Biomedical subjects
Publications and source records attributed to E Maserati.
A female patient with chronic myelocytic leukemia (CML) in chronic phase after busulfan and interferon treatment had four different cell lines in her bone marrow. In addition to cells with a normal karyotype there were cells with the Philadelphia chromosome (Ph1), cells with trisomy 8 and Ph1, and cells with trisomy 8 as the sole anomaly.
We report two cases of refractory anemia with excess of blasts in transformation (RAEB-T) with the translocation (8;21), which is frequent in ANLL but not in myelodysplastic syndromes (MDS). A review of such cases leads us to conclude that myeloproliferative disorders characterized by the t(8;21) may be preceded by an MDS phase.
Four cases resembling ataxia telangiectasia, all characterized by the absence of telangiectasias, are presented. Two are sisters while the other 2 are sporadic cases. The 2 sisters, aged 14 and 12 years, present a progressive neurological disease similar to that characterizing the Louis-Bar syndrome. The clinical picture in 1 of the sporadic cases, a girl aged 13 years, differs from the typical ataxia telangiectasia in having bilateral pyramidal signs in the lower limbs. The last case, a girl aged 8 years, presents an atypical clinical pattern characterized by a severe mental retardation, quite modest cerebellar signs and absence of involuntary movements. The results of the immunological and cytogenetic investigations are presented and discussed.
We describe a novel continuous B-cell line (PV-90) derived from a patient with myelodysplastic syndrome (MDS) and originating from spontaneous infection with the Epstein-Barr virus (EBV). The patient progressed to acute myeloblastic leukaemia (AML) 5 months after clinical onset of MDS. PV-90 is of clonal origin as indicated by the presence of immunoglobulin (Ig) gene rearrangements, monoclonal surface immunoglobulins, and a single DNA restriction fragment corresponding to the EBV genomic termini. PV-90 cells also express a number of myelomonocytic markers, including alpha-naphthyl acetate esterase (ANAE), coagulation factor XIII, and CD68 antigen. Moreover, PV-90 cells constitutively express the c-fms proto-oncogene mRNA as the patient's blast cells did. Whereas a trisomy 11 (+11) was found in the patient's bone marrow cells, PV-90 cells had a normal karyotype initially, but at 4 months showed two different and independent chromosomal abnormalities: 90, XX, -Y, -Y, t(9;16) (q11;p13), and 90, XX, -Y, -Y, t(17;18) (p13;q21), the latter possibly involving the p53 (17,p13) and bcl-2 (18, q21) proto-oncogenes. The early development of these chromosomal aberrations is consistent with a genetic instability of PV-90 cells. Expression of bi-lineage markers and genetic instability may suggest that PV-90 cells originated from transformation of a myelodysplastic progenitor cell capable of both myeloid and B-cell differentiation. The PV-90 cell line might be useful in a number of studies, including the possible role of c-fms in cell differentiation, pathogenetic mechanisms of human preleukaemia and lineage promiscuity in acute leukaemia.
Five cases of Roberts syndrome (RS) in four nuclear families are reported and the wide range of phenotypic variation among them is described. This is in contrast with the remarkable uniformity of the cytogenetic findings. Indirect immunofluorescence with seric antibodies from patients with CREST, revealed that the centromeric structures are normal in RS thus confirming J. German's assumption that the chromatid repulsion is confined to the heterochromatin. The authors quantified the phenomenon of centromeric heterochromatin separation (as occasionally revealed by C-bands in normal subjects) in obligate heterozygotes and possible heterozygotes for RS. The results are indicative of the possibility to screen for heterozygotes. The nosology of RS and related syndromes is discussed in view of the cytogenetic findings and the natural history of the disease.
