Structural and numerical chromosomal abnormalities are frequent findings in neoplastic cells. The... more Structural and numerical chromosomal abnormalities are frequent findings in neoplastic cells. The origin of structural rearrangements is probably due to the existence of specific labile areas on human chromosomes. These areas, named fragile sites (FS), are prone to chromosomal breakage and rearrangements, playing an important role in the first steps of carcinogenesis. The classification of FS, the mechanisms involved in FS induction and their biological significance, specially their relationship with cancer development, are discussed.
Fragile sites are points of preferential breakage that may be involved in chromosome rearrangemen... more Fragile sites are points of preferential breakage that may be involved in chromosome rearrangements. Induction of common fragile sites (c-fra) and spontaneous breakage were analyzed in two New World Monkeys species: Saimiri boliviensis (SBO) and Alouatta caraya (ACA). Spontaneous chromosome aberrations were analyzed on untreated lymphocyte cultures with Brögger's formula (1977). SBO presented a low level of spontaneous breakage, while higher frequencies were detected in ACA in which bands 1q23; 2q13 and 11q19 were significantly affected (p < 0.01). The populational distribution of c-fra was analyzed by the Chi 2 test in FUdR plus caffeine treated cultures. A total of 21 c-fra was identified in SBO and 24 in ACA. Fragile sites A 1 q33, B 1 p21, B 4 p14, C 3 q23 and C 5 q22 were identified in all analyzed SBO specimens. The most frequent c-fra identified in ACA specimens were 1q23, 1q31, 1q33, 2q22, 8q14, 12q31, 13q22, 14q15 and Xq22. Fragile sites A 1 q31, A 1 q33, B 1 q14, B 3 q13, B 4 q21 and Xq22 identified in SBO and 1q31, 1q33, 2q22, 4q21, 6q13, 13q22 and Xq22 from ACA were the most conserved sites. A low coincidence between the location of c-fra and that of heterochromatin and breakpoints involved in euchromatic rearrangements known for these genera, was established.
Spontaneous chromosome aberrations (CAs) and induced fragile sites (FSs) were analysed in 12 untr... more Spontaneous chromosome aberrations (CAs) and induced fragile sites (FSs) were analysed in 12 untreated adult coeliac disease (CD) patients and 8 healthy controls. Blood lymphocytes from each individual were cultured for 72 h at 37 degrees C in F-10 medium with 5% fetal calf serum and 0.1 ml phytohemagglutinine. FSs were induced by FudR (10 micrograms/ml, 24 h before harvesting) and caffeine (2.2 mM. 6 h before harvest). Spontaneous CAs and FSs were analysed on 30-50 Giemsa-stained and G-banded metaphases. The mean frequencies of spontaneous CAs (abnormal cells, gaps/cell and breaks/cell) of CD patients (0.24 +/- 0.02, 0.21 +/- 0.02 and 0.13 +/- 0.02, respectively) were significantly higher than those of controls (0.04 +/- 0.01, 0.02 +/- 0.01 and 0.02 +/- 0.01, respectively) (p &lt; 0.001). Fourteen spontaneous CAs and 5 FSs specific for CD patients presented a strong coincidence (70%) with bands involved in T- and B-cell malignant lymphoma rearrangements. These findings suggest that CD has chromosome instability affecting specific points that could be related to the high prevalence of malignancies in this disorder.
Precise chimerism monitoring is important for the prediction of the success of allogeneic bone ma... more Precise chimerism monitoring is important for the prediction of the success of allogeneic bone marrow transplantation (BMT). Most of the current procedures employed for chimerism follow-up with short tandem repeat (STR) markers are either time-consuming, labor-intensive, or use expensive assays, making it burdensome to perform large-scale studies of transplanted patients. To set-up a simple nonradioactive method to investigate a set of STR markers that could be used in the evaluation of chimerism status after allogeneic BMT. Six dinucleotide STRs (D2S123, D5S107, CRTL1, D7S500, D11S1356, and TP53) were analyzed by touchdown (TD)-PCR followed by medium size non-denaturing polyacrylamide gel electrophoresis and silver staining. The sensitivity of the approach was evaluated by dilution competition assays. Peripheral blood samples were taken from a group of 50 healthy Argentinean donors, two transplanted patients, and their respective bone marrow donors. Buccal mucosa samples were also obtained from the BMT recipients. Four markers, D2S123, D7S500, D11S1356, and TP53, presented the highest heterozygosities (0.67-0.88) under our experimental system. A sensitivity of 0.8-1.6% for chimerism detection was consistently found for the different STR. The usefulness of these STR in chimerism analysis was illustrated with the screening of related siblings analyzing two transplanted patients with persistent mixed chimerism, which were previously studied by fluorescence in situ hybridization (FISH). Similar proportions of mixed chimerism were obtained with STR analysis compared with those estimated by FISH. To our knowledge, this was the first study of mixed chimerism using TD-PCR to achieve a highly specific STR amplification. This approach allows simple and accurate chimerism quantification because it avoids slippage of Taq polymerase on repeat stretches and prevents the differential amplification of the shorter allele. STR heterozygosities and the high level of sensitivity of this method demonstrated that this approach is not only very informative in this population, but is also rapid (taking less than 14 hours) and cost-efficient. The data confirms that this method is a useful tool applicable to routine large-scale STR genotyping and mixed chimerism analysis in low-complexity laboratories worldwide.
