智力低下儿童外周血淋巴细胞染色体畸变及脆性部位表达的研究

采用低叶酸含量的Tc199培养基和阿糖胞苷处理，观察10例智力低下儿童及10例智力正常儿童外周血淋巴细胞染色体畸变及脆性部位表达．结果表明，智力低下儿童诱发及自发染色体畸变率及脆性部位表达率均高于正常对照组．经诱发，患者脆性部位3p14，7q32，4q31，1p32，10q22，14q23等出现频率较多。     

先天性智能低下儿的染色体脆性位点探讨

对１０４例先天性智能低下儿和３７例正常儿分别进行叶酸敏感型染色体脆性位点表达、外周血淋巴细胞培养、染色体制备和核型分析，结果为：智能低下儿染色体脆性位点表达率明显高于正常儿（Ｐ＜０．０１）。脆性位点在各组（Ａ－Ｇ）和Ｘ染色体表现众数为Ａ、Ｃ组，表达率较高为Ａ、Ｃ组和Ｘ染色体。本文研究不仅得出了染色体脆性位点的表达和分布，而且进一步说明了染色体脆性位点的检测对智能低下儿的诊断提供了有价值的实验资料。     

非小细胞肺癌患者外周血染色体稳定性研究

在非小细胞肺癌患者外周血培养液中加入诱变剂，结果发现患者染色体畸变率（１４％）较正常对照组明显增高，主要的畸变有１ｐ－、６ｑ、７ｐ－、７ｑ－。说明患者染色体不稳定，并且有一定的遗传基础。此外，患者脆性位点表达率（９４．９％）明显高于正常对照组（３４．１％）（Ｐ〈０．０１）。患者染色体断裂点有７２％与脆性位点一致。两者可能有共同的遗传基础。     

非特异型精神发育迟滞患者的染色体脆性位点研究

为了解精神发育迟滞患者染色体的稳定性及与临床的关系,采用低叶酸TC199培养诱导法,对300名非特异型精神发育迟滞患者作染色体脆性位点表达检测和断裂点细胞频率统计。结果普通型脆性位点表达23例(7.7%),遗传型脆性位点表达31例(10.3%),染色体断裂或裂隙的细胞频率10.8%,与正常对照组相比较,差异均有显著性,本文认为这类患者较高的脆性位点阳性表率和断裂点细胞频率,是其染色体不稳定性的表现之一。     

染色体脆性位点fra(10)(q25)的自然表达

过去曾报导过若干人类染色体具有遗传性脆性位点,其中大多数位点要在缺乏叶酸的培养基中才能得到最大的表达。也有人曾报导过仅在培养基内加入BrdU诱发脆性位点fra(10)(q25)的出现。本文最近发现一个家庭有fra(10)(q25)的自发表达。先证者为1例16岁的女患者,她患有明显的进行性运动失调,伴有视力障碍,轻度精     

反复性流产患者染色体脆性位点的分析

目的探讨习惯性流产患者细胞遗传学病因。方法采用低叶酸TC199培养诱导法,观察了86例染色体核型无异常的反复自然流产患者染色体脆性位点,并观察了脆性位点的分布。结果实验组染色体脆性位点的频率为12%;对照组为4.94%,两组相比差异非常显著。染色体脆性位点的分布两组基本一致。结论反复性流产与染色体脆性位点频率增高有关与脆性位点分布关系不大。     

远霉素A诱发脆性位点的性质

目前业已证实人类染色体上有五个由远霉素A诱发的脆性位点,即fra(8)(q24.1),fra(11)(p15.1),fra(16)(p12.1),fra(16)(q22)和fra(17)(p12)。表1列出了这些脆性位点的群体发生率。到目前为止,在所报告之罕见常染色体脆性位点当中,fra(16)(q22)和fra(17)(p12)这两个位点颇为常见(1/20～1/100)。日本人和德国人群体中这些脆性位点基因及其未表达的等位基因似乎作为染色体的多态性而存在。据Sherman和Sutherland的分离分析,绝大多数携带叶酸敏感的常染色体脆性位点(包括11个位点),Brdu诱导的脆性位点、fra(10)(q25)的先证者均接受其母亲的基因。远霉素A诱发的脆性位点fra(16)(q22),其分离具有     

