Molecular genetics of the transcription factor GLIS3 identifies its dual function in beta cells and neurons

The GLIS family zinc finger 3 isoform (GLIS3) is a risk gene for Type 1 and Type 2 diabetes, glaucoma and Alzheimer's disease endophenotype. We identified GLIS3 binding sites in insulin secreting cells (INS1) (FDR q < 0.05; enrichment range 1.40–9.11 fold) sharing the motif wrGTTCCCArTAGs, which were enriched in genes involved in neuronal function and autophagy and in risk genes for metabolic and neuro-behavioural diseases. We confirmed experimentally Glis3-mediated regulation of the expression of genes involved in autophagy and neuron function in INS1 and neuronal PC12 cells. Naturally-occurring coding polymorphisms in Glis3 in the Goto-Kakizaki rat model of type 2 diabetes were associated with increased insulin production in vitro and in vivo, suggestive alteration of autophagy in PC12 and INS1 and abnormal neurogenesis in hippocampus neurons. Our results support biological pleiotropy of GLIS3 in pathologies affecting β-cells and neurons and underline the existence of trans?nosology pathways in diabetes and its co-morbidities.     

The effect of NaCl stress and relief on gas exchange properties of two olive cultivars differing in tolerance to salinity

Young olive plants (Olea europaea L.) were grown either in hydroponic or soil culture in a glasshouse over two growing seasons. Plants were exposed to NaCl concentrations between 0 and 200 mM for 34–35 days followed by 30–34 days of relief from stress to determine the effect of salinity on gas exchange of two cultivars ('Frantoio' and 'Leccino') differing in salt-exclusion capacity. Salinity stress brought about a reduction in net CO₂ assimilation and stomatal conductance in both cultivars, but the effect was more pronounced in the salt tolerant 'Frantoio' than in the salt-sensitive 'Leccino' cultivar. Therefore, gas exchange parameters may be misleading if used to evaluate the salt tolerance of olive genotypes. Recovery in gas exchange parameters during relief from stress was slower in the salt sensitive cultivar. In general, the decline in assimilation reflected the salt-induced reduction in stomatal conductance, but a marked effect on carboxylation efficiency and CO₂ compensation point was measured in plants treated with 200 mM NaCl for four weeks. The cultivar 'Frantoio' showed a 50% reduction in assimilation and stomatal conductance at 146 and 78 mM leaf Na+ concentration (tissue water molar basis) respectively, whereas the corresponding 50% thresholds for the cultivar 'Leccino' were at 275 and 264 mM, respectively.     

Cyclic pentapeptides of chiral sequence DLDDL as scaffold for antagonism of G‐protein coupled receptors: Synthesis,activity and conformational analysis by NMR and molecular dynamics of ITF 1565 a substance P inhibitor

Under the hypotheses of a structurally related binding site for antagonists of G‐protein coupled receptors and the ability of cyclic pentapeptides of chiral sequence D ¹L ²D ³D ⁴L ⁵ to form rigid structures with which probe the pharmacophoric specificity of these receptors, inhibitors of substance P were designed based on available structure–activity relationships. ITF 1565, cyclo[D ‐Trp¹‐Pro²‐D ‐Lys³‐D ‐Trp⁴‐Phe⁵], antagonized substance P activity mediated by type 1 neurokinin receptor (NK1) whereas it acted weakly against NK2 and did not inhibit endothelin at all. The preferential conformation of the peptide was obtained from nmr spectroscopy and computer calculations, and shown to contain the same βII‐turn and γ′‐turn found in other cyclic pentapeptides with the same chiral sequence. The structure of the peptide was compared with that of the β‐D ‐glucose molecule that has been proposed as a semirigid scaffold for antagonists of G‐protein coupled receptors. The γ′‐turn of the cyclic peptide superimposed well with β‐D ‐glucose in the chair conformation. Furthermore, when the side chains were considered, the aromatic groups of the two molecules were found to generally overlap. These results support the view of G‐protein coupled receptors as possessing structurally similar binding sites for antagonists and suggest that cyclic pentapeptides of chiral sequence D ¹L ²D ³D ⁴L ⁵ may be useful as semirigid scaffolds for the design of antagonists of this family of receptors. © 1999 John Wiley & Sons, Inc. Biopoly 50: 211–219, 1999     

