The influence of cytogenetic aberrations on gene replication in chronic lymphocytic leukemia patients

Chronic lymphocytic leukemia (CLL) is the most common leukemia in humans, with the major cytogenetic aberrations of trisomy 12 and deletion of 13q14. This study examined the influence of these aberrations on general gene replication. The study group included three subgroups: (1) 15 CLL patients, (2) 4 CLL patients with trisomy 12, (3) 3 CLL patients with deletions in 13q14. Five healthy individuals served as a control group. Monocolor fluorescence in situ hybridization (FISH) with probes for c-myc, HER-2/neu, and p53 was applied to lymphocyte nuclei for the evaluation of replication timing. Asynchronous replication (SD) rate was significantly higher in all CLL patients (P < 0.01) when compared to the control group and was even higher in the group of CLL patients with trisomy 12 and 13q14 deletion (P < 0.01). The asynchrony rate was significantly higher in cells with trisomy 12 for all three probes analyzed, compared to "healthy" cells in the same patients (P < 0.001). To conclude, in CLL patients with a chromosomal aberration such as trisomy 12 and 13q14 deletion we were able to demonstrate a high rate of asynchrony of replication. The high correlation between cells with trisomy 12 and SD pattern could reflect direct influence of the aberration on gene replication and cell cycle control.     

Random aneuploidy and telomere capture in chronic lymphocytic leukemia and chronic myeloid leukemia patients

Telomeric regions of the human genome are of particular interest, because rearrangements of these regions are difficult to identify by conventional chromosome banding technology. With the advent of molecular cytogenetic techniques such as fluorescence in situ hybridization (FISH), it has been possible to investigate the terminus in cytogenetically visible terminal deletions and telomere rearrangements. We investigated telomere capture and aneuploidy rates in chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML) patients, as well as in healthy control subsets. Using a FISH technique, we estimated the random aneuploidy and telomere capture of the 21q22, SNRPN, and 15qter loci. Higher aneuploidy rates were found in the leukocytes of CLL and CML patients, compared with the control group, for the 21q22 and SNRPN loci. There was no difference in the aneuploidy rate between the CML and CLL groups. Telomere capture was found in the two groups (CLL and CML), but not in the control group. We propose that the telomere capture phenomenon is much more common than has been reported in the literature; however, its prognostic significance is yet to be established.     

Chromosome aberrations in B-cell chronic lymphocytic leukemia: reassessment based on molecular cytogenetic analysis

In B-cell chronic lymphocytic leukemia (B-CLL) clonal chromosome aberrations are detected in approximately 40–50% of tumors when using conventional chromosome banding analysis. Most studies find trisomy 12 to be the most frequent chromosome aberration, followed by structural aberrations of the long arm of chromosomes 13 and 14. Trisomy 12 and the ”14q+” marker are associated with shorter survival times, while the patients with 13q abnormalities have a favorable outcome, similar to those with a normal karyotype. The development of molecular cytogenetic techniques has greatly improved our ability to detect chromosome aberrations in tumor cells. Using fluorescence in situ hybridization, chromosome aberrations can be detected not only in dividing cells but also in interphase nuclei, an approach referred to as interphase cytogenetics. The prevalence of specific aberrations in B-CLL is currently being reassessed by interphase cytogenetics. By far the most frequent abnormality are deletions involving chromosome band 13q14, followed by deletions of the genomic region 11q22.3-q23.1, trisomy 12, deletions of 6q21-q23, and deletions/mutations of the TP53 tumor suppressor gene at 17p13. The evaluation of the true incidence of these aberrations now provides the basis for more accurate correlations with clinical characteristics and outcome. Deletions/mutations of the TP53 gene have been shown to be associated with resistance to treatment and to be an independent marker for poor survival. 11q deletions have been associated with extensive nodal involvement, rapid disease progression, and short survival times. Whether trisomy 12, 13q14, and 6q deletions have a prognostic impact awaits further study. The application of these molecular cytogenetic techniques will also contribute to the identification of the pathogenetically relevant genes that are affected by the chromosome aberrations in B-CLL. Received: 2 February 1998 / Accepted: 31 March 1998     