白血病和淋巴瘤染色体脆性部位研究

本文观察了53例白血病和淋巴瘤患者以及50例正常人外周血淋巴细胞的染色体脆性部位,实验结果表明:1）白血病和淋巴瘤患者染色体畸变率和脆性部位检出率均显著高于对照组。2）淋巴瘤患者检出44种脆性位点,有21种与癌断裂点对位;白血病患者检出的30种脆性位点中有19种与癌断裂点对位,两者之间具有显著的相关关系。3）实验组患者检出的部分脆性位点与癌基因位点一致,以上结果提示脆性部位在白血病和淋巴瘤的发病过程中可能起着重要的作用。     

喉癌及鼻腔鼻窦癌患者淋巴细胞染色体不稳定性的研究

本实验用TC199培养基,对37例喉癌、鼻腔鼻窦癌和20例正常人外周血淋巴细胞的染色体不稳定性进行了研究。结果表明,两种癌症患者淋巴细胞自发的染色体畸变率、微核率及平阳霉素(博莱霉素)诱发的染色体畸变率,微核率分别是11.73%、23.68‰、23.97%及47.16‰;对照组正常人淋巴细胞自发的染色体畸变率,微核率及平阳霉素诱发的染色体畸变率,微核率分别是1.95%、6.15‰、5.45%及15.85‰。两组上述各率彼此相比差异均有显著性(P<0.01)。提示喉癌及鼻腔鼻窦癌患者的淋巴细胞存在着染色体不稳定性。     

结直肠癌患者外周血染色体脆性位点研究

目的研究结直肠癌的发生机理,期望发现与结直肠癌发生有关的染色体脆性位点,以指导结直肠癌高危人群的筛查和防治.方法对50例结直肠癌患者和50例健康正常人外周血淋巴细胞染色体脆性位点研究.结果50例结直肠癌患者中有32例的染色体结构有异常表达,结构畸变较常累及1号染色体,以1q11,1q21区的裂隙、断裂、重复最为常见,1q21与原癌基因SKI毗邻.结论1q21可能与结直肠癌的发生有关,并对结直肠癌高危人群的筛查和防治有一定的指导意义.     

Chromosome abnormalities and rare fragile sites detected in azoospermia patients

Summary We have examined constitutional chromosome abnormalities and fragile sites in 40 patients with azoospermia. Chromosome abnormalities were found in four cases. Three cases showed a deletion of the long arm of the Y chromosome 46,X,del(Yq) and the other case had a ring of G group chromosome 46,XY,r(G). In a rare fragile sites test, four fragile site carriers were detected and three rare autosomal fragile sites were identified; fra(8)(q24.1), fra(11)(p15.1), and fra(17)(p12). The expression of these fragile sites were induced specifically by AT-specific DNA ligands, such as distamycin A and Hoechst 33258. In addition, one patient was found to be the case of double ascertainment of fragile sites, fra(8)(q24.1) and fra(17)(p12). The overall frequency of distamycin A-inducible fragile sites in azoospermia patients appeared to be higher than those reported for Japanese healthy subjects and cancer patients. However, no significant relation among fragile sites, clinical and histological findings has been detected so far.     