Evidence for gene dosage effect for beta-glucuronidase (GUSB) and phosphoserine phosphatase (PSP), whose genes are mapped on chromosome 7, was searched in a group of 13 patients with myeloproliferative disorders and acquired monosomy 7. The monosomy 7 was the sole anomaly in nine patients and was associated with other chromosome changes in four. A group of 19 patients with similar diseases but with normal karyotype or with anomalies not involving chromosome 7 served as control. beta-galactosidase and arylsulphatase A, whose genes are not on chromosome 7, were tested as control enzymes. We obtained evidence for a gene dosage effect for GUSB, but not for PSP. When all cases with monosomy 7 were compared with controls, no dosage effect was observed for PSP, but when this group was split into two, according to the presence of anomalies additional to the monosomy 7, the values of activity in the group with additional anomalies were significantly lower than in the controls. Thus, in the case of PSP, the loss of one allele is not followed immediately by reduction in activity, and this could be due to the specific importance of PSP in nucleic acid metabolism. We postulate that some regulatory mechanisms are able to keep normal levels of PSP even in the presence of only one allele, and that they are overwhelmed only when additional chromosome changes are present. These changes tend to involve chromosomes carrying genes for enzymes involved in a metabolic pathway closely related to PSP functions, and only then is a gene dosage effect for PSP detectable.
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We have isolated a human DNA fragment (laboratory acronym G98) that detects related sequences in mammals, chicken and Drosophila DNAs. This sequence has been mapped to human chromosome 7 p14-p15 by in situ hybridization. Probe G98 recognizes an insertion-deletion type polymorphism, with allelic frequencies of about 0.5, which can be detected with at least six different restriction enzymes. A second polymorphism, which can be detected in human DNA digested with TaqI, is in non-complete linkage disequilibrium with the first polymorphism. About 70% of the individuals analysed have been found to be heterozygous at this locus.
A female with chronic myelocytic leukemia (CML) in blastic phase (BP) showed a masked Ph chromosome that had originated by a translocation between chromosomes 8 and 22, with no obvious involvement of chromosome 9. A duplication of the masked Ph and trisomy 13 were present as additional anomalies. The karyotype on peripheral blood unstimulated cultures was 48,XX,t(8;22)(p12;q11),+13,+der(22) t(8;22)/47,XX,t(8;22)(p12;q11),+der(22)t(8;22). While the duplication of the Ph is a frequent finding in BP of CML, we did not find any other case in the literature with duplication of a masked Ph. In situ hybridization with c-abl and bcr probes showed that a 3' bcr sequence was translocated to the der(8) chromosome, while the c-abl oncogene was transposed to the masked Ph.
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Two sisters, 11 and 9 years old respectively, had the clinical features of a progressive neurological disorder similar to the ataxia-telangiectasia (AT) syndrome. The two patients have ataxia and chromosome instability with rearrangements of chromosomes 7 and 14 but no telangiectasia, nor the range of immunological anomalies typical of AT. Comparison with similar cases from the literature leads to the conclusion that either there is a specific disorder characterized by ataxia-without-telangiectasia and with the same cytogenetic pattern of AT, or AT shows a wider variability of phenotypic expression than thought before.
47,XXY chromosome complement is relatively frequent (1/750-1000 male newborns) but has so far not been reported in association with malformative syndromes. Three cases of 47,XXY karyotype associated with an unrelated malformative pattern, the Silver-Russell syndrome in two cases and Noonan syndrome in one case are reported. The possibility of a phenotypic alteration of patients with the XXY karyotype by these malformative syndromes is considered.
A patient described as a 45,X male (Forabosco et al. 1977) was examined for the presence of Y-specific DNA by using various probes detecting restriction fragments from different regions of the Y chromosome. Positive hybridization signals were obtained for Yp fragments only. In situ hybridization with two different probes, pDP31 and the pseudoautosomal probe 113F, led to a clear assignment of the Yp sequences to the short arm of one chromosome 18. Cytogenetically, the presence of all of Yp including the Y centromere on 18p could be demonstrated replacing a segment of similar size of 18p. Thus, the Y/18 translocation chromosome is dicentric structurally, but it was shown to be monocentric functionally with the no. 18 centromere active. Gene dosage studies with the probe B74 defining a sequence at 18p11.3 demonstrated a single dose of this sequence in the patient. In agreement with these observations, the patient shows clinical signs of the 18p-syndrome. It is concluded that in XO males in general, the X is of maternal origin while the maleness is due to a de novo Y/autosome translocation derived from the father. Depending on the nature of the autosomal deficiency caused by the Y/autosome translocation, the patient may have congenital malformations.
