Bag of Marbles controls the size and organization of the Drosophila hematopoietic niche through interactions with the Insulin-like growth factor pathway and Retinoblastoma-family protein.

Bag of Marbles (Bam) is known to function as a positive regulator of hematopoietic progenitor maintenance in the lymph gland blood cell-forming organ during Drosophila hematopoiesis. Here, we demonstrate a key function for Bam in cells of the lymph gland posterior signaling center (PSC), a cellular domain proven to function as a hematopoietic niche. Bam is expressed in PSC cells, and gene loss-of-function results in PSC overgrowth and disorganization, indicating that Bam plays a crucial role in controlling the proper development of the niche. It was previously shown that Insulin receptor (InR) pathway signaling is essential for proper PSC cell proliferation. We analyzed PSC cell number in lymph glands double-mutant for bam and InR pathway genes, and observed that bam genetically interacts with pathway members in the formation of a normal PSC. The elF4A protein is a translation factor downstream of InR pathway signaling, and functional knockdown of this crucial regulator rescued the bam PSC overgrowth phenotype, further supporting the cooperative function of Bam with InR pathway members. Additionally, we documented that the Retinoblastoma-family protein (Rbf), a proven regulator of cell proliferation, was present in cells of the PSC, with a bam function-dependent expression. By contrast, perturbation of Decapentaplegic or Wingless signaling failed to affect Rbf niche cell expression. Together, these findings indicate that InR pathway-Bam-Rbf functional interactions represent a newly identified means to regulate the correct size and organization of the PSC hematopoietic niche.

Germ line differentiation factor Bag of Marbles is a regulator of hematopoietic progenitor maintenance during Drosophila hematopoiesis.

Bag of Marbles (Bam) is a stem cell differentiation factor in the Drosophila germ line. Here, we demonstrate that Bam has a crucial function in the lymph gland, the tissue that orchestrates the second phase of Drosophila hematopoiesis. In bam mutant larvae, depletion of hematopoietic progenitors is observed, coupled with prodigious production of differentiated hemocytes. Conversely, forced expression of Bam in the lymph gland results in expansion of prohemocytes and substantial reduction of differentiated blood cells. These findings identify Bam as a regulatory protein that promotes blood cell precursor maintenance and prevents hemocyte differentiation during larval hematopoiesis. Cell-specific knockdown of bam function via RNAi expression revealed that Bam activity is required cell-autonomously in hematopoietic progenitors for their maintenance. microRNA-7 (mir-7) mutant lymph glands present with phenotypes identical to those seen in bam-null animals and mutants double-heterozygous for bam and mir-7 reveal that the two cooperate to maintain the hematopoietic progenitor population. By contrast, analysis of yan mutant lymph glands revealed that this transcriptional regulator promotes blood cell differentiation and the loss of prohemocyte maintenance. Expression of Bam or mir-7 in hematopoietic progenitors leads to a reduction of Yan protein. Together, these results demonstrate that Bam and mir-7 antagonize the differentiation-promoting function of Yan to maintain the stem-like hematopoietic progenitor state during hematopoiesis.

Antioxidant supplementation prevents exercise-induced lipid peroxidation, but not inflammation, in ultramarathon runners.

To determine if 6 weeks of supplementation with vitamins E and C could alleviate exercise-induced lipid peroxidation and inflammation, we studied 22 runners during a 50 km ultramarathon. Subjects were randomly assigned to one of two groups: (1) placebos (PL) or (2) antioxidants (AO: 1000 mg vitamin C and 300 mg RRR-alpha-tocopheryl acetate). Blood samples were obtained prior to supplementation (baseline), after 3 weeks of supplementation, 1 h pre-, mid-, and postrace, 2 h postrace and for 6 days postrace. Plasma levels of alpha-tocopherol (alpha-TOH), ascorbic acid (AA), uric acid (UA), F2-isoprostanes (F2-IsoPs), tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and C-reactive protein (CRP) were measured. With supplementation, plasma alpha-TOH and AA increased in the AO but not the PL group. Although F2-IsoP levels were similar between groups at baseline, 28 +/- 2 (PL) and 27 +/- 3 pg/ml (AO), F2-IsoPs increased during the run only in the PL group (41 +/- 3 pg/ml). In PL women, F2-IsoPs were elevated postrace (p <.01), but returned to prerace concentrations by 2 h postrace. In PL men, F2-IsoP concentrations were higher postrace, 2 h postrace, and 1, 2, 3, 4, and 6 days postrace (PL vs. AO group, each p <.03). Markers of inflammation were increased dramatically in response to the run regardless of treatment group. Thus, AO supplementation prevented endurance exercise-induced lipid peroxidation but had no effect on inflammatory markers.