Deep genomic analysis of the Chlorella sorokiniana SAG 211-8k chloroplast

The chloroplast genome contains information that is applicable in many scientific fields, such as plant systematics, phylogenetic reconstruction and biotechnology, because its features are highly conserved among species. To date, several complete green algal chloroplast genomes have been sequenced and assembled. In this study, the nucleotide sequence of the chloroplast genome (cpDNA) of Chlorella sorokiniana SAG 211-8k is reported and compared for the first time to the chloroplast genomes of 10 Chlorellaceae. The recently updated Chlorella sorokiniana cpDNA sequence, assembled as a circular map of 109?811 bp, encodes 113 genes. Similar to other Chlorella strains, this chloroplast genome does not show a quadripartite structure and lacks the large rRNA operon-encoding Inverted Repeat (IR). The Chlorella sorokiniana plastid encodes the tRNA(Ile)-lysidine synthetase (tilS), which is responsible for modifying the CAU anticodon of a unique tRNA. Gene ordering and clustering highlight the close relationships among Chlorella clade members and the preservation of crucial gene clusters in photosynthetic strains. The features of Chlorella sorokiniana presented here reinforce the monophyletic character of Chlorellaceae and provide important information that sheds light on chloroplast genome evolution among species of Chlorella.     

Non-organ-specific autoantibodies in renal transplant recipients: relation to BK virus infection

Polyomavirus BK reactivation is common in renal transplant recipients and may cause nephropathy with significant graft dysfunction. The induction of anti-double stranded DNA (anti-dsDNA) antibodies by BKV has been described in experimental animals and during primary infection, and has been implicated in the pathogenesis of systemic lupus erythematosus. This study evaluated the occurrence of anti-dsDNA antibodies and non-organ-specific autoantibodies (NOSA) by indirect immunofluorescence before transplantation and at 3 and 6 months post-transplantation in 90 renal transplant recipients and the association with BKV reactivation, demographic and clinical features. Moreover, the relation to HCMV infection, as detected by pp65-antigenemia, was also evaluated. Post-transplantation NOSAs were present in 23/90 (25.6%) and anti-dsDNA antibodies in 17/90 (18.9%). BK viremia was detected in at least one serum sample in 22 patients: 9 anti-dsDNA antibody-positive vs 13 negative (p<0.01). No significant correlation between the occurrence of NOSAs and anti-dsDNA antibodies and demographic and clinical features was found. No significant association with pp65-antigenemia-positivity was found, although antigenemia was positive in 6/23 NOSA-positive patients (26.1%). Although a relation seems to exist between BKV and the occurrence of anti-dsDNA antibodies in renal transplant patients, the lack of correlation with other epidemiological and clinical features does not allow any conclusion. The role of autoimmune response in this context and the relation with other patient-related factors and infectious agents should be further investigated.     

The autoimmune regulator PHD finger binds to non-methylated histone H3K4 to activate gene expression

Mutations in the gene autoimmune regulator (AIRE) cause autoimmune polyendocrinopathy candidiasis ectodermal dystrophy. AIRE is expressed in thymic medullary epithelial cells, where it promotes the expression of tissue-restricted antigens. By the combined use of biochemical and biophysical methods, we show that AIRE selectively interacts with histone H3 through its first plant homeodomain (PHD) finger (AIRE-PHD1) and preferentially binds to non-methylated H3K4 (H3K4me0). Accordingly, in vivo AIRE binds to and activates promoters containing low levels of H3K4me3 in human embryonic kidney 293 cells. We conclude that AIRE-PHD1 is an important member of a newly identified class of PHD fingers that specifically recognize H3K4me0, thus providing a new link between the status of histone modifications and the regulation of tissue-restricted antigen expression in thymus.     

The timing of differentiation of adult hippocampal neurons is crucial for spatial memory

Adult neurogenesis in the dentate gyrus plays a critical role in hippocampus-dependent spatial learning. It remains unknown, however, how new neurons become functionally integrated into spatial circuits and contribute to hippocampus-mediated forms of learning and memory. To investigate these issues, we used a mouse model in which the differentiation of adult-generated dentate gyrus neurons can be anticipated by conditionally expressing the pro-differentiative gene PC3 (Tis21/BTG2) in nestin-positive progenitor cells. In contrast to previous studies that affected the number of newly generated neurons, this strategy selectively changes their timing of differentiation. New, adult-generated dentate gyrus progenitors, in which the PC3 transgene was expressed, showed accelerated differentiation and significantly reduced dendritic arborization and spine density. Functionally, this genetic manipulation specifically affected different hippocampus-dependent learning and memory tasks, including contextual fear conditioning, and selectively reduced synaptic plasticity in the dentate gyrus. Morphological and functional analyses of hippocampal neurons at different stages of differentiation, following transgene activation within defined time-windows, revealed that the new, adult-generated neurons up to 3–4 weeks of age are required not only to acquire new spatial information but also to use previously consolidated memories. Thus, the correct unwinding of these key memory functions, which can be an expression of the ability of adult-generated neurons to link subsequent events in memory circuits, is critically dependent on the correct timing of the initial stages of neuron maturation and connection to existing circuits.