Three different samples of translocations were considered in an attempt to identify those chromosomal bands preferentially involved in variant Philadelphia chromosome (Ph1) translocations, and to compare them with bands preferentially broken in constitutional and sporadic translocations. The first sample included 204 cases of variant Ph1 translocations with 221 identified break-points (bp), the second consisted of 106 cases of non-Robertsonian constitutional translocations with 213 bp identified, and the third one of 185 bp identified in sporadic translocations found occasionally in single cells of subjects with normal karyotypes and without haematological disorders. A statistical analysis demonstrated that there are some bands preferentially broken in each of the samples, and this with a high level of significance (P less than 0.001). The analysis of the distributions of the chi 2 components permitted us to identify the 12 bands preferentially involved in variant Ph1 translocations and the 13 and 9 bands preferentially involved in constitutional and sporadic translocations, respectively. The comparison among the groups of preferential bp showed that the bands most involved in the three samples are different. Some theoretical problems related to the origin of the Ph1 chromosome are discussed.
Two new cases of Robert's Syndrome (R.S.) are presented. Both clinic and cytogenetic aspects of R.S. are rapidly reviewed. The significance of cytogenetic findings in R.S. is discussed.
Myelodysplastic syndromes (MDS) are clonal disorders of the multipotent hematopoietic stem cell characterized by ineffective hematopoiesis and associated with marrow hypercellularity, increased intramedullary cell death and peripheral cytopenias of varying severity. Patients with myelodysplasia have a propensity (20% to 30% of cases) to undergo transformation into acute myeloid leukemia (AML), and a large body of evidence indicates that MDS represent steps in the multiphasic evolution of AML. Progression of the disease is characterized by expansion of the abnormal clone and inhibition of normal hematopoiesis leading to deterioration of the blood cell count and/or development of AML. MDS are relatively unusual in childhood, representing only 3% of pediatric hematological malignancies, although it has been reported that up to 17% of pediatric AML cases may have a previous myelodysplastic phase. The first systematic attempt at morphological classification of MDS was provided by the French-American-British (FAB) group. However, the FAB classification of MDS is only partially applicable in children. Some variants are extremely rare or absent (refractory anemia with ring sideroblasts and chronic myelomonocytic leukemia), and other peculiar pediatric disorders, represented by juvenile chronic myelogenous leukemia (JCML) and the monosomy 7 syndrome, are not included. Moreover, since there is a partial overlap between pediatric MDS and myeloproliferative disorders and the variants occurring in young children have rather specific features, some confusion still surrounds the nosographical definition of childhood MDS, so that none of the proposed classifications are widely accepted and used. Characteristically, some genetic conditions such as Fanconi's anemia, Shwachman's and Down's syndromes predispose to the development of MDS in childhood. The most common variants of childhood MDS are represented by JCML and the monosomy 7 syndrome, both disorders typically occurring in young children. JCML is characterized by a spontaneous growth of granulocyte-macrophage progenitors that show a striking hypersensitivity to granulocyte-macrophage colony-stimulating factor. Clinical presentation resembles that of some myeloproliferative disorders, with massive organomegaly usually not observed in the classically reported variants of MDS. Clinical features of the monosomy 7 syndrome resemble those observed in JCML and a differential diagnosis between these two entities relies upon the higher percentage of fetal hemoglobin, the more pronounced decrease in platelet count and, in some cases, the lack of the peculiar cytogenetic abnormality in the latter. With the number of children being cured of cancer constantly rising, a significant increase in secondary or chemotherapy-related myelodysplasia is being observed, and these disorders represent a formidable challenge for pediatric hematologists due to their poor response to chemotherapy.(ABSTRACT TRUNCATED AT 400 WORDS)