A Versatile Murine Model of Subcortical White Matter Stroke for the Study of Axonal Degeneration and White Matter Neurobiology.

Stroke affecting white matter accounts for up to 25% of clinical stroke presentations, occurs silently at rates that may be 5-10 fold greater, and contributes significantly to the development of vascular dementia. Few models of focal white matter stroke exist and this lack of appropriate models has hampered understanding of the neurobiologic mechanisms involved in injury response and repair after this type of stroke. The main limitation of other subcortical stroke models is that they do not focally restrict the infarct to the white matter or have primarily been validated in non-murine species. This limits the ability to apply the wide variety of murine research tools to study the neurobiology of white matter stroke. Here we present a methodology for the reliable production of a focal stroke in murine white matter using a local injection of an irreversible eNOS inhibitor. We also present several variations on the general protocol including two unique stereotactic variations, retrograde neuronal tracing, as well as fresh tissue labeling and dissection that greatly expand the potential applications of this technique. These variations allow for multiple approaches to analyze the neurobiologic effects of this common and understudied form of stroke.

Registered report: Interactions between cancer stem cells and their niche govern metastatic colonization.

The Reproducibility Project: Cancer Biology seeks to address growing concerns about reproducibility in scientific research by replicating selected results from a substantial number of high-profile papers in the field of cancer biology published between 2010 and 2012. This Registered report describes the proposed replication plan of key experiments from 'Interactions between cancer stem cells and their niche govern metastatic colonization' by Malanchi and colleagues, published in Nature in 2012 (Malanchi et al., 2012). The key experiments that will be replicated are those reported in Figures 2H, 3A, 3B, and S13. In these experiments, Malanchi and colleagues analyze messenger RNA levels of periostin (POSTN) in pulmonary fibroblasts, endothelial cells, and immune cells isolated from mice with micrometastases to determine which cell type is producing POSTN in the metastatic niche (Figure 2H; Malanchi et al., 2012). Additionally, they examine MMTV-PyMT control or POSTN null mice to test the effect of POSTN on primary tumor growth and metastasis (Figures 3A, 3B, and S13; Malanchi et al., 2012). The Reproducibility Project: Cancer Biology is a collaboration between the Center for Open Science and Science Exchange, and the results of the replications will be published in eLife.

A profile of transcriptomic changes in the rd10 mouse model of retinitis pigmentosa.

PURPOSE: Retinitis pigmentosa (RP) is a photoreceptor disease that affects approximately 100,000 people in the United States. Treatment options are limited, and the prognosis for most patients is progressive vision loss. Unfortunately, understanding of the molecular underpinnings of RP initiation and progression is still limited. However, the development of animal models of RP, coupled with high-throughput sequencing, has provided an opportunity to study the underlying cellular and molecular changes in this disease. METHODS: Using RNA-Seq, we present the first retinal transcriptome analysis of the rd10 murine model of retinal degeneration. RESULTS: Our data confirm the loss of rod-specific transcripts and the increased relative expression of Müller-specific transcripts, emphasizing the important role of reactive gliosis and innate immune activation in RP. Moreover, we report substantial changes in relative isoform usage among neuronal differentiation and morphogenesis genes, including a marked shift to shorter transcripts. CONCLUSIONS: Our analyses implicate remodeling of the inner retina and possible Müller cell dedifferentiation.

Virally delivered channelrhodopsin-2 safely and effectively restores visual function in multiple mouse models of blindness.

Previous work established retinal expression of channelrhodopsin-2 (ChR2), an algal cation channel gated by light, restored physiological and behavioral visual responses in otherwise blind rd1 mice. However, a viable ChR2-based human therapy must meet several key criteria: (i) ChR2 expression must be targeted, robust, and long-term, (ii) ChR2 must provide long-term and continuous therapeutic efficacy, and (iii) both viral vector delivery and ChR2 expression must be safe. Here, we demonstrate the development of a clinically relevant therapy for late stage retinal degeneration using ChR2. We achieved specific and stable expression of ChR2 in ON bipolar cells using a recombinant adeno-associated viral vector (rAAV) packaged in a tyrosine-mutated capsid. Targeted expression led to ChR2-driven electrophysiological ON responses in postsynaptic retinal ganglion cells and significant improvement in visually guided behavior for multiple models of blindness up to 10 months postinjection. Light levels to elicit visually guided behavioral responses were within the physiological range of cone photoreceptors. Finally, chronic ChR2 expression was nontoxic, with transgene biodistribution limited to the eye. No measurable immune or inflammatory response was observed following intraocular vector administration. Together, these data indicate that virally delivered ChR2 can provide a viable and efficacious clinical therapy for photoreceptor disease-related blindness.

Towards optogenetic sensory replacement.

Over the last several years we have developed a rapidly-expanding suite of genetically-encoded reagents (e.g., ChR2, Halo, Arch, Mac, and others) that, when expressed in specific neuron types in the nervous system, enable their activities to be powerfully and precisely activated and silenced in response to light. If the genes that encode for these reagents can be delivered to cells in the body using gene therapy methods, and if the resultant protein payloads operate safely and effectively over therapeutically important periods of time, these molecules could subserve a set of precise prosthetics that use light as the trigger of information entry into the nervous system, e.g. for sensory replacement. Here we discuss the use of ChR2 to make the photoreceptor-deprived retina, as found in diseases such as retinitis pigmentosa, sensitive to light, enabling restoration of functional vision in a mouse model of blindness. We also discuss arrays of light sources that could be useful for delivering patterned sensory information into the nervous system.