Giemsa banding patterns of human chromosomes

Genomic imbalances in 5918 malignant epithelial tumors: an explorative meta-analysis of chromosomal CGH data

BACKGROUND

Chromosomal abnormalities have been associated with most human malignancies, with gains and losses on some genomic regions associated with particular entities.

METHODS

Of the 15429 cases collected for the Progenetix molecular-cytogenetic database, 5918 malignant epithelial neoplasias analyzed by chromosomal Comparative Genomic Hybridization (CGH) were selected for further evaluation. For the 22 clinico-pathological entities with more than 50 cases, summary profiles for genomic imbalances were generated from case specific data and analyzed.

RESULTS

With large variation in overall genomic instability, recurring genomic gains and losses were prominent. Most entities showed frequent gains involving 8q2, while gains on 20q, 1q, 3q, 5p, 7q and 17q were frequent in different entities. Loss "hot spots" included 3p, 4q, 13q, 17p and 18q among others. Related average imbalance patterns were found for clinically distinct entities, e.g. hepatocellular carcinomas (ca.) and ductal breast ca., as well as for histologically related entities (squamous cell ca. of different sites).

CONCLUSION

Although considerable case-by-case variation of genomic profiles can be found by CGH in epithelial malignancies, a limited set of variously combined chromosomal imbalances may be typical for carcinogenesis. Focus on the respective regions should aid in target gene detection and pathway deduction.

Induced sister chromatid exchange frequency is not increased in homogeneously staining regions that contain amplified genes

Gene amplification is a process by which cells become resistant to selective agents by increasing gene copy number and overproducing specific enzymes. The molecular mechanism by which gene amplification occurs is unknown, but unequal sister chromatid exchange (SCE) has been suggested as one possibility. Unequal SCE results in one chromatid containing an extra copy of a selected gene that is deleted in the sister chromatid. Two predictions of the unequal SCE model are that agents that increase SCE frequency would increase gene amplification, and that SCE would be more prevalent in arrays of amplified units. We examined SCE frequency in the Chinese hamster ovary cell line MK42, which contains amplified dihydrofolate reductase genes that are stably integrated as a homogeneously staining region in chromosome #2. Under treatment conditions known to increase amplification of the dihydrofolate reductase gene, a number of agents did increase SCE frequency in MK42 cells. The frequency of SCE in the amplified region of chromosome #2, however, was no different from that expected if SCE were induced randomly as a function of chromosome length. These data, therefore, do not support the prediction of unequal SCE as a model for gene amplification. Our experiments, however, do not test the idea that unequal SCE at normal frequencies may lead to gene amplification, nor do they rule out the possibility of transient periods early in amplification, during which the homogeneously staining region may be a "hot spot" for SCE.

Rearrangement and possible amplification of the ribosomal RNA gene sites in the human chronic myelogenous leukemia cell line K562

We have studied the location of the nucleolar organizer regions (NORs) in the human chronic myeloid leukemia cell line K562. In man, the NORs are normally found on the short arms of the acrocentric chromosomes. We show that in the K562 line, the NORs are substantially rearranged with both insertional and terminal NORs. In addition, the putative t(15;17) marker chromosome had three insertional NORs that may have arisen through gene amplification.

Arsenic and SCE in human lymphocytes

The effects of tri- and penta-valent arsenic compounds on sister-chromatid exchange (SCE) in both G0 and 5-bromodeoxyuridine (BrdU) substituted chromosomes was investigated. ¿Of 4 donors whose lymphocytes were exposed to sodium arsenate for 2 cell cycles 1 showed an increase, 2 a decrease, and 1 neither an increase or decrease over baseline levels. Exposure to sodium arsenite produced a similar result with 2 of 4 donors showing a significant increase in SCE. G0 lymphocytes exposed to either sodium arsenate or sodium arsenite did not show increased SCE. These results indicate that although arsenic can induce SCEs in human lymphocytes, there is considerable variation in SCE response among individuals. Furthermore, the data suggest that the increased SCEs seen in patients exposed to arsenic may be due to the patient's condition and not arsenic exposure.

Nonrandom cytogenetic changes in New Zealand patients with acute myeloid leukemia

Bone marrow clones with abnormal chromosomes were observed in 56% of 66 patients with forms of acute myeloid leukemia [French-American-British (FAB) M1-M6]. Acute myeloblastic leukemia (AML, M1 and M2) was the most common form, and 65% of these patients showed chromosomal abnormalities compared with 41% of patients with acute myelomonocytic leukemia (AMMoL, M4). The recognized nonrandom chromosomal abnormalities found were trisomy 8, monosomy 5 or 7, trisomy 1q, t(6;9), t(8;21), t(15;17), and abnormalities in 17q. There was also a strong involvement of chromosome No. 11: Abnormalities were found in eight patients when their leukemia was diagnosed and in a further three patients during the course of karyotypic evolution. Six of these patients had AMMoL or AMoL. Complex or multiple clones were found in 37% of AML patients at diagnosis. Our AML patients had a reduced frequency of abnormalities in chromosome No. 5 or 7 and an increased frequency of abnormalities in chromosome No. 8 compared with studies reported in other countries (p = 0.01). This difference suggests that in New Zealand AML might be caused by factors different from those operating in more industrialized centers.

