band in conformity with a Poisson distribution. A higher frequency of chromosomal lesions for cases than controls was found for the following bands: 1q32, 5q31, and 11q23, the 1q32 being considered a fragile site. Although no evident neuropsychiatric etiological component has been mapped to the 1q32 region so far, this finding may lead to further investigation of a possible linkage between genetic markers of this region and bipolar disorder.

Bipolar Disorder↗
PubMedDate not supplied

Juxta-centromeric fragility of chromosomes 1, 2, 9, 16, and immunodeficiency. Special reference to the fragility of chromosome 2 and its oncogenic potential.

Juxta-centromeric fragility of chromosomes 1, 2, 9, 16, has been described at least thrice in unrelated patients in association with combined immunodeficiency. This association has been confirmed by our findings in both immunodeficient and cancer patients. In our opinion, both the fragility and the immunodeficiency are the results of persistent viral infections by certain DNA (i.e.: Herpes-, Papova-) viruses or RNA (retro-) viruses (i.e. HTLV), which are lymphotropic. The immunodeficiency may be due to virus-cell, cell to cell, or virus-virus interactions. According to our findings, centromeric fragility of chromosome 2 appears to have a particular oncogenic potential probably because of its location in proximity to immunoglobulins genes. We suggest that centromeric fragility of chromosomes 1, 2, 9, 16, may be one of the symptoms of an incipient Acquired Immunodeficiency Syndrome (AIDS) which will not necessarily develop fully.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Ultrastructure of the fragile X chromosome: new observations on the fragile site.

Using a nonair-drying modification of a method for longitudinal sectioning of metaphase spreads on glass slides [Wen et al., 1997], we have studied 14 preidentified X chromosomes (10 from fragile X specimens and 4 controls) with transmission electron microscopy (TEM). Four of 10 X chromosomes from fragile X specimens exhibited lighter chromatin density in the area of and distal to the fragile site, most pronounced under dark-field TEM. A clear line of separation at the fragile site locus was also observed by TEM in an X chromosome with no visible fragile site after Q-banding. We hypothesize that these areas of lighter density, including lines of separation, precede the appearance of the fragile site that is commonly observed using light microscopy.

Chromosome Fragile Sites↗
PubMed2001

[Psycholinguistic aspects of fragile X chromosome syndrome].

Fragile X syndrome is the first cause of hereditary mental retardation. Numerous studies have approached the physical and behavioural phenotypes. This paper will review the main characteristics of speech and language in children with fragile X syndrome. Boys show a late language acquisition, differing comprehension and expression levels, good semantic and syntax acquisition, and speech problems: perseverance, unequal rythm and pragmatic difficulties: respect for conversation turns, speech maintenance, active avoidance of visual contact. A lesser degree of speech problems is described for FXS girls and the influence of social anxiety and hypersensitivity to social and sensorial stimuli on language production is discussed.

Child↗
PubMed1990

[Genetic etiology of esophageal cancer. V. Fragile sites on chromosome of cultured lymphocytes from members of high risk cancer families in Linxian County].

The chromosome fragile sites of cultured peripheral lymphocytes from 40 members of 4 high risk cancer families and 10 members of 4 low risk cancer families in Linxian County were analysed. The results showed that 46 fragile sites in 7045 lymphocytes expression at 502 times (7.13%) were found in high risk cancer families and 8 fragile sites in 1053 lymphocytes expression at 26 times (2.47%) were found in low risk cancer families. There was a significant difference between the two groups (P less than 0.01). In 46 fragile sites carried by 40 members of high risk cancer families, 27 were common, 5 rare, 12 provisional and 2 new fragile sites. Among them, the fragile sites at 1p22-p36 and 4q21-q31 were detected in members of high risk cancer families and in patients with esophageal cancer, meanwhile, uniform breakpoint in chromosome deletion and rearrangement was also found in 4 esophageal cancer cell lines. Therefore, the author conjectures that these fragile sites at 1p13-p36 and 4q21-q31 may be fragile site-specific for high risk cancer families and patients with esophageal cancer, and they may be breakpoint-specific for esophageal cancer cells. These fragile sites may play an important role in esophageal carcinogenesis in high risk cancer families.

Adolescent↗
PubMed1992

Population cytogenetics of aphidicolin-induced fragile sites.

Chromosome fragile sites are inducible by aphidicolin in cultured human lymphocytes. To assess the frequency and distribution of these common fragile sites in the general population, a cytogenetic survey was performed on 126 subjects, 59 males and 67 females, whose age ranged from 1 day to 72 years. Common fragile sites, induced by aphidicolin, were widespread and showed a remarkably different sensitivity among individuals; age influenced the overall frequency of fragile sites. Moreover, both age and sex seemed to modulate the expression of specific fragile sites. In our population, the most common fragile sites were: 3p14, 16q23, Xp22, 6q26, 1p31, 4q31, 1p22, 7q22, 2q33, 3q27, 2q31, 7q32, 14q24, 10q22, 5q31, 2q37, 6p21.

Adolescent↗
PubMed1993

Murine radiation myeloid leukaemogenesis: relationship between interstitial telomere-like sequences and chromosome 2 fragile sites.