Cytogenetic studies were performed in celiac disease (CD) patients to determine if the presence o... more Cytogenetic studies were performed in celiac disease (CD) patients to determine if the presence of chromosome instability is related to the predisposition to cancer. Chromosome aberrations (CA) and sister chromatid exchange (SCE) frequencies in peripheral blood lymphocyte cultures from untreated CD patients and healthy controls were analyzed. Patients showed aberrations in 23% of cells, while only 3% were detected in the control group (p &lt; 0.0001). The mean frequencies of gaps, breaks and total CA were found to be higher in CD patients compared to controls (p &lt; 0.0001). Breakpoint distribution was nonrandom among chromosomes from celiac patients (p = 0.01), but not among controls (p = 0.04). The frequency of SCE/cell showed a mean value of 6.9 +/- 0.6 in CD patients and 7.3 +/- 0.2 in controls. No statistical differences were found. Breakpoints involved in CD patients presented a strong coincidence with the location of fragile sites (78.6%) and sites of cancer chromosome rearrangements (57.1%), most of them (75%) associated with malignant non-Hodgkin lymphomas. These results suggest that CD is a condition with increased chromosome instability characterized by a high level of CA and normal SCE frequencies, probably related to the increased incidence of cancer.
Structural and numerical chromosomal abnormalities are frequent findings in neoplastic cells. The... more Structural and numerical chromosomal abnormalities are frequent findings in neoplastic cells. The origin of structural rearrangements is probably due to the existence of specific labile areas on human chromosomes. These areas, named fragile sites (FS), are prone to chromosomal breakage and rearrangements, playing an important role in the first steps of carcinogenesis. The classification of FS, the mechanisms involved in FS induction and their biological significance, specially their relationship with cancer development, are discussed.
Fragile sites are points of preferential breakage that may be involved in chromosome rearrangemen... more Fragile sites are points of preferential breakage that may be involved in chromosome rearrangements. Induction of common fragile sites (c-fra) and spontaneous breakage were analyzed in two New World Monkeys species: Saimiri boliviensis (SBO) and Alouatta caraya (ACA). Spontaneous chromosome aberrations were analyzed on untreated lymphocyte cultures with Brögger's formula (1977). SBO presented a low level of spontaneous breakage, while higher frequencies were detected in ACA in which bands 1q23; 2q13 and 11q19 were significantly affected (p < 0.01). The populational distribution of c-fra was analyzed by the Chi 2 test in FUdR plus caffeine treated cultures. A total of 21 c-fra was identified in SBO and 24 in ACA. Fragile sites A 1 q33, B 1 p21, B 4 p14, C 3 q23 and C 5 q22 were identified in all analyzed SBO specimens. The most frequent c-fra identified in ACA specimens were 1q23, 1q31, 1q33, 2q22, 8q14, 12q31, 13q22, 14q15 and Xq22. Fragile sites A 1 q31, A 1 q33, B 1 q14, B 3 q13, B 4 q21 and Xq22 identified in SBO and 1q31, 1q33, 2q22, 4q21, 6q13, 13q22 and Xq22 from ACA were the most conserved sites. A low coincidence between the location of c-fra and that of heterochromatin and breakpoints involved in euchromatic rearrangements known for these genera, was established.