The effect of chlorpromazine on SCE frequency in human chromosomes

Schizophrenic patients who were receiving, or who had received chlorpromazine showed SCE levels similar to those in a normal control population. Of 8 normal individuals whose lymphocytes were exposed in vitro to chlorpromazine (0.05-2.00 micrograms/ml) for two cell cycles, 4 showed a significant increase in SCE, 3 showed no increase and 1 a decrease compared with untreated lymphocytes. Lymphocytes from a further 8 donors treated with 2.0 micrograms/ml chlorpromazine prior to mitogen stimulation (G0 lymphocytes) showed a similar SCE response. Only 3 of the 8 donors showed a significant increase in SCEs over the baseline level. When proliferating lymphocytes were exposed to chlorpromazine 38 h after culture initiation and prior to the addition of BrdUrd to the culture medium, metaphase chromosomes from only 3 of the 8 individuals studied showed increased levels of exchange. These results indicate that chlorpromazine can induce SCEs in vitro but that there is considerable variation in SCE response among individuals. Furthermore, our data emphasises the importance of using more than 1 or 2 donors when analysing SCE response in human chromosomes.

A complex Ph1 translocation in a patient with primary thrombocythaemia

Routine blood examination of a 27-year-old female revealed a platelet count of 2000 X 10(9)/l. Bone marrow cells showed the Philadelphia chromosome which was one product of a complex rearrangement of chromosomes 9, 22 and X. Her platelet count was lowered by plateletphoresis and chemotherapy. She remains in good health 19 months later, but her thrombocythaemia is considered to be an early manifestation of chronic myeloid leukaemia.

The effects of beta-radiation on sister-chromatid exchanges in cultured human lymphocytes

The incidence of Sister-Chromatid Exchanges (SCEs) due to beta-radiation was investigated in cultured human lymphocytes using the BrdU/Giemsa technique. Cultures treated continuously with 0.001 and 0.01 microCi of [3H]uridine showed no increase in either chromosome abnormalities or SCEs. Continuous treatment with 0.1 microCi resulted in a significant increase in chromosome aberrations but no increase in SCEs, while treatment with 0.2 microCi gave both an increase in chromosome aberrations and SCEs. Cultures given a 4-h pulse with 1.0 microCi showed a significant increase in both SCEs and chromosome aberrations. The results indicate that low levels of beta-radiation do not cause an increase in SCEs in human lymphocytes, and, that a number, if not all the exchanges observed at low levels of beta-radiation with autoradiography, may be spontaneous events.

The frequency and distribution of sister chromatid exchanges in human chromosomes

The distribution of sister chromatid exchanges (SCEs) both between and within chromosomes was studied in cultured human lymphocytes using the BRDU-Giemsa technique. In general, the distribution of SCEs between chromosomes was a function of chromosome length. However, chromosomes of the B group had more exchanges than expected on this basis, while the E, F, and G groups had less than expected. Analysis of cells showing both G-banding and sister chromatid differential staining indicates that the distribution of exchanges within the chromosomes is non-random and possible reasons for the observed distribution pattern are discussed.

Mosaic trisomy 9: two additional cases

Two unrelated patients were found to be mosaic for an extra chromosome 9 (46,XX/47,XX,+9). The first patient showed a prominent nose, deep set eyes, carp shaped mouth and complex congenital cardiac anomalies. She died of congestive cardiac failure at the age of 10 days. The second patient, was a 7 1/2 year old female who had persistent alacrimia and mental retardation.

Major karyotypic abnormality in a child born to a woman with untreated malignant melanoma

The karyotype of a 7-month-old child had 46 chromosomes, including five abnormal chromosomes in cultured lymphocytes. G-banding indicated the presence of reciprocal translocation products between chromosomes 1 and 7 and between chromosomes 4 and 15. A probable third translocation involved the same chromosome 4p arm and 12q. All metaphases showed these changes. C-band markers and the presence of reciprocal exchange products indicated that the chromosome changes occurred in the zygote or a post-zygotic cell of the child. The mother developed malignant melanoma while carrying the child but did not receive therapy before its birth. The suggestion is made that an undetected common agent was involved in the aetiology of the mother's tumour and the clastogenic change to the child's chromosomes.

Evidence that chromosome band 22q12 is concerned with cell proliferation in chronic myeloid leukaemia

A man and two of his three children carried an abnormally short chromosome 22 resembling the Philadelphia chromosome (Ph1). Giemsa banding showed that the abnormal chromosome resulted from a translocation t(11;22) (q25;q13). The breakpoint on chromosome 22 was at the q12/q13 band interface compared with the breakpoint of Ph1 at the q11/q12 band interface. The absence of leukaemia or haematological disorder in members of this family suggests that the critical genetic site on chromosome 22 concerned with abnormal myeloid cell proliferation in human leukaemia is contained in the 22q12 band.