Multicolor FISH in chronic lymphocytic leukemia. An interphase study of patients with early-onset disease

Trisomy 12 and deletions of 13q14.2 and 14q32 are the most common chromosome abnormalities in patients with B-chronic lymphocytic leukemia (B-CLL), but whether specific chromosomal defects influence the course of B-CLL is still a matter of discussion. The aim of our study was to assess the possible correlation between cytogenetic findings and clinical characteristics. Thirty patients with previously untreated early-onset B-CLL were recruited. The incidence of trisomy 12, and observations of 13q14.2 and 14q32 was analyzed in unstimulated bone marrow cells by means of multicolor interphase FISH. No correlation was found between trisomy 12 and the patients' clinical characteristics. The analysis of the patients with trisomy 12 and observations of 13q14.2 and 14q32 revealed heterogeneity of the leukemic cell population, thus indicating that these chromosomal abnormalities are probably a secondary event in CLL leukemogenesis. The finding of RB1 gene nullisomy and 14q32 deletions in patients at an advanced clinical stage suggests a possible correlation between these rearrangements and disease progression. Multicolor FISH analysis in B-CLL provides important diagnostic, clinical, and prognostic information that may help in assessing prognosis and making treatment decisions.     

Genetic abnormalities and clinical outcome in chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia in the elderly population. Under conventional cytogenetic (CC) analysis, approximately 50% of CLL cases show clonal aberrations. Using fluorescent in situ hybridization (FISH), the percentage of patients with abnormalities rises to almost 80%, the most frequent being 13q14, ATM, and TP53 deletions and trisomy 12. The aim of this study was to establish the incidence of genetic changes in B-CLL patients using CC and FISH and to evaluate the prognostic implications. Of the 65 patients analyzed, genetic aberrations were found in 36.7% with CC and in 68.4% with FISH. The frequencies of abnormalities were as follows: 13q deletion, 42.1%; trisomy 12, 19.2%; ATM deletion, 17.5%; and TP53 deletion, 8.7%. Significant differences were observed when the overall survival was correlated with Rai stage (P = 0.000). FISH abnormalities were correlated with age, sex, morphology, white blood cell count, CD38 expression, Rai stage, disease status, and survival. Significant differences were obtained with age (P = 0.05) and disease status (P = 0.01). Deletion of 13q was the most frequent abnormality (36.6%) among old patients (> or =60); trisomy 12 was the most frequent (31.3%) in younger patients (<60). Half of the patients with stable disease showed 13q deletion, and the most frequent abnormality in patients with progressive disease was ATM deletion (22.2%).     

Genomic aberrations and survival in chronic lymphocytic leukemia

BACKGROUND: Fluorescence in situ hybridization has improved the detection of genomic aberrations in chronic lymphocytic leukemia. We used this method to identify chromosomal abnormalities in patients with chronic lymphocytic leukemia and assessed their prognostic implications. METHODS: Mononuclear cells from the blood of 325 patients with chronic lymphocytic leukemia were analyzed by fluorescence in situ hybridization for deletions in chromosome bands 6q21, 11q22-23, 13q14, and 17p13; trisomy of bands 3q26, 8q24, and 12q13; and translocations involving band 14q32. Molecular cytogenetic data were correlated with clinical findings. RESULTS: Chromosomal aberrations were detected in 268 of 325 cases (82 percent). The most frequent changes were a deletion in 13q (55 percent), a deletion in 11q (18 percent), trisomy of 12q (16 percent), a deletion in 17p (7 percent), and a deletion in 6q (7 percent). Five categories were defined with a statistical model: 17p deletion, 11q deletion, 12q trisomy, normal karyotype, and 13q deletion as the sole abnormality; the median survival times for patients in these groups were 32, 79, 114, 111, and 133 months, respectively. Patients in the 17p- and 11q-deletion groups had more advanced disease than those in the other three groups. Patients with 17p deletions had the shortest median treatment-free interval (9 months), and those with 13q deletions had the longest (92 months). In multivariate analysis, the presence or absence of a 17p deletion, the presence or absence of an 11q deletion, age, Binet stage, the serum lactate dehydrogenase level, and the white-cell count gave significant prognostic information. CONCLUSIONS: Genomic aberrations in chronic lymphocytic leukemia are important independent predictors of disease progression and survival. These findings have implications for the design of risk-adapted treatment strategies.     