Investigation of genetic susceptibility to non-small cell lung cancer by fragile site expression

Fragile sites are non-staining gaps and breaks in specific points of chromosomes that are inducible by various culture conditions. Previous studies have shown that various clastogenic agents increase expression of fragile sites. In this study, the expression of common fragile sites induced by aphidicolin was evaluated on prometaphase chromosomes obtained from peripheral blood lymphocytes. Chromosomal aberrations and fragile site expression of 60 individuals, including 20 patients with non-small cell lung cancer (NSCLC), 20 of their clinically healthy family members, and 20 age-matched normal healthy controls without history of any cancer type were studied. Both the proportion of damaged cells (P < 0.001) and the mean number of gaps and breaks per cell (P < 0.001) were significantly higher in both the patients and relatives' groups when compared with the control group. However, they were insignificant when the patients were compared to their relatives (P > 0.05). We determined four aphidicolin type common fragile sites in our study. These sites in patients with NSCLC and relatives were the following: 1p21, 2q33, 3p14, and 16q23. In these fragile sites, 2q33, 3p14, and 16q23 sites were statistically significant when compared with control group (P < 0.001, P < 0.0005, and P < 0.05, respectively). Consequently, we believe that fragile site studies may be helpful to detection of cancer risk.     

Distamycin A-inducible fragile sites and cancer proneness

To determine the baseline frequency of autosomal rare fragile sites in cancer patients, we conducted a population cytogenetic study of 370 patients with leukemias, solid tumors, and other neoplastic disorders. Twenty carriers of rare fragile sites were detected in this patient group. The rare autosomal fragile sites were at fra(8)(q24), fra(11)(p15), fra(16)(p12.1), fra(16)(q22), and fra(17)(p12). All of these fragile sites were found to be distamycin A inducible. Compared with a population incidence in healthy subjects (44 of 845, 5.21%), the overall incidence of distamycin A-inducible fragile sites was not higher in the patient group (20 of 370, 5.41%). Analysis of these individual fragile sites and particular diseases, however, suggests that the distamycin A-inducible fragile sites may play a role in the etiology of leukemia, myeloproliferative disorders, and benign tumors.     

Common fragile sites: their prevalence in subjects with constitutional and acquired chromosomal instability

Chromosomal fragile sites that are inducible by methotrexate and aphidicolin are frequent in the human population. To assess the frequency and distribution of these common fragile sites, we performed a cytogenetic survey on lymphocytes from subjects known to be particularly prone to breakage because of constitutional chromosomal instability, the possession of a rare fragile site, or Fanconi anemia. Furthermore, a group of cancer patients was included in this study in view of possible acquired chromosomal instability. Lymphocyte chromosomes from several healthy donors were analyzed under identical conditions. We found that methotrexate- and aphidicolin-induced fragile sites are widespread in the general population, showing a similar breakpoint distribution. Ten fragile sites (3p14, 16q23, 2q32, 6q25, 4p16, 4q31, 14q24, 1p31, 20p12, 7q21) were observed in at least 40% of the individuals among the different groups. Our data point out a significantly increased breakage induced by aphidicolin in lymphocytes from cancer patients and, to a lesser extent, from rare fragile sites carriers. These results suggest that common fragile sites are enhanced in some constitutional and acquired conditions.     

The expression frequency of common fragile sites and genetic predisposition to colon cancer

The expression frequency of common fragile sites induced by aphidicolin (Apc), bromodeoxyuridine (BrdU), and caffeine was evaluated on prometaphase chromosomes obtained from the peripheral blood lymphocytes of 32 patients with colon cancer, 30 of their clinically healthy family members and 30 age-matched normal controls. The proportion of damaged cells (P < 0.001), the mean number of chromosomal aberrations and the expression frequencies of fragile sites were significantly higher in the patient and relative groups compared to the control group. Our findings show an increased genetic instability in patients with colon cancer and their first-degree relatives. In addition, common fragile sites can be used as a suitable marker for determining genetic predisposition to cancer.     

New lethal acrofacial dysostosis syndrome

Peripheral blood lymphocytes from boxer dogs with a history of cutaneous mast cell tumors were cultured for fragile site expression. As in a control group of dogs, cells from these dogs expressed folate-sensitive autosomal and X chromosome fragile sites. Cells from boxer dogs with mast cell tumors expressed the same three common fragile sites on the X chromosome as cells from control dogs. Three folate-sensitive autosomal fragile sites not observed in cells from the control dogs were identified in cells from boxers with mast cell tumors. These included fragile sites near the telomeres of the arms of chromosomes 3 and 4 and a fragile site on the distal half of chromosome 15. Cells from boxers with mast cell tumors showed a greater frequency of fragile site expression than did cells from control dogs, but this observation was attributed to an unintended selection bias for younger boxer dogs without mast cell tumors and older boxer dogs with mast cell tumors and an increased frequency of fragile site expression with increasing age in dogs of the boxer breed.     

