Regulation of microtubule dynamics by the neuronal growth-associated protein SCG10.

Dynamic assembly and disassembly of microtubules is essential for cell division, cell movements, and intracellular transport. In the developing nervous system, microtubule dynamics play a fundamental role during neurite outgrowth, elongation, and branching, but the molecular mechanisms involved are unknown. SCG10 is a neuron-specific protein that is membrane-associated and highly enriched in growth cones. Here we show that SCG10 binds to microtubules, inhibits their assembly, and can induce microtubule disassembly. We also show that SCG10 overexpression enhances neurite outgrowth in a stably transfected neuronal cell line. These data identify SCG10 as a key regulator of neurite extension through regulation of microtubule instability.

Factors determining the spontaneous activation of splenic dendritic cells in culture.

Dendritic cells (DCs) serve as a link between the innate and adaptive immune systems. The activation state of DCs is crucial in this role. However, when DCs are isolated from lymphoid tissues, purified and placed in culture they undergo 'spontaneous' activation. The basis of this was explored, using up-regulation of DC surface MHC II, CD40, CD80 and CD86 as indicators of DC activation. No evidence was found for DC damage during isolation or for microbial products causing the activation. The culture activation of spleen DCs differed from that of Langerhans cells when released from E-cadherin-mediated adhesions, since E-cadherin was not detected and activation still occurred with β-catenin null DCs. Much of the activation could be attributed to DC-DC interactions. Although increases in surface MHC II levels occurred under all culture conditions tested, the increase in expression of CD40, CD80 and CD86 was much less under culture conditions where such interactions were minimised. DC-to-DC contact under the artificial conditions of high DC concentration in culture induced the production of soluble factors and these, in turn, induced the up-regulation of co-stimulatory molecules on the DC surface.

Cholinergic neurons of fetal rat telencephalon in aggregating cell culture respond to NGF as well as to protein kinase C-activating tumor promoters.

Serum-free aggregating cell cultures of fetal rat telencephalon treated with the potent tumor promoter phorbol 12-myristate 13-acetate (PMA) showed a dose-dependent, persistent stimulation of the enzymes choline acetyltransferase (ChAT), glutamic acid decarboxylase and glutamine synthetase. After elimination of the proliferating cells by treatment of the cultures with Ara-C (0.4 microM) only the cholinergic marker enzyme, ChAT, could be stimulated by tumor promoters. The non-promoting phorbol ester, 4 alpha-phorbol 12,13-didecanoate proved to be inactive in these cultures, whereas the potent non-phorbol tumor promoter, mezerein, produced an even greater stimulatory effect than PMA. Since PMA and mezerein are potent and specific activators of protein kinase C, the present results suggest a role for this second messenger in the development of cholinergic telencephalon neurons. Stimulation of ChAT required prolonged exposure (48 h) of the cultures to PMA and the responsiveness of the cholinergic neurons to the tumor promoters decreased with progressive cellular maturation. The cholinergic telencephalon neurons showed the same pattern of responsiveness for tumor promoters as for nerve growth factor (NGF). However, the combined treatment with NGF and either PMA or mezerein produced an additive stimulatory effect, suggesting somewhat different mechanisms of action.

Insights into neuronal cell metabolism using NMR spectroscopy: uridyl diphosphate N-acetyl-glucosamine as a unique metabolic marker.

Making the switch: Compounds 1 and 2 are used as metabolic markers for NMR detection. When neuronal cells switch to a glycolytic state, an uneven distribution of (13) C in the N-acetyl group results, thus giving a mixture of the metabolites 1 and 2. It is therefore possible to monitor flux through different metabolic pathways, such as glycolysis, the tricarboxylic acid cycle, and the hexosamine biosynthetic pathway, using a single molecule.

Neuronal traits are required for glucose-induced insulin secretion.

The transcriptional repressor RE1 silencer transcription factor (REST) is an important factor that restricts some neuronal traits to neurons. Since these traits are also present in pancreatic beta-cells, we evaluated their role by generating a model of insulin-secreting cells that express REST. The presence of REST led to a decrease in expression of its known target genes, whereas insulin expression and its cellular content were conserved. As a consequence of REST expression, the capacity to secrete insulin in response to mitochondrial fuels, a particularity of mature beta-cells, was impaired. These data provide evidence that REST target genes are required for an appropriate glucose-induced insulin secretion.

In Bacillus subtilis W23, the duet sigmaXsigmaM, two sigma factors of the extracytoplasmic function subfamily, are required for septum and wall synthesis under batch culture conditions.

The synthesis of poly(RboP), the main Bacillus subtilis W23 teichoic acid, is encoded by tarDF-tarABIJKL operons, the latter being controlled by two promoters designated PtarA-int and PtarA-ext. Analysis by lacZ fusions reveals that PtarA-int activity exhibits sharp increases at the beginning and end of the transition between exponential and stationary growth phase. As confirmed by mRNA quantification, these increases are mediated by ECF sigma factors sigmaX and sigmaM respectively. In liquid media, strain W23 sigX sigM double mutants experience serious difficulties in the transition and stationary growth phases. Inactivation of sigmaX- and sigmaM-controlled regulons, which precludes transcription from PtarA-int, leads to (i) delays in chromosome segregation and septation and (ii) a transient loss of up to 30% of the culture OD or lysis. However, specific inactivation of PtarA-int, leading mainly to a shortage of poly(RboP), does not affect growth while, nevertheless, interfering with normal septation, as revealed by electron microscopy. The different sigM transcription in strains W23 and 168 is discussed. In W23, expression of tarA and sigM, which is shown to control divIC, is inversely correlated with growth rate, suggesting that the sigM regulon is involved in the control of cell division.

Perceptions of aging across 26 cultures and their culture-level associates

College students (N = 3,435) in 26 cultures reported their perceptions of age-related changes in physical cognitive, and socioemotional areas of functioning and rated societal views of aging within their culture. There was widespread cross-cultural consensus regarding the expected direction of aging trajectories with (a) perceived declines in societal views of aging, physical attractiveness, the ability to perform everyday tasks, and new learning; (b) perceived increases in wisdom, knowledge, and received respect; and (c) perceived stability in family authority and life satisfaction. Cross-cultural variations in aging perceptions were associated with culture-level indicators of population aging, education levels, values, and national character stereotypes. These associations were stronger for societal views on aging and perceptions of socioemotional changes than for perceptions of physical and cognitive changes. A consideration of culture-level variables also suggested that previously reported differences in aging perceptions between Asian and Western countries may be related to differences in population structure.

Leukemic cluster growth in culture is an independent risk factor for acute myeloid leukemia and short survival in patients with myelodysplastic syndrome

In patients with myelodysplastic syndrome (MDS) precursor cell cultures (colony-forming unit cells, CFU-C) can provide an insight into the growth potential of malignant myeloid cells. In a retrospective single-center study of 73 untreated MDS patients we assessed whether CFU-C growth patterns were of prognostic value in addition to established criteria. Abnormalities were classified as qualitative (i.e. leukemic cluster growth) or quantitative (i.e. strongly reduced/absent growth). Thirty-nine patients (53%) showed leukemic growth, 26 patients (36%) had strongly reduced/absent colony growth, and 12 patients showed both. In a univariate analysis the presence of leukemic growth was associated with strongly reduced survival (at 10 years 4 vs. 34%, p = 0.004), and a high incidence of transformation to AML (76 vs. 32%, p = 0.01). Multivariate analysis identified leukemic growth as a strong and independent predictor of early death (relative risk 2.12, p = 0.03) and transformation to AML (relative risk 2.63, p = 0.04). Quantitative abnormalities had no significant impact on the disease course. CFU- C assays have significant predictive value in addition to established prognostic factors in MDS. Leukemic growth identifies a subpopulation of MDS patients with poor prognosis.