C. Fuster

Expression of fragile sites in human sperm and lymphocyte chromosomes

SummarySperm and lymphocyte chromosome studies in a normal, fertile male have shown a high degree of coincidence between chromosome lesions and fragile sites in both types of cells. In this donor we also found that some fragile sites expressed in sperm chromosomes coincided with those expressed in lymphocyte chromosomes. These results indicate that the chromosome lesions expressed in sperm do not occur at random and that they are not technical artifacts. The fragility expression in sperm chromosomes could reflect in vivo conditions. The presence in some sperm metaphases of acentric fragments suggests that chromosome fragility can result in the loss of chromosome fragments or give rise to de novo structural rearrangements. However, the incidence of sperm with chromosomal abnormalities observed in this man was within the normal range.

Lymphocyte and sperm chromosome studies in cancer-treated men

SummaryTo evaluate the reliability of the quantitative extrapolation of the long-term effect of cancer therapies from somatic cells to germ cells, we compared the frenuency of chromosome abnormalities in 303 lymphocytes from four individuals treated with radio- and/or chemotherapy 5–18 years earlier with the frequency in 422 spermatozoa from the same individuals. The mean frequency of structurally abnormal complements was much higher in germ cells than in somatic cells (P = 2.08 × 10−6). The fact that spermatogenic cells share cytoplasm is suggested as a possible factor in the increased viability of germ cells with chromosome aberrations. In addition, in spermatozoa the incidence of structural chromosome abnormalities was much higher in treated individuals than in controls (P < 0.00060), while in lymphocytes no statistically significant differences could be observed. This observation and the apparent lack of relationship between individual frequencies in the two kinds of cells suggest that the long-term effect of antitumor treatments on germ cells cannot be extrapolated from the analysis of somatic cells.

Spontaneous chromosome fragility in chorionic villus cells

Human fragile sites are only very rarely expressed spontaneously. In this paper we report the presence of non-random spontaneous chromosome lesions (CL) in chorionic villus samples and their coincidence with fragile site (FS) bands. The average number of CL was about 9% both in RPMI-1640 and in Chang media. To determine any possible influence of external factors other than culture media, the results were grouped according to age of gestation. No differences were observed among the different groups. A total of 101 chromosome lesions could be precisely identified by sequential Leishman Staining/Wright G-banding; 76.2% of them coincided with FS-bands. The most affected region was at 1q12-1q21.1 (15.8% of total CL); other FS with a clustering of breakpoints in our study were 1p36, 1q44, 2q37, 3p24, 3q27, 10q22 and 16q23. These results suggest that spontaneous expression of some FS could be a characteristic of embryonic tissues.

Cytogenetic Analysis using Simultaneous and Sequential Fluorescence In Situ Hybridization

A sequential fluorescence in situ hybridization (FISH) technique is described. This method allows the detection of up to eighteen chromosome pairs in consecutive hybridizations (8 steps) on the same metaphase using centromeric, whole chromosome painting, and single copy DNA probes with different fluorochromes. The technique may be used with diagnostic purposes in cases with poor cytogenetic material.

Telomere association of chromosomes induced by aphidicolin in a normal individual.

SummaryTelomere association of chromosomes of a phenotypically and mentally normal individual was detected in 11.7% of metaphases cultured in RPMI-1640 with aphidicolin. No preferential involvement of any chromosome pair was detected. In two other individuals the frequency of telomere associations was much lower (1.9% and 0.7% respectively) under the same culture conditions. In the first individual the high number of telomere associations in cultures with aphidicolin along with the presence of telomere association (2.4%) in cultures with F.10 medium alone could reflect a constitutional telomere anomaly that is more often expressed in the presence of aphidicolin.

Induction of premature centromere division affecting all chromosomes under culture conditions of fragile site expression

In a study of chromosome fragility carried out under folate and thymidine deficiency conditions, we observed a seven- to ninefold increase of the incidence of premature centromere divisions (PCDs) affecting all chromosomes. This early separation of centromeres is clearly a culture effect and distinct from PCD and centromere splitting (CS), which imply a defect in the centromere of one or more chromosomes.

Fragile sites and breakpoints in constitutional rearrangements and in human sperm chromosomes

SummaryRecently, it has been suggested that an association exists between breakpoints involved in constitutional rearrangements and fragile sites; however, statistical analyses of this relationship are controversial. We have analyzed 1200 breakpoint from different constitutional rearrangements, 1522 breakpoints with respect to their recurrence and 217 breakpoints from sperm chromosomes as reported by several authors. The coincidence between breakpoints and fragile sites was 35.3%, 43.6% and 41.9% respectively. The statistical significance of these coincidences depends on whether factors such as the relative length of the bands or the recurrence of the rearrangements are taken into account.

Chromatid segregation analysis in native human lymphocyte anaphases using sequential fluorescence in situ hybridization

A sequential multiprobe fluorescence in situ hybridization technique was developed to study the 13, 18, 21, X and Y chromatid segregation in human lymphocytes anaphases cultures without antimitotic treatment. This method was used to know if exist any different chromosomes segregation in lymphocytes from Down syndrome patients and compared it with controls. The results show that the prevalent sequence of centromere separation was X, 13, 21, Y and 18 in Down syndrome patients and Y, 13, X, 21 and 18 in controls. Chromatid segregation in early anaphase was asynchronic for all chromosome pairs studied. Late anaphase showed a frequency of non-disjunction of 4.5% in the controls, affecting only chromosomes 18 and Y; in the Down syndrome patients, the frequency was higher (20.3%) and affected all chromosomes studied. This technique could be applicated to know the incidence of non disjunction in couples with repetitive abortions or in cases with different aneuploidies in the offspring.