Hif1a inactivation rescues photoreceptor degeneration induced by a chronic hypoxia-like stress

Reduced choroidal blood flow and tissue changes in the ageing human eye impair oxygen delivery to photoreceptors and the retinal pigment epithelium. As a consequence, mild but chronic hypoxia may develop and disturb cell metabolism, function and ultimately survival, potentially contributing to retinal pathologies such as age-related macular degeneration (AMD). Here, we show that several hypoxia-inducible genes were expressed at higher levels in the aged human retina suggesting increased activity of hypoxia-inducible transcription factors (HIFs) during the physiological ageing process. To model chronically elevated HIF activity and investigate ensuing consequences for photoreceptors, we generated mice lacking von Hippel Lindau (VHL) protein in rods. This activated HIF transcription factors and led to a slowly progressing retinal degeneration in the ageing mouse retina. Importantly, this process depended mainly on HIF1 with only a minor contribution of HIF2. A gene therapy approach using AAV-mediated RNA interference through an anti-Hif1a shRNA significantly mitigated the degeneration suggesting a potential intervention strategy that may be applicable to human patients

Data from: FOXP2 exhibits neuron class specific expression, but is not required for multiple aspects of cortical histogenesis

The expression patterns of the transcription factor FOXP2 in the developing mammalian forebrain have been described, and some studies have tested the role of this protein in the development and function of specific forebrain circuits by diverse methods and in multiple species. Clinically, mutations in FOXP2 are associated with severe developmental speech disturbances, and molecular studies indicate that impairment of Foxp2 may lead to dysregulation of genes involved in forebrain histogenesis. Here, anatomical and molecular phenotypes of the cortical neuron populations that express FOXP2 were characterized. Additionally, Foxp2 was removed from the developing mouse cortex at different prenatal ages using two Cre-recombinase driver lines. Detailed molecular and circuit analyses were undertaken to identify potential disruptions of development. Surprisingly, the results demonstrate that Foxp2 function is not required for many function s that it has been proposed to regulate, and therefore plays a more limited role in cortical development than previously thought

Specific Connectivity and Unique Molecular Identity of MET Receptor Tyrosine Kinase Expressing Serotonergic Neurons in the Caudal Dorsal Raphe Nuclei

Molecular characterization of neurons across brain regions has revealed new taxonomies for understanding functional diversity even among classically defined neuronal populations. Neuronal diversity has become evident within the brain serotonin (5-HT) system, which is far more complex than previously appreciated. However, until now it has been difficult to define subpopulations of 5-HT neurons based on molecular phenotypes. We demonstrate that the MET receptor tyrosine kinase (MET) is specifically expressed in a subset of 5-HT neurons within the caudal part of the dorsal raphe nuclei (DRC) that is encompassed by the classic B6 serotonin cell group. Mapping from embryonic day 16 through adulthood reveals that MET is expressed almost exclusively in the DRC as a condensed, paired nucleus, with an additional sparse set of MET+ neurons scattered within the median raphe. Retrograde tracing experiments reveal that MET-expressing 5-HT neurons provide substantial serotonergic input to the ventricular/subventricular region that contains forebrain stem cells, but do not innervate the dorsal hippocampus or entorhinal cortex. Conditional anterograde tracing experiments show that 5-HT neurons in the DRC/B6 target additional forebrain structures such as the medial and lateral septum and the ventral hippocampus. Molecular neuroanatomical analysis identifies 14 genes that are enriched in DRC neurons, including 4 neurotransmitter/neuropeptide receptors and 2 potassium channels. These analyses will lead to future studies determining the specific roles that 5-HT^MET+ neurons contribute to the broader set of functions regulated by the serotonergic system

Nogo receptor 1 limits tactile task performance independent of basal anatomical plasticity.

