Inter-Synaptic Lateral Diffusion of GABAA Receptors Shapes Inhibitory Synaptic Currents

The lateral mobility of neurotransmitter receptors has been shown to tune synaptic signals. Here we report that GABAA receptors (GABAARs) can diffuse between adjacent dendritic GABAergic synapses in long-living desensitized states, thus laterally spreading "activation memories" between inhibitory synapses. Glutamatergic activity limits this inter-synaptic diffusion by trapping GABAARs at excitatory synapses. This novel form of activity-dependent hetero-synaptic interplay is likely to modulate dendritic synaptic signaling.

Synergic Functions of miRNAs Determine Neuronal Fate of Adult Neural Stem Cells

Adult neurogenesis requires the precise control of neuronal versus astrocyte lineage determination in neural stem cells. While microRNAs (miRNAs) are critically involved in this step during development, their actions in adult hippocampal neural stem cells (aNSCs) has been unclear. As entry point to address that question we chose DICER, an endoribonuclease essential for miRNA biogenesis and other RNAi-related processes. By specific ablation of Dicer in aNSCs in vivo and in vitro, we demonstrate that miRNAs are required for the generation of new neurons, but not astrocytes, in the adult murine hippocampus. Moreover, we identify 11 miRNAs, of which 9 have not been previously characterized in neurogenesis, that determine neurogenic lineage fate choice of aNSCs at the expense of astrogliogenesis. Finally, we propose that the 11 miRNAs sustain adult hippocampal neurogenesis through synergistic modulation of 26 putative targets from different pathways.

•

Dicer depletion in aNSCs impairs neurogenesis and stimulates astrogliogenesis

•

Synergy of 11 miRNAs sustains neuronal fate of aNSCs

•

miRNA converge on multiple targets in different pathways to induce neurogenesis

Lenalidomide restrains motility and overangiogenic potential of bone marrow endothelial cells in patients with active multiple myeloma

PURPOSE

To determine the in vivo and in vitro antiangiogenic power of lenalidomide, a "lead compound" of IMiD immunomodulatory drugs in bone marrow (BM) endothelial cells (EC) of patients with multiple myeloma (MM) in active phase (MMEC).

EXPERIMENTAL DESIGN

The antiangiogenic effect in vivo was studied using the chorioallantoic membrane (CAM) assay. Functional studies in vitro (angiogenesis, "wound" healing and chemotaxis, cell viability, adhesion, and apoptosis) were conducted in both primary MMECs and ECs of patients with monoclonal gammopathies (MGUS) of undetermined significance (MGEC) or healthy human umbilical vein endothelial cells (HUVEC). Real-time reverse transcriptase PCR, Western blotting, and differential proteomic analysis were used to correlate morphologic and biological EC features with the lenalidomide effects at the gene and protein levels.

RESULTS

Lenalidomide exerted a relevant antiangiogenic effect in vivo at 1.75 μmol/L, a dose reached in interstitial fluids of patients treated with 25 mg/d. In vitro, lenalidomide inhibited angiogenesis and migration of MMECs, but not of MGECs or control HUVECs, and had no effect on MMEC viability, apoptosis, or fibronectin- and vitronectin-mediated adhesion. Lenalidomide-treated MMECs showed changes in VEGF/VEGFR2 signaling pathway and several proteins controlling EC motility, cytoskeleton remodeling, and energy metabolism pathways.

CONCLUSIONS

This study provides information on the molecular mechanisms associated with the antimigratory and antiangiogenic effects of lenalidomide in primary MMECs, thus giving new avenues for effective endothelium-targeted therapies in MM.