Chromosome aberrations in B-cell chronic lymphocytic leukemia. Pathogenetic and clinical implications

Chromosome analyses were performed on leukemic cells from 102 patients with B-CLL, of whom 84 were untreated. B-cell mitogen-induced CLL cells yielded suitable metaphases in 85 patients, and 55 showed clonal chromosomal aberrations. Trisomy 12 was found in 26 patients. In nine patients the + 12 was a single aberration. A 14q + chromosome or deletions of the long arm of chromosomes 6, 11, or 13 were other recurrent aberrations. Patients with Rai stage I or more had more frequently clonal aberrations than patients with stage 0 disease (p less than .02). Patients with clonal aberrations had poorer 5-year survival than those with a normal karyotype (p less than .05). Patients with a high percentage of abnormal metaphases in the sample had poorer prognosis than patients with high admixture of normal metaphases (p less than .01). Of the specific clonal aberrations those with 14q + or trisomy 12 tended to have slightly poorer and those with 6q- or structural aberrations involving the long arm of chromosome 13 tended to have better prognosis than patients with other chromosomal aberrations. A complex karyotype tended to be an adverse prognostic sign. Clonal evolution is rare: complex karyotypes are found at diagnosis and clones with single aberrations did not acquire additional chromosome aberrations despite progressive disease and treatment. Nine hundred and seventy-nine published cases are reviewed, and pathogenetic mechanisms, such as oncogenes and gene dosage, are discussed.     

Different distribution of NOTCH1 mutations in chronic lymphocytic leukemia with isolated trisomy 12 or associated with other chromosomal alterations

Chronic lymphocytic leukemia (CLL) is the most common leukemia among adults in Western countries. Chromosomal abnormalities commonly found using conventional cytogenetics and FISH are del(11)(q22-23), trisomy 12, del(13)(q14), and del(17)(p13). Trisomy 12 is the most frequent numerical abnormality in CLL. It can appear isolated or associated with other chromosomal aberrations, including t(14;18)(q32;q21) and trisomy 18. The aim of this study was to determine whether CLL patients with isolated trisomy 12 or associated with other chromosomal alterations have different clinico-pathological features, including a different distribution NOTCH1 mutation. Patients were classified into four groups: Group 1, isolated trisomy 12 (n=14); Group 2, trisomy 12 plus trisomy 18 (n=4); Group 3, trisomy 12 plus t(14;18) (n=8); and Group 4: patients with trisomy 12 plus other abnormalities not involving BCL2 (n=28). The Binet stage and expression of ZAP70 were significantly different among cytogenetic groups. NOTCH1 mutations were detected in 6/12 (50%) patients from Group 1, 4/25 (16%) patients from Group 4, and in no patient from groups 2 and 3 (P=0.020). Patients in Group 2 had a more rapid disease progression (median Treatment-free Survival 2 months) as against patients from Groups 1 (50 months), 3 (69 months), or 4 (68 months; P=0.001). These findings indicate that the distribution of NOTCH1 mutations in CLL with trisomy 12 is heterogeneous and that the presence of additional chromosomal abnormalities such as trisomy 18 could change the prognosis of these patients.     

