Podcasts about meis1

Chromosomal translocations are common in human leukemias. Detailed studies of chromosomal translocation have been useful in understanding the pathogenesis and identifying therapeutic targets in hematologic malignancies. Some translocations result in the formation of fusion genes. These fusion proteins play an important role in leukemogenesis. The t(10;11)(p12;q14) translocation is rare but recurring and results in the formation of the CALM/AF10 fusion protein. Patients with this translocation have a bad prognosis. To understand how CALM/AF10 leads to leukemia, various mouse models have been established. In a murine bone marrow retroviral transduction and transplantation model Deshpande et al. (2006) showed that mice expressing CALM/AF10 in their bone marrow cells developed an acute myeloid leukemia with a penetrance of 100% and a short latency period of 110 days. Using a transgenic mouse model, in which CALM/AF10 was under the control of Vav promoter, Peter Aplan and colleagues demonstrated that only 40% to 50% of mice developed leukemia after a long latency of 10 to 12 months. Two classical transgenic CALM/AF10 models were established in our group using the immunoglobulin heavy chain enhancer/promoter (IgH-CALM/AF10) and proximal murine LcK promoter (pLck-CALM/AF10) to drive CALM/AF10 expression. These transgenic mice did not show any leukemic phenotype even after an observation period of 15 months. Taken together these studies strongly suggest that additional collaborating factors are required for the CALM/AF10 fusion gene to induce leukemia. Meis1, a Hox cofactor, is known to collaborate with several Hox genes and Hox fusion genes such as HOXA9 and NUP98-HOXD13. In these studies, Meis1 played a critical role in accelerating the development of leukemia. It could also be shown that MEIS1 is highly expressed in CALM/AF10 positive human leukemia cells. Therefore, I sought to determine whether the homeobox gene Meis1 collaborates with CALM/AF10 in inducing leukemia. In order to achieve this goal, lethally irradiated non-transgenic mice were transplanted with IgH-CALM/AF10 transgenic bone marrow cells transduced with a Meis1 expressing retrovirus. The transplanted mice developed an acute leukemia with a penetrance of 100% and a median latency period of 187 days. The leukemia showed predominantly myeloid features such as the presence of myeloid marker positive cells. The myeloid blast cells infiltrated in multiple hematopoietic as well as non-hematopoietic organs. The leukemic cells were also positive for the B-cell marker B220. Cells that were positive for both lymphoid and myeloid markers, a characteristic feature of CALM/AF10-induced leukemia, were also detected in all the mice. The leukemic cells had clonal DJH rearrangements. Overall, these data suggest that the transformed cell might be an early progenitor cell capable of lymphoid as well as myeloid differentiation or that the leukemia was initiated by a B220+ IgH DJ rearranged cell with blocked lymphoid differentiation, which started a default myeloid differentiation program. By performing serial secondary and tertiary transplantations the leukemic nature of the disease could be confirmed. Colony forming cell assays showed that CALM/AF10 in collaboration with Meis1 failed to induce the transformation of hematopoietic progenitors in vitro. This could either be due to the lack of required growth factors and conditions necessary for the proliferation of the transformable cell or lack of additional events essential for progression towards leukemia development. In conclusion, I have demonstrated that Meis1 collaborates with CALM/AF10 in inducing acute myeloid leukemia. Additional, detailed analyses of the leukemia initiating cell in these models would help to better understand the pathogenesis of CALM/AF10-induced leukemia.

Restless legs syndrome (RLS) is a sleep related movement disorder that occurs both in an idiopathic form and in symptomatic varieties. RLS is a frequent and distressing comorbidity in end stage renal disease (ESRD). For idiopathic RLS (iRLS), genetic risk factors have been identified, but their role in RLS in ESRD has not been investigated yet. Therefore, a case-control association study of these variants in ESRD patients was performed.

The PR interval on the electrocardiogram reflects atrial and atrioventricular nodal conduction time. The PR interval is heritable, provides important information about arrhythmia risk, and has been suggested to differ among human races. Genome-wide association (GWA) studies have identified common genetic determinants of the PR interval in individuals of European and Asian ancestry, but there is a general paucity of GWA studies in individuals of African ancestry. We performed GWA studies in African American individuals from four cohorts (n = 6,247) to identify genetic variants associated with PR interval duration. Genotyping was performed using the Affymetrix 6.0 microarray. Imputation was performed for 2.8 million single nucleotide polymorphisms (SNPs) using combined YRI and CEU HapMap phase II panels. We observed a strong signal (rs3922844) within the gene encoding the cardiac sodium channel (SCN5A) with genome-wide significant association (p < 2.5 > 10(-8)) in two of the four cohorts and in the meta-analysis. The signal explained 2% of PR interval variability in African Americans (beta = 5.1 msec per minor allele, 95% CI = 4.1-6.1, p = 3 x 10(-23)). This SNP was also associated with PR interval (beta = 2.4 msec per minor allele, 95% CI = 1.8-3.0, p = 3 x 10(-16)) in individuals of European ancestry (n = 14,042), but with a smaller effect size (p for heterogeneity < 0.001) and variability explained (0.5%). Further meta-analysis of the four cohorts identified genome-wide significant associations with SNPs in SCN10A (rs6798015), MEIS1 (rs10865355), and TBX5 (rs7312625) that were highly correlated with SNPs identified in European and Asian GWA studies. African ancestry was associated with increased PR duration (13.3 msec, p = 0.009) in one but not the other three cohorts. Our findings demonstrate the relevance of common variants to African Americans at four loci previously associated with PR interval in European and Asian samples and identify an association signal at one of these loci that is more strongly associated with PR interval in African Americans than in Europeans.

