G2 chromosomal radiosensitivity in families with ataxia-telangiectasia

Summary Ataxia-telangiectasia (A-T) is an autosomal recessive disease involving chromosomal instability, susceptibility to cancer and X-ray hypersensitivity. The latter two features are expressed to a limited extent in the heterozygous carriers of A-T mutations. Although fibroblast lines from A-T heterozygotes clearly show increased susceptibility to the lethal effect of X-irradiation, the difference in post-irradiation survival between cell lines and normal controls is not always large enough to allow the use of X-ray sensitivity as a laboratory assay for carrier detection in A-T. Recently, we have shown in a blind study, that the extent of chromatid damage induced in the G₂ phase of the cell cycle by moderate doses of X-rays is markedly higher in A-T heterozygous cells than in normal controls. We have now applied this test to 6 additional obligatory heterozygotes and 24 individuals with different risks of being A-T carriers, from three Israeli A-T families. All 6 cell lines from the obligatory heterozygotes showed the typical hypersensitivity to the clastogenic action of X-rays in G₂; of the 24 cell lines with unknown A-T genotype, 16 showed the same hypersensitivity, and 8 responded in a normal way. The proportion of cell lines showing the A-T-heterozygous phenotype was in accord with the expected value, based on Mendelian chance calculations. Since these observations were made, a daughter of two hypersensitive parents in one of these families has been diagnosed as having A-T. This confirmed the presumed A-T heterozygosity of the parents, as indicated by the laboratory assay.     

Cytogenetic assay in apoptosis investigations

The mitotic figure, named premature anaphase (PA) or C-anaphase, could be considered as a cytogenetic forerunner of following cell apoptosis in G1 phase. To confirm this hypothesis the comparative analysis was performed using cytogenetic, cytologic, flow cytometric and DNA fragmentation methods upon the cells with different proliferative ability and degree of differentiation. PA level was significantly increased in bone marrow and blood cells in vitro in cases of acute lymphoblastic leukemia and non-Hodgkin lymphoma, decreased until total disappearance in remission and not revealed in control. Particularly high PA level was registered in embryonal liver's haemopoetic stem cells ex vivo. Flow cytometry measurements showed appearance of additional sub-G1 peak of apoptotic DNA loss both in leukaemic and embryonal cells, whereas DNA-ladder phenomenon was revealed just only in embryonal samples in vivo. Significant positive correlation between the frequency of cells with apoptotic DNA loss and PA level on the chromosomal preparations was registered. Thus, premature anaphase phenomenon is considered as non-random event, associated with high risk of following cell death.     

Cytogenetic investigations in a family with ataxia telangiectasia

Summary Cytogenetic findings on a family with ataxia telangiectasia (A-T) in which three of four sibs were affected are described. The affected individuals had approximately twice the level of spontaneous chromosome breakage of a normla control, while the parents and the normal sib had no significant increase. Lymphocytes from all three A-T homozygotes showed specific stable chromosomal rearrangements involving chromosomes 7 and 14. All of these abnormalities involved breakage at the usual four sites associated with A-T (7p14, 7q35, 14q12, and 14q32). Two rearrangements detected in the eldest and most severely affected patient were clones, one of which [t(14;14)(p11;q12)] is not commonly found in A-T cells. No chromosomal rearrangements were encountered in lymphocytes from the control, the parents, or the normal sib. Lymphocytes from the A-T patients also were found to be 7–11 times more sensitive to the induction of chromatid aberrations by X-irradiation than control cells. Lymphocytes from the parents and normal sib showed a moderately increased frequency of X-ray induced aberrations compared with that of the control.     

Cytogenetic investigations in mentally retarded and normal males from 14 families with the fragile site at Xq28

Summary Lymphocyte cultures from 27 mentally retarded males aged 1 year to 77 years, and from 11 normal brothers from a total of 14 families with the fragile X segregating have been examined cytogenetically employing three different culture methods including methods for induction of fra(X) by FUdR (fluorodeoxyuridine) or MTX (methotrexate). All mentally retarded males showed unequivocal fra(X) expression. No statistically significant correlation between fra(X) expression and age could be demonstrated. No enhancement with FUdR was observed. Fibroblast cultures from 10 retarded males expressed fra(X) in a dose-response relationship to increasing concentrations of FUdR. None of the normal males showed fra(X). In vivo folic acid treatment of seven mentally retarded males resulted in marked reduction in fra(X) expression in lymphocyte cultures grown in medium 199. However, reinduction was achieved by FUdR or MTX, except in one case who temporarily received very high doses of folic acid.     

Cytogenetic investigations in Cucurbitaceae I. Interspecific hybridization in Luffa

In two interspecific hybrids of Luffa, i.e., L. acutangula x L. graveolens and L. echinata x L. graveolens, various types of chromosome associations, from univalents to quadrivalents were observed. The hydrid L. echinata x L. graveolens showed a much higher frequency of univalents than the other hybrid, but the pairing data of both indicate partial homology among most of the chromosomes of the three species. The study of these F₁ hybrids has been utilised for establishing the phylogenetic relationship among the various species and to trace the trend of evolution in the genus Luffa. The two wild species, L. graveolens and L. echinata, are closely related, whereas, L. graveolens is more distantly related to L. acutangula than to L. echinata. It has also been concluded that dioecism in L. echinata is a derived feature, established after diverging from the monoecious prime species L. graveolens.This research has been financed in part by a grant made by the United States Department of Agriculture under PL 480.     