Imatinib-loaded polyelectrolyte microcapsules for sustained targeting of BCR-ABL+ leukemia stem cells

Aim: The lack of sensitivity of chronic myeloid leukemia (CML) stem cells to imatinib mesylate (IM) commonly leads to drug dose escalation or early disease relapses when therapy is stopped. Here, we report that packaging of IM into a biodegradable carrier based on polyelectrolyte microcapsules increases drug retention and antitumor activity in CML stem cells, also improving the ex vivo purging of malignant progenitors from patient autografts. Materials & methods: Microparticles/capsules were obtained by layer-by-layer (LbL) self-assembly of oppositely charged polyelectrolyte multilayers on removable calcium carbonate (CaCO3) templates and loaded with or without IM. A leukemic cell line (KU812) and CD34+ cells freshly isolated from healthy donors or CML patients were tested. Results & discussion: Polyelectrolyte microcapsules (PMCs) with an average diameter of 3 µm, fluorescently labelled multilayers sensitive to the action of intracellular proteases and 95–99% encapsulation efficiency of IM, were prepared. Cell uptake efficiency of such biodegradable carriers was quantified in KU812, leukemic and normal CD34+ stem cells (range: 70–85%), and empty PMCs did not impact cell viability. IM-loaded PMCs selectively targeted CML cells, by promoting apoptosis at doses that exert only cytostatic effects by IM alone. More importantly, residual CML cells from patient leukapheresis products were reduced or eliminated more efficiently by using IM-loaded PMCs compared with freely soluble IM, with a purging efficiency of several logs. No adverse effects on normal CD34+ stem-cell survival and their clonogenic potential was noticed in long-term cultures of hematopoietic progenitors in vitro. Conclusion: This pilot study provides the proof-of-principle for the clinical application of biodegradable IM-loaded PMC as feasible, safe and effective ex vivo purging agents to target CML stem cells, in order to improve transplant outcome of resistant/relapsed patients or reduce IM dose escalation.

Advantages and disadvantages of human dichromacy

We compared the visual detection thresholds for cone-isolating stimuli of trichromats (those with normal color vision) with those of X-linked dichromats, who lack either the long-wavelength-sensitive (L) cones (protanopes) or middle-wavelength-sensitive (M) cones (deuteranopes). At low (1 Hz) temporal frequencies, dichromats have significantly higher (twofold) thresholds for all colored stimuli than trichromats; whereas at high (16 Hz) temporal frequencies, they perform as well or better than trichromats. The advantages of dichromats in detecting high temporally modulated targets can be related to an increased number, through replacement, of the remaining L- or M-cone type. However, their disadvantages in detecting low temporally modulated targets, even in directions of color space where their increased number of cone photoreceptors might be expected to be beneficial, are best explained in terms of the loss of L-M cone opponency and the inability of the visual pathways to reorganize to allow the detection of low-frequency luminance modulation.

Visual acuity and X-linked color blindness

PURPOSE

Optimal sampling for visual acuity requires a fine array of cones with identical sensitivity. Thus, dichromats, whose inner fovea is made up of cones having the same spectral sensitivity, may have better than normal visual acuity. We investigated this by comparing the visual acuities of trichromats and X-linked dichromats, while taking into account the different molecular genetics underlying the disorder.

METHODS

Our subjects were age- and refraction-matched groups of normals (n=8) and X-linked dichromats (n=13). The dichromats (four protanopes and nine deuteranopes) were genotyped and classified according to whether they carried a single (n=6) or multiple (n=7) visual pigment genes on their X-chromosome. Visual acuity was measured in both eyes with the Freiburger Visual Acuity Test.

RESULTS

Normal trichromats and ungenotyped dichromats do not significantly differ in visual acuity, nor do ungenotyped protanopes and deuteranopes. However, multi-gene dichromats, who possess more than one photopigment gene in the array, all of which encode for the same long- or middle-wavelength sensitive photopigment, have significantly higher visual acuity than either normal trichromats or dichromats who have only a single-gene.

CONCLUSIONS

Multi-gene dichromats may benefit from a reduction in chromatic aberration and chromatic noise in the high acuity channel, normally a consequence of combining signals from different cone photoreceptor types and of cone-specific patterns of retinal image defocus and blur. Single-gene dichromats may not share in the advantage because of other molecular differences that influence the development of the retinal mosaic and/or its visual pathways.