Project description:Background: The halophyte Mesembryanthemum crystallinum (ice plant) is a model for studying salt tolerance. The morphology, physiology, metabolism, and gene expression of ice plant have been studied for over 40 years. Although the complete genome sequence has not been revealed, large-scale analyses of gene expression profiling have drawn an outline of salt tolerance in ice plant. Despite ample information in the transcriptome, miRNA information has not been documented. Results: We examined responses to a sudden increase in salinity in ice plant seedlings. Using a fluorescent dye to detect Na+, we found that ice plant roots respond to an increased flux of Na+ by either secreting or storing Na+ in specialized cells. High-throughput sequencing was used to identify small RNA profiles in three-day-old seedlings treated with or without 200 mM NaCl. Totally 132 conserved miRNAs belonging to 22 families were found. The hairpin precursor of 19 conserved mcr-miRNAs and 12 novel mcr-miRNAs were identified. Target genes are involved in a broad range of biological processes: transcription factors that regulate growth and development, enzymes that catalyze miRNA biogenesis for the most conserved mcr-miRNA, and proteins that are involved in ion homeostasis and drought-stress responses for some novel mcr-miRNAs. After 6 h of salt stress, the expressions of most mcr-miRNAs were down-regulated, whereas the expressions of their corresponding target genes were up-regulated. Analyses of the functions of target genes revealed that cellular processes, including growth and development, metabolism, and ion transport activity were up-regulated in roots under salt stress. Conclusions: Analyses of small RNA profile of ice plant seedlings identified many conserved miRNA families and several novel miRNAs. The expression of ten conserved miRNAs and three novel miRNAs were reciprocally correlated to predicted targets hourly after salt stress. Based on the expression pattern of miRNA and target genes in combination with the observation of Na+ distribution, we suggest that ice plant roots respond effectively to increased salinity by using Na+ as an osmoticum for cell expansion and guard cell opening. Excessive Na+ could either be secreted through root epidermis or stored in specialized leaf epidermal cells. These responses are partially regulated at the miRNA-mediated post-transcriptional level.

Project description:Therapy-related acute myeloid leukemia (t-AML) is a severe complication of the cytotoxic therapy used for primary cancer treatment. The outcome of these patients is poor compared to people who develop de novo acute myeloid leukemia (p-AML). Chromosome abnormalities in t-AML are partly dependent on the induction agent. Partial or total losses of chromosome 5 and/or 7 are observed after therapy with alkylating agents. Balanced translocations, most of which involve 11q23 with MLL rearrangement, are found after treatment with the topoisomerase II inhibitor. Complex cases are also more frequent. The aim of this study was to compare t-AML to p-AML using high-resolution array CGH in order to identify gene-specific copy number abnormalities (CNA). Thirty t-AML versus thirty-six p-AML patient samples were studied. In t-AML, 99 CNAs were observed with 63 losses and 36 gains while the mean number was 3,3 per case. In p-AML, 64 CNAs were observed with 30 losses and 34 gains with a mean number of 1.78 per case. A few very complex cases (>8 chromosomal abnormalities) contributed considerably to the chromosomal burden in p-AML. Several minimal critical regions (MCR) that contain proteins and microRNA genes implicated in leukemogenesis were found in t-AML. On 7p15.2, a HOXA gene cluster involved in the processes of hematopoietic progenitor cell development and leukemogenesis was recurrently gained. Loss of a 5 Mb MCR located on 5q31.3q32 (142,91-148,19 Mb) was found distal to a previously described MCR; it harbored 29 genes. A 40kb deleted MCR pointed to RUNX1 on 21q22, a gene coding for a transcription factor implicated in frequent rearrangements in leukemia and in familial thrombocytopenia with susceptibility to AML. The sequence revealed no abnormality in 3 patients and a mutation in one patient, resulting in complete deficiency of RUNX1. In de novo AML a gain of 21q22<38,41-39,36> harboring ERG and ETS2 was observed in two patients with very complex rearrangements.

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