应用荧光原位杂交技术检测84例慢性淋巴细胞白血病遗传学异常及预后分析

 摘要 目的：探讨荧光原位杂交 (fluorescence in situ hybridization,FISH) 技术检测慢性淋巴细胞白血病(chronic lymphocytic leukemia,CLL)患者的遗传学异常,并分析与其他预后指标的相关性及预后价值。方法：回顾性分析采用FISH技术进行着丝粒探针CSP12(12p11.1～12q11.1)和序列特异性探针D13s25(13q14.3)、ATM (11q22.3)、RB1(13q14)、p53(17p13.1)检测过的84例CLL患者的临床以及实验室资料。分析FISH技术检测CLL患者中遗传学异常的发生率,并分析遗传学异常与CLL患者年龄、性别、Binet分期、血清乳酸脱氢酶(lactate dehydrogenase,LDH)、CD38表达、生存期之间的相关性。结果：(1)84例CLL患者中,62例有至少有一种遗传学异常。遗传学异常的检出率为73.8%。(2)共发现5种遗传学异常,依次为13q14缺失（56%）、P53缺失（28.6%）、-12（16.7%）、ATM缺失（13.1%）、+12（13.1%）。其中-12为CLL病人中新发现遗传学异常。(3)分析上述5种遗传学异常与年龄、性别、Binet分期、LDH水平、CD38表达的关系,在>60岁年龄病人里,+12阳性率显著高于<60岁病人(24%VS3%, P=0.042),与性别、Bient分期、LDH水平、CD38表达无关。(4)在LDH增高组中,CD38高表达的病例比例增高（67%VS20%, P=0.015）。(5) 伴有del(17p13)或del(11q22)或复杂异常中位生存时间为75个月,单纯具有del(13q14)异常组的中位生存时间为150个月,其他中位生存时间为120月,但两两比较没有达到统计学差异。结论：(1)FISH技术是一种在分析CLL患者遗传学异常方面较为快速、准确和敏感的方法; (2)CLL病人中除了常见13q14缺失、P53缺失、ATM缺失、+12之外,还可以出现-12异常。     

Intratumoral genetic heterogeneity and number of cytogenetic aberrations provide additional prognostic significance in chronic lymphocytic leukemia

PurposeChronic lymphocytic leukemia (CLL) is a heterogeneous disease with cytogenetic aberrations that are still considered the gold standard of prognostic factors. However, heterogeneity remains within each cytogenetic group, especially in patients with concomitant cytogenetic aberrations.MethodsA panel of DNA probes was used to detect cytogenetic aberrations, including RB1/D13S25 at 13q14, ATM at 11q22, TP53 at 17p13, CEP12 and IGH translocation at 14q32, by fluorescence in situ hybridization. A comprehensive method integrating the number of cytogenetic aberrations and intratumoral genetic heterogeneity was used to analyze the prognosis for patients with concomitant aberrations.ResultsWithin the conventional favorable or neutral prognostic groups (i.e., with del 13q, trisomy 12, and/or t(14q32)), the coincidence of these three aberrations worsened survival in terms of time to first therapy, progression-free survival, and overall survival. However, within the conventional unfavorable prognostic group (i.e., del 11q or del 17p), patients with a minor unfavorable clone had an unexpected survival advantage compared with patients with a major unfavorable clone. A new cytogenetic prognostic system that integrates the number of cytogenetic aberrations and intratumoral genetic subclones was more precise than the conventional system.ConclusionThe number of cytogenetic aberrations and the size of intratumoral genetic subclones should be comprehensively considered to determine the prognosis for CLL.     

Retinoblastoma gene deletions in B-cell chronic lymphocytic leukemia.

Approximately 10% of B-cell chronic lymphocyte leukemia (B-CLL) cases have structural chromosomal aberrations involving band 13q14. To evaluate a possible role of RBl gene deletions in B-CLL we investigated the malignant cells of 27 patients by molecular genetic and cytogenetic techniques. Four of the cases had chromosomal aberrations that involved 13q14 (including one case with a 13q14 deletion that was observed in a single metaphase cell), and 11 had other chromosomal abnormalities, whereas the malignant cells of 12 patients were either cytogenetically normal or failed to divided in vitro. Eight patients (30%) were found to have hemizygous deletions of the RBl gene. These cases included all four patients with chromosomal changes at 13q14, but also three patients without chromosome abnormalities and one case with a chromosomal aberration not involving 13q. The deletions were interstitial in all cases but one, as defined by probes located centromeric and telomeric of the RBl locus. Inactivation of RBl may thus be a significant event in the development of some B-CLL clones.     

