The regulation of mitochondrial DNA copy number in glioblastoma cells

As stem cells undergo differentiation, mitochondrial DNA (mtDNA) copy number is strictly regulated in order that specialized cells can generate appropriate levels of adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS) to undertake their specific functions. It is not understood whether tumor-initiating cells regulate their mtDNA in a similar manner or whether mtDNA is essential for tumorigenesis. We show that human neural stem cells (hNSCs) increased their mtDNA content during differentiation in a process that was mediated by a synergistic relationship between the nuclear and mitochondrial genomes and results in increased respiratory capacity. Differentiating multipotent glioblastoma cells failed to match the expansion in mtDNA copy number, patterns of gene expression and increased respiratory capacity observed in hNSCs. Partial depletion of glioblastoma cell mtDNA rescued mtDNA replication events and enhanced cell differentiation. However, prolonged depletion resulted in impaired mtDNA replication, reduced proliferation and induced the expression of early developmental and pro-survival markers including POU class 5 homeobox 1 (OCT4) and sonic hedgehog (SHH). The transfer of glioblastoma cells depleted to varying degrees of their mtDNA content into immunocompromised mice resulted in tumors requiring significantly longer to form compared with non-depleted cells. The number of tumors formed and the time to tumor formation was relative to the degree of mtDNA depletion. The tumors derived from mtDNA depleted glioblastoma cells recovered their mtDNA copy number as part of the tumor formation process. These outcomes demonstrate the importance of mtDNA to the initiation and maintenance of tumorigenesis in glioblastoma multiforme.     

Lactoferricin mediates anti‐inflammatory and anti‐catabolic effects via inhibition of IL‐1 and LPS activity in the intervertebral disc

The catabolic cytokine interleukin‐1 (IL‐1) and endotoxin lipopolysaccharide (LPS) are well‐known inflammatory mediators involved in degenerative disc disease, and inhibitors of IL‐1 and LPS may potentially be used to slow or prevent disc degeneration in vivo. Here, we elucidate the striking anti‐catabolic and anti‐inflammatory effects of bovine lactoferricin (LfcinB) in the intervertebral disc (IVD) via antagonism of both IL‐1 and LPS‐mediated catabolic activity using in vitro and ex vivo analyses. Specifically, we demonstrate the biological counteraction of LfcinB against IL‐1 and LPS‐mediated proteoglycan (PG) depletion, matrix‐degrading enzyme production, and enzyme activity in long‐term (alginate beads) and short‐term (monolayer) culture models using bovine and human nucleus pulposus (NP) cells. LfcinB significantly attenuates the IL‐1 and LPS‐mediated suppression of PG production and synthesis, and thus restores PG accumulation and pericellular matrix formation. Simultaneously, LfcinB antagonizes catabolic factor mediated induction of multiple cartilage‐degrading enzymes, including MMP‐1, MMP‐3, MMP‐13, ADAMTS‐4, and ADAMTS‐5, in bovine NP cells at both mRNA and protein levels. LfcinB also suppresses the catabolic factor‐induced stimulation of oxidative and inflammatory factors such as iNOS, IL‐6, and toll‐like receptor‐2 (TLR‐2) and TLR‐4. Finally, the ability of LfcinB to antagonize IL‐1 and LPS‐mediated suppression of PG is upheld in an en bloc intradiscal microinjection model followed by ex vivo organ culture using both mouse and rabbit IVD tissue, suggesting a potential therapeutic benefit of LfcinB on degenerative disc disease in the future. J. Cell. Physiol. 228: 1884–1896, 2013. © 2013 Wiley Periodicals, Inc.     

Persistence in peripheral refugia promotes phenotypic divergence and speciation in a rainforest frog

It is well established from the fossil record and phylogeographic analyses that late Quaternary climate fluctuations led to substantial changes in species' distribution, but whether and how these fluctuations resulted in phenotypic divergence and speciation is less clear. This question can be addressed through detailed analysis of traits relevant to ecology and mating within and among intraspecific lineages that persisted in separate refugia. In a biogeographic system (the Australian Wet Tropics [AWT]) with a well-established history of refugial isolation during Pleistocene glacial periods, we tested whether climate-mediated changes in distribution drove genetic and phenotypic divergence in the rainforest frog Cophixalus ornatus. We combined paleomodeling and multilocus genetics to demonstrate long-term persistence within, and isolation among, one central and two peripheral refugia. In contrast to other AWT vertebrates, the three major lineages differ in ecologically relevant morphology and in mating call, reflecting divergent selection and/or genetic drift in the peripheral isolates. Divergence in mating call and contact zone analyses suggest that the lineages now represent distinct species. The results show that climate shifts can promote genetic and phenotypic divergence and, potentially, speciation and direct attention toward incorporating adaptive traits into phylogeographic studies to better resolve the mechanisms of speciation.     

