Misfolded SOD1 Associated with Motor Neuron Mitochondria Alters Mitochondrial Shape and Distribution Prior to Clinical Onset

Mutations in superoxide dismutase (SOD1) are causative for inherited amyotrophic lateral sclerosis. A proportion of SOD1 mutant protein is misfolded onto the cytoplasmic face of mitochondria in one or more spinal cord cell types. By construction of mice in which mitochondrially targeted enhanced green fluorescent protein is selectively expressed in motor neurons, we demonstrate that axonal mitochondria of motor neurons are primary in vivo targets for misfolded SOD1. Mutant SOD1 alters axonal mitochondrial morphology and distribution, with dismutase active SOD1 causing mitochondrial clustering at the proximal side of Schmidt-Lanterman incisures within motor axons and dismutase inactive SOD1 producing aberrantly elongated axonal mitochondria beginning pre-symptomatically and increasing in severity as disease progresses. Somal mitochondria are altered by mutant SOD1, with loss of the characteristic cylindrical, networked morphology and its replacement by a less elongated, more spherical shape. These data indicate that mutant SOD1 binding to mitochondria disrupts normal mitochondrial distribution and size homeostasis as early pathogenic features of SOD1 mutant-mediated ALS

Motor neuron mitochondria are rounder in mutant SOD1 mice.

<p>MitoEGFP (<i>green</i>) expression in spinal cord motor neurons in control MitoEGFP (A) and SOD1^G37R early symptomatic animals (B–D). The control neuron has normal mitochondria of diverse shapes and sizes. In contrast, SOD1^G37R motor neurons have rounded swollen mitochondria with uneven distribution. Arrows indicate possible axon hillocks. Motor neuron boundaries have been outlined with dotted line. Quantification of mitochondrial length (E) and aspect ratio (F) in motor neuron cell bodies of mutant SOD1 animals of various ages and age-matched MitoEGFP control animals. ***, p<0.0005. Scale bars, 10 µm.</p

Mitochondria morphology is altered in mutant SOD1 axons.

<p>MitoEGFP (<i>green</i>) expressed in the sciatic nerves in control (A), asymptomatic SOD1^G85R 7 months (B and C), SOD1^G85R 8 months (D and E), and SOD1^G37R early symptomatic (F and G) labeled with Fluoromyelin red (<i>red</i>). Round and evenly distributed mitochondria are seen in both SOD1^G85R (symptomatic stage) and SOD1^G37R (early symptomatic stage). Mitochondria `pile-up or clusters are also seen in the proximal side of SLIs (arrows) in the SOD1^G37R axons. Arrowheads indicate “strings” of mitochondria. Arrows indicate SLIs (H) Schematic indicating proximal and distal locations of SLIs. Mitochondrial area (I), length (J), aspect ratio (K), and density (L) were evaluated in motor axons of the sciatic nerves of and mutant SOD1 animals of various ages and age-matched MitoEGFP control animals, as described in detail in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022031#s4" target="_blank">Materials and Methods</a>. Statistics are indicated: *, p<0.05; **, p<0.005; ***, p<0.0005.</p

Generation of a novel transgenic mouse with mitochondria labeled uniquely in motor neurons.

<p>(A) Schematic of Hb9-MitoEGFP transgene. (B) Immunoblot of spinal cord homogenates of Hb9-MitoEGFP founders (F34, F17, F36, F20) and F34 sublines probed for EGFP and tubulin (loading control). (C–G) MitoEGFP <i>(green)</i> expression in spinal cord motor neurons (C & D), sciatic nerve (E), and L5 motor axons (F & G) labeled with SMI32 (C, <i>red</i>), cytochrome <i>c</i> (D & F, <i>red</i>), and Fluoromyelin Red (F & G, <i>blue/red</i>). Note that mitochondria have typical tubular and punctate morphologies and MitoEGFP expression is excluded from Schwann cells. (G & H) 15% of large caliber (>4.5 µm) L5 motor axons express MitoEGFP in 12 months animal. The expected biphasic distribution of axonal caliber in adult C57Bl/6 mice is indicated in the upper right corner. Comparison of axonal and somal mitochondrial length (I), width (J) and aspect ratio (K) in Hb9-MitoEGFP mice. Scale bars, 10 µm.</p

Neotropical freshwater fisheries : A dataset of occurrence and abundance of freshwater fishes in the Neotropics

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large-scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications