MTAP-related increased erythroblast proliferation as a mechanism of polycythaemia vera

Polycythaemia vera (PV) is a haematological disorder caused by an overproduction of erythroid cells. To date, the molecular mechanisms involved in the disease pathogenesis are still ambiguous. This study aims to identify aberrantly expressed proteins in erythroblasts of PV patients by utilizing mass spectrometry-based proteomic analysis. Haematopoietic stem cells (HSCs) were isolated from newly-diagnosed PV patients, PV patients who have received cytoreductive therapy, and healthy subjects. In vitro erythroblast expansion confirmed that the isolated HSCs recapitulated the disease phenotype as the number of erythroblasts from newly-diagnosed PV patients was significantly higher than those from the other groups. Proteomic comparison revealed 17 proteins that were differentially expressed in the erythroblasts from the newly-diagnosed PV patients compared to those from healthy subjects, but which were restored to normal levels in the patients who had received cytoreductive therapy. One of these proteins was S-methyl-5′-thioadenosine phosphorylase (MTAP), which had reduced expression in PV patients’ erythroblasts. Furthermore, MTAP knockdown in normal erythroblasts was shown to enhance their proliferative capacity. Together, this study identifies differentially expressed proteins in erythroblasts of healthy subjects and those of PV patients, indicating that an alteration of protein expression in erythroblasts may be crucial to the pathology of PV

cel-mir-237 and its homologue, hsa-miR-125b, modulate the cellular response to ionizing radiation.

Elucidating the mechanisms involved in sensitizing radioresistant tumors to ionizing radiation (IR) treatments while minimizing injury to surrounding normal tissue is an important clinical goal. Due to their sequence-derived specificity and properties as gene regulators in IR-affected pathways, microRNAs (miRNAs) could serve as adjuvant therapeutic agents that alter cellular sensitivity to radiation treatment. To identify radiosensitizing miRNAs, we initially utilized the Caenorhabditis elegans vulval cell model, an in vivo system developed to study IR-dependent radiosensitivity as a measure of clonogenic cell death. We tested several candidate miRNA-deletion mutants post γ-irradiation and identified cel-mir-237 as a miRNA which when deleted caused animals to be more resistant to IR, whereas cel-mir-237 overexpressing strains were IR sensitive. In addition, wild-type animals downregulated cel-mir-237 levels post IR in a time-dependent manner. We identified jun-1 (JUN transcription factor homolog) as a novel target of cel-mir-237. Specifically, jun-1 transcript levels increased in wild-type animals post γ-irradiation, and loss of cel-mir-237 also resulted in higher jun-1 expression. As expected, loss of jun-1 resulted in IR sensitivity, similar to the phenotype of cel-mir-237 overexpressors. As miR-237 is the homolog of human miR-125, we validated our findings in MCF-7 and MDA-MB-231 breast cancer cell lines, which harbor lower hsa-miR-125b levels than normal human mammary epithelial cells (HMECs). Forced expression of hsa-miR-125b in these cells resulted in radiosensitivity, as seen by reduced clonogenic survival, enhanced apoptotic activity and enhanced senescence post IR. Finally, re-expression of c-JUN in MDA-MB-231 cells promoted radioresistance and abrogated miR-125-mediated radiosensitization. Our findings suggest that overexpression of cel-mir-237 and its homolog, hsa-miR-125b, functions as sensitizers to γ-irradiation in both a nematode in vivo model and breast cancer cells, and could potentially be utilized as an adjuvant therapeutic to enhance radiation sensitivity

cel-mir-237 and its homologue, hsa-miR-125b, modulate the cellular response to ionizing radiation.