Chromosomes in old age: a six year longitudinal study

This first longitudinal study on aged subjects confirms previous cross-sectional observations of increasing aneuploidy with advancing age in women but not in men. In this study of 17 aged twins (mean age 89.7 years), 11 women and 6 men, spanning an interval of approximately 6 years between examinations, only women showed a significant increase in hypodiploidy (also hyperdiploidy and monosomy C). This increase in hypodiploidy was not due to a high frequency of chromosome loss in a few subjects but rather was exhibited by most of the subjects. While men showed a loss in G-group chromosomes during this 6-year interval, that loss was not statistically significant. These findings confirm for the first time by means of longitudinal follow-up that women and not men, even in the ninth decade of life, show a significant increase in hypodiploidy.

Description of the banding patterns of human chromosomes by acriding orange reverse banding (RFA) and comparison with the Paris banding diagram

A reference diagram is presented which is comparable to the Paris banding diagram but which was based primarily on chromosomes studied by acridine orange reverse banding. Comparison with the Paris Conference (1971) banding diagram was made. Bands were combined in 13 instances and subdivided in 10 cases. The number of bands was found to depend primarily upon the length and quality of the chromosomes. No major differences between the present diagram and the Paris banding diagram were observed. Moreover, the results with acriding orange reverse banding were comparable to those previously reported with Giemsa R banding. In addition, sequential Q banding and R banding were carried out in the same cells. No significant differences in resolution of bands were observed when these two techniques were compared.

Variation in the centromeric banding of chromosome 19

The centromeric banding pattern of chromosomes 19 exhibited considerable variation. The variants were present in the majority of cells from an individual and consisted of additional dark-staining areas. There was no abnormal phenotypic effect associated with any variant and it is concluded that these additional dark-staining areas do not contain any functional genes.

A mechanism of x chromosome aneuploidy in lymphocytes of aging women

One and sometimes both X chromosomes in cultured lyphocytes of women donors showed division of the centromere when the centromeres of other chromosomes were entire. This premature centromere division (PCD) was associated with evidence of non-disjunction of the X chromosome. On average, 2% of metaphases from 32 women donors showed PCD, but the incidence was 4 times greater in women over 59 years of age than in women under 40 years. Increased X chromosome aneuploidy was associated with the higher frequency of PCD in cultured lymphocytes from older women. PCD of the X chromosome is considered to be the mechanism of non-disjunction causing the previously described aneuploidy in cultured lymphocytes of aging women.

Premature centromere division: a mechanism of non-disjunction causing X chromosome aneuploidy in somatic cells of man

Apparent acentric fragments which replaced a C-group chromosome in cultured blood lymphocytes from a woman patient were shown by autoradiography, G-banding and C-banding to be complete X chromosomes in which the centromere had divided prematurely in relation to the centromeres of other chromosomes in the same metaphase. Metaphases with multiple 'fragments' suggested that non-disjunction of the 'fragments' had occurred. This anomaly of the X chromosome was associated with increased aneuploidy of a C-group chromosome, presumed to be X. Premature centromere division of the X chromosome (PCD, X) appeared to be a mechanism of non-disjunction which caused significant monosomy and trisomy of the X chromosome in blood cells and skin fibroblasts. The frequency of cells with multiple fragments and the extent of the aneuploidy in 48 hr. blood cultures indicated that this mechanism of non-disjunction operated during mitosis both in vivo and in vitro. Premature centromere division occurred at a lower frequency in normal women donors, and was age-related, being four times more frequent in women 60 years and older than in women under 40. Associated with the higher frequency of PCD, the older women also showed evidence of increased X chromosome aneuploidy. Premature centromere division of the X chromosome is considered to be the mechanism of non-disjunction, causing the well-documented increased number of 45, -C metaphases in ageing women. Premature centromere division was rare in men, but an age effect was again suggested.

Isochromosome for the short arm of X: a human mosaic 45,x/46,XXpi

An 18 year female patient with short stature, amenorrhoea and poorly developed secondary sexual characteristics, has subnormal oestrogen excretion and increased levels of plasma gonadotrophin. Laparoscopy revealed streak ovaries. A reduced number of buccal mucosal cells showed positive sex chromatin. Chromosome studies of blood lymphocytes indicated mosaicism: the major cell line was characterized by an isochromosome for the X short arm, 46,XXpi; the minor cell line had a single X chromosome, 45,X.

Giemsa banding of the chromosomes of the domestic sheep (Ovis aries)

A Giemsa banding procedure was used to construct a basic G-band idiogram for the domestic sheep. The idiogram is labelled in a systematic manner according to the routine recommended for human chromosomes. This pattern based on NaOH treatment, provides a standard of comparison for further studies on intra- and interspecific chromosome homologies in addition to identification of chromosomal abnormalities.Late replicating regions of chromosomal DNA were detected with tritiated thymidine. Partial homologies between G-bands and these late replicating areas were found. Previously reported areas of prevalent secondary constrictions were seen to coincide with late replicating, G-positive regions on the metacentric and X chromosomes.