Invasive ants reduce abundance of small rainforest skinks

Biodiversity and Conservation - Invasive ants are among the world’s most damaging invasive species, often directly or indirectly affecting native fauna. Insecticidal baits are the main method...     

Brain-derived neurotrophic factor produced by human umbilical tissue-derived cells is required for its effect on hippocampal dendritic differentiation

The potential for nonembryonic cells to promote differentiation of neuronal cells has therapeutic implications for regeneration of neurons damaged by stroke or injury and avoids many ethical and safety concerns. The authors have assessed the capacity of human umbilical tissue-derived cells (hUTC) and human mesenchymal stromal cells (hMSC) to enhance differentiation of rodent hippocampal neurons. Co-culture of hippocampal cells with hUTC or hMSC in transwell inserts for 3 days resulted in increase of several dendritic parameters including the number and length of primary dendrites. The effect of hUTC or hMSC on dendritic maturation was only apparent on neurons grown for 2 weeks in vitro prior to co-culture. Changes in dendritic morphology in the presence of hUTC were also accompanied by increased expression of the presynaptic marker synaptotagmin and the postsynaptic marker postsynaptic density protein 95 kDa (PSD95) suggesting that there may also be an increase in the number of synapses formed in the presence of hUTC. The effect of hUTC and hMSC on hippocampal cells in co-culture was comparable to those induced by treatment with recombinant human brain-derived neurotrophic factor (BDNF) implying that a similar factor may be released from hUTC or hMSC. Analysis of hUTC-conditioned medium by ELISA demonstrated that BDNF was indeed secreted. An antibody that blocks the actions of BDNF partially inhibited the actions of hUTC on dendritic morphology suggesting that BDNF is at least one of the factors secreted from the cells to promote dendritic maturation. These results indicate that hUTC secrete biologically active BDNF, which can affect dendritic morphology.     

Murine anti-CD3 monoclonal antibody induces potent cytolytic activity in both T and NK cell populations

Antibodies specific for the CD3 complex have the capacity to both stimulate and inhibit a variety of T cell functions. We show here that a monoclonal antibody to the epsilon chain of CD3 can induce efficient non-MHC-restricted cytolytic activity in murine lymphocytes with peak activity occurring after 48 hr of incubation. In a panel of targets, the anti-CD3-activated effectors lysed tumor cells but not normal lymphoblasts. Cytolysis was not dependent on the presence of the antibody in the cytolytic assay. Moderate to high cytolytic activity was elicited from lymph nodes, spleen, and thymus by anti-CD3 treatment in vitro, whereas only low activity was apparent in bone marrow. The precursors of anti-CD3-activated cells consisted largely of mature T cells, although a smaller component of immature T cells was also involved. Thus, separation of thymocytes based on adhesion to peanut agglutinin revealed that both positive (immature) and negative (mature) fractions could be activated, while cytotoxic pretreatment of spleen cells with an antibody (J11d) to immature T cells before anti-CD3 activation significantly decreased the resulting cytotoxicity. The majority of precursors in spleen were Thy 1+ and CD8+ and/or AGM1+. Antibody depletion studies showed that the effector cells have both a T and a NK component consisting of Thy 1+, CD5+, CD8+, CD4-, and AGM1- cells and Thy 1-, CD5-, CD8-, CD4-, and AGM1+ cells, respectively. The production of significant amounts of IL-2 and TNF in culture following anti-CD3 treatment, along with the synergistic effect of exogenously added IL-2, suggests that one or both of the effector cell types could be induced by lymphokines. The intraperitoneal administration of the anti-CD3 antibody induces cytolytic activity in vivo. Therefore, the direct activation of cytolysis by anti-CD3 antibody and the additional effects, both direct and synergistic, of lymphokines produced by the activated lymphocytes could conceivably provide a potent anti-tumor therapy.