Spontaneous chromosome aberrations (CAs) and induced fragile sites (FSs) were analysed in 12 untr... more Spontaneous chromosome aberrations (CAs) and induced fragile sites (FSs) were analysed in 12 untreated adult coeliac disease (CD) patients and 8 healthy controls. Blood lymphocytes from each individual were cultured for 72 h at 37 degrees C in F-10 medium with 5% fetal calf serum and 0.1 ml phytohemagglutinine. FSs were induced by FudR (10 micrograms/ml, 24 h before harvesting) and caffeine (2.2 mM. 6 h before harvest). Spontaneous CAs and FSs were analysed on 30-50 Giemsa-stained and G-banded metaphases. The mean frequencies of spontaneous CAs (abnormal cells, gaps/cell and breaks/cell) of CD patients (0.24 +/- 0.02, 0.21 +/- 0.02 and 0.13 +/- 0.02, respectively) were significantly higher than those of controls (0.04 +/- 0.01, 0.02 +/- 0.01 and 0.02 +/- 0.01, respectively) (p &lt; 0.001). Fourteen spontaneous CAs and 5 FSs specific for CD patients presented a strong coincidence (70%) with bands involved in T- and B-cell malignant lymphoma rearrangements. These findings suggest that CD has chromosome instability affecting specific points that could be related to the high prevalence of malignancies in this disorder.
Precise chimerism monitoring is important for the prediction of the success of allogeneic bone ma... more Precise chimerism monitoring is important for the prediction of the success of allogeneic bone marrow transplantation (BMT). Most of the current procedures employed for chimerism follow-up with short tandem repeat (STR) markers are either time-consuming, labor-intensive, or use expensive assays, making it burdensome to perform large-scale studies of transplanted patients. To set-up a simple nonradioactive method to investigate a set of STR markers that could be used in the evaluation of chimerism status after allogeneic BMT. Six dinucleotide STRs (D2S123, D5S107, CRTL1, D7S500, D11S1356, and TP53) were analyzed by touchdown (TD)-PCR followed by medium size non-denaturing polyacrylamide gel electrophoresis and silver staining. The sensitivity of the approach was evaluated by dilution competition assays. Peripheral blood samples were taken from a group of 50 healthy Argentinean donors, two transplanted patients, and their respective bone marrow donors. Buccal mucosa samples were also obtained from the BMT recipients. Four markers, D2S123, D7S500, D11S1356, and TP53, presented the highest heterozygosities (0.67-0.88) under our experimental system. A sensitivity of 0.8-1.6% for chimerism detection was consistently found for the different STR. The usefulness of these STR in chimerism analysis was illustrated with the screening of related siblings analyzing two transplanted patients with persistent mixed chimerism, which were previously studied by fluorescence in situ hybridization (FISH). Similar proportions of mixed chimerism were obtained with STR analysis compared with those estimated by FISH. To our knowledge, this was the first study of mixed chimerism using TD-PCR to achieve a highly specific STR amplification. This approach allows simple and accurate chimerism quantification because it avoids slippage of Taq polymerase on repeat stretches and prevents the differential amplification of the shorter allele. STR heterozygosities and the high level of sensitivity of this method demonstrated that this approach is not only very informative in this population, but is also rapid (taking less than 14 hours) and cost-efficient. The data confirms that this method is a useful tool applicable to routine large-scale STR genotyping and mixed chimerism analysis in low-complexity laboratories worldwide.
Cytogenetic studies were performed in celiac disease (CD) patients to determine if the presence o... more Cytogenetic studies were performed in celiac disease (CD) patients to determine if the presence of chromosome instability is related to the predisposition to cancer. Chromosome aberrations (CA) and sister chromatid exchange (SCE) frequencies in peripheral blood lymphocyte cultures from untreated CD patients and healthy controls were analyzed. Patients showed aberrations in 23% of cells, while only 3% were detected in the control group (p &lt; 0.0001). The mean frequencies of gaps, breaks and total CA were found to be higher in CD patients compared to controls (p &lt; 0.0001). Breakpoint distribution was nonrandom among chromosomes from celiac patients (p = 0.01), but not among controls (p = 0.04). The frequency of SCE/cell showed a mean value of 6.9 +/- 0.6 in CD patients and 7.3 +/- 0.2 in controls. No statistical differences were found. Breakpoints involved in CD patients presented a strong coincidence with the location of fragile sites (78.6%) and sites of cancer chromosome rearrangements (57.1%), most of them (75%) associated with malignant non-Hodgkin lymphomas. These results suggest that CD is a condition with increased chromosome instability characterized by a high level of CA and normal SCE frequencies, probably related to the increased incidence of cancer.
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