Chromosomal fragile site expression in dogs: II. Expression in boxer dogs with mast cell tumors

Peripheral blood lymphocytes from boxer dogs with a history of cutaneous mast cell tumors were cultured for fragile site expression. As in a control group of dogs, cells from these dogs expressed folate-sensitive autosomal and X chromosome fragile sites. Cells from boxer dogs with mast cell tumors expressed the same three common fragile sites on the X chromosome as cells from control dogs. Three folate-sensitive autosomal fragile sites not observed in cells from the control dogs were identified in cells from boxers with mast cell tumors. These included fragile sites near the telomeres of the arms of chromosomes 3 and 4 and a fragile site on the distal half of chromosome 15. Cells from boxers with mast cell tumors showed a greater frequency of fragile site expression than did cells from control dogs, but this observation was attributed to an unintended selection bias for younger boxer dogs without mast cell tumors and older boxer dogs with mast cell tumors and an increased frequency of fragile site expression with increasing age in dogs of the boxer breed.     

Fragile sites and genitourinary tumors

We tested for fragile sites in lymphocytes from nine patients with genitourinary tumors to determine if a correlation existed between their cancer chromosome breakpoints and fragile sites. Induction was done for rare fragile sites in all known classes by exposure of cells to fluorodeoxyuridine and bromodeoxyuridine (BrdU). No rare fragile sites were found. Induction was also done for common fragile sites in all known classes using aphidicolin (Apc), 5-azacytidine, and BrdU. Although 56 common fragile sites were detected, only a single site corresponded in location to a genitourinary tumor chromosome breakpoint. That was the common fragile site in band 3p14. No overall correlation was found between fragile sites and chromosome rearrangements in carcinoma of the kidney, ureter, bladder, and testis. The sole known candidate for a possible biologic role is the 3p14 common fragile site in renal cell carcinoma.     

Fragile sites, Alzheimer's disease, and aging.

The fragile site expression under conditions of folate deprivation was compared in the chromosomes from 5 Alzheimer's disease (AD) female patients, 5 healthy elderly females and 5 healthy young females. Although different fragile sites were observed in the three groups, nevertheless, more similarities were found between the AD patients and elderly normal donors. The only fragile site common to all groups was 3p14. This site was the most frequent in the young donors group. In both AD and elderly control groups we observed a higher frequency of fragility in 6p21, but not in the young controls. Other interesting fragility points observed in these two groups were: 6q21 and 14q24 (in the AD patients) and 9q13, 14q24 and 17q21 (in the healthy aged). 6p21 and 17q21 have been proposed as 'new' fragile sites. We confirm the existence of these fragile sites and comment that in these bands the genes MTBT2 and MTBT1, which are microtubule (beta) associated protein tau-like and tau 1, respectively, are mapped. The tau protein is a component of paired helical filaments which accumulate in degenerating neurons in the brain of patients with AD and with less intensity of normal elderly individuals.     

Chromosome instability in lymphocytes from two patients affected by three sequential primary cancers: the role of fragile sites

The chromosomal aberration rate and the expression of fragile sites induced by aphidicolin were evaluated in metaphase chromosomes obtained from peripheral blood lymphocytes of two untreated patients with multiple primary cancers. Spontaneous aberrations of chromosome number and structure and chromosome fragility were compared with controls with the use of the same methods. Chromosomal aberration rates and expression frequencies of fragile sites were significantly higher in the patients than in normal control subjects. In the patients, all but one structural chromosome aberration involved at least one fragile site. Our results suggest that fragile sites may be unstable regions of the human genome, which might play an important role in the genetic instability associated with cancer predisposition.