Cytogenetic investigations on children with acute non-lymphocytic leukemia

Cytogenetic data from 30 children with acute non-lymphocytic leukemia (ANLL) are evaluated in connection with patient's age, morphological type of leukemia and prognosis. In 20 out of 30 patients clonal chromosome aberrations were found. The frequency of chromosome aberrations and the prognostic parameters in the various morphological and age groups proved to be different and no direct relationship could be found in a given group between the frequency of aberrations and the prognosis. A more detailed analysis of data, however, provided some evidence that chromosome aberrations observed at diagnosis had a prognostic value independent of age and the morphological properties of blast cells: the normal karyotype and the pseudodiploidy proved to be of a favorable value but the hyperdiploidy and polyploidy an unfavorable prognostic parameter. Besides the known cytogenetic differences between childhood and adult ANLL, some similarities are also emphasized.     

Cytogenetic investigations in rye,wheat and triticale

Summary Chromosomes of tetra- and hexaploid wheat have been individually characterized by Giemsa and/or Leishman C-banding techniques. Appropriate methodological modifications resulted in almost identical staining of chromosomes of tetraploid wheat with Giemsa and Leishman solutions. Additionally comparison of Giemsa banded chromosomes of the A- and B-genome of Triticum turgidum 34 and Triticum aestivum cv Jubilar reveals similar or corresponding patterns in all homologous chromosomes with the exception of chromosome 7B. Apart from this intervarietal variation in certain homologous chromosomes of both wheat cultivars, intravarietal polymorphism is verified.     

Cytogenetic investigations onOenothera wolfii (Onagraceae)

Oenothera wolfii, endemic in coastal Northern California and Southern Oregon, has been analysed cytogenetically. It is a permanent structural heterozygote composed of two nearly identical genomic complexes which are closely related to the neighboring maritime ecotype of the homozygousOe. elata subsp.hookeri. — Oe wolfii is believed to have evolved recently from its homozygous ancestor by the accumulation of reciprocal translocations and the acquisition of balanced lethals. Forms such asOe. wolfii represent an important connecting link in our understanding of the evolution of the complexheterozygous species ofOenothera. Dedicated to Prof. Dr.Josef Straub for His 75th birthday.     

Cytogenetic investigations onOenothera nutans (Onagraceae)

Oenothera nutans, common to the Appalachian Mts between 650 and 1 700 m altitude, was investigated cytogenetically and taxonomically. The species is permanently structurally heterozygous. It consists of two genomes of the B-type which are more or less indistinguishable phenotypically. Nearly all of the strains investigated possess a self-incompatibility factor in one of the two complexes. Both complexes show a close relationship to the predominantly homozygousO. grandiflora, a native of the southern lowlands.O. nutans andO. grandiflora possess the same plastid type, plastome III. Probably,O. nutans evolved by an accumulation of reciprocal translocations within an originally structurally homozygous population, which must be regarded ancestral to the present forms ofO. grandiflora.     

Cytogenetic investigations in 150 cases with complaints of sterility or primary amenorrhea

Summary Cytogenetic investigations were carried out on 150 individuals. Out of these 107 were females and 43 males. Eighty seven of the above (43 males and 44 females) had been referred for sterility. Sixty three patients had primary amenorrhea and had been referred directly to this laboratory by clinicians, having been suspected of genetic abnormalities. Twenty-two cases (14.7%) involved in this study showed chromosomal abnormalities and seven cases (4.7%) showed chromosomal polymorphism. Of the 107 females (44 sterile and 63 with primary amenorrhea), 11 (10.2%) showed numerical or structural sex chromosomal abnormalities. Five patients (4.67%) showed chromosomal polymorphism involving the paracentromeric and centromeric regions of chromosomes 1 and 9, double satellites, and giant satellites. Of the 43 males, 11 (25.59%) showed numerical and structural abnormalities. Ten cases were anomalies involving the sex chromosomes. One case of a triple autosomal translocation in an otherwise phenotypically normal azoospermic male was of particular interest. Two cases (4.65%) showed double satellites of the acrocentrics.     

Cytogenetic investigations on leucocytes of workers from a cadmium plant.

Chromosome analysis has been performed on workers from a cadmium plant who were exposed to fumes and dust of cadmium and lead. The 35 workers were classified, according to the type and duration of exposure, into a group (cadmium service) exposed to high levels of lead and cadmium in the absence of zinc (23 people) and a group of rolling-mill workers subjected mostly to zinc but also to lower levels of lead and cadmium (12 people). A higher yield of severe chromosome anomalies (chromatid exchange, disturbance of spiralization, chromosome translocation, ring and dicentric chromosomes) together with a total lower number of structural aberrations was observed in the cadmium workers when compared with the rolling-mill group.     