The genes that govern how experience refines neural circuitry and alters synaptic structural plasticity are poorly understood. The nogo-66 receptor 1 gene (ngr1) is one candidate that may restrict the rate of learning as well as basal anatomical plasticity in adult cerebral cortex. To investigate if ngr1 limits the rate of learning we tested adult ngr1 null mice on a tactile learning task. Ngr1 mutants display greater overall performance despite a normal rate of improvement on the gap-cross assay, a whisker-dependent learning paradigm. To determine if ngr1 restricts basal anatomical plasticity in the associated sensory cortex, we repeatedly imaged dendritic spines and axonal varicosities of both constitutive and conditional adult ngr1 mutant mice in somatosensory barrel cortex for two weeks through cranial windows with two-photon chronic in vivo imaging. Neither constant nor acute deletion of ngr1 affected turnover or stability of dendritic spines or axonal boutons. The improved performance on the gap-cross task is not attributable to greater motor coordination, as ngr1 mutant mice possess a mild deficit in overall performance and a normal learning rate on the rotarod, a motor task. Mice lacking ngr1 also exhibit normal induction of tone-associated fear conditioning yet accelerated fear extinction and impaired consolidation. Thus, ngr1 alters tactile and motor task performance but does not appear to limit the rate of tactile or motor learning, nor determine the low set point for synaptic turnover in sensory cortex

Cranial windows are properly positioned over S1 barrel cortex and are a stable preparation for imaging cortical spine dynamics.

<p>(A) An example of optical imaging of intrinsic signals reveals the cortical region responsive to stimulation of the C2 whisker. Scale bar = 0.5 mm (B) Apical dendrites of layer V neurons in the boxed region (yellow) are shown at higher magnification in panels C and D. Scale bar = 50 µm (C) Higher magnification images of the boxed region (yellow) in panel B at day 0 (D) Higher magnification images of the boxed region (yellow) in panel B at day 12 (E) Higher magnification image of the boxed region in panel C on day 0. (F) Higher magnification image of the boxed region in panel D on day 12.</p

Role of Combustion Chemistry in Low-Temperature Deposition of Metal Oxide Thin Films from Solution

Metal-oxide thin films find many uses in (opto)­electronic and renewable energy technologies. Their deposition by solution methods aims to reduce manufacturing costs relative to vacuum deposition while achieving comparable electronic properties. Solution deposition on temperature-sensitive substrates (e.g., plastics), however, remains difficult due to the need to produce dense films with minimal thermal input. Here, we investigate combustion thin-film deposition, which has been proposed to produce high-quality metal-oxide films with little externally applied heat, thereby enabling low-temperature fabrication. We compare chemical composition, chemical structure, and evolved species from reactions of several metal nitrate [In­(NO₃)₃, Y­(NO₃)₃, and Mg­(NO₃)₂] and fuel additive (acetylacetone and glycine) mixtures in bulk and thin-film forms. We observe combustion in bulk materials but not in films. It appears acetylacetone is removed from the films before the nitrates, whereas glycine persists in the film beyond the annealing temperatures required for ignition in the bulk system. From analysis of X-ray photoelectron spectra, the oxide and nitrate content as a function of temperature are also inconsistent with combustion reactions occurring in the films. In­(NO₃)₃ decomposes alone at low temperature (∼200–250 °C) without fuel, and Y­(NO₃)₃ and Mg­(NO₃)₂ do not decompose fully until high temperature even in the presence of fuel when used to make thin films. This study therefore distinguishes bulk and thin-film reactivity for several model oxidizer-fuel systems, and we propose ways in which fuel additives may alter the film formation reaction pathway

Axonal bouton turnover and stability are normal in <i>ngr1</i>−/− mice.

<p>(A) Examples of axons imaged repeatedly by repeated <i>in vivo</i> two-photon microscopy through cranial windows. Solid arrowheads (yellow) are examples of new boutons. Outlined arrowheads (yellow) are examples of boutons lost. Scale bar = 10 µm (B) Higher magnification of the boxed region (yellow) in panel A. Scale bar = 5 µm. (C) The turnover of axonal boutons every four days in WT (n = 4, 424 boutons) and <i>ngr1</i>−/− mice (n = 5, 749 boutons) is similar across 4-day intervals in S1 barrel cortex (p>0.2). (D) The average percent of axonal boutons gained and lost is similar between WT and <i>ngr1−/−</i> mice (gained p>0.5; lost p>0.6). (E) The survival fraction of boutons present on day 0 is similar at days 4, 8, and 12. (F) The percent of persistent boutons (p>0.1) and new boutons (p>0.3) present on day 12 is comparable between WT and <i>ngr1−/−</i> mice.</p

Dendritic spine turnover and stability are normal in <i>ngr1</i>−/− mice.