Background: Restless legs syndrome (RLS) is associated with common variants in three intronic and intergenic regions in MEIS1, BTBD9, and MAP2K5/LBXCOR1 on chromosomes 2p, 6p and 15q.Methods: Our study investigated these variants in 649 RLS patients and 1230 controls from the Czech Republic (290 cases and 450 controls), Austria (269 cases and 611 controls) and Finland (90 cases and 169 controls). Ten single nucleotide polymorphisms (SNPs) within the three genomic regions were selected according to the results of previous genome-wide scans. Samples were genotyped using Sequenom platforms.Results: We replicated associations for all loci in the combined samples set (rs2300478 in MEIS1, p = 1.26×10-5, odds ratio (OR) = 1.47, rs3923809 in BTBD9, p = 4.11×10-5, OR = 1.58 and rs6494696 in MAP2K5/LBXCOR1, p = 0.04764, OR = 1.27). Analysing only familial cases against all controls, all three loci were significantly associated. Using sporadic cases only, we could confirm the association only with BTBD9.Conclusion: Our study shows that variants in these three loci confer consistent disease risks in patients of European descent. Among the known loci, BTBD9 seems to be the most consistent in its effect on RLS across populations and is also most independent of familial clustering.

The t(10;11)(p13;q14) is a recurring translocation resulting in the fusion of the CALM and AF10 genes. The leukemogenic CALM/AF10 fusion genes codes for a 1595 amino acids protein. This translocation was first identified in a patient with hystiocytic lymphoma and was subsequently found in patients with AML, T-ALL and malignant lymphoma. This translocation is found in younger patients and is associated with a poor prognosis. The CALM/AF10-associated leukemias can exhibit myeloid, lymphoid or mixed lymphoid-meyloid features, indicating a stem cell or an early commited progenitor as the target cell of leukemic transformation. At the present time the target cells in CALM/AF10-associated leukemogenesis are unknown. It is also not known which target genes are up or downregulated by the presence of the CALM/AF10 fusion protein. To answer these questions, the following experiments were performed: 1) Five transgenic mouse lines, two expressing CALM/AF10 under the control of the immunoglobulin heavy chain enhancer promoter and three under the control of the murine proximal Lck promoter were generated. Although the CALM/AF10 expression was confirmed to be present and specific to the cells targeted by the promoters used (B- and T-cell progenitors for IgH and Lck promoters, respectively), the transgenic animals did not show a phenotype that could be detected after meticulous clinical, haematological, immunological, flow cytometrical and immunohistopatological analysis . 2) We performed molecular characterization of several CALM/AF10 patient samples: A group of 13 patients with different types of leukemia: case 1 (AML M2), case 2 (Acute Biphetnotypic leukemia), case 3 (Pre T-ALL), case 4 (Acute Undifferentiated Leukemia), case 5 (PreT-ALL), cases 6 and 7 (ProT-ALL), case 8 (T-ALL), case 9 (AML), case 14 (T-ALL), case 15, 16 and 17 (AML) with a t(10;11) translocation detected by cytogenetic analysis suggesting a CALM/AF10-rearrangement. The samples were analyzed for the presence of the CALM/AF10 and AF10/CALM fusion transcripts by RT-PCR and sequence analysis. All these patients were found to be positive for the CALM/AF10 fusion. In addition, we analyzed a series of twenty-nine patients with T-ALL with T-cell receptor ≥¥ rearrangement. Among these patients, four (case 10 to 13) were positive for the CALM/AF10 fusion transcript, indicating a high incidence of CALM/AF10 fusions in this group of leukemia. Three different breakpoints in CALM at nucleotide 1926, 2091 and a new exon, with 106 bases inserted after nt 2064 of CALM in patient 4 were found. In AF10 four breakpoints were identified: at nucleotide position 424, 589, 883 and 979. In patient 16 we found an extra exon before nt 424 of AF10. In seven patients it was also possible to amplify the reciprocal AF10/CALM fusion transcript (case 1, 3, 4, 8, 9, 10 and 14). There was no correlation between disease phenotype and breakpoint location. Ten CALM/AF10 positive patients were analyzed using oligonucleotide microarrays representing 33,000 different genes (U133 set, Affymetrix). Analysis of microarray gene expression signatures of these patients revealed high expression levels of the polycomb group gene BMI1, the homeobox gene MEIS1 and the HOXA cluster genes HOXA1, HOXA4, HOXA5, HOXA7, HOXA9, and HOXA10. The overexpression of HOX genes seen in these CALM/AF10 positive leukemias is reminiscent to the pattern seen in leukemias with rearrangements of the MLL gene, normal karyotypes and complex aberrant karyotypes suggesting a common effector pathway (i.e. HOX gene deregulation) for these diverse leukemias. In addition, the general pattern of gene expression of CALM/AF10 patients when compared to other leukemia subtypes and to normal bone marrow was dominated by a global downregulation of genes some of them with function identified as related to important molecular mechanisms, such as membrane trafficking, cell growth regulation, proliferation, differentiation and tumor suppression. 3) We cloned CALM/AF10 fusion gene into a vector that allowed us to induce the expression of CALM/AF10 using doxycycline in transiently and stably-transfected NIH3T3 and HEK293 cells. This system will be an important tool to identify direct CALM/AF10 target genes and to answer the question whether continued CALM/AF10 expression is necessary to maintain the CALM/AF10-associated expression pattern.