More extensive genetic alterations in unmutated than in hypermutated cases of chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (CLL) is not a uniform disease entity; approximately half of the CLL cases have undergone immunoglobulin V(H) gene hypermutation, whereas the other half display unmutated V(H) genes. We investigated genome changes in 12 hypermutated cases (M-CLL) and 22 unmutated cases (UM-CLL) by use of comparative genomic hybridization, G-banding, and multicolor fluorescence in situ hybridization (m-FISH) after optimal mitogen stimulation and FISH analysis of typical CLL aberrations: 11q deletion, 13q deletion, and trisomy 12. Very high frequencies of aberrations were found in both groups: 82% in UM-CLL and 83% in M-CLL. Deletions of 11q and 13q were equally distributed in M-CLL and UM-CLL. However, larger aberrations detectable by CGH, trisomy 12, and complex aberrations were less frequent in M-CLL than in UM-CLL. These observations led to a hypothesis that unmutated and mutated CLL have different biological Backgrounds, given that large and/or complex chromosomal aberrations and hypermutation of the CLL progenitor cells tend to be mutually exclusive.     

应用组合荧光原位杂交技术检测慢性淋巴细胞白血病的基因组异常

目的 探讨应用组合荧光原位杂交(panel fluorescence in situ hybridization，panel FISH)技术对慢性淋巴细胞性白血病(chronic lymphocytic leukaemia，CLL)基因组异常检测的价值。方法 分别应用3号、12号、18号的着丝粒探针和序列探针D13S272(13q14．3)、ATM(11q23)等5种荧光素标记的DNA探针，对22例CLL患者进行FISH检测，并和常规细胞遗传学检测结果进行比较，以确定何种方法对检测CLL的染色体和基因组异常更为敏感可靠。结果 22例CLL患者中，常规细胞遗传学检测出8例(36．3％)有染色体异常，包括单纯 123例； 3、 12l例； 3、 12、 18 1例；t(5；15)1例；13q-1例；3q-、18p 1例；4q 和13q-1例；组合FISH检测出15例(68，1％)有染色体异常，包括 34例、 126例、 18l例、11q-6例、13q-8例。结论组合。FISH技术是检测CLL患者染色体基因组异常的有效手段，与常规细胞遗传学方法相结合则可明显提高CLL染色体异常的检出率。     

A case of chronic lymphocytic leukemia with a constitutional pericentric inversion of chromosome 1

Chronic lymphocytic leukemia (CLL) has been reported to be associated with various chromosomal aberrations, the most common being trisomy 12 and structural rearrangements involving 13q, 11q, and 17p. We present a case of CLL with a constitutional pericentric inversion of chromosome 1.     

Search for imprinted regions on chromosome 14: comparison of maternal and paternal UPD cases with cases of chromosome 14 deletion

Over the past few years, regions of genomic imprinting have been identified on a small number of chromosomes through a search for the etiology of various disorders. Distinct phenotypes have been associated with both maternal and paternal uniparental disomy (UPD) for chromosome 14. This observation indicates that there are imprinted genes present on chromosome 14, although none have been identified to date. In order to focus the search for imprinted genes on chromosome 14, we analyzed cases of maternal and paternal UPD 14 and compared them with cases of chromosome 14 deletions. Cases of paternal UPD were compared with maternal deletions and maternal UPD compared with paternal deletions. The paternal UPD anomalies seen in maternal deletion cases allowed us to associate the following features and chromosomal regions: Hirsute forehead: del(14)(q12q13. 3) and del(14)(q32); blepharophimosis: del(14)(q32); small thorax: del(14)(q11.2q13); and joint contractures: del(14)(q11.2q13) and del(14)(q31). Comparison of maternal UPD and paternal deletion cases revealed fleshy nasal tip to be most often associated with del(14)(q32), scoliosis with del(14) (q23q24.2), and del(14)(q32. 11qter) and small size at birth to be associated with del(14)(q11q13) and del(14)(q32). Our study, in conjunction with a prior study of UPD 14 and partial trisomy 14 cases, and what is known of imprinting in regions of mouse chromosomes homologous to human chromosome 14, leads us to conclude that 14q23-q32 is likely an area where imprinted genes may reside.     

