Rosa Miró

A Polymorphic Genomic Duplication on Human Chromosome 15 Is a Susceptibility Factor for Panic and Phobic Disorders

Anxiety disorders are complex and common psychiatric illnesses associated with considerable morbidity and social cost. We have studied the molecular basis of the cooccurrence of panic and phobic disorders with joint laxity. We have identified an interstitial duplication of human chromosome 15q24-26 (named DUP25), which is significantly associated with panic/agoraphobia/social phobia/joint laxity in families, and with panic disorder in nonfamilial cases. Mosaicism, different forms of DUP25 within the same family, and absence of segregation of 15q24-26 markers with DUP25 and the psychiatric phenotypes suggest a non-Mendelian mechanism of disease-causing mutation. We propose that DUP25, which is present in 7% control subjects, is a susceptibility factor for a clinical phenotype that includes panic and phobic disorders and joint laxity.

Repair of human sperm chromosome aberrations in the hamster egg.

SummaryIn order to study the repair capacity of fertilized hamster eggs for the lesions present or induced in human sperm, we have examined the potentiating effect of caffeine, a DNA repair inhibitor, on the frequency and types of sperm chromosome aberrations. Sperm samples were donated by an individual treated with chemotherapy for a testicular cancer 3 years previously. Exposure of spermatozoa and inseminated oocytes to caffeine led to an increase of sperm chromosome aberrations, indicating that the damage to human sperm can be repaired in untreated hamster egg cytoplasm. The potentiating effect of caffeine was mainly reflected in an increase of unrejoined aberrations, indicating that the formation of chromosomal rearrangements is also inhibited. Since both chromatid-type and chromosome-type aberrations increase after treatment with caffeine, damage to human sperm can probably be repaired inside the hamster egg cytoplasm by pre and post-replication repair mechanisms.

Genetic Imbalances in Progressed B-Cell Chronic Lymphocytic Leukemia and Transformed Large-Cell Lymphoma (Richter's Syndrome)

Chromosomal imbalances were examined by comparative genomic hybridization in 30 cases of B-cell chronic lymphocytic leukemia (CLL) at diagnosis, in sequential samples from 17 of these patients, and in 6 large B-cell lymphomas transformed from CLL [Richters syndrome (RS)] with no available previous sample. The most common imbalances in CLL at diagnosis were gains in chromosome 12 (30%), and losses in chromosomes 13 (17%), 17p (17%), 8p (7%), 11q (7%), and 14q (7%). The analysis of sequential samples showed an increased number of chromosomal imbalances in 6 of 10 (60%) patients with clinical progression and in 2 patients with stable stage C disease. No karyotypic evolution was observed in four cases with stable stage A disease and in one RS clonally unrelated to the previous CLL. Gains of 2pter, and 7pter, and losses of 8p, 11q, and 17p were recurrent alterations associated with karyotype progression. RS showed a higher number of gains, losses, total alterations, and losses of 8p and chromosome 9 than CLL at diagnosis. 17p losses were associated with p53 gene mutations and with a significantly higher number of chromosomal imbalances than tumors with normal chromosome 17 profile. However, no relationship was observed between 9p deletions and p16(INK4a) gene alterations. Losses of 17p and an increased number of losses at diagnosis were significantly associated with a shorter survival. These findings indicate that CLL has frequent chromosomal imbalances, which may increase during the progression of the disease and transformation into large cell lymphoma. Genetic alterations detected by comparative genomic hybridization may also be of prognostic significance.

Cytogenetic analysis of lymphocytes from hospital workers occupationally exposed to low levels of ionizing radiation

Cytogenetic studies were performed in lymphocytes from hospital workers exposed to low doses of radiation (1.6-42.71 mSv). When compared with controls, exposed workers showed a significant increase in structural chromosome-type aberrations, acentric fragments being the most frequent alteration. Our results suggest that acentric fragments are good indicators of exposure to very low doses of radiation, although no dose-effect correlation was observed. The incidence of numerical abnormalities (hyperdiploidy) was significantly increased.

Cytogenetic Characterization of Two Colon Cell Lines by Using Conventional G-Banding, Comparative Genomic Hybridization, and Whole Chromosome Painting

The heterogeneous nature of genetic alterations in cancer cells handicaps the full characterization of its occurrence and the analysis of their molecular bases and relation to biological processes. Although many cancer cells are highly aneuploid, in other cases, as in a subset of colorectal carcinomas displaying microsatellite instability, chromosomal aberrations are scarce. The aim of this study was to fully characterize both qualitatively and quantitatively, the karyotypes of two established colon carcinoma cell lines (LoVo and HCT 116) previously reported as being near diploid. An array of complementary cytogenetic techniques were used: G-banding, comparative genome hybridization (CGH), and whole-chromosome painting (WCP). Combinations of these techniques provided an accurate karyotype for the two cell lines: LoVo cells showed 49,XY,t(2;12)(q13;p11.2),+5,+7,+12,i(15)(q10) and HCT 116 cells showed 45,X,-Y,dup(10)(q24q26),der(16)t(8;16)(q13;p13), der(18)t(17;18)(q21;p11.3). Heterogeneity was also observed in both cell lines as shown by G-banding. Chromosomal unbalances determined by CGH (many of them related to structural reorganizations) were characterized by WCP, allowing the reliable identification of those chromosome markers that could not be completely identified by G-banding. We show that combined analysis with classical and molecular cytogenetic techniques provides an accurate map of chromosomal aberrations in these two cell lines not identified in previous investigations.