While the specific nature of chromosomal fragile sites and their relationship to human leukaemogenesis remain obscure, there is evidence that chromosomal fragility may, in some circumstances, be associated with telomere-like repeat sequences and that chromosome 2 fragility in the mouse is involved in the initiation of myeloid leukaemia by ionising radiation. Here we describe the molecular cloning and characterisation of two murine telomere-like sequences, one having an inverted repeat structure and the other a simple tandem repeat organisation. The inverted telomere repeat clone generates an in situ chromosome 2 hybridisation pattern very similar to the distribution of the radiation-sensitive fragile sites previously found to be associated with leukaemogenic initiation. Furthermore, statistical comparison of the distributions of radiation induced breakpoints and sites of inverted telomere repeat hybridization indicates concordance at all chromosome 2 sites excluding the terminal regions. These data are discussed with respect to mechanisms of radiation-induced, site-specific chromosome 2 rearrangement and their implications for leukaemogenic initiation.

Acute Disease↗
PubMed1985

Analysis of the fragile-X chromosome: localization and detection of the fragile site in high resolution preparations.

Fragile X chromosome preparations were analyzed at levels of up to 850 bands per haploid set. We were able to consistently sublocalize the Xqter fragile site to band Xq27.3 using high-resolution methods. Chromosome length versus the frequency of fragile X expression was also compared. The fragile site appeared at a higher percentage in more condensed chromosome preparations. The importance of this finding is that high-resolution chromosome preparations do not optimize fragile-X detection.

Chromosome Banding↗
PubMed1983

[X chromosome-linked mental retardation with fragile X chromosome and macro-orchidism].

Description of the first Swiss family with the new syndrome of X-linked mental retardation. The three brothers described are the first of all males traced back for four generations to be affected. In two of the brothers macroorchidism and the fragile X-chromosome were demonstrated, while the third brother died before diagnosis. As expected, the fragile X was not demonstrable in the 75-year-old mother of the three brothers.

Adolescent↗
PubMed1988

Cytological evidence of defective template in the fragile X chromosome.

In cells of fragile X patients, the changed X segment may appear as a poorly staining region or a gap, or as a deletion, involving one or both chromatids. To find out whether the fragile site represents an incompletely replicated DNA sequence, as has been suggested recently, we analyzed the four chromatids of methotrexate-induced endoreduplicated fragile X chromosomes. Our main observations were: (1) a deleted chromatid was never internal to a poorly staining one; (2) an endoreduplicated X chromosome with a fragile site never included a normal chromatid. These results can be explained by assuming that DNA at the fragile site, when replicated in the presence of methotrexate, may undergo defective replication and give rise to improperly packaged chromatin, appearing as a chromatid with a poorly staining region or a gap in the following metaphase. The same DNA may fail to function as a template in the following S-phase and give rise to a chromatid with a single-stranded segment, appearing as a deleted chromatid in the following metaphase.

Cell Cycle↗
PubMed1997

Transmission electron microscopy of chromosomes by longitudinal section preparation: application to fragile X chromosome analysis.

We developed a method for the preparation of ultrathin longitudinal sections of chromosomes enabling TEM studies of whole chromosomes. By using a novel "repeat chill" method of exposing the glass slide and plastic block interface to liquid nitrogen, it was possible to separate consistently hardened epoxy resin-embedded chromosome spreads from glass slides for ultrathin longitudinal sectioning of entire spreads and of individual chromosomes. The method was applied to analyze the fragile X chromosome. The ultrastructure of centromeres, telomeres, fragile sites and other chromosomal areas can now be studied in detail.

Centromere↗
PubMedDate not supplied

[The clinico-genetic aspects of mental retardation related to the fragile-X chromosome].

This review deals with main problems of syndrome of X-fragile chromosome. The history of discovery and subsequent study of diseases as well as methods of examination, main clinical symptoms, methods of treatment and prophylaxis have been described. Some hypotheses, explaining complicated mechanism of fra-X syndrome inheritance are discussed. The recent achievements of molecular and genetic investigations of mental backwardness, associated with X-fragile chromosome are included in review.

Chromosome Fragility↗
PubMed1988

Frequency of tri- and multiradial configurations in fragile X chromosomes.

The appearance of tri- or multiradial configurations in fragile chromosomes is affected by the number of cell cycles in the folate antagonist system. In this study the lymphocytes were incubated for 96 h in a medium 199 without calf serum, and tri- or multiradial configurations were observed in 6 of 12 cases of fra(X) chromosome. The frequency ranged from 0.6% to 7.4% of fra(X) chromosomes.

Adolescent↗
PubMed2003

Fragile-X syndrome and skewed X-chromosome inactivation within a family: a female member with complete inactivation of the functional X chromosome.

Fragile X syndrome is the most common form of inherited mental retardation. It is caused by the increase in length of a stretch of CGG triplet repeats within the FMR1 gene. A full mutation (> 200 repeats) leads to methylation of the CpG island and silencing of the FMR1 gene. We present here two sisters that are compound heterozygotes for a full mutation and a 53 repeat intermediate allele, one of them showing mental retardation and clinical features of an affected male (speech delay, hyperactivity, large ears, prominent jaw, gaze aversion), while the other is borderline normal (mild delay). Southern blot and FMRP expression analysis showed that the sister with mental retardation had the normal FMR1 gene totally methylated and no detectable protein, while her sister had 70% of her cells with the normal FMR1 gene unmethylated and normal FMRP levels. We found that the observed phenotypic differences between both sisters who are cytogenetically normal, are caused by extreme skewed X-chromosome inactivation. Analysis of the extended family showed that most of the other female family members that carry a pre-mutation or a full mutation showed some degree of skewing in their X-chromosome inactivation. The presence of several family members with skewed X inactivation and the direction and degree of skewing is inconsistent with a mere selection during development, and suggests a genetic origin for this phenomenon.

Adolescent↗