Molecular cytogenetic parameters in fibroblasts of ataxia telangiectasia carrier

Ataxia telangiectasia (AT) is a pleiotropic and rare (1:40,000 to 1:100,000) recessive disease. Laboratory investigations have failed to detect any consistent anomaly in cells from AT heterozygotes. To estimate random aneuploidy, we applied a fluorescence in situ hybridization technique with alpha-satellite probes for chromosomes 8 and 9 and replication pattern for RB-1, HER-2/neu, and the imprinted SNRPN loci on primary AT carrier fibroblasts. Higher random aneuploidy was not found in the carrier fibroblasts compared to control amniocytic cells. The asynchrony pattern was higher in the AT carrier cells with the RB-1 locus (P=0.057) and significantly higher with the HER-2/neu locus (P < 0.001) compared to control cells. As for the imprinted locus SNRPN, there was a significantly lower asynchrony rate in the AT carriers (P < 10(-5)) compared to the control group. Molecular cytogenetic parameters of random aneuploidy and replication pattern may reflect predisposition for the development of cancer. It is possible that in some AT carriers the genetic instability phenomena associated with the abnormal replication pattern may represent their potential for developing malignancies.     

Prognostic relevance of monosomy at the 13q14 locus detected by fluorescence in situ hybridization in B-cell chronic lymphocytic leukemia

Deletion of the chromosome band 13q14, which contains the putative deleted in B-cell malignancy (DBM) gene, and trisomy 12 have been demonstrated by fluorescence in situ hybridization (FISH) techniques in malignant B-cells from patients with B cell chronic lymphocytic leukemia (B-CLL). However, the prognostic relevance of 13q14 abnormalities as detected by FISH is unknown. We prospectively studied malignant blood cells from 54 consecutive, untreated B-CLL patients using FISH probes to the RB1 locus and DBM (markers D13S25 and D13S319) for band 13q14, as well as probes to chromosome 12. The cells from all cases were CD5+ CD20+, expressed clonally restricted surface immunoglobulin light chain, and had typical features for B-CLL on careful blood smear morphologic evaluation. Patients were followed for a mean of 3.9 years and treatment-free survival (TFS) was used in the prognostic factor analysis. Twenty-four (44%) patients were observed to have monosomy of the RB1 locus and 26 (48%) monosomy of D13S25 and D13S319. The 26 patients who had a deletion at at least one of these loci had a 48.4 month (mo) median TFS vs 31.1 mo for those without evidence of deletion at any 13q14 locus (p = 0.07). The seven patients found to have trisomy 12 had a median TFS of 6.9 mo vs 39.3 mo for those diploid for chromosome 12 (p < 0.01). When these seven patients with trisomy 12 were excluded from the analysis, patients who had a deletion at 13q14 tended to have a longer median TFS (50.1 vs 36.2 mos), but this was not statistically significant (p = 0.2). This study confirms the prevalence of 13q14 deletions in B-CLL and suggests that patients with this abnormality have a better TFS than those with trisomy 12.     

Molecular cytogenetic abnormalities in patients with concurrent chronic lymphocytic leukemia and multiple myeloma shown by interphase fluorescence in situ hybridization: evidence of distinct clonal origin

The coexistence of chronic lymphocytic leukemia (CLL) and multiple myeloma (MM) is rare, and there is no consensus about the clonal relationship of the two disorders when they occur in the same individual. We investigated chromosomal abnormalities in two patients with concurrent CLL and MM using interphase fluorescence in situ hybridization (FISH) with a panel of region-specific DNA probes. In patient 1, the clonal plasma cells harbored IgH translocations (14q32); however, FISH with probes for the four most frequent IgH partner genes in MM (CCND1, FGFR3, MAF, and MYC) did not detect translocations involving any of them. The CLL cells were characterized by deletions of 13q14, 11q23, and 17p13, as well as trisomy 12, none of which were found in the MM cells. In patient 2, deletions of 13q14 and 17p13 were detected in CLL cells, but no cytogenetic abnormalities were found in the MM cells. Both patients had relapsed MM following chemotherapy and had autologous stem-cell transplant, whereas their CLL has been stable and not requiring treatment. Our results show that the cytogenetic profiles differ between CLL and MM within the same patients, and provide evidence for two distinct malignant clones in both patients.     