Elucidating the mechanisms involved in sensitizing radioresistant tumors to ionizing radiation (IR) treatments while minimizing injury to surrounding normal tissue is an important clinical goal. Due to their sequence-derived specificity and properties as gene regulators in IR-affected pathways, microRNAs (miRNAs) could serve as adjuvant therapeutic agents that alter cellular sensitivity to radiation treatment. To identify radiosensitizing miRNAs, we initially utilized the Caenorhabditis elegans vulval cell model, an in vivo system developed to study IR-dependent radiosensitivity as a measure of clonogenic cell death. We tested several candidate miRNA-deletion mutants post γ-irradiation and identified cel-mir-237 as a miRNA which when deleted caused animals to be more resistant to IR, whereas cel-mir-237 overexpressing strains were IR sensitive. In addition, wild-type animals downregulated cel-mir-237 levels post IR in a time-dependent manner. We identified jun-1 (JUN transcription factor homolog) as a novel target of cel-mir-237. Specifically, jun-1 transcript levels increased in wild-type animals post γ-irradiation, and loss of cel-mir-237 also resulted in higher jun-1 expression. As expected, loss of jun-1 resulted in IR sensitivity, similar to the phenotype of cel-mir-237 overexpressors. As miR-237 is the homolog of human miR-125, we validated our findings in MCF-7 and MDA-MB-231 breast cancer cell lines, which harbor lower hsa-miR-125b levels than normal human mammary epithelial cells (HMECs). Forced expression of hsa-miR-125b in these cells resulted in radiosensitivity, as seen by reduced clonogenic survival, enhanced apoptotic activity and enhanced senescence post IR. Finally, re-expression of c-JUN in MDA-MB-231 cells promoted radioresistance and abrogated miR-125-mediated radiosensitization. Our findings suggest that overexpression of cel-mir-237 and its homolog, hsa-miR-125b, functions as sensitizers to γ-irradiation in both a nematode in vivo model and breast cancer cells, and could potentially be utilized as an adjuvant therapeutic to enhance radiation sensitivity

Chromosomal Locations of Quantitative Trait Loci (QTL) for Natural Variation in Petal Form in <i>Arabidopsis thaliana</i>.

<p>The chromosomal location of identified QTLs is shown on the five <i>Arabidopsis</i> chromosomes. The location of several known floral or growth regulatory genes are indicated and the centromeres marked as open circles. QTLs identified using Columbia (Col-4)×Landsberg <i>erecta</i> (L<i>er</i>) recombinant inbred lines are shown in black and named <i>CL</i>, and those identified from Columbia (Col-0)×Estland (Est) recombinant inbred lines are shown in white and named <i>CE</i>. Each QTL is indicated by a shape, with the extent of the shape indicating the 1-LOD support interval: triangle (area), rectangle (length), diamond (width), or oval (shape) and named as A, L, W, or S, respectively. The location of each QTL peak is marked with a black horizontal line and the 2-LOD support interval boundary is indicated by arrows. Where the 1-LOD and 2-LOD boundaries are the same for a QTL, no arrows are marked. Adjacent to each QTL the Percentage of Variance Explained (PVE) is noted.</p

Natural Variation Identifies Multiple Loci Controlling Petal Shape and Size in <em>Arabidopsis thaliana</em>

<div><p>Natural variation in organ morphologies can have adaptive significance and contribute to speciation. However, the underlying allelic differences responsible for variation in organ size and shape remain poorly understood. We have utilized natural phenotypic variation in three <em>Arabidopsis thaliana</em> ecotypes to examine the genetic basis for quantitative variation in petal length, width, area, and shape. We identified 23 loci responsible for such variation, many of which appear to correspond to genes not previously implicated in controlling organ morphology. These analyses also demonstrated that allelic differences at distinct loci can independently affect petal length, width, area or shape, suggesting that these traits behave as independent modules. We also showed that <em>ERECTA</em> (<em>ER</em>), encoding a leucine-rich repeat (LRR) receptor-like serine-threonine kinase, is a major effect locus determining petal shape. Allelic variation at the <em>ER</em> locus was associated with differences in petal cell proliferation and concomitant effects on petal shape. <em>ER</em> has been previously shown to be required for regulating cell division and expansion in other contexts; the <em>ER</em> receptor-like kinase functioning to also control organ-specific proliferation patterns suggests that allelic variation in common signaling components may nonetheless have been a key factor in morphological diversification.</p> </div

<i>ERECTA</i> Corresponds to the Petal Shape Quantitative Trait Locus (QTL) <i>CL-S1</i> on Chromosome II.

<p>(<b>A</b>) Chromosome II diagram showing introgression lines and mutants used for QTL fine mapping. The Stepped Aligned Inbred Recombinant Strain (STAIRS) introgression lines are numbered and their L<i>er</i> -0 introgressions are drawn to scale in black and the otherwise entirely Columbia (Col-4) background is shown in white. The location of the <i>CL-S1</i> 2-LOD interval is drawn to scale with the boundaries marked as black horizontal lines, and the <i>er</i> mutants used, such as <i>er-105</i>, have an <i>er</i> mutation in an otherwise entirely Columbia (Col-0) background (apart from L<i>er</i>-0 which is an <i>er</i> mutant in a Landsberg background). (<b>B</b>) Histogram showing shape measurements of stage 13 petals using STAIRS, natural isolates, and <i>er</i> mutants. Error bars indicate 95% confidence intervals. For each line a minimum of 20 petals were scored. (<b>C</b>) Stage 13 representative petal images. Scale bar = 1 mm.</p