Mutations associated with variant phenotypes in ataxia-telangiectasia.

We have identified 14 families with ataxia-telangiectasia (A-T) in which mutation of the ATM gene is associated with a less severe clinical and cellular phenotype (approximately 10%-15% of A-T families identified in the United Kingdom). In 10 of these families, all the homozygotes have a 137-bp insertion in their cDNA caused by a point mutation in a sequence resembling a splice-donor site. The second A-T allele has a different mutation in each patient. We show that the less severe phenotype in these patients is caused by some degree of normal splicing, which occurs as an alternative product from the insertion-containing allele. The level of the 137-bp PCR product containing the insertion was lowest in two patients who showed a later onset of cerebellar ataxia. A further four families who do not have this insertion have been identified. Mutations detected in two of four of these are missense mutations, normally rare in A-T patients. The demonstration of mutations giving rise to a slightly milder phenotype in A-T raises the interesting question of what range of phenotypes might occur in individuals in whom both mutations are milder. One possibility might be that individuals who are compound heterozygotes for ATM mutations are more common than we realize.     

Epstein-Barr-virus-carrying lymphoma in a patient with ataxia-telangiectasia.

An undifferentiated lymphocytic lymphoma of mesenteric lymph nodes occurred in a young boy with ataxia-telangiectasia. Two independent tests, Epstein-Barr virus (EBV)-cRNA/DNA hybridisation and EBV DNA/DNA reassociation kinetic analysis, showed 53 and 68 EBV genome equivalents per cell respectively, which was compatible with an EBV-genome-carrying tumour. Whether this was a polyclonal lymphoproliferation or a monoclonal tumour could not be determined owing to lack of suitable material. The presence of EBV genomes should be sought in lymphomas arising in ataxia-telangiectasia and other immunodeficiencies.     

Congenital malformations and developmental disabilities in ataxia-telangiectasia, Fanconi anemia, and xeroderma pigmentosum families.

Heterozygous carriers of an ataxia-telangiectasia (A-T), Fanconi anemia (FA), or xeroderma pigmentosum (XP) gene may be predisposed to some of the same congenital malformations or developmental disabilities that are common among homozygotes. To test this hypothesis, medical records, death certificates, and questionnaires from 27 A-T families, 25 FA families, and 31 XP families were reviewed. Eleven XP blood relatives (out of 1,100) were found with moderate or severe unexplained mental retardation, a significant excess compared to the FA and A-T families (3/1,439). There were four microcephalic XP blood relatives and none in the FA or A-T families. In the A-T families, idiopathic scoliosis and vertebral anomalies were in excess, while genitourinary and distal limb malformations were found in the FA families. A-T, FA, or XP heterozygotes may constitute an important proportion of individuals at risk for specific malformations or developmental abnormalities.     

Cytogenetic investigations in a new case of Bloom's syndrome

Summary Cytogenetic studies of an 8-year-old caucasian girl with typical but mild manifestation of Bloom's syndrome showed a characteristic increase of homologous chromatid translocations and prematurely condensed chromosomes. The average frequency of sister chromatid exchanges (SCE) in lymphocytes with 133 was much higher than in skin fibroblasts with 49. The inter- and intrachromosomal distributions of SCE in lymphocytes were analyzed.Prof. Dr. H.-R. Wiedemann to his 60th birthday.     

Cytogenetic investigations in three cell types of a Saudi family with ataxia telangiectasia

Summary Chromosomal analyses were performed on lymphocytes, fibroblasts and lymphoblastoid cell lines derived from a Saudi family with ataxia telangiectasia (AT). The three siblings of a consanguineous marriage were all affected. The lymphocytes of the AT homozygotes (probands) showed an increase of 2- to 6-fold and 4- to 8-fold respectively, in the frequency of spontaneous and X-ray-induced chromosomal aberrations compared with controls, while the parents (obligate heterozygotes) of the patients showed no notable difference. The unirradiated lymphocytes from the oldest AT sibling, an 11-year-old boy (AT1), showed specific rearrangements involving chromosomes 7 and 14 [t(7;14)(q35;q12)] and 12 and 14 [t(12;14)(q23;q12)] in two different clones. The most severely affected sibling was a 9-year-old girl (AT2) who presented with a clone showing a novel rearrangement involving chromosomes 14 and 17, namely: del(14) (q31q32) and dup(17)(q21–q24). The lymphocytes from the third sibling, a 2-year-old boy (AT3), showed a t(2;14)(p24;q12). In addition, an inv(14)(q12q32) was observed in all three AT patients, while inv(7)(p14q35) was found only in patients 2 and 3. The lymphocytes from the AT parents and controls showed normal karyotypes. The breakpoints involving chromosomes 2,12 and 17, observed in our studies, have rarely been reported in other series of AT patients. No non-random chromosomal rearrangements were observed either in the skin fibroblasts or in the lymphoblastoid cell lines derived from the AT patients, although all cell lines showed an increase in both spontaneous and radiation-induced chromosomal breaks per cell. The present study constitutes the first report on a cytogenetic analysis of a Saudi family with three AT siblings.