Human sperm chromosomes: Long-term effect of cancer treatment☆

The long-term cytogenetic effect of radio- or chemotherapy or both on male germ cells was evaluated by study of the chromosomal abnormalities in spermatozoa of four men treated for cancer 5-18 years earlier. The cytogenetic analysis of 422 sperm metaphases showed no differences in the aneuploidy rate. The incidence of structural chromosome aberrations was 14.0%, however, which is much higher than in controls. Thus, the high incidence of structurally aberrant spermatozoa observed in our long-term study indicates that antitumoral treatments affect stem-cell spermatogonia and that aberrant cells can survive germinal selection and produce abnormal spermatozoa.

Shortened telomeres join to DNA breaks interfering with their correct repair

Telomeres cap chromosome ends, avoiding end-to-end fusions and subsequent chromosome instability. Telomeric functions and DNA repair pathways are closely related. Telomere dysfunction has been shown to result in hypersensitivity to ionizing radiation. In this study, we have used the telomerase knockout model to investigate how telomere shortening influences the correct repair of broken chromosomes. We show that the correct repair of double-strand breaks is impaired in telomerase knockout mice. The chromosomes with shortened telomeres fuse to radiation-induced breaks, interfering with the correct rejoining of the broken ends. This type of fusion is responsible for the increased chromosome instability observed in this mouse model, after exposure to ionizing radiation. Our finding may be important for understanding the increased radiation sensitivity associated with age in humans, as well as for comprehending the interindividual differences to the cytotoxic effects of radiation therapy in cancer patients.

DNA copy number changes and evaluation of MYC, IGF1R, and FES amplification in xenografts of pancreatic adenocarcinoma.

We analyzed eight samples of xenografted human pancreatic tumors and two metastases developed in mice by comparative genomic hybridization (CGH). The most recurrent changes were: gains on chromosomes 8 (8q24-qter; 7/8 cases), 15 (15q25-q26; 6/8 cases), 16 (16p in 6/8 cases; 16q in 5/8 cases), 20 (20q; 6/8 cases), and 19 (19q; 5/8 cases); and losses on chromosomes 18 (18q21; 6/8 cases), 6 (6q16-q21 and 6q24-qter; 5/8 cases each), and 9 (9p23-pter; 5/8 cases). The two metastases maintained the aberrations of the original pancreatic tumor plus gain of 11q12-q13 and 22q. Loss of heterozygosity analysis was carried out for 10p14-pter, a region that was lost in 3/8 samples. All of them presented allelic imbalance for all the informative loci. Fluorescence in situ hybridization and Southern analysis were performed to test some candidate oncogenes in 8q24 (MYC) and 15q25-qter (IGF1R and FES). Two of seven tumors showed high-level amplification of MYC relative to the centromere (> 3-fold), another two tumors had low-level amplification (1.5- to 3.0-fold), and one displayed 5.5 MYC signals/cell. In relation to the FES gene, low-level amplification was found in three tumors. Southern analysis showed five cases with a low-level amplification of IGF1R. Our data suggest that either few extra gene copies may be enough for cancer progression or other genes located in these regions are responsible for the amplifications found by CGH.

Detection of chromosomal imbalances in papillary bladder tumors by comparative genomic hybridization

OBJECTIVES To identify those genetic alterations that are associated with bladder cancer invasion and progression. METHODS A total of 30 specimens of transitional cell carcinoma of the bladder were analyzed by comparative genomic hybridization. The results were compared and summarized with previously reported studies. RESULTS The most frequent chromosome changes detected in our series of tumors were losses in 9q, 9p, 8p, and 11p and gains in 8q, 1q, 20q, and 11q. Three regions of deletion on chromosome 9 were delineated, at 9p21-p22, 9q13-q22, and 9q31-q34. Gains in 1q and losses on 11p were significantly more frequent in pT1G2 tumors than in superficial (pTa) ones. In our study, the most striking differences were seen between pT1G3 and pT1G2 tumors. Gains on 10p and 6p and losses at 5q, 6q, and 18q were significantly more frequent in the former. CONCLUSIONS A summary of our results and those available from published reports suggest that several groups of chromosomal imbalances may be associated with specific steps along bladder cancer progression. These genetic changes assume two different patterns: those that are shared, but are more intensive in one stage than in the other, and those such as a gain on 3p that are unique to invasive tumors.

Genetic instability and divergence of clonal populations in colon cancer cells in vitro.

The accumulation of multiple chromosomal abnormalities is a characteristic of the majority of colorectal cancers and has been attributed to an underlying chromosomal instability. Genetic instability is considered to have a key role in the generation of genetic and phenotypic heterogeneity in cancer cells. To shed light on the dynamics of chromosomal instability in colon cancer cells, we have analyzed genetic divergence in clonal and subclonal derivates of chromosomally unstable (SW480) and stable (HCT116, LoVo) cell lines. Conventional G-banding karyotyping and arbitrarily primed PCR (AP-PCR) fingerprinting were used to calculate genetic distances among clones and parental cells, and to trace tree-type phylogenies among individual cells and clonal cell populations. SW480 cells showed enhanced karyotypic heterogeneity in clones as compared with parental cells. Moreover, genetic clonal divergence was also increased after two consecutive episodes of single-cell cloning, demonstrating that the homogeneity induced by the bottleneck of cloning is disrupted by genetic instability during clonal expansion and, as a consequence, heterogeneity is restored. These results demonstrate genetic drift in clonal populations originated from isolated cells. The generated cell heterogeneity coupled with selection provides the grounds for the reported feasibility of pre-neoplastic and neoplastic cells to generate new phenotypic variants with increased evolutionary potential.