<p>(A) Repeated <i>in vivo</i> two-photon imaging through cranial windows in EGFP-M transgenic mice reveals the turnover and stability of dendritic spines on the apical dendrites of layer V pyramidal neurons in S1 barrel cortex. Scale bar = 10 µm. The boxed region (yellow) is shown at higher magnification in panel B. (B) Dendritic spines were imaged every four days for twelve days. Solid arrowheads (yellow) are examples of spine gains. Outlined arrowheads (yellow) are examples of spines lost. Scale bar = 2 µm. (C) The turnover of dendritic spines every four days in WT (n = 5; 1512 spines) and <i>ngr1</i>−/− mice (n = 4; 1106 spines) is similar across 4-day intervals (p>0.4). The average across all sessions is also comparable (p>0.9). (D) The average percent of spines gained and lost is similar between WT (n = 5) and <i>ngr1−/−</i> mice (n = 4) (gained p>0.2; lost p>0.9). (E) The survival fraction of spines present on day 0 re-examined at days 4, 8, and 12 is nearly identical (p>0.8) (F) The percent of new spines present on day 12 is similar between WT and <i>ngr1−/−</i> mice. (p>0.2) (G) The fraction of new spines appearing on day 4 that are transient (p>0.3), surviving less than 4 days, those lasting less than 8 days (present only on day 4 and 8) (p>0.8), and persistent spines surviving more than 8 days (p>0.1) are similar between WT and <i>ngr1−/−</i> mice. (H) Timeline of acute deletion of <i>ngr1</i> in <i>ngr1flx/flx;Cre-ER</i> mice following tamoxifen injection and imaging schedule as NgR1 protein levels decline. (I) Basal cortical spine dynamics in S1 barrel cortex are unaffected by acute deletion of <i>ngr1</i>. The turnover ratio does not change with the decline or absence of NgR1 protein (n = 3, 6 neurons, 1083 spines) (p>0.9).</p

Mice lacking <i>ngr1</i> perform better on the gap cross assay but display normal tactile learning across sessions.

<p>(A) A schematic of the gap cross assay. The movement of a mouse from the starting, or ‘home’, platform to the target platform across a given gap distance is detected with motion sensors positioned at the back and edge of each platform. (B) Activation of each sensor (grey box) indicates the position of the mouse. (C) Successful crosses are defined as the movement of the mouse from the starting platform to the target platform (green circles). Failures are defined as trials in which the mouse approaches the edge of the home or target platform and returns to the back of the home platform (red crosses). (D) <i>ngr1−/−</i> mice cross ‘whisker’ distances at a significantly higher success rate (WT, n = 19; <i>ngr1−/−</i>, n = 14; p>.01 for distances 5.5 and 6 cm; p>.32 for distances 3.5 and 4 cm, two-way ANOVA). This greater success rate is most significant at longer distances, 5.5 cm and 6 cm (**, p>.01 with Bonferroni correction for multiple comparisons). (E) Despite better overall performance, the percent improvement for a given gap distance from the first 4 sessions (left value for each distance) to the second 4 sessions (right value for each distance) is similar for WT and <i>ngr1−/−</i> mice for a given gap distance. (F) WT mice improve with experience at ‘whisker’ gap distances (WT, n = 19, *, p<.05, two-way repeated measures ANOVA) from the first 4 sessions (Early, grey line) to the second 4 sessions (Late, black line). (G) <i>Ngr1</i> mutant mice improve with experience at ‘whisker only’ gap distances (<i>ngr1−/−</i>, n = 14, *, p<.05, two-way repeated measures ANOVA) from the first 4 sessions (Early, pink line) to the second 4 sessions (Late, red line).</p