Genomic imprinting: potential function and mechanisms revealed by the Prader-Willi and Angelman syndromes

The Prader-Willi (PWS) and Angelman (AS) syndromes are two clinically distinct syndromes which result from lack of expression of imprinted genes within chromosome 15q11-q13. These two syndromes result from 15q11-q13 deletions, chromosome 15 uniparental disomy (UPD), imprinting centre mutations and, for AS, probable mutations in a single gene. The differential phenotype results from a paternal genetic deficiency in PWS patients and a maternal genetic deficiency in AS patients. Within 15q11-q13, four genes (SNRPN, IPW, ZNF127, FNZ127) and two expressed sequence tags (PAR1 and PAR5) have been found to be expressed only from the paternally inherited chromosome, and therefore all must be considered candidate genes involved in the pathogenesis of PWS. A candidate AS gene (UBE3A) has very recently been identified. The mechanisms of imprinted gene expression are not yet understood, but it is clear that DNA methylation is involved in both somatic cell expression and inheritance of the imprint. The presence of DNA methylation imprints that distinguish the paternally and maternally inherited alleles is a common characteristic of all known imprinted genes which have been studied extensively, including SNRPN and ZNF127. Recently, several PWS and AS patients have been found that have microdeletions in a region upstream of the SNRPN gene referred to as the imprinting centre, or IC. Paternal IC deletions in PWS patients and maternal IC deletions in AS patients result in uniparental DNA methylation and uniparental gene expression at biparentally inherited loci. The IC is a novel genetic element which controls initial resetting of the parental imprint in the germline for all imprinted gene expression over a 1.5-2.5 Mb region within chromosome 15q11-q13.      

Cytogenetyczne i molekularne uwarunkowania agresywnej postaci przewlekłej białaczki limfocytowej

Chronic lymphocytic leukemia (CLL) mainly affects people older than 60 years. Accumulation of morphologically mature but dysfunctional B-lymphocytes in the bone marrow, lymph nodes and peripheral blood is a characteristic feature of this disease. Chromosomal aberrations are observed in lymphocytes of most CLL patients. Typical alterations include deletions of 13q14 and 11q, trisomy 12, and deletions of 17p. Altered expression of the genes located within involved regions, i.e. microRNA15/16 (13q14.3), ATM (11q22-q23) or TP53 (17p13) may be associated with the development and progression of the disease. Cryptic mutations may also contribute to leukemogenesis. Among others, they affect TP53, NOTCH1, SF3B1 and BIRC genes.CLL is a disease with heterogeneous course. There are two clinical forms – indolent and aggressive. The former is characterized by long time to first treatment and demise usually occurs because of coexisting diseases or is associated with leukemia-dependent immunodeficiency. Rapid clinical course and short overall survival, sometimes in spite of appropriate treatment implementation, is typical for aggressive form of CLL. For patients with this form, the moment of treatment initiation and the choice of first-line therapy are especially important, and depend inter alia on prognostic and predictive factors.Established poor prognostic factors in CLL include chromosomal aberrations, i.e., deletion of 17p or 11q, high ZAP-70 kinase expression, mutations/deletions of TP53, and lack of mutation of immunoglobulin heavy chain variable region genes (IgVH).In this paper we tried to point out the importance of some of the prognostic and predictive factors used routinely in the diagnostic management of CLL. Prognostic and predictive potential of microRNA expression level and recently described cryptic changes in the TP53, NOTCH1, SF3B1 and BIRC3 have also been presented.