The importance of gene dosage studies: mutational analysis of the parkin gene in early-onset parkinsonism.

Early-onset parkinsonism (EOP) may be associated with different mutations in the parkin gene, including exon deletions and duplications. To test for gene dosage alterations, we developed a new method of quantitative duplex PCR using the fluorescence resonance energy transfer technique on the LightCycler (Roche Diagnostics). In 21 patients with EOP, three mutations (a single base pair substitution in exon 3 and small deletions in exon 9) were detected by conventional mutational screening (single-strand conformation polymorphism and sequence analysis), while alterations of gene dosage were found in seven patients. We identified heterozygous and compound heterozygous deletions of exons 2, 3, 5 and 7. The latter was also found in the homozygous state. In addition, two heterozygous duplications of exon 4 were observed. Remarkably, two patients carried more than two parkin mutations. This is the first study systematically screening all 12 exons of parkin by real-time, kinetic quantification and clearly shows that mutational analysis of the parkin gene should include gene dosage studies. Furthermore, our method of quantitative PCR is easily applicable to any other gene to be screened for deletions or duplications of whole exons.

Peripheral blood monoclonal B-cells predict the event free survival in multiple myeloma.

Reinfusion of myeloma progenitor cells may contribute to relapse of multiple myeloma after autologous stem cell transplantation. The aim of our study was to investigate whether monoclonal B-cells are present in the apheresis product and to evaluate the clinical relevance of these cells. Leukapheresis products of 55 patients were purged with anti-B-cell-Monoclonal antibodies (MoAbs) and immunobeads. Monoclonal B-cells were found in 85% of patients within the B-cell population. In one third of all myeloma patients, the majority of B-cells was represented by monoclonal myeloma progenitor B-cells, whereas in two thirds of patients monoclonal cells only represented a small part of the entire B-cell population. As shown by sequence analysis, monoclonal precursor B-cells and malignant plasma cells had the identical genetic CDR III sequence. The purging efficacy, using a negative selection system, was a median of 3 logs (range 1,5-3,5). No statistical difference in the purging efficacy was found when 3, 4 or 5 MoAbs against B-cells antigens were used. However, a tumor specific signal could be detected in the purged harvest of all patients, when the highly sensitive ASO-PCR approach was used. Furthermore, we found a direct correlation between the amount of remaining monoclonal cells after negative selection and the event free survival of myeloma patients. 10/15 patients with a median of 20 x 10(3) monoclonal cells in the purged product relapsed at a median of 1,4 years, whereas only 6/24 patients with an oligoclonal pattern including a low number of remaining monoclonal cells relapsed at a median of 2,2 years. The event free survival (EFS) was statistically different between the two groups (p = 0,014).

The relationship between monoclonal myeloma precursor B cells in the peripheral blood stem cell harvests and the clinical response of multiple myeloma patients.

The aim of this study was to determine the presence of monoclonal myeloma precursor B cells in peripheral blood stem cell harvests and to investigate their role in the clinical outcome of multiple myeloma patients. A total of 39 multiple myeloma patients were treated with a sequential therapy including double high-dose melphalan therapy followed by a double transplant procedure. The apheresis products for the second transplant were purged using a panel of four or five different mouse monoclonal antibodies against B-cell antigens (CD10, CD19, CD20, CD22 and CD37). In 19/39 patients a tumour-specific CDR III signal was identified in the diagnostic bone marrow. Gene scan analysis after CDR III PCR of the magnetic bead isolated B-cell fraction from the apheresis products in these 19 patients revealed three different patterns: 32% of patients had a predominantly monoclonal B-cell population; 63% of patients had an identifiable monoclonal signal within an oligoclonal B-cell population. In only 1/19 patients were no monoclonal B cells identified in the B-cell population of the apheresis product. A correlation between the clonal pattern and the clinical response after sequential chemotherapy was found. Patients with a predominance of monoclonal myeloma or myeloma precursor B cells had an early relapse or achieved a minimal response or a partial remission. Patients with an oligo- and/or polyclonal pattern achieved a high percentage of partial as well as complete remissions.

Simultaneous detection of FV Q506 and prothrombin 20210 A variation by allele-specific PCR.

BACKGROUND AND OBJECTIVE: Factor V Leiden is the most important risk factor for hereditary thromboembolism, whereas the mutation in the 3'-untranslated region of the prothrombin gene seems to be only a mild risk factor for thrombotic events. On the other hand the factor V mutation (Arg 506) is frequently coinherited with the prothrombin 3'-untranslated region G20210A variant and there is increasing evidence that the co-segregated prothrombin variant is an additional risk factor for venous thromboembolism, contributing to thrombotic manifestations. A rapid, simple and cost-effective screening method is, therefore, required for the detection of both factor V Leiden and the prothrombin variant A20210G. DESIGN AND METHODS: Eighty-eight patients were enrolled in this study. Forty-four had a previously identified factor V and/or prothrombin mutation, the remaining 44 patients served as negative controls. A multiplex allele specific oligonucleotide PCR was established for the simultaneous detection of the two genetic risk factors for thrombophilia. To test the specificity of the simultaneous ASO PCR approach, the mutated and physiological factor V and prothrombin amplification products were sequenced. RESULTS: The factor V Leiden mutation and the prothrombin variant were correctly identified in all of 44 patients with known mutations. Furthermore the test was able to detect the mutated factor V and the II variant alone, as well as in the cosegregated pattern. Five patients with a homozygous pattern of factor V Leiden or prothrombin variant were also correctly identified. The sensitivity of the test is therefore 100%. In none of the 44 control cases were false positive results seen. INTERPRETATION AND CONCLUSIONS: The ASO PCR test is a rapid, simple and cost-effective screening test for thrombophilia.