Inhibition of sphingolipid synthesis improves outcomes and survival in GARP mutant wobbler mice, a model of motor neuron degeneration.

Numerous mutations that impair retrograde membrane trafficking between endosomes and the Golgi apparatus lead to neurodegenerative diseases. For example, mutations in the endosomal retromer complex are implicated in Alzheimer's and Parkinson's diseases, and mutations of the Golgi-associated retrograde protein (GARP) complex cause progressive cerebello-cerebral atrophy type 2 (PCCA2). However, how these mutations cause neurodegeneration is unknown. GARP mutations in yeast, including one causing PCCA2, result in sphingolipid abnormalities and impaired cell growth that are corrected by treatment with myriocin, a sphingolipid synthesis inhibitor, suggesting that alterations in sphingolipid metabolism contribute to cell dysfunction and death. Here we tested this hypothesis in wobbler mice, a murine model with a homozygous partial loss-of-function mutation in Vps54 (GARP protein) that causes motor neuron disease. Cytotoxic sphingoid long-chain bases accumulated in embryonic fibroblasts and spinal cords from wobbler mice. Remarkably, chronic treatment of wobbler mice with myriocin markedly improved their wellness scores, grip strength, neuropathology, and survival. Proteomic analyses of wobbler fibroblasts revealed extensive missorting of lysosomal proteins, including sphingolipid catabolism enzymes, to the Golgi compartment, which may contribute to the sphingolipid abnormalities. Our findings establish that altered sphingolipid metabolism due to GARP mutations contributes to neurodegeneration and suggest that inhibiting sphingolipid synthesis might provide a useful strategy for treating these disorders.

Keeping the Zika Virus Out of the Assisted Reproductive Technology Laboratory.

The Zika virus (ZIKV) epidemic spreading through South and Central America, as well as several U.S. territories has created worldwide concern as the linkage between ZIKV infection and microcephaly has been established. Both travel associated and sexually transmitted cases have put couples who live in nonendemic areas at risk of falling victim to effects of Zika. The presence of ZIKV within reproductive tissues may pose a significant threat to patients seeking fertility services and to safety of the tissues currently housed in assisted reproductive technology (ART) laboratories. There are still many unanswered questions regarding the mechanism of ZIKV sexual transmission. Just as strict guidelines have been set regarding the screening and handling of human immunodeficiency virus, hepatitis C virus, and hepatitis B virus-positive patient tissues, similar recommendations are needed to prevent contamination and inadvertent transmission within the ART laboratory.

Rac1 drives intestinal stem cell proliferation and regeneration.

Adult stem cells are responsible for maintaining the balance between cell proliferation and differentiation within self-renewing tissues. The molecular and cellular mechanisms mediating such balance are poorly understood. The production of reactive oxygen species (ROS) has emerged as an important mediator of stem cell homeostasis in various systems. Our recent work demonstrates that Rac1-dependent ROS production mediates intestinal stem cell (ISC) proliferation in mouse models of colorectal cancer (CRC). Here, we use the adult Drosophila midgut and the mouse small intestine to directly address the role of Rac1 in ISC proliferation and tissue regeneration in response to damage. Our results demonstrate that Rac1 is necessary and sufficient to drive ISC proliferation and regeneration in an ROS-dependent manner. Our data point to an evolutionarily conserved role of Rac1 in intestinal homeostasis and highlight the value of combining work in the mammalian and Drosophila intestine as paradigms to study stem cell biology.

Far-field plasmonic resonance enhanced nanoparticle image velocimetry within a microchannel.

In this paper, a novel far-field plasmonic resonance enhanced nanoparticle-seeded particle image velocimetry has been demonstrated to measure the velocity profile in a microchannel. Chemically synthesized silver nanoparticles have been used to seed the flow in the microchannel. By using discrete dipole approximation, plasmonic resonance enhanced light scattering has been calculated for spherical silver nanoparticles with diameters ranging from 15 to 200 nm. Optimum scattering wavelength is specified for the nanoparticles in two media: water and air. The diffraction-limited plasmonic resonance enhanced images of silver nanoparticles at different diameters have been recorded and analyzed. By using standard particle image velocimetry techniques, the velocity profile within the microchannel has been determined from the images.