Diaphragm muscle weakness in mice is early-onset post-myocardial infarction and associated with elevated protein oxidation.

Heart failure induced by myocardial infarction (MI) causes diaphragm muscle weakness, with elevated oxidants implicated. We aimed to determine whether diaphragm muscle weakness is 1) early-onset post-MI (i.e., within the early left ventricular remodeling phase of 72 h); and 2) associated with elevated protein oxidation. Ligation of the left coronary artery to induce MI (n = 10) or sham operation (n = 10) was performed on C57BL6 mice. In vitro contractile function of diaphragm muscle fiber bundles was assessed 72 h later. Diaphragm mRNA and protein expression, enzyme activity, and individual carbonylated proteins (by two-dimensional differential in-gel electrophoresis and mass spectrometry) were subsequently assessed. Infarct size averaged 57 ± 1%. Maximal diaphragm function was reduced (P < 0.01) by 20% post-MI, with the force-frequency relationship depressed (P < 0.01) between 80 and 300 Hz. The mRNA expression of inflammation, atrophy, and regulatory Ca(2+) proteins remained unchanged post-MI, as did the protein expression of key contractile proteins. However, enzyme activity of the oxidative sources NADPH oxidase and xanthine oxidase was increased (P < 0.01) by 45 and 33%, respectively. Compared with sham, a 57 and 45% increase (P < 0.05) was observed in the carbonylation of sarcomeric actin and creatine kinase post-MI, respectively. In conclusion, diaphragm muscle weakness was rapidly induced in mice during the early left ventricular remodeling phase of 72 h post-MI, which was associated with increased oxidation of contractile and energetic proteins. Collectively, these findings suggest diaphragm muscle weakness may be early onset in heart failure, which is likely mediated in part by posttranslational oxidative modifications at the myofibrillar level.

Novel CHD7 mutations contributing to the mutation spectrum in patients with CHARGE syndrome.

CHARGE syndrome is an autosomal dominant inherited multiple malformation disorder typically characterized by coloboma, choanal atresia, hypoplastic semicircular canal, cranial nerve defects, cardiovascular malformations and ear abnormalities. Mutations in the chromodomain helicase DNA-binding protein 7 (CHD7) gene are the major cause of CHARGE syndrome. Mutation analysis was performed in 18 patients with firm or tentative clinical diagnosis of CHARGE syndrome. In this study eight mutations distributed across the gene were found. Five novel mutations - one missense (c.2936T > C), one nonsense (c.8093C > A) and three frameshift mutations (c.804_805insAT, c.1757_1770del14, c.1793delA) - were identified. As far as familial data were available these mutations were found to have arisen de novo. Comparison of the clinical features of patients with the same mutation demonstrates that expression of the phenotype is highly variable. The mutation detection rate in this study was 44.4% in patients with a clinically established or suspected diagnosis of CHARGE syndrome.

Clonal heterogeneity in childhood myelodysplastic syndromes--challenge for the detection of chromosomal imbalances by array-CGH.

To evaluate whether copy number alterations (CNAs) are present that may contribute to disease development and/or progression of childhood myelodysplastic syndromes (MDS), 36 pediatric MDS patients were analyzed using array-based comparative genome hybridization (aCGH). In addition to monosomy 7, the most frequent chromosome aberration in childhood MDS, novel recurrent CNAs were detected. They included a loss of 3p14.3-p12.3, which contains the putative tumor suppressor gene FHIT, a loss of 7p21.3-p15.3, a loss of 9q33.3-q34.3 (D184) and microdeletions in 17p11.2, 6q23 containing MYB, and 17p13 containing TP53. In this small patient cohort, patients without CNA, patients with monosomy 7 only and patients with one CNA in addition to monosomy 7 did not differ in their survival. As expected, all patients with complex karyotypes, including two patients with deletions of TP53, died. A challenge inherent to aCGH analysis of MDS is the low percentage of tumor cells. We evaluated several approaches to overcome this limitation. Genomic profiles from isolated granulocytes were of higher quality than those from bone marrow mononuclear cells. Decreased breakpoint calling stringency increased recognition of CNAs present in small clonal populations. However, further analysis using a custom-designed array showed that these CNAs often did not confirm the findings from 244k arrays. In contrast, constitutional CNVs were reliably detected on both arrays. Moreover, aCGH on amplified DNA from distinct myeloid clusters is a new approach to determine CNAs in small subpopulations. Our results clearly emphasize the need to verify array-CGH results by independent methods like FISH or quantitative PCR.

Large-scale mapping of mutations affecting zebrafish development.

BACKGROUND: Large-scale mutagenesis screens in the zebrafish employing the mutagen ENU have isolated several hundred mutant loci that represent putative developmental control genes. In order to realize the potential of such screens, systematic genetic mapping of the mutations is necessary. Here we report on a large-scale effort to map the mutations generated in mutagenesis screening at the Max Planck Institute for Developmental Biology by genome scanning with microsatellite markers. RESULTS: We have selected a set of microsatellite markers and developed methods and scoring criteria suitable for efficient, high-throughput genome scanning. We have used these methods to successfully obtain a rough map position for 319 mutant loci from the Tübingen I mutagenesis screen and subsequent screening of the mutant collection. For 277 of these the corresponding gene is not yet identified. Mapping was successful for 80 % of the tested loci. By comparing 21 mutation and gene positions of cloned mutations we have validated the correctness of our linkage group assignments and estimated the standard error of our map positions to be approximately 6 cM. CONCLUSION: By obtaining rough map positions for over 300 zebrafish loci with developmental phenotypes, we have generated a dataset that will be useful not only for cloning of the affected genes, but also to suggest allelism of mutations with similar phenotypes that will be identified in future screens. Furthermore this work validates the usefulness of our methodology for rapid, systematic and inexpensive microsatellite mapping of zebrafish mutations.

Effects of telomerase modulation in human hematopoietic progenitor cells.

Loss of telomeric repeats has been causally linked to replicative senescence and aging in human cells. In contrast to normal somatic cells, which are telomerase-negative, hematopoietic stem cells have low levels of telomerase, which can be transiently upregulated upon cytokine stimulation. To examine whether ectopic expression of telomerase can overcome telomere erosion in hematopoietic progenitor cells, we overexpressed telomerase in CD34+ and AC133+ cord blood (CB) cells using retroviral vectors containing hTERT, the catalytic component of telomerase. Although the hTERT-transduced CB cells exhibited significantly elevated telomerase activity (approximately 10-fold), the mean telomere length was only increased up to 600 bp, which was in contrast to hTERT-transduced fibroblast cells gaining more than 2-kb telomeric repeats. Moreover, ectopic telomerase activity did not prevent overall telomere shortening, which was in the range of 1.3 kb in serum-free expansion culture. We also blocked endogenous telomerase activity by ectopic expression of dominant-negative hTERT. Whereas CB cells with absent telomerase activity showed reduced absolute numbers of colony-forming cells, we observed increased rates only for burst-forming units erythroid when the enzyme was overexpressed. These results suggest that telomere shortening in human hematopoietic progenitor cells cannot be compensated by increased levels of telomerase alone and is likely to be dependent on other factors, such as telomere binding proteins. Furthermore, telomerase function seems to be directly associated with the proliferative capacity of stem cells and may exert an additional role in lineage differentiation.