Centromere protein A dynamics in human pluripotent stem cell self-renewal, differentiation and DNA damage

Human pluripotent stem cells (hPSCs) hold significant promise for use in regenerative medicine, or as a model to understand human embryo development. However, the basic mechanisms required for proliferation and self-renewal of hPSCs have not been fully uncovered. Proliferation in all eukaryotes is dependent upon highly regulated expression of the histone H3 variant Centromere protein A (CENP-A). In the current study, we demonstrate that hPSCs have a unique messenger ribonucleic acid (mRNA) reserve of CENP-A not found in somatic fibroblasts. Using short hairpin RNA technology to reduce but not ablate CENP-A, we show that CENP-A-depleted hPSCs are still capable of maintaining a functional centromeric mark, whereas fibroblasts are not. However, upon induction of differentiation or DNA damage, hPSCs with depleted CENP-A arrest in G2/M and undergo apoptosis. Analysis of CENP-A dynamics following DNA damage in hPSCs reveals that 60 min after irradiation, CENP-A is found in multiple small nuclear foci that are mutually exclusive to γH2AX as well as CENP-C. Furthermore, following irradiation, hPSCs with depleted CENP-A mount a normal apoptotic response at 6 h; however at 24 h, apoptosis is significantly increased in CENP-A-depleted hPSCs relative to control. Taken together, our results indicate that hPSCs exhibit a unique mechanism for maintaining genomic integrity by possessing the flexibility to reduce the amount of CENP-A required to maintain a functional centromere under self-renewing conditions, and maintaining a reserve of CENP-A mRNA to rebuild the centromere following differentiation or DNA damage

VPLYV ZADLZENOSTI POL'NOHOSPODARSKYCH FIRIEM HOSPODARIACICH V ROZNYCH PRIRODNYCH PODMIENKACH NA ICH RENTABILITU

The primary goal of the article is to evaluate the effects of indebtedness on the profitability of agricultural farms located in less favoured areas (LFA), and the farms which are not located in the LFA. For evaluation of this situation there were used selected financial indicators, development of which was accounted in the period 2000-2005. The base of the data vere created, by aggregate data of corporate bodies. Data comes from the VU EPP database. Indebtedness of agricultural farms reaches in average 35 %. In accordance with an average Slovak company, which indebtedness is 75 %, and in accordance with direction value 50 % it is still under the tolerable value. Lower indebtedness of agricultural farms results from specific factors of agricultural basic industry. These factors are land and climatic conditions, seasonality of production, lower profit margin, and long cycle of production, which means distinction between production and sales phase that causes ups and downs in cash flows of the companies. The relationship between profitability and indebtedness shows non-linear development in the period 2000-2005

Mitochondrial CB₁ receptors regulate neuronal energy metabolism

The mammalian brain is one of the organs with the highest energy demands, and mitochondria are key determinants of its functions. Here we show that the type-1 cannabinoid receptor (CB(1)) is present at the membranes of mouse neuronal mitochondria (mtCB(1)), where it directly controls cellular respiration and energy production. Through activation of mtCB(1) receptors, exogenous cannabinoids and in situ endocannabinoids decreased cyclic AMP concentration, protein kinase A activity, complex I enzymatic activity and respiration in neuronal mitochondria. In addition, intracellular CB(1) receptors and mitochondrial mechanisms contributed to endocannabinoid-dependent depolarization-induced suppression of inhibition in the hippocampus. Thus, mtCB(1) receptors directly modulate neuronal energy metabolism, revealing a new mechanism of action of G protein-coupled receptor signaling in the brain