A Drosophila Model of Intellectual Disability Caused by Mutations in the Histone Demethylase KDM5

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Primary Cilium-Mediated Retinal Pigment Epithelium Maturation Is Disrupted in Ciliopathy Patient Cells

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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.     

LTW4 Protein on Mouse Chromosome 1 Is a Member of a Family of Antioxidant Proteins

Based on its map position, polymorphism pattern, and expression in the kidney, the gene encoding liver 20,000–30,000 MW protein 4 (LTW4) can be considered a potential candidate for theJckm2modifying locus, which mediates the severity of polycystic kidney disease in thejuvenile cystic kidneymouse. Using two-dimensional gel electrophoresis, we identified variants of a 26-kDa polypeptide that differed in their isoelectric points between the C57BL/6J and the DBA/2J inbred strains in a pattern similar to that originally described for LTW4 protein. N-terminal amino acid sequence was obtained by microsequencing analysis, and full-length clones were obtained by RT-PCR amplification and characterized. The map position of the cloned gene was determined and corresponded to that previously described forLtw4.The gene has homology to a class of proteins characterized as thiol-specific antioxidants that are protective against damage caused by oxidative stress. The murine MER5 gene is also a member of this gene family and has recently been renamedAntioxidant protein 1 (Aop1),based on its functional characterization. We therefore propose that the gene encoding LTW4 be calledAop2.     

Gelsolin Modulates Phospholipase C Activity In Vivo through Phospholipid Binding

Gelsolin and CapG are actin regulatory proteins that remodel the cytoskeleton in response to phosphatidylinositol 4,5-bisphosphate (PIP₂) and Ca²⁺ during agonist stimulation. A physiologically relevant rise in Ca²⁺ increases their affinity for PIP₂ and can promote significant interactions with PIP₂ in activated cells. This may impact divergent PIP₂- dependent signaling processes at the level of substrate availability. We found that CapG overexpression enhances PDGF-stimulated phospholipase C_γ (PLC_γ) activity (Sun, H.-q., K. Kwiatkowska, D.C. Wooten, and H.L. Yin. 1995. J. Cell Biol. 129:147–156). In this paper, we examined the ability of gelsolin and CapG to compete with another PLC for PIP₂ in live cells, in semiintact cells, and in vitro. We found that CapG and gelsolin overexpression profoundly inhibited bradykinin-stimulated PLC_β. Inhibition occurred at or after the G protein activation step because overexpression also reduced the response to direct G protein activation with NaF. Bradykinin responsiveness was restored after cytosolic proteins, including gelsolin, leaked out of the overexpressing cells. Conversely, exogenous gelsolin added to permeabilized cells inhibited response in a dose-dependent manner. The washout and addback experiments clearly establish that excess gelsolin is the primary cause of PLC inhibition in cells. In vitro experiments showed that gelsolin and CapG stimulated as well as inhibited PLC_β, and only gelsolin domains containing PIP₂-binding sites were effective. Inhibition was mitigated by increasing PIP₂ concentration in a manner consistent with competition between gelsolin and PLC_β for PIP₂. Gelsolin and CapG also had biphasic effects on tyrosine kinase– phosphorylated PLC_γ, although they inhibited PLC_γ less than PLC_β. Our findings indicate that as PIP₂ level and availability change during signaling, cross talk between PIP₂-regulated proteins provides a selective mechanism for positive as well as negative regulation of the signal transduction cascade.     

The Terminal Oxidase in the Marine Bacterium Pseudomonas nautica 617

The molecular properties of a novel membrane quinol oxidase from the marine bacterium Pseudomonas nautica 617 are presented. The protein contains 2b hemes/mole which may be distinguished by EPR spectroscopy but not by optical spectroscopy and electrochemistry. Respiration, though being cyanide insensitive, is not inhibited by carbon monoxide and oxygen reduction is carried out only half-way with production of hydrogen peroxide. The terminal oxidase represents, therefore, a unique example in the large family of terminal oxidases known up to date.     

ThesacB gene cannot be used as a counter-selectable marker inPasteurella multocida

The use of theBacillus subtilis sacB gene as a counter-selectable marker was assessed in serogroup A and B strains ofPasteurella multocida. Expression ofsacB failed to render any of the strains sensitive to sucrose, indicating that thesacB gene can not be used as a positive selection system inP. multocida.