Chromosome fragility and predisposition to childhood malignancies.

In order to clarify the possible connection between autosomal folate sensitive Fragile Sites (FS) and genetic susceptibility to haemopoetic disease in children we investigated the frequency and distribution of FS in the Peripheral Blood Lymphocytes (PBL) of 56 children with newly diagnosed and untreated haematologic malignancies and their parents. The incidence was compared with that of 146 normal controls (children and adults). In all patients the Bone Marrow (BM) karyotype was also determined. Heritable FS were detected in 49 patients (87.5%). 20 children had more than one FS and in all cases it was inherited from one of their parents, although there was a significant excess of transmitting mothers. 19 different FS were identified: 14 common, 4 rare and one, 22q11, which has not been previously reported, but it is considered as important as it coincides with the cancer breakpoint resulting in the formation of the Philadelphia (Ph) chromosome. The frequency of FS in the PBL of the patients was significantly higher than in the controls and this increase was independent of any abnormality detected in the malignant cells of the BM. However, patients with an abnormal BM karyotype displayed increased frequency of FS induction as compared to patients with a normal karyotype. In three cases the heritable FS was found to be at or near the breakpoints of the chromosomal rearrangements detected in the malignant cells. The findings are discussed with regard to cancer specific breakpoints, oncogene loci and sites where viral DNA can be inserted to the genome. The results of this study suggest that autosomal folate sensitive FS may increase the risk for haematologic malignancies through a complex mechanism which remains to be clarified.

Fetal cells in maternal blood: isolation by magnetic cell sorting and confirmation by immunophenotyping and FISH.

Fetal cells entering the maternal circulation during pregnancy constitute a potential source for safe and reliable non invasive prenatal diagnosis. However, selecting the appropriate fetal cell type and methods of enrichment are areas of paramount importance. Most investigators consider fetal nucleated red blood cells (NRBCs) to be the cell type of choice, since they are mononuclear, abundant in fetal blood, relatively well differentiated and have a limited life span. Twenty ml of peripheral blood samples were collected from 40 pregnant women in the 16th to 18th week of pregnancy. To enrich for NRBCs, found within an excess of maternal cells, negative magnetic cell sorting (MACS) was used. Leukocytes were depleted from maternal blood by treatment with anti CD45 monoclonal antibody, as this surface antigen is not expressed in NRBCs. NRBCs were detected in 35 of the 40 maternal samples with May Grunwald-Giemsa staining. In 30 cases UCH gamma positive cells were identified after immunophenotyping with a monoclonal antibody directed against the gamma chain of fetal hemoglobin. The mean number of isolated NRBCs was 6 (range 1-15). In 5 cases we were able to successfully perform FISH on the immunophenotyped cells and determine correctly the fetal gender using X and Y chromosome specific probes.

Autosomal folate sensitive fragile sites in normal and mentally retarded individuals in Greece.

The frequencies of autosomal folate sensitive fragile sites were compared in populations of mentally retarded fra(X) negative (N = 220) and normal children (N = 76) in Greece. In addition, the frequency of autosomal fragile sites was studied in 20 known fra(X) children in order to test if the fra(X) syndrome is associated with general chromosome instability. The frequencies of both common and rare autosomal fragile sites did not differ significantly between the mentally retarded and the normal children, although the rate of expression was considerably higher in the retarded group. Autosomal fragile sites were not increased in the fra(X) patients. Fra(3)(p14) was by far the most frequent one in all groups. The frequency of fra(6)(q26) was found to be considerably higher among the mentally retarded children, this difference being almost statistically significant. Further cytogenetic studies of normal and retarded individuals are required in order to elucidate this point further.

Martin-Bell syndrome in Greece, with report of another 47,XXY fragile X patient.

A cytogenetic investigation was carried out among 200 mentally retarded boys in Greece for the detection of the fragile X [fra(X)] syndrome. Thirteen patients were found to carry fra(X) (6.5%). Of those, six boys had a history of familial X-linked mental retardation, two had the phenotype of the Martin-Bell syndrome, four had only mental retardation of unknown etiology, and one was a mentally retarded patient with Klinefelter syndrome. The remaining 187 boys were fra(X) negative. Our findings emphasize the importance of early identification of this syndrome in the diagnosis and prevention, through proper genetic counselling, of mental retardation.

A familial X/Y translocation in a boy with ichthyosis, hypogonadism and mental retardation.

A 14-year-old boy is described with hypogonadism, ichthyosis and mental retardation. His karyotype was 46,Y, der(X),t(X;)(p22;q11). His mother's karyotype was 46,X,der(X),t(X;Y)(p22;q11). Thus the son is nullisomic for the region Xp22 leads to pter and the mother is monosomic for the same region. The steroid sulfatase activity in this boy is discussed in relationship to the enzyme's locus on the X chromosome and the manifestation of ichthyosis.

Fetal karyotypes from fetoscopy blood samples.

The fetal karyotype was determined in 42 out of 45 cases from fetal blood obtained by fetoscopy for prenatal diagnosis of beta-thalassemia. The procedure described is quick and reliable and it is recommended for women over 35 years of age undergoing prenatal diagnosis for haemoglobinopathies.

Parental chromosome translocations and fetal loss.

The authors report on the incidence of translocations detected among 300 Greek couples referred for cytogenetic investigation because of repeated abortion, stillbirth, and/or the birth of children with multiple congenital anomalies. Translocations were detected in 16 cases, ie, 1 of 19 couples. However, the incidence of the translocations was unevenly distributed. Nine translocations (3.3%, or 1 of 29 couples) were identified among couples with repeated abortions and stillbirths only, whereas 7 translocations (21.2%, or 1 of 5 couples) were detected among couples who, in addition to having had repeated abortions, had also given birth to children with congenital anomalies. This difference is statistically significant.

Trisomy 3 mosaicism in a live-born infant.

We report on the first case of trisomy 3 detected in the lymphocytes of a live-born infant who died at the age of 5 months. A normal 46,XX karyotype was found in skin fibroblast cultures, which could account for the child's viability and lack of gross phenotypic malformations.

Polymorphism of chromosome 9 in 600 Greek subjects.

The morphologic variations of C-band heterochromatin of chromosome 9 were studied in 600 Greek subjects referred for cytogenetic investigation. There was great variability in the location and length of the heterochromatic bands. The location and length of the heterochromatic band were equal in 177 individuals and unequal in 423. Twenty-five subjects (4%) carried a pericentric inversion on one of the homologs, and 12 individuals (2%) had an extremely elongated C-band in one homolog 9. Our findings are compared with those reported in the literature, and the ethnic variation is discussed and evaluated.

Chromosome studies in couples with repeated spontaneous abortions.

Karyotypes were prepared from peripheral blood leukocytes in 77 couples in whom there was no apparent cause for recurrent spontaneous abortion. In addition to conventional staining, chromosomes were stained by the new technics for Q-, G-, or C-banding. Translocations were found in 5 of 154 persons (3.25% or 1:31 individuals). The frequency of translocations in the general adult population is 0.4% (1:255). Two translocations were apparent only with the new technics for banding. The incidence of chromosomal microanomalies was 7.79% (2.6% in the general population). Karyotyping of couples with recurrent abortion is recommended, with use of the new staining technics.